Peptide Comparisons

Each comparison opens with a one-sentence answer, then a table, then the detail.

• Semaglutide vs TirzepatideBoth are FDA-approved once-weekly injections for weight management; tirzepatide (Zepbound) acts on GIP and GLP-1 receptors and produced larger average weight loss in its pivotal trial (−20.9% at 15 mg over 72 weeks) than semaglutide 2.4 mg did in STEP 1 (−14.9% over 68 weeks).
• Tirzepatide vs RetatrutideTirzepatide is FDA-approved (Zepbound, Mounjaro); retatrutide is investigational, not approved, and Lilly plans to file for approval in Q1 2027. Retatrutide adds glucagon-receptