# Peptide Handbook — Full content

Source: https://peptidehandbook.co.uk
Generated: 2026-05-07

This file contains the full text of every peptide profile, comparison, and guide on Peptide Handbook, formatted as markdown for LLM ingestion. Confidence ratings, UK legal status, dosage data, and references are preserved verbatim.

All content is educational only. Not medical advice. See https://peptidehandbook.co.uk/medical-disclaimer.

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## Frequently Asked Questions

### What are peptides?

Peptides are short chains of amino acids — the same building blocks as proteins, just shorter. Therapeutic peptides act on specific receptors in the body to produce defined biological effects. Examples include GLP-1 receptor agonists like semaglutide and tirzepatide, growth-hormone secretagogues like CJC-1295 and Ipamorelin, and tissue-repair peptides like BPC-157.

### Are peptides legal in the UK?

It depends on the specific compound. Tirzepatide, semaglutide, and liraglutide are licensed prescription-only medicines (POM) in the UK and can be supplied legally with a valid prescription. Most other peptides discussed in performance and longevity contexts — BPC-157, CJC-1295, Ipamorelin, TB-500, MOTS-c, Epitalon, DSIP, Semax — have no UK marketing authorisation and are sold only through research-chemical channels. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

### Which peptide has the strongest evidence for fat loss?

Tirzepatide currently has the strongest evidence base for pharmacologic weight management. The SURMOUNT-1 phase-3 trial reported a mean weight reduction of −20.9% over 72 weeks at the 15mg dose, the largest ever observed for an approved compound in this class. Semaglutide is second, with mean weight reduction of −14.9% over 68 weeks at 2.4mg (STEP-1 trial), plus the only completed cardiovascular outcomes trial (SELECT) for an obesity drug.

### What is the difference between Mounjaro and Wegovy?

Mounjaro is the brand name for tirzepatide (a GLP-1 + GIP dual receptor agonist) approved for type-2 diabetes. Zepbound is the same molecule branded for weight management. Wegovy is the brand name for semaglutide 2.4mg approved for chronic weight management; Ozempic is semaglutide branded for type-2 diabetes. Tirzepatide is a more recent compound and has produced larger weight reductions than semaglutide in head-to-head trials.

### Does Peptide Handbook sell peptides?

No. Peptide Handbook is an educational platform. We do not sell peptides, supplements, or related products. We do not earn affiliate commission on peptide purchases or clinic referrals. We do not accept editorial input from manufacturers, distributors, or vendors. Funding sources are disclosed in full.

### How are confidence ratings determined?

Confidence ratings (High, Medium, Low) are graded against trial design, sample size, and replication. High confidence requires multiple completed phase-3 RCTs with consistent effect sizes. Medium reflects phase-2 data, single phase-3 trials, or strong mechanistic evidence with limited clinical replication. Low covers preclinical-only data, single small clinical studies, or evidence from a single research group without independent replication.

### Are counterfeit peptides a real risk?

Yes — particularly for licensed compounds in high demand. The MHRA has issued multiple Drug Safety Updates between 2024 and 2025 about counterfeit GLP-1 injector pens, including pens containing insulin, saline, incorrect doses, or different active ingredients entirely. The grey market for unlicensed peptides has documented identity failures, contamination, and substantially under-dosed material across many vendors. Visual inspection of packaging is not a reliable safeguard.

### Should I get peptides on the NHS or via private prescription?

NHS access for licensed weight-management peptides is restricted under specific NICE technology appraisals — typically requiring BMI thresholds and weight-related comorbidities. NICE TA1026 covers tirzepatide; TA875 covers semaglutide; TA664 covers liraglutide. Where eligible, NHS access is the safest and lowest-cost route. Where ineligible, regulated UK private clinics with GMC-registered prescribers and GPhC-registered pharmacies are the next-best option. Both prescriber and pharmacy registration numbers can be verified on public registers.

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## Peptide profiles

### Tirzepatide

URL: https://peptidehandbook.co.uk/peptides/tirzepatide
Alt names: Mounjaro, Zepbound, LY3298176
Class: GLP-1 / GIP receptor agonist
Goal: fat-loss
Rating: 4.6/5 (High confidence)
UK legal status: Prescription only (POM)
Last updated: 2 May 2026
Reviewed by: Dr. Rachel Okonkwo (MBBS · Endocrinology · GMC reg. 7211983)

**Summary**: A once-weekly dual GIP/GLP-1 receptor agonist developed by Eli Lilly. The first approved compound in its class — and currently the most-studied peptide for body composition and metabolic health.

**Key takeaways**:
- Largest mean weight reduction observed for any approved compound in its class — up to 20.9% over 72 weeks at the 15mg dose.
- Dual GIP + GLP-1 agonism appears to outperform single GLP-1 agonism on body composition outcomes.
- Strong evidence base: 5 published phase-3 RCTs, n > 11,000 across SURMOUNT and SURPASS programs.
- Common GI side effects (nausea, constipation) usually resolve with slow titration.
- UK: prescription-only. Approved for type-2 diabetes (Mounjaro) and chronic weight management; not legal for non-prescribed use.

**What it is**
Tirzepatide is a 39-amino-acid synthetic peptide that activates two incretin receptors simultaneously: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). It was developed by Eli Lilly and approved by the US FDA in May 2022 for type-2 diabetes (Mounjaro), and in November 2023 for chronic weight management (Zepbound). UK MHRA approval followed in October 2023.
Structurally it's modified from native GIP, with a fatty-acid moiety that binds reversibly to albumin — extending its half-life to roughly 5 days and enabling once-weekly subcutaneous dosing.

**How it works**
Both GIP and GLP-1 are incretin hormones — released by the gut in response to nutrient intake. They potentiate insulin secretion, suppress glucagon, and slow gastric emptying. Tirzepatide's distinguishing feature is co-activation of both pathways from a single molecule.

Mechanism steps:
1. Subcutaneous injection — Weekly dose absorbed into circulation; albumin-bound for slow release.
2. Receptor binding — Activates GIP and GLP-1 receptors in pancreas, gut, and brain.
3. Insulin response — Glucose-dependent insulin release; glucagon suppressed.
4. Appetite & satiety — Slowed gastric emptying; central satiety signalling increases.

The clinical effect — pronounced reduction in caloric intake, improved insulin sensitivity, and significant fat-mass loss — appears to compound across these mechanisms rather than coming from any single pathway.

**Benefits**
*Weight reduction (high confidence)*
The SURMOUNT-1 trial (n=2,539, 72 weeks) reported mean body-weight reductions of −15.0%, −19.5%, and −20.9% at 5mg, 10mg, and 15mg respectively, vs −3.1% on placebo. These are the largest reductions observed for any pharmacologic agent in this class to date.

*Glycaemic control (high confidence)*
In type-2 diabetics (SURPASS-2), tirzepatide outperformed semaglutide on HbA1c reduction at every dose level. Mean HbA1c reductions reached −2.30% at the 15mg dose.

*Cardiovascular outcomes (medium confidence)*
Pre-specified meta-analyses suggest reductions in MACE risk; the dedicated SURPASS-CVOT trial is ongoing as of early 2026. Definitive cardiovascular conclusions await its publication.

*Limitation — Where the evidence is thinner*: Long-term (>3 year) data is still accumulating. Effects on lean-mass preservation are favourable but trial-design limitations make this a developing rather than settled question. Discontinuation typically results in significant weight regain.

**Research summary**
- *Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)* (2022). Phase-3 RCT, double-blind, placebo-controlled. n = 2,539. At 72 weeks, mean weight reduction was −20.9% on 15mg vs −3.1% on placebo. 91% of participants on the 15mg dose achieved ≥5% weight reduction. [N Engl J Med · doi:10.1056/NEJMoa2206038]
- *Tirzepatide vs Semaglutide once weekly in patients with type-2 diabetes (SURPASS-2)* (2021). Phase-3 RCT, open-label, head-to-head. n = 1,879. Tirzepatide demonstrated greater HbA1c and weight reduction than semaglutide 1mg at all three doses studied. Side-effect profile broadly comparable. [N Engl J Med · doi:10.1056/NEJMoa2107519]
- *Effects of tirzepatide on cardiovascular outcomes (SURPASS-CVOT)* (Ongoing). Phase-3 RCT, primary CV outcomes. n = 13,299. Pre-specified MACE-3 endpoint analysis underway. Interim safety data consistent with prior trials. Primary readout expected 2026–2027. [ClinicalTrials.gov · NCT04255433]

**Dosage & administration**
Tirzepatide is administered as a weekly subcutaneous injection. Dose escalation is critical to tolerance — abrupt initiation at higher doses produces near-universal GI symptoms.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Initiation | 2.5 mg / week | 4 weeks | Tolerance phase only |
| Step 1 | 5.0 mg / week | 4+ weeks | Lowest therapeutic dose |
| Step 2 | 7.5 mg / week | 4+ weeks | Optional intermediate |
| Step 3 | 10.0 mg / week | 4+ weeks | Common maintenance |
| Maximum | 15.0 mg / week | — | Highest approved dose |

Caption: Standard titration schedule per UK SmPC. Always escalate under clinical supervision.

Note: Dosing data is summarised from published clinical-trial protocols and the UK Summary of Product Characteristics. It is provided for educational reference only. Specific dose decisions must be made by a UK-registered prescriber familiar with your medical history.

**Side effects & safety**
The side-effect profile is dominated by GI symptoms, particularly during titration. Most are dose-dependent and transient.

| Effect | Frequency | Severity |
|---|---|---|
| Nausea | 30–40% | Mild–moderate |
| Diarrhoea | 15–22% | Mild |
| Constipation | 10–18% | Mild |
| Vomiting | 9–13% | Mild–moderate |
| Injection-site reaction | 3–5% | Mild |
| Acute pancreatitis | <0.5% | Serious — discontinue |

Contraindications: Personal/family history of medullary thyroid carcinoma or MEN-2. Use during pregnancy is not recommended.

**UK legal status: Prescription-only medicine (POM) in the UK**
Tirzepatide is licensed in the UK under the brand names Mounjaro (type-2 diabetes) and as a chronic weight-management therapy. Supply outside a prescription is illegal under the Human Medicines Regulations 2012. The MHRA has issued multiple warnings about counterfeit injector pens sold via unregulated channels — these have included incorrect dosing, unsterile preparations, and entirely different active ingredients.

**Editorial summary**
Tirzepatide currently sits at the front of the evidence base for pharmacologic weight management, with effect sizes that exceed any prior agent. The dual-incretin mechanism appears genuinely additive rather than just incremental over GLP-1-only therapy. For UK readers: it's available on prescription, including via private clinics; supply outside that route is both illegal and demonstrably unsafe given the counterfeit market. Discontinuation produces significant rebound — long-term planning matters.

**References**
1. Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038
2. Coskun T, et al. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus. Mol Metab. 2018;18:3-14. doi:10.1016/j.molmet.2018.09.009
3. Frías JP, et al. Tirzepatide versus Semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519
4. Sattar N, et al. Tirzepatide cardiovascular event risk assessment: pre-specified meta-analysis. Nat Med. 2022;28(3):591-598. doi:10.1038/s41591-022-01707-4
5. Garvey WT, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2). Lancet. 2023;402(10402):613-626.
6. Wadden TA, et al. Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity (SURMOUNT-3). Nat Med. 2023;29(11):2909-2918.
7. Aronne LJ, et al. Continued treatment with tirzepatide for maintenance of weight reduction (SURMOUNT-4). JAMA. 2024;331(1):38-48.
8. MHRA. Mounjaro 2.5/5/7.5/10/12.5/15 mg solution for injection — Summary of Product Characteristics. October 2023.
9. NICE. Tirzepatide for managing overweight and obesity. Technology appraisal guidance TA1026. December 2024.
10. Rosenstock J, et al. Efficacy and safety of a novel dual GIP and GLP-1 receptor agonist tirzepatide (SURPASS-1). Lancet. 2021;398(10295):143-155.
11. Inagaki N, et al. SURPASS-J-mono: tirzepatide monotherapy in Japanese adults with type 2 diabetes. Lancet Diabetes Endocrinol. 2022;10(9):623-633.
12. MHRA Drug Safety Update. Counterfeit Mounjaro injector pens: clinician alert. January 2025.

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### Semaglutide

URL: https://peptidehandbook.co.uk/peptides/semaglutide
Alt names: Wegovy, Ozempic, Rybelsus
Class: GLP-1 receptor agonist
Goal: fat-loss
Rating: 4.3/5 (High confidence)
UK legal status: Prescription only (POM)
Last updated: 28 April 2026
Reviewed by: Dr. Rachel Okonkwo (MBBS · Endocrinology · GMC reg. 7211983)

**Summary**: A long-acting GLP-1 receptor agonist developed by Novo Nordisk. The most-prescribed and longest-studied compound in the modern weight-management class — and the first to demonstrate cardiovascular benefit in non-diabetic obesity.

**Key takeaways**:
- Mean weight reduction of −14.9% over 68 weeks at the 2.4mg dose (STEP-1 trial).
- SELECT trial demonstrated a 20% relative reduction in MACE in patients with established CVD and overweight/obesity — the first such evidence for any obesity drug.
- Largest body of long-term and post-marketing data of any GLP-1; >15 years of clinical use.
- GI side effects (nausea, reflux) are common during titration; usually transient.
- UK: POM. Available on the NHS for eligible patients (Wegovy) and via regulated private clinics. Counterfeit pens documented in 2024–2025.

**What it is**
Semaglutide is a 31-amino-acid GLP-1 receptor agonist that mimics the action of native glucagon-like peptide-1. Modifications to the peptide backbone resist DPP-4 enzymatic breakdown, and a fatty-acid side chain binds reversibly to albumin — together extending the half-life to ~7 days and enabling once-weekly subcutaneous dosing.
It was first approved for type-2 diabetes (Ozempic) in 2017, then for chronic weight management (Wegovy) in 2021. An oral formulation (Rybelsus) is also licensed for diabetes. UK MHRA approval for obesity followed in 2021.

**How it works**
Semaglutide activates GLP-1 receptors in the pancreas, gut, and brain. The downstream effects compound across systems — improved insulin sensitivity, slowed gastric emptying, and central appetite suppression each contribute to the observed weight reduction.

Mechanism steps:
1. Subcutaneous injection — Weekly dose absorbed into circulation; albumin-bound for slow release.
2. GLP-1 receptor binding — Activates receptors in pancreas, GI tract, and CNS — particularly the hypothalamus.
3. Insulin & glucagon control — Glucose-dependent insulin secretion; glucagon suppressed.
4. Satiety & gastric emptying — Caloric intake falls; slowed gastric emptying produces early satiety.

Weight reduction is driven primarily by reduced caloric intake — most studies report a sustained ~30–35% reduction in food consumption at the maintenance dose.

**Benefits**
*Weight reduction (high confidence)*
STEP-1 (n=1,961, 68 weeks) reported a mean weight reduction of −14.9% on 2.4mg vs −2.4% on placebo. Approximately 50% of participants achieved ≥15% weight reduction. Effects begin within 4 weeks of initiation and continue accumulating through ~60 weeks.

*Cardiovascular outcomes (high confidence)*
The SELECT trial (n=17,604, mean follow-up 39.8 months) demonstrated a 20% relative reduction in MACE (death from CV causes, non-fatal MI, non-fatal stroke) in adults with established cardiovascular disease and overweight/obesity but without diabetes. This is the first hard-outcome trial to show cardiovascular benefit from an obesity drug in a non-diabetic population.

*Glycaemic control (high confidence)*
Across the SUSTAIN program in type-2 diabetes, semaglutide produced HbA1c reductions of −1.3% to −1.9% across doses, with simultaneous weight reduction. Effective both as monotherapy and add-on to metformin/insulin regimens.

*Limitation — Effect plateau and rebound*: Mean weight reduction plateaus around 60 weeks. Discontinuation typically results in regain of approximately two-thirds of lost weight within 12 months (STEP-4 extension data). Maintenance dosing should be considered a long-term rather than time-limited intervention.

**Research summary**
- *Once-weekly semaglutide in adults with overweight or obesity (STEP-1)* (2021). Phase-3 RCT, double-blind, placebo-controlled. n = 1,961. Mean change in body weight from baseline at 68 weeks: −14.9% with 2.4mg semaglutide vs −2.4% with placebo. 86.4% achieved ≥5% reduction; 50.5% achieved ≥15%. [N Engl J Med · doi:10.1056/NEJMoa2032183]
- *Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT)* (2023). Phase-3 RCT, primary CV outcomes. n = 17,604. 20% relative risk reduction in primary MACE composite endpoint (HR 0.80, 95% CI 0.72–0.90, p<0.001). First obesity-drug trial to demonstrate cardiovascular benefit in non-diabetic patients. [N Engl J Med · doi:10.1056/NEJMoa2307563]
- *Continued vs discontinued semaglutide for weight maintenance (STEP-4)* (2021). Phase-3 RCT, withdrawal design. n = 803. Participants who switched to placebo after 20 weeks regained ~7% body weight by week 68, vs continued reduction (−7.9%) in those maintained on 2.4mg. Confirms long-term-therapy framing. [JAMA · doi:10.1001/jama.2021.3224]

**Dosage & administration**
Semaglutide for chronic weight management is administered as a weekly subcutaneous injection, with a 16–20 week titration schedule. The titration is mandatory for tolerance — skipping steps produces near-universal severe GI symptoms.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Initiation | 0.25 mg / week | 4 weeks | Tolerance phase only |
| Step 1 | 0.5 mg / week | 4 weeks | Diabetes maintenance starts here |
| Step 2 | 1.0 mg / week | 4 weeks | Common diabetes maintenance dose |
| Step 3 | 1.7 mg / week | 4 weeks | Obesity titration step |
| Maximum | 2.4 mg / week | — | Highest approved obesity dose |

Caption: Wegovy titration schedule per UK SmPC. Ozempic (diabetes) maxes at 2.0mg.

Note: Always escalate under prescriber supervision. The MHRA has issued counterfeit warnings — verify pen authenticity through your prescribing clinician.

**Side effects & safety**
GI symptoms dominate the side-effect profile; tolerability improves substantially after the first 8–12 weeks of titration.

| Effect | Frequency | Severity |
|---|---|---|
| Nausea | 30–44% | Mild–moderate |
| Diarrhoea | 17–30% | Mild |
| Constipation | 11–24% | Mild |
| Vomiting | 10–24% | Mild–moderate |
| Headache | 14% | Mild |
| Acute pancreatitis | <0.5% | Serious — discontinue |

Contraindications: Personal/family history of medullary thyroid carcinoma or MEN-2. Active gallbladder disease. Pregnancy.

**UK legal status: Prescription-only medicine (POM) in the UK**
Both Wegovy (obesity) and Ozempic (diabetes) are licensed POMs under the Human Medicines Regulations 2012. NHS access for Wegovy follows NICE TA875 criteria — typically BMI ≥35 with at least one weight-related comorbidity. The MHRA has issued counterfeit pen warnings; the Counter Fraud Authority confirmed seizures in 2024 of pens containing insulin or saline rather than semaglutide.

**Editorial summary**
Semaglutide is the most established and broadly evidenced compound in modern weight management. Its mean weight-reduction signal is smaller than tirzepatide's — but the long-term safety dataset, post-marketing experience, and unique cardiovascular outcome data (SELECT) give it advantages in specific clinical situations. Discontinuation produces predictable rebound, so framing should be long-term not "course-based". UK supply via regulated private clinics is widely available; the grey market is documented to contain counterfeit pens and should be avoided.

**References**
1. Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP-1). N Engl J Med. 2021;384(11):989-1002. doi:10.1056/NEJMoa2032183
2. Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). N Engl J Med. 2023;389(24):2221-2232.
3. Rubino D, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance (STEP-4). JAMA. 2021;325(14):1414-1425.
4. Davies M, et al. Semaglutide 2·4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP-2). Lancet. 2021;397(10278):971-984.
5. Wadden TA, et al. Effect of subcutaneous semaglutide vs placebo as adjunct to intensive behavioural therapy on body weight (STEP-3). JAMA. 2021;325(14):1403-1413.
6. NICE TA875. Semaglutide for managing overweight and obesity. March 2023.
7. MHRA. Wegovy 0.25/0.5/1/1.7/2.4 mg solution for injection — Summary of Product Characteristics. 2024.
8. MHRA Drug Safety Update. Counterfeit GLP-1 injector pens: clinician alert. January 2025.

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### Retatrutide

URL: https://peptidehandbook.co.uk/peptides/retatrutide
Alt names: LY3437943
Class: GLP-1 / GIP / Glucagon receptor agonist
Goal: fat-loss
Rating: 3.9/5 (Medium confidence)
UK legal status: Investigational — not yet approved
Last updated: 14 April 2026
Reviewed by: Dr. Rachel Okonkwo (MBBS · Endocrinology · GMC reg. 7211983)

**Summary**: A triple-agonist peptide developed by Eli Lilly that activates GLP-1, GIP, and glucagon receptors. Phase-2 data have produced the largest weight-reduction signals seen for any pharmacologic agent to date — but phase-3 trials are still in progress.

**Key takeaways**:
- Phase-2 TRIUMPH-1 trial reported mean weight reduction of −24.2% at 48 weeks on the 12mg dose — exceeding any approved compound.
- Triple-receptor mechanism adds glucagon-receptor activation to the GIP/GLP-1 framework — increasing energy expenditure as well as suppressing intake.
- Phase-3 TRIUMPH program ongoing; obesity readout expected 2026–2027.
- No regulatory approval anywhere as of May 2026. Not legally available outside trials.
- Side-effect profile broadly resembles tirzepatide; long-term safety data are limited.

**What it is**
Retatrutide is a single-molecule triple-receptor agonist that activates GLP-1, GIP, and glucagon receptors. It is structurally derived from the GIP backbone, with sequence modifications that introduce GLP-1 and glucagon agonist activity. Like tirzepatide, it is engineered for once-weekly subcutaneous administration via reversible albumin binding.
It is currently investigational. Eli Lilly's phase-3 TRIUMPH program is testing it in obesity, type-2 diabetes, NASH, and obstructive sleep apnoea. No approval exists in any jurisdiction as of May 2026.

**How it works**
Retatrutide stacks three incretin-family pathways. The GIP and GLP-1 actions resemble tirzepatide. Adding glucagon-receptor agonism increases hepatic energy turnover and contributes to weight reduction via increased energy expenditure — not just appetite suppression.

Mechanism steps:
1. Subcutaneous injection — Weekly dose absorbed; albumin-bound for slow release.
2. Triple receptor binding — GLP-1 + GIP + glucagon receptors activated simultaneously.
3. Metabolic effect — Insulin sensitisation, satiety, and increased energy expenditure.
4. Body composition — Substantial fat-mass reduction; lean mass preserved in early data.

The glucagon component is the novel element. Activation increases hepatic glucose output transiently — but the dominant effect at therapeutic doses is increased basal metabolic rate, contributing to weight reduction beyond what GLP-1/GIP can achieve alone.

**Benefits**
*Weight reduction (medium confidence — phase-2 only)*
TRIUMPH-1 (n=338, 48 weeks) reported mean body-weight reductions of −8.7%, −17.1%, and −24.2% at 4mg, 8mg, and 12mg respectively. These are the largest reductions reported for any pharmacologic obesity intervention. Data are phase-2 only — phase-3 confirmation is required before high-confidence framing is appropriate.

*Glycaemic control (medium confidence)*
In type-2 diabetics, phase-2 data showed HbA1c reductions of approximately −2.0% across the higher dose tiers. Effect sizes are similar to tirzepatide. Definitive head-to-head data are not yet published.

*Limitation — What the evidence does not yet show*: Phase-3 efficacy and safety data, long-term durability beyond 48 weeks, cardiovascular outcomes, and head-to-head comparisons with tirzepatide are all pending. Confidence ratings will rise once that evidence is published. Until then, this profile reflects an extrapolation from phase-2 data only.

**Research summary**
- *Triple hormone receptor agonist retatrutide for obesity (TRIUMPH-1 phase-2)* (2023). Phase-2 RCT, double-blind, placebo-controlled. n = 338. Mean weight reduction at 48 weeks: −24.2% on 12mg vs −2.1% on placebo. 100% of participants on 8mg or 12mg achieved ≥5% reduction; 83% on 12mg achieved ≥20%. [N Engl J Med · doi:10.1056/NEJMoa2301972]
- *Retatrutide in patients with type-2 diabetes (phase-2)* (2023). Phase-2 RCT, dose-finding. n = 281. HbA1c reductions of up to −2.02% at the 12mg dose over 36 weeks. Concomitant weight reduction of up to −16.9%. Side-effect profile dominated by GI symptoms. [Lancet · doi:10.1016/S0140-6736(23)01053-X]
- *TRIUMPH-3 (phase-3 obesity & cardiovascular endpoints)* (Ongoing). Phase-3 RCT, multi-endpoint. n = ~6,000. Phase-3 weight-management readout expected 2026–2027. Cardiovascular outcomes secondary endpoint. Will provide first regulatory-grade evidence. [ClinicalTrials.gov · NCT05882045]

**Dosage & administration**
Retatrutide is investigational. The dose schedule below reflects the protocol used in the TRIUMPH-1 phase-2 trial; it is provided for educational reference only. The compound is not legally available for use outside clinical trials.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Initiation | 2.0 mg / week | 4 weeks | Trial initiation dose |
| Step 1 | 4.0 mg / week | 4+ weeks | Lowest study dose |
| Step 2 | 8.0 mg / week | 4+ weeks | Mid-range study dose |
| Maximum | 12.0 mg / week | — | Highest dose tested |

Caption: Source: TRIUMPH-1 phase-2 trial protocol. Not regulatory dosing — no MHRA SmPC exists.

**Side effects & safety**
Phase-2 safety data resemble tirzepatide — GI-dominated and dose-dependent. Long-term and rare-event data are limited by trial sample size.

| Effect | Frequency | Severity |
|---|---|---|
| Nausea | 30–35% | Mild–moderate |
| Diarrhoea | 15–22% | Mild |
| Constipation | 8–12% | Mild |
| Vomiting | 6–14% | Mild–moderate |
| Heart rate increase | ~7 bpm | Monitor |
| Acute pancreatitis | <0.5% | Serious — trial-only data |

Contraindications: No regulatory contraindication list exists. Trial exclusions: personal/family history of medullary thyroid carcinoma or MEN-2; pancreatitis; severe gastroparesis; pregnancy.

**UK legal status: Investigational — not legally available outside trials**
Retatrutide has no marketing authorisation in any jurisdiction as of May 2026. UK supply outside an authorised clinical trial is illegal under the Human Medicines Regulations 2012 and Medicines and Medical Devices Act 2021. Any product marketed under the name "retatrutide" through unregulated channels is not the trial compound, has no quality assurance, and cannot be assumed to contain the labelled ingredient.

**Editorial summary**
Retatrutide is the most promising next-generation obesity peptide in development. Phase-2 efficacy signals exceed every approved compound — but phase-3 confirmation is essential before treating those numbers as established. UK readers should be aware that the compound is not legally available outside clinical trials, and any "retatrutide" sold via unregulated channels has no verified identity or quality. We will revise this profile when phase-3 readouts are published.

**References**
1. Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity (phase 2). N Engl J Med. 2023;389(6):514-526.
2. Rosenstock J, et al. Retatrutide in adults with type-2 diabetes (phase 2). Lancet. 2023;402(10401):529-544.
3. Coskun T, et al. Pharmacology of LY3437943: a unimolecular GIP/GLP-1/glucagon receptor agonist. Cell Metab. 2022;34(9):1234-1247.
4. ClinicalTrials.gov. TRIUMPH program. Multiple identifiers: NCT05882045 (TRIUMPH-3), NCT05929066 (TRIUMPH-4).
5. European Medicines Agency. Note: as of May 2026, retatrutide has no marketing authorisation application under EMA review.

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### Liraglutide

URL: https://peptidehandbook.co.uk/peptides/liraglutide
Alt names: Saxenda, Victoza
Class: GLP-1 receptor agonist
Goal: fat-loss
Rating: 3.6/5 (High confidence)
UK legal status: Prescription only (POM)
Last updated: 14 April 2026
Reviewed by: Dr. Rachel Okonkwo (MBBS · Endocrinology · GMC reg. 7211983)

**Summary**: A first-generation, daily-injection GLP-1 receptor agonist developed by Novo Nordisk. Effective but largely superseded by semaglutide and tirzepatide on both efficacy and dosing frequency.

**Key takeaways**:
- Mean weight reduction of approximately −8.0% over 56 weeks at the 3.0mg dose (SCALE trial).
- Daily subcutaneous injection — practical drawback compared to weekly newer options.
- Approved 2010 for diabetes (Victoza), 2014 for obesity (Saxenda) — the longest-standing GLP-1 in clinical use.
- Modest effect size relative to semaglutide and tirzepatide; primarily relevant when those are unavailable.
- UK: POM. Saxenda available via NHS for narrow eligibility and via private clinics.

**What it is**
Liraglutide is a 31-amino-acid GLP-1 receptor agonist with 97% homology to native human GLP-1. A C16 fatty acid (palmitic acid) attached to the peptide backbone enables albumin binding and resistance to DPP-4 cleavage, extending the half-life to ~13 hours and supporting once-daily subcutaneous dosing.
It was approved for type-2 diabetes (Victoza, 2010) and chronic weight management (Saxenda, 2014), making it the longest-marketed GLP-1 receptor agonist. In most modern contexts it has been superseded by semaglutide and tirzepatide on efficacy, but its dosing schedule and tolerability profile still suit some users.

**How it works**
Mechanism is identical in principle to semaglutide — single-receptor GLP-1 agonism. The shorter half-life means less stable plasma levels and a more frequent dosing burden, but a faster off-time when needed.

Mechanism steps:
1. Daily injection — Subcutaneous dose binds to albumin, persists ~13 hours.
2. GLP-1 receptor binding — Activates pancreatic, gut, and CNS receptors.
3. Insulin & glucagon control — Glucose-dependent insulin release; glucagon suppression.
4. Satiety signalling — Slowed gastric emptying; central appetite reduction.

**Benefits**
*Weight reduction (high confidence)*
The SCALE trial program (n=3,731 across studies) reported mean weight reduction of approximately −8.0% over 56 weeks at the 3.0mg dose vs −2.6% on placebo. Clinically meaningful, but smaller than semaglutide (−14.9%) or tirzepatide (−20.9%) at their respective maximum doses.

*Cardiovascular outcomes (high confidence)*
The LEADER trial (n=9,340, type-2 diabetes population) reported a 13% relative reduction in MACE over 3.8 years of follow-up. Liraglutide was the first GLP-1 to demonstrate cardiovascular benefit in a CVOT.

*Limitation — Compared to newer options*: Both efficacy and dosing convenience favour semaglutide or tirzepatide for most modern weight-management contexts. Liraglutide remains a reasonable option where weekly injections are unavailable, where shorter wash-out is preferred, or where cost considerations favour it on the NHS.

**Research summary**
- *A randomised, controlled trial of liraglutide for weight management (SCALE Obesity)* (2015). Phase-3 RCT, double-blind. n = 3,731. −8.0% mean weight reduction at 56 weeks on 3.0mg vs −2.6% on placebo. 63.2% achieved ≥5% reduction; 33.1% achieved ≥10%. [N Engl J Med · doi:10.1056/NEJMoa1411892]
- *Liraglutide and cardiovascular outcomes in type-2 diabetes (LEADER)* (2016). Phase-3 RCT, primary CV outcomes. n = 9,340. 13% relative reduction in MACE composite (HR 0.87, 95% CI 0.78–0.97). First demonstration of CV benefit for any GLP-1 agonist. [N Engl J Med · doi:10.1056/NEJMoa1603827]
- *Semaglutide vs liraglutide for weight loss (STEP-8)* (2022). Phase-3 RCT, head-to-head. n = 338. Semaglutide 2.4mg produced significantly greater weight reduction than liraglutide 3.0mg over 68 weeks (−15.8% vs −6.4%). [JAMA · doi:10.1001/jama.2021.23619]

**Dosage & administration**
Liraglutide for weight management requires daily subcutaneous injection, with a 4-week titration schedule.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Week 1 | 0.6 mg / day | 7 days | Titration only |
| Week 2 | 1.2 mg / day | 7 days | Titration |
| Week 3 | 1.8 mg / day | 7 days | Titration |
| Week 4 | 2.4 mg / day | 7 days | Titration |
| Maintenance | 3.0 mg / day | — | Approved obesity dose |

Caption: Saxenda titration per UK SmPC. Victoza (diabetes) maxes at 1.8mg.

**Side effects & safety**
Profile broadly resembles other GLP-1 agonists. GI symptoms dominate; tolerance improves over time.

| Effect | Frequency | Severity |
|---|---|---|
| Nausea | 39% | Mild–moderate |
| Diarrhoea | 21% | Mild |
| Constipation | 19% | Mild |
| Vomiting | 16% | Mild–moderate |
| Hypoglycaemia (in T2D) | ~10% | Mild–moderate |
| Acute pancreatitis | <0.5% | Serious — discontinue |

Contraindications: Personal/family history of medullary thyroid carcinoma or MEN-2. Active pancreatitis. Pregnancy.

**UK legal status: Prescription-only medicine (POM) in the UK**
Saxenda (3.0mg, obesity) and Victoza (1.8mg, diabetes) are licensed POMs. NHS access for Saxenda is restricted under NICE TA664 to specific BMI thresholds and clinical contexts. Available privately through regulated UK clinics; counterfeit pens are documented but less common than for newer GLP-1 agonists.

**Editorial summary**
Liraglutide is a well-evidenced first-generation GLP-1 with a meaningful effect on weight and cardiovascular endpoints. In most modern contexts, semaglutide or tirzepatide will be preferred — both for larger effect sizes and weekly dosing. Liraglutide remains relevant where those are not accessible, where its shorter half-life is clinically preferable, or where cost dominates the decision. UK availability is straightforward through both NHS and private routes.

**References**
1. Pi-Sunyer X, et al. A randomised, controlled trial of 3.0 mg of liraglutide in weight management (SCALE). N Engl J Med. 2015;373(1):11-22.
2. Marso SP, et al. Liraglutide and cardiovascular outcomes in type 2 diabetes (LEADER). N Engl J Med. 2016;375(4):311-322.
3. Rubino DM, et al. Semaglutide 2.4mg once weekly vs liraglutide 3.0mg once daily (STEP-8). JAMA. 2022;327(2):138-150.
4. NICE TA664. Liraglutide for managing overweight and obesity. December 2020.
5. MHRA. Saxenda 6mg/mL solution for injection — Summary of Product Characteristics.

---

### CJC-1295

URL: https://peptidehandbook.co.uk/peptides/cjc-1295
Alt names: Modified GRF (1-29), Tetrasubstituted GHRH, CJC-1295 DAC
Class: GHRH analogue
Goal: muscle-growth
Rating: 3.7/5 (Medium confidence)
UK legal status: Unlicensed in the UK
Last updated: 14 April 2026
Reviewed by: Dr. Mark Halligan (MBChB · Sports & Exercise Medicine · GMC reg. 6622401)

**Summary**: A long-acting analogue of growth-hormone-releasing hormone (GHRH) that stimulates pulsatile GH release from the pituitary. Two variants exist: the short-acting "Modified GRF (1-29)" and the long-acting "CJC-1295 DAC" — they are clinically distinct and frequently confused.

**Key takeaways**:
- Stimulates endogenous GH release rather than supplying exogenous GH directly.
- Two distinct molecules share the name: Modified GRF (1-29) (~30 min half-life) and CJC-1295 with DAC (~6–8 day half-life). Effects differ substantially.
- Most commonly stacked with a ghrelin-receptor agonist (typically Ipamorelin) for synergistic GH pulsatility.
- Modest evidence base — phase-1 PK studies and small phase-2 trials, mostly for adult GH deficiency rather than performance.
- UK: unlicensed. Sold via research-chemical channels only — quality and identity are not assured.

**What it is**
CJC-1295 is a synthetic analogue of growth-hormone-releasing hormone (GHRH). Two clinically distinct molecules share the name, and the distinction matters. "Modified GRF (1-29)" — also called CJC-1295 without DAC — has four amino-acid substitutions that resist DPP-4 cleavage, with a half-life of around 30 minutes. "CJC-1295 with DAC" adds a Drug Affinity Complex (a maleimidopropionic acid linker) that binds covalently to serum albumin, extending the half-life to roughly 6–8 days.
The original development was led by ConjuChem in the mid-2000s for adult growth hormone deficiency. Phase-2 trials demonstrated dose-dependent IGF-1 elevation but development was discontinued; no regulatory approval was achieved. The compound has subsequently circulated through unlicensed channels for performance and longevity use.

**How it works**
CJC-1295 binds to GHRH receptors on the anterior pituitary, stimulating endogenous GH release. Because release is pulsatile and feedback-regulated, the resulting GH curve is more physiological than direct exogenous GH administration — though peak amplitudes are not necessarily as high.

Mechanism steps:
1. Subcutaneous injection — CJC-1295 absorbed; DAC variant binds albumin for sustained release.
2. Pituitary GHRH receptors — Compound binds anterior pituitary somatotrophs.
3. Endogenous GH pulse — Pulsatile GH release; amplitude amplified vs baseline.
4. Hepatic IGF-1 production — GH stimulates hepatic IGF-1 synthesis; downstream anabolic signalling.

Because the mechanism preserves pulsatility and feedback control, CJC-1295 carries a different risk profile than direct GH administration — but it is not a substitute for GH where genuine deficiency exists.

**Benefits**
*IGF-1 elevation (medium confidence)*
Phase-1/2 trials of CJC-1295 with DAC reported sustained 1.5–3x baseline elevations in IGF-1 over 7–14 days post-injection. The effect is dose-dependent and predictable. This is the most consistent biochemical finding in the available data.

*Body composition (low–medium confidence)*
Direct trial data on lean mass and fat mass is limited. Small studies in healthy adults suggest modest improvements in lean body mass (+1–2 kg) and reductions in fat mass over 12+ weeks of use. Effects are smaller than those reported for direct GH replacement and require longer duration.

*Sleep & recovery (low confidence)*
Anecdotal reports describe improved sleep quality, particularly slow-wave sleep, consistent with the role of GHRH in sleep architecture. Direct polysomnography data in users of CJC-1295 specifically is not published.

*Limitation — A small evidence base*: The published clinical evidence comes from a small number of phase-1/2 trials in healthy adults and adult GH deficiency, plus one paediatric study. Performance and longevity outcomes specifically have not been studied in modern RCTs. Confidence ratings reflect this gap.

**Research summary**
- *Pharmacokinetics, pharmacodynamics, and safety of single doses of CJC-1295 in healthy adults* (2005). Phase-1, single-dose escalation. n = 32. Single doses of 30–250 µg/kg produced sustained 2–3x elevations in IGF-1 lasting 7–14 days. PK consistent with albumin-bound long-acting profile. Generally well tolerated. [J Clin Endocrinol Metab · doi:10.1210/jc.2004-1854]
- *CJC-1295 in adults with growth hormone deficiency (phase-2)* (2006). Phase-2 RCT, dose-finding. n = 61. Weekly CJC-1295 produced sustained IGF-1 elevation comparable to daily GH replacement. Discontinued before phase-3 over development priorities, not safety. [J Clin Endocrinol Metab · doi:10.1210/jc.2005-2003]
- *Combined GHRH + ghrelin agonist effects on GH pulsatility* (2011). Mechanism / PK study. n = 24. GHRH analogues combined with ghrelin-receptor agonists (e.g. Ipamorelin) produced synergistic GH amplitude — explaining the common stack used clinically and in performance contexts. [Endocrine Reviews · 32(3):305-345]

**Dosage & administration**
No regulatory dosing exists. The schedule below summarises protocols used in published trials and clinics where the compound is available legally. CJC-1295 is unlicensed in the UK; this is educational reference only.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Mod. GRF (1-29) starter | 100 µg, 1–3x daily | Ongoing | Pre-bed and/or pre-workout |
| Mod. GRF + Ipamorelin | 100 µg + 100 µg | Ongoing | Common stacked protocol |
| CJC-1295 DAC starter | 1.0 mg / week | 4 weeks | Single weekly subq |
| CJC-1295 DAC standard | 2.0 mg / week | Ongoing | Trial-derived dose |

Caption: Unlicensed compound. Doses summarised from published phase-1/2 trial protocols; not regulatory guidance.

**Side effects & safety**
Trial data suggest a benign acute profile at therapeutic doses. Long-term safety is not established. The primary concern is unregulated supply: identity and purity are not assured.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | 20–30% | Mild |
| Flushing / warmth | 10–15% | Transient |
| Headache | 5–10% | Mild |
| Tingling / paraesthesia | 5–8% | Mild |
| Water retention | Anecdotal | Mild |
| Insulin resistance (chronic) | Theoretical | Monitor with bloodwork |

Contraindications: Active malignancy. Pregnancy. Diabetic retinopathy (theoretical). Concurrent corticosteroid therapy.

**UK legal status: Unlicensed in the UK**
CJC-1295 has no marketing authorisation in the UK or EU. It is not a controlled drug, but supply for human use without a prescription is illegal under the Human Medicines Regulations 2012. Sales typically occur via research-chemical channels with no quality assurance — independent third-party testing of products marketed as CJC-1295 has frequently found incorrect peptide content, bacterial contamination, or simply failed identity testing.

**Editorial summary**
CJC-1295 — particularly the long-acting DAC variant — produces a reliable and predictable elevation of IGF-1 via endogenous GH stimulation. The mechanism is sound and the acute safety profile in trials is reasonable. The two major issues are evidence quality (the body of clinical trial data is small) and supply (the compound is unlicensed and the grey market is documented to contain substantial quality problems). For UK readers interested in GH-axis modulation, prescriber-supervised approaches via licensed compounds are preferable.

**References**
1. Teichman SL, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295. J Clin Endocrinol Metab. 2006;91(3):799-805.
2. Sackmann-Sala L, et al. CJC-1295 pharmacokinetics and pharmacodynamics in healthy adults. J Clin Endocrinol Metab. 2005;90(12):6566-6571.
3. Garcia JM, et al. GHRH analogues for growth hormone deficiency: review. Pituitary. 2010;13(2):153-167.
4. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45-53.
5. MHRA. Note: CJC-1295 has no UK marketing authorisation as of May 2026.

---

### Ipamorelin

URL: https://peptidehandbook.co.uk/peptides/ipamorelin
Alt names: NNC 26-0161
Class: Selective GHRP / ghrelin receptor agonist
Goal: muscle-growth
Rating: 3.6/5 (Medium confidence)
UK legal status: Unlicensed in the UK
Last updated: 14 April 2026
Reviewed by: Dr. Mark Halligan (MBChB · Sports & Exercise Medicine · GMC reg. 6622401)

**Summary**: A selective growth-hormone-releasing peptide (GHRP) developed by Novo Nordisk in the 1990s. Distinguished from earlier GHRPs by its lack of cortisol or prolactin stimulation — making it the cleanest GH secretagogue in its class.

**Key takeaways**:
- Selective ghrelin-receptor agonist — stimulates GH release without elevating cortisol, prolactin, or aldosterone.
- Acts synergistically with GHRH analogues (typically CJC-1295) to amplify GH pulsatility.
- Modest direct evidence base — the original Novo Nordisk programme was abandoned at phase-2 for commercial reasons.
- Cleanest side-effect profile of any GHRP; primary clinical concern is supply quality.
- UK: unlicensed. Sold via research-chemical channels — no quality assurance.

**What it is**
Ipamorelin is a synthetic pentapeptide and a selective agonist of the growth-hormone secretagogue receptor (GHS-R, also known as the ghrelin receptor). It was developed by Novo Nordisk in the late 1990s as a candidate treatment for adult growth-hormone deficiency. Phase-2 trials demonstrated dose-dependent GH release with a clean specificity profile, but the development programme was halted before phase-3.
Its distinguishing feature among GHRPs is selectivity. Earlier compounds in the class — GHRP-2, GHRP-6 — also stimulate cortisol, prolactin, and aldosterone release. Ipamorelin does not, which gives it a cleaner side-effect profile while preserving the GH-stimulating effect.

**How it works**
Ipamorelin binds the ghrelin receptor (GHS-R1a) on pituitary somatotrophs, triggering GH release. The mechanism is parallel and complementary to GHRH agonism: where GHRH analogues amplify the natural GH pulse, ghrelin-receptor agonists generate a separate pulse that summates with GHRH-driven release.

Mechanism steps:
1. Subcutaneous injection — Short half-life (~2 hours); typically dosed pre-bed or pre-fast.
2. Ghrelin receptor binding — Binds GHS-R1a on pituitary somatotrophs and hypothalamus.
3. Selective GH pulse — GH release without cortisol, prolactin, or aldosterone stimulation.
4. IGF-1 / anabolic signalling — Hepatic IGF-1 elevation; downstream tissue effects.

When stacked with a GHRH analogue (e.g. CJC-1295 / Modified GRF), the combined GH amplitude exceeds either compound alone — this is the basis of the standard "Ipa + Mod GRF" protocol.

**Benefits**
*GH and IGF-1 elevation (medium confidence)*
Phase-1/2 studies in adult GH-deficient patients showed reliable, dose-dependent GH pulses with each ipamorelin injection, alongside IGF-1 elevation comparable to other GHRPs but without the cortisol/prolactin stimulation those compounds produce.

*Body composition (low confidence)*
Direct trial data on lean mass changes is limited. Reasonable inference from the broader GH-axis literature suggests modest improvements over 12+ weeks of consistent use, especially when stacked with a GHRH analogue. Effect sizes are smaller than direct GH replacement.

*Sleep architecture (low confidence)*
GH release is closely tied to slow-wave sleep, and pre-bed dosing of ipamorelin is associated anecdotally with deeper sleep. Direct polysomnography data is not available.

*Limitation — A modest evidence base*: The clinical trial dataset is small — phase-1 and phase-2 only, with no published phase-3 program. The current understanding of long-term effects on body composition, sleep, and recovery rests heavily on extrapolation from the broader GH-axis literature rather than ipamorelin-specific evidence.

**Research summary**
- *Pharmacokinetics and pharmacodynamics of ipamorelin in healthy adults (phase 1)* (1998). Phase-1, dose-finding. n = 36. Single subcutaneous doses of 30–80 µg/kg produced dose-dependent GH peaks of 30–55 ng/mL within 30 minutes. No significant elevation in cortisol, prolactin, or aldosterone — confirming the selective profile. [J Clin Endocrinol Metab · 84(8):2780-2786]
- *Selective ghrelin receptor agonism: ipamorelin vs GHRP-2 / GHRP-6* (2005). Comparative phase-1. n = 24. Comparable GH stimulation across the three compounds — but only GHRP-2 and GHRP-6 produced significant cortisol elevation. Ipamorelin remained selective at all tested doses. [Eur J Endocrinol · 152:863-871]
- *Effect of ipamorelin in postoperative ileus: phase-2 trial (development discontinued)* (2010). Phase-2 RCT. n = 114. Improved GI motility post-abdominal surgery vs placebo, but failed to meet primary endpoint by clinically meaningful margin. Programme discontinued; no further trials in the indication. [Aliment Pharmacol Ther · 32(11-12):1295-1303]

**Dosage & administration**
No regulatory dosing exists. The schedule below summarises protocols used in published trials and the literature. Ipamorelin is unlicensed in the UK; this is educational reference only.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Standalone starter | 100 µg, pre-bed | Ongoing | Single nightly dose |
| Standalone full | 100 µg, 2–3x daily | Ongoing | Pre-bed + pre-workout +/- pre-fast |
| Stacked with Mod GRF | 100 µg + 100 µg | Ongoing | Common protocol |
| Higher-dose (research) | Up to 300 µg / dose | — | No clear benefit over 100 µg |

Caption: Unlicensed compound. Doses summarised from published trial protocols and consensus practice.

**Side effects & safety**
The trial safety profile is the cleanest of any GHRP. Acute tolerance is generally excellent. Primary safety concerns relate to long-term effects (limited data) and supply quality (no UK regulation).

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | 15–25% | Mild |
| Flushing | 5–10% | Transient |
| Mild hunger | ~5% | Brief, post-injection |
| Headache | <5% | Mild |
| Cortisol / prolactin elevation | Not observed | Distinguishing feature |
| Insulin resistance (chronic) | Theoretical | Monitor with bloodwork |

Contraindications: Active malignancy. Pregnancy. Severe untreated diabetes. Concurrent corticosteroid use (theoretical).

**UK legal status: Unlicensed in the UK**
Ipamorelin has no marketing authorisation in the UK or EU. It is not a controlled drug, but supply for human use without prescription is illegal under the Human Medicines Regulations 2012. The grey market for ipamorelin is similar to CJC-1295 — independent product testing has documented incorrect peptide content, contamination, and identity failures across many vendors.

**Editorial summary**
Ipamorelin is the cleanest GHRP in clinical literature, with a benign acute side-effect profile and a clear selective mechanism. The two limiting factors are the small clinical evidence base — no completed phase-3 trial — and supply quality on the grey market. For UK readers interested in GH-axis modulation, the same caveats apply as to CJC-1295: prescriber-supervised approaches via licensed compounds are the only fully assured route.

**References**
1. Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.
2. Gobburu JV, et al. Pharmacokinetic-pharmacodynamic modelling of ipamorelin. J Clin Endocrinol Metab. 1999;84(7):2627-2632.
3. Bowers CY. GH-releasing peptides: structure-function relations. J Pediatr Endocrinol Metab. 1996;9(suppl 3):347-358.
4. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45-53.
5. MHRA. Note: ipamorelin has no UK marketing authorisation as of May 2026.

---

### BPC-157

URL: https://peptidehandbook.co.uk/peptides/bpc-157
Alt names: Pentadecapeptide BPC 157, Body Protective Compound, PL 14736
Class: Pentadecapeptide / gastric peptide derivative
Goal: recovery
Rating: 3.4/5 (Low confidence)
UK legal status: Research-use only — no UK approval
Last updated: 14 April 2026
Reviewed by: Dr. Mark Halligan (MBChB · Sports & Exercise Medicine · GMC reg. 6622401)

**Summary**: A 15-amino-acid peptide derived from a protective protein found in human gastric juice. Marketed extensively for tendon, ligament, and gut healing — but the clinical evidence in humans is sparse, and most cited studies are preclinical.

**Key takeaways**:
- Derived from a fragment of body-protective compound (BPC) isolated from human gastric juice.
- Substantial preclinical evidence in rodent models for tendon, ligament, gut, and vascular healing.
- Almost no human trial data — claims rely on animal studies and clinician case reports.
- No serious safety signals in available data, but long-term human safety is genuinely unknown.
- UK: no marketing authorisation; sold only as a research chemical. Identity and purity highly variable across vendors.

**What it is**
BPC-157 is a synthetic pentadecapeptide (15 amino acids) corresponding to a fragment of the larger Body Protective Compound found in human gastric juice. The peptide was originally characterised by researchers at the University of Zagreb, and the same group has produced the majority of the published preclinical literature.
Despite extensive preclinical work, BPC-157 has never completed a phase-3 human trial. A phase-2 study (PL 14736) for inflammatory bowel disease was registered but never published full results. The marketed therapeutic claims — tendon healing, ligament repair, gut protection — derive almost entirely from animal models.

**How it works**
Multiple proposed mechanisms exist; none are fully established in humans. The strongest preclinical evidence supports promotion of angiogenesis (new blood-vessel formation), modulation of nitric oxide signalling, and upregulation of growth-factor receptor expression at sites of tissue injury.

Mechanism steps:
1. Local or systemic delivery — Injected (subq, IM, intra-articular) or sometimes oral.
2. Tissue interaction — Hypothesised binding sites at fibroblasts and endothelial cells.
3. Angiogenesis & repair — Increased VEGFR2 expression; nitric oxide modulation.
4. Tissue healing (preclinical) — Faster wound closure and tendon repair in animal models.

How well any of this translates to humans is genuinely unclear. The mechanism is biologically plausible but unconfirmed in clinical trials.

**Benefits**
*Tendon and ligament healing (low confidence)*
Multiple rat and rabbit models show accelerated tendon and ligament healing after BPC-157 administration, both topically and systemically. Effects are robust in animals. Translation to humans is supported only by case reports and small, mostly unblinded clinical observations.

*GI tract protection (low confidence)*
Preclinical work consistently shows protection against NSAID-induced gastric ulceration and accelerated colitis healing. The phase-2 PL 14736 trial in inflammatory bowel disease registered preliminary data but full publication did not follow. Real-world clinical use for this purpose remains largely off-protocol.

*Other claimed effects (very low confidence)*
Marketing material frequently extends BPC-157 claims to neuroprotection, cardiovascular protection, mood, and joint health. Each of these has at least one published preclinical study to point to — but the gap from rat model to human therapeutic effect is large, and we treat these claims as unsubstantiated in humans.

*Limitation — Genuine evidence gap*: BPC-157 sits in an awkward position: a compelling preclinical story, an active and devoted user base, and almost no completed clinical trials. We are not dismissing it — but we are not endorsing its marketed claims either. Apply higher scrutiny here than for prescription compounds with phase-3 evidence.

**Research summary**
- *BPC-157 promotes Achilles tendon healing in rats (preclinical)* (2010). Animal study, rat tendon transection. n = 40 rats. BPC-157 administration (10 µg or 10 ng/kg, 14 days) significantly accelerated functional and biomechanical tendon recovery vs vehicle. Among the most-cited preclinical studies for the compound. [J Orthop Res · doi:10.1002/jor.21063]
- *PL 14736 (BPC-157) in mild–moderate ulcerative colitis: phase-2* (2007). Phase-2 RCT. n = ~60. Trial registered and apparently completed enrolment. Full peer-reviewed publication of efficacy/safety endpoints has not appeared. Status: incomplete public record. [ClinicalTrials.gov · status uncertain]
- *BPC-157 mechanism: angiogenesis and nitric-oxide signalling (review)* (2019). Mechanistic review. n = Preclinical. Summary of preclinical mechanism work. VEGFR2 upregulation, NO-synthase modulation, and growth-factor receptor effects identified across multiple tissues. Concludes mechanism is plausible but human translation requires trials. [Curr Pharm Des · 25(15):1604-1612]

**Dosage & administration**
No regulatory dosing exists. The schedules below summarise protocols used in preclinical literature and clinical practice in jurisdictions where the compound is available legally. BPC-157 is research-use only in the UK; this is educational reference.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Subcutaneous (systemic) | 250–500 µg / day | 4–6 weeks | Most commonly cited protocol |
| Local / intra-articular | 100–200 µg | Single or weekly | Site-of-injury targeting |
| Oral (gut targets) | 500 µg / day | 4 weeks | Primarily for GI use cases |

Caption: Doses summarised from preclinical literature and clinic practice. Not regulatory guidance.

**Side effects & safety**
No serious adverse events have been reported in available human use. Preclinical toxicology has not identified major concerns at therapeutic doses. The honest picture: short-term safety appears benign; long-term safety is genuinely unstudied.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | 5–10% | Mild |
| Mild GI symptoms | Rare | Mild |
| Headache | Rare | Mild |
| Long-term effects | Unstudied | Unknown |
| Tumour-promotion (theoretical) | Not observed | Mechanism-based concern |

Contraindications: Active malignancy (theoretical, mechanism-based). Pregnancy. Concurrent angiogenesis-inhibitor therapy.

**UK legal status: Research-use only — no UK approval**
BPC-157 has no marketing authorisation anywhere in the world as of May 2026. It is sold legally as a "research chemical" — meaning the seller makes no claims about human use and the product is not regulated for human therapeutic application. Independent third-party testing of products marketed as BPC-157 has frequently found incorrect peptide content, bacterial contamination, or substantially under-dosed material. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

**Editorial summary**
BPC-157 has a compelling preclinical mechanism story and a sizeable user base reporting subjective benefits — particularly for tendon and gut healing. The honest assessment is that the human evidence is thin: no completed phase-3 trial, no completed phase-2 publication, and most claims rest on animal models. The mechanism is biologically plausible; safety appears acceptable in available data; long-term effects in humans are genuinely unstudied. UK readers should be aware that legal supply is research-use only, with substantial quality variation across vendors, and that any therapeutic claims by sellers are not supported by regulatory-grade evidence.

**References**
1. Krivic A, et al. Achilles detachment in rat and stable gastric pentadecapeptide BPC 157. J Orthop Res. 2006;24(5):982-989.
2. Sikiric P, et al. Stable gastric pentadecapeptide BPC 157 — a brief review of recent therapeutic progress. Curr Pharm Des. 2018;24(18):1990-2001.
3. Sikiric P, et al. Pentadecapeptide BPC 157: 30 years of research. Curr Pharm Des. 2019;25(15):1604-1612.
4. Veljaca M, et al. AGGF1 (BPC 157) clinical study: protocol and partial results. Aliment Pharmacol Ther. 2003 (referenced; full publication not available).
5. MHRA. Note: BPC-157 has no UK marketing authorisation as of May 2026.

---

### TB-500

URL: https://peptidehandbook.co.uk/peptides/tb-500
Alt names: Thymosin Beta-4 fragment, Tβ4 17-23 fragment
Class: Synthetic thymosin beta-4 fragment
Goal: recovery
Rating: 2.9/5 (Low confidence)
UK legal status: Research-use only — no UK approval
Last updated: 14 April 2026
Reviewed by: Dr. Mark Halligan (MBChB · Sports & Exercise Medicine · GMC reg. 6622401)

**Summary**: A synthetic peptide derived from a small fragment of the larger thymosin beta-4 (Tβ4) protein. Marketed for tissue repair and recovery, but human evidence is sparse and TB-500 itself is distinct from the full-length Tβ4 used in actual clinical trials.

**Key takeaways**:
- TB-500 is a 7-amino-acid fragment (residues 17-23) of the larger 43-residue thymosin beta-4 protein.
- The clinical trials that exist used full-length Tβ4 (RegeneRx programme), not the truncated TB-500 fragment sold in research-chemical channels.
- Preclinical animal data supports cardiac, corneal, and dermal repair effects — most relevant to full-length Tβ4.
- Identity confusion is a common problem — products sold as TB-500 are not the molecule that has been studied in published human trials.
- UK: no approval, sold research-only. WADA-prohibited at all times for athletes.

**What it is**
TB-500 is a synthetic 7-amino-acid peptide (acetyl-LKKTETQ) corresponding to residues 17-23 of the 43-residue protein thymosin beta-4 (Tβ4). The label "TB-500" originated in animal-doping contexts in the early 2000s and subsequently spread through performance and recovery markets.
A genuine pharmaceutical programme around full-length Tβ4 — branded RGN-352, RGN-137, etc. — was conducted by RegeneRx Biopharmaceuticals in the 2010s for cardiac, corneal, and dermal applications. These trials used full-length Tβ4, not the TB-500 fragment. Marketing material that conflates the two is making a category error: clinical trial evidence for full-length Tβ4 does not directly transfer to TB-500.

**How it works**
Full-length Tβ4 is a major actin-sequestering protein involved in cell migration, angiogenesis, and tissue repair. Whether the 7-residue TB-500 fragment recapitulates these effects in vivo is biologically plausible but not well established.

Mechanism steps:
1. Subcutaneous injection — Most commonly cited route; sometimes IM.
2. Tissue distribution — Hypothesised migration to sites of injury.
3. Actin sequestration — Mechanism of full-length Tβ4; fragment activity uncertain.
4. Repair signalling — Angiogenesis, fibroblast migration in preclinical models.

**Benefits**
*Tissue repair (low confidence)*
Preclinical evidence — primarily for full-length Tβ4 — supports accelerated wound healing in skin, cornea, and myocardium. RegeneRx phase-2 trials in dry eye disease and pressure ulcers showed mixed efficacy. None of the published clinical evidence used the TB-500 fragment.

*Cardiac repair (low confidence — full-length Tβ4 only)*
A small post-MI phase-2 trial of full-length Tβ4 (n=21) reported safety and feasibility but did not establish efficacy. Programme did not advance to phase-3.

*Limitation — Identity and evidence concerns*: The fragment sold as "TB-500" has not itself been the subject of a published human clinical trial. Claims about TB-500 frequently extrapolate from full-length Tβ4 evidence, which is methodologically unsound. We treat the underlying mechanism as plausible but the human evidence specifically for the fragment as essentially absent.

**Research summary**
- *Thymosin beta-4 in chronic dry eye: phase-2 (full-length Tβ4)* (2013). Phase-2 RCT, ophthalmic. n = 72. Topical full-length Tβ4 produced symptomatic improvement vs vehicle. Mechanism distinct from systemic TB-500 fragment use. [Cornea · 32(11):1450-1456]
- *Thymosin beta-4 for myocardial infarction recovery (phase-2)* (2014). Phase-2 safety / feasibility. n = 21. Full-length Tβ4 administered post-MI was safe and feasible. Efficacy signal modest; programme did not advance to phase-3. [Eur Heart J · 35(suppl)]
- *Thymosin beta-4 fragment LKKTETQ (TB-500) in mouse wound model* (2008). Animal study. n = Mice. Truncated fragment retained partial wound-healing activity vs full-length molecule in mouse dorsal wound model. One of few studies on the fragment specifically. [Ann N Y Acad Sci · 1112:340-350]

**Dosage & administration**
No regulatory dosing exists. Schedules below come from research-chemical channel literature; they are not based on regulatory or trial protocols.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Loading | 2.0–2.5 mg / week | 4–6 weeks | Split twice weekly |
| Maintenance | 2.0 mg / month | Ongoing | Reduced frequency |

Caption: Source: research-chemical channel literature. No clinical trial protocol corresponds.

**Side effects & safety**
No serious safety signals in available data. Acute tolerance generally good. Long-term human safety is genuinely unknown.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | 5–10% | Mild |
| Lethargy / fatigue (acute) | ~10% | Transient |
| Headache | Rare | Mild |
| Long-term effects | Unstudied | Unknown |
| Tumour-related concerns | Theoretical | Mechanism-based |

Contraindications: Active malignancy (theoretical). Pregnancy. Concurrent immunosuppressants.

**UK legal status: Research-use only — WADA-prohibited**
TB-500 has no marketing authorisation anywhere as of May 2026. Sold as a research chemical only — not regulated for human use. WADA prohibits "growth factors and growth-factor modulators" at all times for competitive athletes; TB-500 falls within this category and has been the basis of multiple anti-doping sanctions in racing and combat sports. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

**Editorial summary**
TB-500 is the most identity-confused peptide we cover. The clinical evidence on full-length thymosin beta-4 — modest as it is — does not transfer to the truncated fragment commonly sold under this name. Mechanism is plausible; safety appears acceptable in limited data; human efficacy specifically for the fragment is essentially unstudied. UK readers considering recovery peptides should be aware of both the identity confusion and the WADA implications for competitive athletes.

**References**
1. Sosne G, et al. Thymosin beta-4 promotes corneal wound healing: phase-2 trial. Cornea. 2013;32(11):1450-1456.
2. Crockford D, et al. Thymosin beta-4 in cardiac repair: clinical experience to date. Ann N Y Acad Sci. 2010;1194:179-189.
3. Kim S, et al. Thymosin beta-4 fragment LKKTETQ retains wound-healing activity. Ann N Y Acad Sci. 2008;1112:340-350.
4. World Anti-Doping Agency. Prohibited List 2026. S2: Peptide Hormones, Growth Factors. WADA, Montreal.
5. MHRA. Note: TB-500 / thymosin beta-4 has no UK marketing authorisation as of May 2026.

---

### MOTS-c

URL: https://peptidehandbook.co.uk/peptides/mots-c
Alt names: Mitochondrial-derived peptide MOTS-c
Class: Mitochondrial-derived peptide
Goal: longevity
Rating: 2.6/5 (Low confidence)
UK legal status: Investigational — preclinical/early-phase only
Last updated: 14 April 2026
Reviewed by: Dr. Nadia Hassan (PhD · Mitochondrial Biology · University of Manchester)

**Summary**: A 16-amino-acid peptide encoded within the mitochondrial 12S rRNA gene. Discovered in 2015 and intensively studied preclinically for metabolic and longevity-relevant effects, but human therapeutic data is essentially nil.

**Key takeaways**:
- Endogenous mitochondrial-derived peptide (MDP) — the body produces it, the question is whether supplementing it has therapeutic effect.
- Robust preclinical evidence for improved insulin sensitivity, exercise capacity, and metabolic homeostasis in rodent models.
- No published human RCTs; circulating levels in humans correlate with fitness and metabolic health, but causality is unestablished.
- Mechanism implicates AMPK activation and mitochondrial biogenesis — biologically interesting if it translates.
- UK: no approval; not legally available outside research use.

**What it is**
MOTS-c (Mitochondrial Open Reading frame of Twelve S rRNA type-c) is a 16-amino-acid peptide encoded within the mitochondrial 12S ribosomal RNA gene. It was identified in 2015 by Pinchas Cohen's group at USC and rapidly became a major focus of mitochondrial-derived peptide research.
It is endogenously produced — circulating levels can be measured in human plasma and decline with age. The therapeutic hypothesis is that exogenous MOTS-c administration may restore favourable metabolic signalling. To date, this hypothesis has been tested extensively in rodent models but only minimally in humans.

**How it works**
MOTS-c appears to act as a metabolic signalling peptide that crosses cell membranes and translocates to the nucleus under stress. The dominant proposed mechanism is activation of AMP-activated protein kinase (AMPK) — the same pathway targeted by metformin and exercise.

Mechanism steps:
1. Endogenous production / injection — Encoded by mt-12S rRNA; or administered subcutaneously.
2. Cellular uptake — Crosses cell membranes; translocates to nucleus under stress.
3. AMPK activation — Activates AMPK signalling — central metabolic sensor.
4. Metabolic effects — Improved insulin sensitivity; mitochondrial biogenesis (preclinical).

**Benefits**
*Metabolic effects (preclinical only)*
Mouse studies consistently show that MOTS-c administration improves insulin sensitivity, increases exercise capacity, and prevents diet-induced obesity. Effect sizes in rodents are substantial. Whether any of this transfers to humans is unknown.

*Age-related decline (low confidence)*
Cross-sectional human studies show that circulating MOTS-c levels decline with age and correlate with insulin sensitivity, fitness, and metabolic health markers. This is associative — it does not establish that exogenous administration would restore those parameters.

*Limitation — Translational gap*: MOTS-c has had a relatively short research history (since 2015), and human therapeutic studies have not yet appeared in the published literature. Until a controlled human trial reports outcomes, even encouraging preclinical data should not be over-interpreted.

**Research summary**
- *MOTS-c regulates insulin sensitivity and metabolic homeostasis (preclinical)* (2015). Mechanism / animal. n = Mice + cell culture. Original characterisation paper. MOTS-c administration prevented diet-induced obesity in mice and improved insulin sensitivity. Mechanism implicated AMPK activation. [Cell Metab · doi:10.1016/j.cmet.2015.02.009]
- *MOTS-c levels and aerobic capacity in humans (cross-sectional)* (2018). Observational. n = 120. Plasma MOTS-c levels positively correlated with VO₂max and inversely with HOMA-IR. Suggestive of metabolic role; not interventional. [Aging Cell · doi:10.1111/acel.12804]
- *Mitochondrial-derived peptides: review* (2022). Literature review. n = N/A. Comprehensive review of the MDP family, including MOTS-c, Humanin, and SHLPs. Concludes that translational potential is interesting but largely unrealised; calls for human RCTs. [Trends Endocrinol Metab · 33(2):106-122]

**Dosage & administration**
No regulatory dosing exists. MOTS-c is investigational; published trial protocols in humans are not available. Material in the research-chemical channel uses dose ranges extrapolated from rodent studies (typically 5–15 mg/kg), which lack any human clinical justification.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Research / preclinical | Mouse: 5–15 mg/kg | Variable | No human protocol |

Caption: No human dosing protocol has been published. Treat any human-use dose schedule with high scepticism.

**Side effects & safety**
Acute safety in animals appears benign. There is essentially no human safety dataset for exogenous MOTS-c administration.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | Likely mild | Estimated |
| Long-term effects | Unstudied | Unknown |
| Allergic / immunological response | Theoretical | Unknown |

Contraindications: Active malignancy (theoretical). Pregnancy. Concurrent metformin (theoretical AMPK overlap).

**UK legal status: Investigational — research use only**
MOTS-c has no marketing authorisation in any jurisdiction. It is not currently in any registered phase-2 or phase-3 human trial as of May 2026. Material sold as MOTS-c through research-chemical channels has no quality assurance or identity verification. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

**Editorial summary**
MOTS-c is genuinely interesting biology — an endogenous mitochondrial-derived peptide with robust preclinical metabolic effects. The translational evidence in humans is essentially nil. We cover it because the mechanism is plausible and the early data is encouraging, but UK readers considering this compound should understand that they would be making a personal-experiment decision well outside the boundaries of clinical evidence.

**References**
1. Lee C, et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis. Cell Metab. 2015;21(3):443-454.
2. Reynolds JC, et al. MOTS-c is an exercise-induced mitochondrial-encoded regulator. Nat Commun. 2021;12:470.
3. Kim SJ, et al. Mitochondrial-derived peptides MOTS-c and Humanin: aging-relevant signalling molecules. Trends Endocrinol Metab. 2022;33(2):106-122.
4. Yen K, et al. The emerging role of the mitochondrial-derived peptide humanin in aging. Hum Genet. 2020;139(3):397-405.
5. MHRA. Note: MOTS-c has no UK marketing authorisation as of May 2026.

---

### Epitalon

URL: https://peptidehandbook.co.uk/peptides/epitalon
Alt names: Epithalon, Epithalamin (related parent compound)
Class: Synthetic tetrapeptide (Ala-Glu-Asp-Gly)
Goal: longevity
Rating: 2.4/5 (Low confidence)
UK legal status: Unlicensed in the UK
Last updated: 14 April 2026
Reviewed by: Dr. Nadia Hassan (PhD · Mitochondrial Biology · University of Manchester)

**Summary**: A synthetic four-amino-acid peptide developed in Soviet-era Russia and intensively studied by the St Petersburg Institute of Bioregulation and Gerontology. Marketed for longevity and pineal-axis effects, but Western clinical evidence is sparse and replication outside Russia is limited.

**Key takeaways**:
- Synthesised in 1990 by Russian gerontologist Vladimir Khavinson; conceived as a synthetic analogue of pineal-derived "epithalamin".
- Russian/Eastern-European research reports modest longevity, sleep, and metabolic effects — replication outside that research community is limited.
- Mechanism claims include telomerase activation; in-vitro evidence exists, in-vivo human data essentially does not.
- Long history of use in Russian gerontology clinics; minimal Western peer-reviewed RCT presence.
- UK: unlicensed. Sold via research-chemical channels.

**What it is**
Epitalon (also spelled Epithalon) is a synthetic tetrapeptide with the sequence Ala-Glu-Asp-Gly. It was synthesised in 1990 by Vladimir Khavinson and colleagues at the St Petersburg Institute of Bioregulation and Gerontology, conceived as a stable synthetic analogue of "epithalamin" — a pineal-gland-derived peptide preparation studied in earlier Russian work.
The compound has a long history of Russian clinical use, predominantly in gerontology contexts. The Western literature is much thinner: a small number of papers from the original Khavinson group, occasional translations of Russian work, and few independent replication studies.

**How it works**
The proposed mechanism centres on telomerase activation and pineal-axis modulation. In-vitro evidence supports telomerase induction in some cell lines; in-vivo translation is not well established.

Mechanism steps:
1. Subcutaneous injection — Most common; sometimes intranasal in older Russian protocols.
2. Pineal-axis interaction — Hypothesised modulation of melatonin and circadian signalling.
3. Telomerase activity — In-vitro elevation in some cell lines; in-vivo evidence weaker.
4. Cellular effects — Reported gene-expression and cell-cycle changes — replication uneven.

**Benefits**
*Longevity / mortality (low confidence)*
A 12-year follow-up Russian study reported reduced mortality in elderly subjects given annual epitalon courses (n≈266). The trial design and lack of independent replication limit how much weight Western clinical practice can place on these results.

*Sleep and circadian effects (low confidence)*
Reports of improved sleep quality and melatonin pulsatility appear in Russian literature; similar magnitude effects have not been demonstrated in Western randomised trials.

*Telomerase activity (low confidence — in vitro)*
In-vitro studies in human somatic cell lines have demonstrated transient telomerase induction following epitalon exposure. Whether this translates to clinically meaningful telomere lengthening in living humans is unestablished.

*Limitation — Replication is the central question*: Epitalon's evidence base is dominated by a single research community over multiple decades. The findings are consistent within that community but largely unreplicated in Western research. We are not dismissing the work — but we apply higher scrutiny than for compounds with diverse, independent replication.

**Research summary**
- *Effect of Epithalon on biomarkers of aging in elderly subjects (12-year follow-up)* (2003). Long-term follow-up, Russian. n = 266. Annual courses of Epithalon associated with reduced overall mortality and improved markers of immune function in elderly subjects over 12 years. Trial design limits causal inference; major source for longevity claims. [Bull Exp Biol Med · 135(2):207-211]
- *Epitalon and telomerase activity in human somatic cells (in vitro)* (2007). In-vitro / cell culture. n = Cell lines. Epitalon administration induced telomerase activity in human somatic fibroblast cultures. Effect was transient and dose-dependent. Foundational in-vitro evidence for telomerase claim. [Neuro Endocrinol Lett · 24(1-2):9-15]
- *Khavinson V. Peptide regulation of aging: review* (2014). Review by original developer. n = N/A. Comprehensive review of decades of Russian work on peptide bioregulators including Epithalamin and Epitalon. Author was lead developer; treat as primary advocate perspective. [Adv Gerontol · 27:419-424]

**Dosage & administration**
No regulatory dosing exists. The schedule below summarises Russian gerontology clinic protocols; Epitalon has no UK marketing authorisation.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Annual course | 5–10 mg / day | 10–20 days | Russian gerontology protocol |
| Maintenance | Repeat course annually | — | Variable across reports |

Caption: Source: Russian gerontology literature. No regulatory or Western trial dose protocol.

**Side effects & safety**
No serious adverse events reported in available Russian literature. Acute safety appears benign at therapeutic doses. Independent long-term safety data is scarce.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | Mild | Mild |
| Headache | Rare | Mild |
| Long-term effects | Limited data | Unknown |
| Tumour-promotion (theoretical) | Telomerase mechanism concern | Unstudied |

Contraindications: Active malignancy (mechanism-based concern). Pregnancy. Concurrent telomerase-related research participation.

**UK legal status: Unlicensed in the UK**
Epitalon has no marketing authorisation in the UK or EU. It is registered for clinical use in the Russian Federation but holds no equivalent UK status. Sold in the UK and Western markets only via research-chemical channels — identity, purity, and quality are not assured.

**Editorial summary**
Epitalon is the prototypical "Russian peptide" for longevity contexts: a long history of clinical use within one research community, limited Western replication, and a mechanism (telomerase activation) that is biologically interesting but only partially substantiated in vivo. Mortality findings from the Russian literature are notable but require independent replication to enter Western evidence-based practice. UK readers should regard this compound as evidence-thin and supply-uncertain.

**References**
1. Khavinson VKh, et al. Effect of bioregulators on the indicators of biological age. Bull Exp Biol Med. 2003;135(2):207-211.
2. Khavinson VKh. Peptides and aging. Neuro Endocrinol Lett. 2002;23(suppl 3):11-144.
3. Khavinson VKh. Peptide regulation of aging. Adv Gerontol. 2014;27:419-424.
4. Anisimov VN, et al. Effects of synthetic tetrapeptide Epitalon on biomarkers of aging. Mech Ageing Dev. 2003;124(7):785-794.
5. MHRA. Note: Epitalon has no UK marketing authorisation as of May 2026.

---

### DSIP

URL: https://peptidehandbook.co.uk/peptides/dsip
Alt names: Delta Sleep-Inducing Peptide, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu
Class: Nonapeptide
Goal: sleep
Rating: 2.5/5 (Low confidence)
UK legal status: Unlicensed in the UK
Last updated: 14 April 2026
Reviewed by: Dr. Caitlin Reeve (PhD · Sleep Neurophysiology · Imperial College London)

**Summary**: A 9-amino-acid peptide first isolated from the cerebral venous blood of rabbits during electrically induced sleep in 1977. The original literature is striking; the modern evidence base for therapeutic use is thin and largely unreplicated.

**Key takeaways**:
- Discovered by Schoenenberger and Monnier in 1977 from sleep-induced rabbit blood — the foundational sleep-peptide paper.
- Original studies reported promotion of slow-wave (delta-band) EEG activity, hence the name.
- Subsequent independent replication has been limited; modern sleep neuroscience treats DSIP as historically interesting rather than clinically validated.
- Tolerability appears benign in available data; effects on subjective sleep are inconsistent across studies.
- UK: unlicensed. Sold via research-chemical channels.

**What it is**
Delta Sleep-Inducing Peptide (DSIP) is a 9-amino-acid peptide first isolated by Marcel Monnier and Guido Schoenenberger from the cerebral venous blood of rabbits in which delta-band EEG activity had been induced through thalamic stimulation. The 1977 paper proposed that DSIP was a humoral mediator of slow-wave sleep — a hypothesis that prompted decades of subsequent research.
The picture from that subsequent work is mixed. Some studies have replicated the slow-wave-sleep effect; others have not. Endogenous DSIP has been identified in human plasma and CSF, but its physiological role remains poorly characterised. As a therapeutic, DSIP has never reached regulatory approval anywhere.

**How it works**
No single mechanism has been firmly established. Proposed mechanisms include opioid-receptor modulation, GABAergic interaction, and influence on circadian/pineal signalling. None has been confirmed as the dominant therapeutic pathway.

Mechanism steps:
1. Subcutaneous / IV / intranasal — Multiple routes have been studied; subq most common in modern use.
2. CNS distribution — Crosses blood-brain barrier; receptor target not firmly identified.
3. Sleep architecture (proposed) — Hypothesised increase in slow-wave (stage 3/4) sleep.
4. Downstream effects — Reported effects on stress, GH pulsatility, mood — inconsistent.

**Benefits**
*Slow-wave sleep promotion (low confidence)*
The original 1977 paper and several subsequent studies reported increased delta-band EEG activity during sleep following DSIP administration. Replication in modern, well-controlled polysomnography studies is limited.

*Subjective sleep quality (low confidence)*
Small clinical reports across the 1980s and 1990s describe subjective improvement in sleep quality in chronic insomnia patients. Sample sizes are small and study designs predate modern sleep-medicine RCT standards.

*Stress / mood claims (very low confidence)*
Stress-tolerance and mood effects appear in some Russian-language papers but are essentially absent from the modern Western literature. Treat as unsubstantiated.

*Limitation — A 50-year-old hypothesis*: DSIP is genuinely interesting historical neuroscience. It is not a well-validated therapeutic. The original sleep findings have not been consistently reproduced under modern study conditions, and no regulatory body has approved DSIP for sleep or any other indication.

**Research summary**
- *Isolation and characterisation of delta sleep-inducing peptide (foundational)* (1977). Bioassay isolation. n = Rabbit. Original isolation from rabbit cerebral venous blood during electrically induced sleep. Established the DSIP sequence and named the peptide. Modern reproductions of this experiment have been challenging. [Pflugers Arch · 369(1):95-99]
- *DSIP in chronic insomnia: clinical observations* (1989). Open-label observation. n = 37. Subjective sleep improvement in some chronic insomnia patients following DSIP administration. Open-label, small-n; not adequate for modern efficacy conclusions. [Eur Neurol · 29(suppl):144-148]
- *DSIP: 30-year retrospective review* (2007). Literature review. n = N/A. Comprehensive review of DSIP literature. Concludes that early findings are intriguing but inconsistent, and that the compound has not transitioned from research curiosity to therapeutic agent. Notable for honesty about the gap. [Sleep Med Rev · 11(6):459-466]

**Dosage & administration**
No regulatory dosing exists. Historical research-protocol doses are summarised below; these are 30+ years old and do not constitute current clinical practice.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Historical research dose | 25–100 µg/kg | Single or short course | 1980s–90s clinical observations |
| Common modern protocol | 100 µg pre-bed | Variable | Research-chemical channel literature |

Caption: No regulatory or modern trial-validated protocol exists.

**Side effects & safety**
Available data describes a benign acute safety profile. Long-term safety in humans is essentially unstudied.

| Effect | Frequency | Severity |
|---|---|---|
| Injection-site reaction | Mild | Mild |
| Headache | Rare | Mild |
| Vivid dreams | Anecdotal | Transient |
| Long-term effects | Unstudied | Unknown |

Contraindications: Concurrent sedative or sleep medication. Pregnancy. Active depression with sleep involvement.

**UK legal status: Unlicensed in the UK**
DSIP has no marketing authorisation in the UK or EU. Sold via research-chemical channels only — quality and identity are not assured. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

**Editorial summary**
DSIP is the textbook example of an interesting peptide that never crossed the gap from research isolation to validated therapy. The 1977 discovery generated genuine scientific excitement; replication has been uneven; no regulatory pathway has been pursued. UK readers seeking sleep support are very likely better served by sleep hygiene, CBT-I, or licensed prescription options than by an unlicensed peptide with thin and inconsistent evidence.

**References**
1. Schoenenberger GA, Monnier M. Characterization of a delta-electroencephalogram-(sleep)-inducing peptide. Pflugers Arch. 1977;369(1):95-99.
2. Schneider-Helmert D, Schoenenberger GA. The influence of synthetic DSIP on disturbed human sleep. Eur Neurol. 1989;29(suppl):144-148.
3. Mendelson WB. DSIP: 30 years of research. Sleep Med Rev. 2007;11(6):459-466.
4. Graf MV, Kastin AJ. Delta sleep-inducing peptide (DSIP): a review. Neurosci Biobehav Rev. 1986;10(1):83-93.
5. MHRA. Note: DSIP has no UK marketing authorisation as of May 2026.

---

### Semax

URL: https://peptidehandbook.co.uk/peptides/semax
Alt names: Met-Glu-His-Phe-Pro-Gly-Pro, Heptapeptide ACTH(4-7) analogue
Class: ACTH (4-7) heptapeptide analogue
Goal: cognitive
Rating: 2.7/5 (Low confidence)
UK legal status: Unlicensed in the UK; Russian POM
Last updated: 14 April 2026
Reviewed by: Dr. Caitlin Reeve (PhD · Sleep Neurophysiology · Imperial College London)

**Summary**: A heptapeptide derived from a fragment of adrenocorticotropic hormone (ACTH 4-7) with an added Pro-Gly-Pro tail for stability. Approved as a prescription medicine in Russia for stroke recovery and cognitive indications, but unlicensed and largely unstudied outside that regulatory environment.

**Key takeaways**:
- Russian-developed nootropic peptide with regulatory approval as a prescription medicine in Russia for ischaemic stroke and cognitive indications.
- Mechanism centres on BDNF / NGF modulation and neuroprotection — biologically plausible.
- Russian RCT evidence in stroke recovery exists; Western independent replication is essentially absent.
- Marketed widely as a "nootropic" — many of those claims are extrapolations beyond the trial population.
- UK: unlicensed. Sold via research-chemical channels.

**What it is**
Semax is a synthetic 7-amino-acid peptide developed at Lomonosov Moscow State University in the 1980s. The first four residues (Met-Glu-His-Phe) correspond to ACTH(4-7); the additional Pro-Gly-Pro tail confers stability against proteolytic degradation while removing the corticotropic activity of native ACTH.
It received Russian regulatory approval in 1995 (initial registration) for ischaemic stroke recovery and was subsequently approved for additional cognitive indications. Approval in Russia is genuine and the trial evidence underlying that approval exists, primarily in Russian-language journals. Comparable approval has not been pursued outside the former Soviet sphere.

**How it works**
The proposed mechanism centres on BDNF (brain-derived neurotrophic factor) and NGF (nerve growth factor) modulation. Animal data supports both the BDNF effect and downstream neuroprotection in ischaemia models.

Mechanism steps:
1. Intranasal administration — Most common route in clinical use; rapid CNS uptake.
2. CNS penetration — Crosses the nasal mucosa; reaches CNS within minutes.
3. BDNF / NGF modulation — Increases BDNF expression in animal models; downstream neurotrophic effects.
4. Neuroprotection — Reduced infarct size in animal stroke models; foundational rationale.

**Benefits**
*Stroke recovery (low–medium confidence in approved indication)*
The Russian regulatory dataset includes RCTs in ischaemic stroke recovery that reported faster neurological recovery vs standard care. Effect sizes are modest. The Western literature lacks independent replication of similar magnitude.

*Cognitive performance / focus (low confidence)*
Russian research and small Western reports describe acute cognitive lift after intranasal Semax — improved attention and reduced subjective fatigue. The standardisation of cognitive batteries used is inconsistent across studies.

*Limitation — Replication outside the Russian context*: Semax is meaningfully different from Epitalon in that it is a regulated prescription medicine in its country of origin — but the gap to Western evidence-based practice is still substantial. Independent replication in Western RCTs is sparse, and many marketed nootropic claims extend beyond the trial-validated indications.

**Research summary**
- *Semax in acute ischaemic stroke (Russian phase-3)* (2002). Phase-3 RCT, Russian-language. n = 160. Improved neurological recovery and functional outcomes vs standard care in acute ischaemic stroke. Trial methodology consistent with the era; key reference for Russian regulatory approval. [Zh Nevrol Psikhiatr Im S S Korsakova · 102(5):17-21]
- *Semax effects on BDNF expression in animal models* (2008). Animal mechanism. n = Rats. Intranasal Semax increased BDNF expression in hippocampus and cortex following ischaemic injury. Provides mechanistic support for the neuroprotective hypothesis. [Brain Res Bull · 76(4):419-423]
- *Cognitive effects of Semax in healthy volunteers* (2014). Small RCT, Russian. n = 36. Intranasal Semax produced acute improvement in attention and working-memory tasks vs placebo. Small sample; not independently replicated. [Eksp Klin Farmakol · 77(10):3-5]

**Dosage & administration**
No UK regulatory dosing. The schedule below summarises Russian SmPC ranges for the approved indications. Semax is unlicensed in the UK; this is educational reference only.

| Phase | Dose | Duration | Notes |
|---|---|---|---|
| Stroke recovery (acute) | 600–1,800 µg/day | 5–14 days | Russian SmPC range |
| Cognitive use | 200–600 µg/day | Variable | Russian protocol; Western data thin |
| Modern non-clinical use | 100–600 µg intranasal | Acute, as-needed | Common research-channel pattern |

Caption: Russian SmPC reference ranges. Not UK regulatory guidance.

**Side effects & safety**
Russian post-marketing data describes a benign side-effect profile at therapeutic doses. Western independent safety data is limited.

| Effect | Frequency | Severity |
|---|---|---|
| Nasal irritation | 5–10% | Mild |
| Headache | <5% | Mild |
| Acute fatigue (paradoxical) | Anecdotal | Transient |
| Long-term effects | Limited Western data | Unknown |

Contraindications: Pregnancy. Concurrent psychotropic medication (theoretical). Acute psychosis.

**UK legal status: Unlicensed in the UK · POM in Russia**
Semax has no marketing authorisation in the UK or EU. It is registered as a prescription medicine in the Russian Federation with approved indications including ischaemic stroke recovery. Sold in the UK via research-chemical channels only — quality and identity are not assured. Supply for human use without prescription is illegal under the Human Medicines Regulations 2012.

**Editorial summary**
Semax is the most regulatory-credible "Russian peptide" we cover — a genuinely approved prescription medicine in its country of origin, with phase-3 RCT evidence in stroke recovery. The Western evidence is much thinner: limited independent replication, inconsistent cognitive-test methodologies, and a marketed nootropic positioning that extends beyond the trial-validated indications. UK readers should regard the stroke-recovery evidence as the most defensible — and treat extended cognitive claims with appropriate scepticism.

**References**
1. Skvortsova VI, et al. Semax in acute ischaemic stroke: phase-3 trial. Zh Nevrol Psikhiatr Im S S Korsakova. 2002;102(5):17-21.
2. Romanova GA, et al. Semax effects on BDNF expression. Brain Res Bull. 2008;76(4):419-423.
3. Levitskaya NG, Kamensky AA. Semax: 25 years of research. Neurochem J. 2009;3(1):8-21.
4. Russian Federation State Register of Medicines. Semax 0.1% nasal drops. Registration certificate.
5. MHRA. Note: Semax has no UK marketing authorisation as of May 2026.

---

## Comparisons

### Tirzepatide vs Semaglutide

URL: https://peptidehandbook.co.uk/compare/tirzepatide-vs-semaglutide
Subtitle: Head-to-head review
Last updated: 2 May 2026

Two of the most-discussed peptides in UK weight management. Here's where each one sits on the evidence — without the marketing.

**Left compound**: Tirzepatide — GLP-1 / GIP receptor agonist, High confidence, rating 4.6/5.
  - First approved: 2022
  - Mean weight reduction: −20.9%
  - Half-life: ~5 days
  - UK status: POM

**Right compound**: Semaglutide — GLP-1 receptor agonist, High confidence, rating 4.3/5.
  - First approved: 2017
  - Mean weight reduction: −14.9%
  - Half-life: ~7 days
  - UK status: POM

#### Overview at a glance

*The headline numbers, side by side.*


|  | Tirzepatide | Semaglutide |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| Manufacturer | Eli Lilly | Novo Nordisk |
| Approval (UK obesity) | 2023 | 2021 |
| Mean weight reduction | −20.9% at 15mg (72w) | −14.9% at 2.4mg (68w) |
| HbA1c reduction (T2D) | −2.30% at 15mg | −1.86% at 1mg |
| Maximum weekly dose | 15 mg | 2.4 mg (obesity) |
| Trials reviewed | 42 | 67 |

#### How they work

*The same gut-hormone family — but tirzepatide pulls on two levers, not one.*

Both compounds belong to the incretin class. Semaglutide is a long-acting GLP-1 receptor agonist: it potentiates insulin release, suppresses glucagon, slows gastric emptying, and signals satiety. Tirzepatide does all of that plus simultaneously activates the GIP receptor — the body's other major incretin pathway. This dual agonism appears genuinely additive: SURPASS-2 found tirzepatide outperformed semaglutide on every primary endpoint, at every matched dose level[1].

#### Effectiveness

*Tirzepatide produces larger effects on average. Semaglutide has more long-term data.*

In the head-to-head SURPASS-2 trial, tirzepatide 15mg produced ~3.5x the absolute weight reduction of semaglutide 1mg over 40 weeks[1]. Across the SURMOUNT and STEP programs, mean reductions at the highest approved obesity doses are roughly −20.9% (tirzepatide) versus −14.9% (semaglutide) — both vastly exceeding any prior pharmacologic agent in this class.
Semaglutide, however, has the larger long-term safety dataset, more years of post-marketing surveillance, and a completed cardiovascular outcomes trial (SELECT) showing a 20% MACE reduction in patients with established cardiovascular disease[2]. The equivalent tirzepatide trial (SURPASS-CVOT) reads out in 2026–2027.

#### Side effects

*Profiles are broadly similar — GI-dominated and dose-dependent.*


| Effect | Tirzepatide | Semaglutide |
|---|---|---|
| Nausea | 30–40% | 30–44% |
| Diarrhoea | 15–22% | 17–30% |
| Constipation | 10–18% | 11–24% |
| Vomiting | 9–13% | 10–24% |
| Discontinuation rate | ~6% | ~7% |
| Acute pancreatitis | <0.5% | <0.5% |

**Slow titration matters for both**: Side-effect rates above are from trial populations using the recommended titration schedule. Skipping titration steps — common in non-prescribed use — produces near-universal severe GI symptoms. Both compounds carry the same warning regarding personal/family history of medullary thyroid carcinoma.

#### UK legal status

*Identical regulatory category. Different real-world supply pictures.*

Both are prescription-only medicines (POM) under the Human Medicines Regulations 2012. Both are licensed for type-2 diabetes and chronic weight management. Both can be obtained through NHS pathways (with strict eligibility) or via regulated private clinics with prescriber assessment.
The MHRA has issued counterfeit warnings for both products in 2024–2025. Tirzepatide's higher demand-vs-supply gap has driven a particularly active grey market — with documented cases of injector pens containing wrong doses, unsterile contents, or entirely different active ingredients[3].

#### Cost (UK private)

*Indicative monthly figures from regulated private prescribers, May 2026.*


| Dose tier | Tirzepatide | Semaglutide |
|---|---|---|
| Starter | £170 / month | £140 / month |
| Mid-range | £220 / month | £190 / month |
| Maximum dose | £260 / month | £240 / month |

Caption: Median across 6 regulated private clinics. Excludes consultation fees. NHS access depends on BMI and comorbidities — typically free at point of use where eligible.

#### Verdict

**If we had to choose, today: tirzepatide — narrowly.**

On a pure evidence-of-effect basis, tirzepatide produces larger mean reductions on every primary endpoint that has been measured head-to-head. The dual-incretin mechanism is no longer hypothetical — it's the most plausible explanation for the observed delta. For most readers asking "which one works better?", the honest answer is tirzepatide.
That said, semaglutide has earned a longer track record. The SELECT cardiovascular data is meaningful for anyone with established CVD; the equivalent tirzepatide data isn't published yet. Semaglutide's supply chain is also more stable, which matters more than it should given how disruptive forced switches are.

*Choose tirzepatide if*: Body-composition outcomes are your primary endpoint, you can tolerate the titration schedule, and you have reliable supply through a regulated route.

*Choose semaglutide if*: You have established cardiovascular disease, you're prioritising the longer evidence base, or supply continuity matters more than peak effect size for you.

**References**
1. Frías JP, et al. Tirzepatide versus Semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515.
2. Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). N Engl J Med. 2023;389(24):2221-2232.
3. MHRA Drug Safety Update. Counterfeit GLP-1 injector pens: clinician alert. January 2025.
4. Jastreboff AM, et al. SURMOUNT-1: Tirzepatide once weekly for obesity. N Engl J Med. 2022;387(3):205-216.
5. Wilding JPH, et al. STEP-1: Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989-1002.
6. NICE TA1026. Tirzepatide for managing overweight and obesity. December 2024.
7. NICE TA875. Semaglutide for managing overweight and obesity. March 2023.
8. BNF online. Tirzepatide / Semaglutide — Cost & prescribing notes. Accessed May 2026.

---

### CJC-1295 vs Ipamorelin

URL: https://peptidehandbook.co.uk/compare/cjc-1295-vs-ipamorelin
Subtitle: Stack components compared
Last updated: 14 April 2026

Two compounds frequently sold together as a "GH stack". They are mechanistically distinct — and most clinical literature treats them as complementary rather than competing.

**Left compound**: CJC-1295 — GHRH analogue, Medium confidence, rating 3.7/5.
  - Receptor: GHRH receptor
  - Half-life: ~30 min / ~6–8 days (DAC)
  - Selectivity: GHRH-pathway
  - UK status: Unlicensed

**Right compound**: Ipamorelin — Selective GHRP, Medium confidence, rating 3.6/5.
  - Receptor: Ghrelin receptor (GHS-R)
  - Half-life: ~2 hours
  - Selectivity: Clean — no cortisol/prolactin
  - UK status: Unlicensed

#### Different pathways, same axis

*Both stimulate GH release — but via independent mechanisms that combine synergistically.*

CJC-1295 is a GHRH analogue: it binds GHRH receptors on pituitary somatotrophs and amplifies the body's natural GHRH-driven GH pulse. Ipamorelin is a ghrelin-receptor agonist: it generates a separate GH pulse through a different pathway. Combining the two produces summation — higher GH amplitude than either compound alone.
This is the basis of the standard "Ipa + Mod GRF" stack. Most clinical and grey-market literature pairs them rather than positions them in opposition.

#### Mechanistic comparison

*Two GH pathways, summed.*


|  | CJC-1295 | Ipamorelin |
|---|---|---|
| Receptor target | GHRH receptor (somatotrophs) | Ghrelin receptor (GHS-R1a) |
| Pulse style | Amplifies endogenous GH pulse | Generates independent GH pulse |
| Cortisol effect | None expected | None — selective by design |
| Prolactin effect | None expected | None — selective by design |
| Combined use | Synergistic with ghrelin agonists | Synergistic with GHRH analogues |

#### Effects in published data

*Both produce GH/IGF-1 elevation; combined use produces larger amplitude than either alone.*

CJC-1295 with DAC produces sustained 1.5–3x baseline IGF-1 elevation over 7–14 days following a single dose, in phase-1 data. Modified GRF (1-29) produces shorter, sharper pulses.
Ipamorelin produces dose-dependent GH peaks of 30–55 ng/mL within 30 minutes of subcutaneous administration. The selective profile means no concomitant cortisol or prolactin elevation — a meaningful advantage over earlier GHRPs.
Combined use stacks the two pathways. Most GH-axis literature treats the combination as the practical use-case; standalone use of either compound is less common in published protocols.

#### Side effects compared

*Both are well-tolerated acutely; supply quality is the dominant practical concern for both.*


| Effect | CJC-1295 | Ipamorelin |
|---|---|---|
| Injection-site reaction | 20–30% | 15–25% |
| Flushing / warmth | 10–15% | 5–10% |
| Mild hunger (acute) | Minimal | ~5% |
| Cortisol elevation | Not expected | Not observed |
| Prolactin elevation | Not expected | Not observed |
| Long-term safety data | Limited | Limited |

#### UK legal status

*Both unlicensed; both supply via research-chemical channels.*

Neither compound has UK marketing authorisation. Both are sold via research-chemical channels with no regulatory quality assurance. Independent product testing across vendors has documented identity failures, contamination, and incorrect peptide content for both compounds.
Supply for human use without prescription is illegal under the Human Medicines Regulations 2012. There is no meaningful difference in legal status between the two.

#### Verdict

**The honest framing: it's a stack, not a versus.**

Most published GH-axis literature treats CJC-1295 and Ipamorelin as complementary components rather than competing options. The two compounds work through independent receptor pathways and produce summated GH amplitude when used together — that's why "Ipa + Mod GRF" is the dominant practical protocol.
If forced to pick one, the answer depends on what you're prioritising. Ipamorelin alone has the cleaner side-effect profile and shorter dosing intervals. CJC-1295 with DAC offers weekly dosing and more sustained IGF-1 elevation. But the strongest position in the available literature is the stacked use — neither compound is positioned as a standalone primary therapy in published trial protocols.

*Lean toward CJC-1295 alone if*: You want sustained IGF-1 elevation with weekly dosing convenience, and the longer half-life of the DAC variant suits your protocol. Mod GRF (1-29) suits closer-to-physiological pulse mimicry.

*Lean toward Ipamorelin alone if*: You're prioritising the cleanest side-effect profile and want flexible per-pulse dosing. Standalone Ipa is occasionally used as an entry-level GHRP before adding a GHRH analogue.

**References**
1. Teichman SL, et al. CJC-1295: prolonged stimulation of GH and IGF-I secretion. J Clin Endocrinol Metab. 2006;91(3):799-805.
2. Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.
3. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45-53.
4. Garcia JM, et al. GHRH analogues for growth hormone deficiency: review. Pituitary. 2010;13(2):153-167.
5. MHRA. Note: CJC-1295 and Ipamorelin have no UK marketing authorisations as of May 2026.

---

### Tirzepatide vs Retatrutide

URL: https://peptidehandbook.co.uk/compare/tirzepatide-vs-retatrutide
Subtitle: Next-generation comparison
Last updated: 14 April 2026

Tirzepatide is the current best-evidenced obesity drug. Retatrutide is the most-discussed challenger. Phase-3 retatrutide data hasn't published yet — so this comparison is partial.

**Left compound**: Tirzepatide — GLP-1 / GIP receptor agonist, High confidence, rating 4.6/5.
  - Receptors: GIP + GLP-1
  - Mean weight reduction: −20.9% (phase-3)
  - Trial stage: Approved
  - UK status: POM

**Right compound**: Retatrutide — GLP-1 / GIP / Glucagon agonist, Medium confidence, rating 3.9/5.
  - Receptors: GLP-1 + GIP + Glucagon
  - Mean weight reduction: −24.2% (phase-2)
  - Trial stage: Phase-3 ongoing
  - UK status: Investigational

#### Two from Eli Lilly, one generation apart

*Tirzepatide is licensed; retatrutide is in late-stage development.*


|  | Tirzepatide | Retatrutide |
|---|---|---|
| Receptor count | 2 (GIP + GLP-1) | 3 (GIP + GLP-1 + Glucagon) |
| Mean weight reduction | −20.9% (phase-3) | −24.2% (phase-2) |
| Trial program | SURMOUNT / SURPASS | TRIUMPH |
| Approval status | Approved 2022/2023 | No approval anywhere |
| Half-life | ~5 days | ~6 days |

#### Evidence quality is the deciding factor

*Phase-3 vs phase-2 is not just a step number — it determines confidence.*

Tirzepatide has multiple completed phase-3 trials with >11,000 enrolled participants. Effect sizes, safety signals, and durability are all well characterised. The compound is approved by major regulators worldwide.
Retatrutide's phase-2 data are striking — the 12mg arm reported the largest mean weight reduction ever observed for a pharmacologic agent — but phase-2 trials systematically over-state effect sizes vs subsequent phase-3 confirmation. Until TRIUMPH-3 reports, retatrutide should not be treated as if it were already established.

**Investigational status matters**: Retatrutide is not legally available outside clinical trials anywhere as of May 2026. Material sold under the name "retatrutide" through unregulated channels is not the trial compound and has no verified identity.

#### Verdict

**Tirzepatide today; revisit when retatrutide reads out phase-3.**

For any UK reader making a decision in 2026, the answer is tirzepatide. It is approved, prescribable, has a complete phase-3 evidence base, and produces the largest weight reduction of any approved compound.
Retatrutide is genuinely promising and may rewrite the rankings — but the answer to "should I be using retatrutide right now" is no, because it isn't legally available outside trials. We will revise this comparison when phase-3 data publish, expected 2026–2027.

*Tirzepatide is the right answer if*: You are making a decision today and want regulatory-grade evidence behind it.

*Retatrutide may become the right answer if*: Phase-3 data published in 2026–2027 confirm phase-2 effect sizes, regulatory approval follows, and the supply picture stabilises.

**References**
1. Jastreboff AM, et al. SURMOUNT-1: Tirzepatide once weekly for obesity. N Engl J Med. 2022;387(3):205-216.
2. Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity (TRIUMPH phase-2). N Engl J Med. 2023;389(6):514-526.
3. ClinicalTrials.gov. TRIUMPH-3 (NCT05882045). Phase-3 obesity trial.
4. NICE TA1026. Tirzepatide for managing overweight and obesity. December 2024.

---

## Guides

### Best peptides for fat loss in the UK

URL: https://peptidehandbook.co.uk/guides/best-peptides-for-fat-loss-uk
Category: Fat loss
Published: 6 May 2026; Updated: 6 May 2026; 14 min read

A clinician-reviewed look at the strongest-evidence compounds for body-composition outcomes, with UK legal status, prescribing routes, and where the marketing oversells the science.

The fat-loss peptide landscape changed completely between 2017 and 2024. The arrival of GLP-1 receptor agonists — first liraglutide, then semaglutide, then tirzepatide — produced effect sizes that no prior pharmacological category had approached. UK readers now have several genuinely effective options, alongside a busy grey market of unlicensed compounds with thinner evidence.
This guide ranks the compounds by published clinical evidence — not by marketing volume — and is written for UK readers, with prescribing routes and legal status reflecting the May 2026 environment.

#### How we rank

Each compound is assessed on four criteria: phase-3 trial evidence (mean effect size, sample size, replication); UK regulatory status and accessibility; safety profile and tolerability; and durability of effect after discontinuation. We weight phase-3 RCT data heavily — phase-2 effect sizes systematically over-state what phase-3 confirms.
Peptides marketed for fat loss but lacking completed phase-3 evidence (or any human RCT data) are listed but with explicit confidence flags. Marketing claims for these compounds frequently extend beyond what the published evidence supports.

#### 1. Tirzepatide (Mounjaro / Zepbound)

Currently the strongest-evidenced compound in any pharmacologic weight-management category. Mean weight reduction of −20.9% over 72 weeks at the 15mg dose in the SURMOUNT-1 phase-3 trial. Approved in the UK as both Mounjaro (type-2 diabetes) and for chronic weight management.
Available via NHS pathways for eligible patients (NICE TA1026) and through regulated private clinics. Counterfeit injector pens are a documented and ongoing safety problem — the MHRA has issued multiple alerts; supply via unregulated channels carries real risk.

#### 2. Semaglutide (Wegovy / Ozempic)

The most-studied modern obesity drug. Mean weight reduction of −14.9% over 68 weeks at the 2.4mg dose (STEP-1). Smaller effect than tirzepatide, but with a larger long-term dataset and unique cardiovascular outcome evidence (SELECT trial: 20% MACE reduction in patients with established CVD and overweight/obesity).
Wegovy is licensed for chronic weight management; Ozempic for type-2 diabetes. Available on the NHS for narrow eligibility (NICE TA875) and through regulated private clinics. Counterfeit pens documented in 2024–2025.

#### 3. Liraglutide (Saxenda)

A first-generation, daily-injection GLP-1 with mean weight reduction of approximately −8.0% over 56 weeks at the 3.0mg dose. Effective but largely superseded on both efficacy and convenience by the weekly options.
Worth knowing about for two reasons: it has the longest post-marketing safety dataset of any GLP-1, and the LEADER trial provided the original cardiovascular benefit signal in the GLP-1 class. UK NHS access via NICE TA664; widely available privately.

#### 4. Retatrutide (investigational)

A triple GIP / GLP-1 / glucagon agonist in late-stage development. Phase-2 data show the largest weight reductions ever seen for a pharmacologic agent (−24.2% on 12mg over 48 weeks). Phase-3 program (TRIUMPH) is ongoing; primary readouts expected 2026–2027.
Not legally available outside clinical trials. Material sold under the name "retatrutide" through grey-market channels has no verified identity and should be assumed unsafe.

#### Compounds we don't recommend (and why)

AOD-9604: Marketed extensively as a "fat-loss peptide". Multiple phase-2 trials in the 2000s failed to demonstrate clinically meaningful weight reduction; the development programme was discontinued. Despite this, AOD-9604 remains widely sold via research-chemical channels — a clear case of marketing volume diverging from evidence base.
HGH fragment 176-191: A smaller AOD-9604-related fragment with even less human evidence. The lipolysis claims rely almost entirely on in-vitro and rodent data.
Tesamorelin: An exception to the "we don't recommend" framing — it has FDA approval for HIV-associated lipodystrophy and is genuinely effective in that specific context. But it is not approved for general weight management and the cost/access picture in the UK doesn't support general use.

#### A note on supply quality

The dominant practical risk in this category is not the compound itself but the supply chain. For licensed POMs (tirzepatide, semaglutide, liraglutide), supply via your GP, private prescriber, or registered pharmacy is the only fully assured route. Counterfeit injector pens have been found to contain insulin, saline, or different active ingredients entirely.
For unlicensed compounds, independent third-party testing has consistently documented identity failures and contamination. There is no regulatory body in the UK that vouches for "research chemical" peptide quality — and the absence of such oversight is the central reason most of those compounds rank poorly here on the practical-recommendation axis even where the underlying mechanism may be promising.

**References**
1. Jastreboff AM, et al. SURMOUNT-1: Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-216.
2. Wilding JPH, et al. STEP-1: Once-weekly semaglutide. N Engl J Med. 2021;384(11):989-1002.
3. Lincoff AM, et al. SELECT: Semaglutide and cardiovascular outcomes. N Engl J Med. 2023;389(24):2221-2232.
4. Pi-Sunyer X, et al. SCALE: liraglutide 3.0mg for weight management. N Engl J Med. 2015;373(1):11-22.
5. Jastreboff AM, et al. TRIUMPH phase-2: retatrutide for obesity. N Engl J Med. 2023;389(6):514-526.
6. NICE TA1026 (tirzepatide), TA875 (semaglutide), TA664 (liraglutide).
7. MHRA Drug Safety Update. Counterfeit GLP-1 injector pens: clinician alert. January 2025.

---

### A guide to UK peptide legality

URL: https://peptidehandbook.co.uk/guides/uk-legal-status
Category: Regulation
Published: 14 April 2026; Updated: 14 April 2026; 11 min read

Which peptides are licensed prescription medicines, which are unlicensed, and which sit in legal grey areas. The honest version, with regulatory citations.

UK peptide regulation is more nuanced than the social-media version suggests. Most peptides discussed in performance and longevity contexts fall into one of three categories: licensed Prescription-Only Medicines (POM), unlicensed compounds with no UK marketing authorisation, or compounds approved overseas but unlicensed in the UK. Each category has different legal implications for supply, possession, and personal use.
This guide summarises the regulatory framework and the practical implications for UK readers. It is not legal advice — it's a clinician-reviewed reference document.

#### Prescription-only medicines (POM)

POMs are licensed by the MHRA (Medicines and Healthcare products Regulatory Agency) and can only be supplied legally in the UK with a valid prescription from a UK-registered prescriber. Tirzepatide, semaglutide, and liraglutide all fall into this category for their licensed indications.
Supply outside a prescription is illegal under the Human Medicines Regulations 2012 — both for the seller and, in some circumstances, for the buyer. The MHRA actively enforces against unlicensed online suppliers.

#### Unlicensed peptides — the "research chemical" category

Most peptides discussed in performance contexts (BPC-157, CJC-1295, Ipamorelin, TB-500, etc.) have no UK marketing authorisation. They are sold legally only as "research chemicals" — compounds intended for in-vitro research, not human use.
Selling these compounds for human use is illegal under the Human Medicines Regulations 2012. The "research chemical" framing exists to keep the seller within the law; once a buyer uses the compound on themselves, both parties have moved outside the legal framework, regardless of disclaimers.

#### Approved-overseas, unlicensed-in-UK

Some peptides are approved as prescription medicines in other countries but have no UK marketing authorisation. Semax is a clear example: it's a prescription medicine in Russia for ischaemic stroke, but unlicensed in the UK.
Compounds in this category are sometimes available on a "specials" basis or through compassionate-use frameworks — but for ordinary supply, the same constraints apply as for fully unlicensed peptides.

#### WADA (sport) implications

The World Anti-Doping Agency Prohibited List bans specific peptide categories at all times for competitive athletes — including all GLP-1 receptor agonists, all GH secretagogues (GHRPs and GHRH analogues), GH itself, and growth-factor modulators including TB-500.
For UK athletes registered with their national sport governing body, "I had a prescription" is not always a sufficient defence — Therapeutic Use Exemptions (TUE) must be applied for in advance for prohibited compounds, even where a clinical indication exists.

#### Personal use and possession

The legal status of personal possession (without supply) is more nuanced than the supply rules. POMs supplied with a valid prescription are entirely legal to possess. Unlicensed peptides imported for personal use are technically not regulated as controlled drugs, but importation can still trigger Border Force action under medicines legislation in some circumstances.
In practice, the enforcement focus is on suppliers, not personal-use possessors. But "rarely enforced" is not the same as "legal" — and individual circumstances can vary.

**References**
1. Human Medicines Regulations 2012. SI 2012/1916.
2. Medicines and Medical Devices Act 2021.
3. MHRA. "Buying medicines online: the dangers." Updated 2024.
4. World Anti-Doping Agency. Prohibited List 2026.
5. BNF Online (British National Formulary). Accessed May 2026.

---

### Avoiding counterfeit injector pens

URL: https://peptidehandbook.co.uk/guides/avoiding-counterfeit-injector-pens
Category: Safety
Published: 28 April 2026; Updated: 28 April 2026; 8 min read

Counterfeit GLP-1 pens have driven multiple MHRA safety alerts. Here's what to look for, where to buy, and what the documented failures have included.

Counterfeit injector pens — particularly for tirzepatide and semaglutide — have become one of the most documented medicines-safety problems in modern UK healthcare. The MHRA issued multiple Drug Safety Updates between 2024 and 2025; the Counter Fraud Authority confirmed product seizures; and individual clinicians have published case reports of patients who received counterfeit material.
This is a practical, not theoretical, problem. The compounds work, the demand exceeds licensed supply, and the resulting grey market has been demonstrably hazardous.

#### What has been found in counterfeit pens

Documented findings from MHRA and CFA seizures include: pens containing insulin (life-threatening hypoglycaemia risk in non-diabetic users); pens containing only saline (no therapeutic effect, but injection-site infections); pens with incorrect doses (often higher than labelled, producing severe GI symptoms); and pens with legitimate appearance but fake batch numbers.
In several cases the counterfeit pens were sold via online pharmacies that initially appeared legitimate. Visual inspection of the pen itself is not a reliable safeguard.

#### How to buy safely

Three legitimate routes exist for licensed GLP-1 medicines in the UK: NHS prescription (eligibility-restricted via NICE criteria); private prescription via a GMC-registered prescriber and dispensed by a GPhC-registered pharmacy; or licensed-clinic supply through a regulated private weight-management service.
The two key markers of legitimacy are the prescriber registration (GMC for doctors, GPhC for pharmacists) and the pharmacy registration. Both registration numbers can be verified via public registers — gmc-uk.org for doctors, pharmacyregulation.org for pharmacies.

#### Red flags

Selling without a prescription, requiring no prescriber consultation, claiming "no prescription needed for personal-use quantities", offering substantially below-market pricing (legitimate Mounjaro starts around £170/month privately), shipping from outside the UK without a UK pharmacy involved, accepting cryptocurrency or gift-card payment only, and using messaging apps for orders rather than a regulated platform — any of these patterns should prompt extreme caution.

#### If you think you have a counterfeit

Stop using the product immediately. Report to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk) and to your GP. If you've experienced symptoms — particularly hypoglycaemia, severe GI symptoms, or injection-site infection — seek medical advice.
The MHRA also encourages reporting of suspected counterfeit products even if you haven't used them. This contributes directly to enforcement against unregulated suppliers.

**References**
1. MHRA Drug Safety Update. Counterfeit GLP-1 injector pens: clinician alert. January 2025.
2. NHS Counter Fraud Authority. Annual report 2024. Pharmaceutical fraud section.
3. BMJ Open. Case series of counterfeit semaglutide injector pens. 2024;14(8):e078901.
4. MHRA Yellow Card scheme. https://yellowcard.mhra.gov.uk

---

## Goal categories

### Fat Loss

URL: https://peptidehandbook.co.uk/goals/fat-loss

Compounds that produce sustained reductions in fat mass — primarily through appetite suppression, slowed gastric emptying, and improved insulin sensitivity. The strongest evidence base in the entire peptide field sits here.

What to look for:
- Phase-3 RCT data with mean weight reduction reported, not just responder rates
- Trial duration of at least 56 weeks (shorter trials systematically over-state effect size)
- A clear titration schedule — abrupt initiation produces near-universal GI side effects
- UK MHRA licensing status; counterfeit injector pens are a documented safety risk

### Muscle Growth

URL: https://peptidehandbook.co.uk/goals/muscle-growth

Growth-hormone secretagogues and IGF-axis modulators that increase endogenous GH pulsatility. Effects on lean mass are real but modest compared to anabolic steroid pathways — frame expectations accordingly.

What to look for:
- Studies reporting body-composition outcomes (DEXA), not just GH/IGF-1 surrogate markers
- Realistic effect sizes — most published increases in lean mass are 1–3 kg over 12+ weeks
- Dosing protocols matched to natural GH pulsatility (typically pre-bed or fasted state)
- UK legal status — many GH secretagogues are unlicensed or restricted to research use

### Recovery

URL: https://peptidehandbook.co.uk/goals/recovery

Compounds that may accelerate tissue repair via angiogenesis, fibroblast activity, or growth-factor modulation. Evidence is largely preclinical or anecdotal — promising mechanism, thin clinical data.

What to look for:
- Human trials, not just rat / rabbit tendon models
- Specific tissue claims with mechanism — generic "anti-inflammatory" claims are red flags
- Honest acknowledgement of evidence quality (clinical trial data is sparse here)
- Route of administration evidence (topical, injected, oral all behave very differently)

### Longevity

URL: https://peptidehandbook.co.uk/goals/longevity

Peptides positioned around mitochondrial function, telomere maintenance, or senescent-cell clearance. Evidence in humans is overwhelmingly preliminary; we apply the highest scrutiny here.

What to look for:
- Human data over preclinical mouse/Drosophila studies
- Outcomes that matter (function, biomarkers) rather than mechanism alone
- Independent replication — single-lab results in this field rarely hold up
- Realistic claims, not "reverse ageing" marketing language

### Sleep

URL: https://peptidehandbook.co.uk/goals/sleep

Compounds that modulate sleep architecture — typically by increasing slow-wave (deep) sleep, which carries downstream effects on GH release and recovery. A small evidence base, mostly older sleep-lab studies.

What to look for:
- Polysomnography (sleep-lab) outcome data, not subjective sleep scores
- Effects on slow-wave sleep specifically (not just total sleep time)
- Tolerance / habituation data over 4+ weeks of use
- Interaction warnings with other sedatives or sleep medications

### Cognitive

URL: https://peptidehandbook.co.uk/goals/cognitive

Nootropic peptides claimed to enhance focus, neuroprotection, or memory. Most evidence comes from Russian / Eastern European research with replication challenges. Apply the same scrutiny you would to nootropic supplements.

What to look for:
- Standardised cognitive batteries (e.g. n-back, Stroop) over self-rated focus claims
- Independent (non-original-author) replication
- Acute vs chronic effect distinction — many compounds show acute lift then habituate
- UK legal/regulatory status; many cognitive peptides are unlicensed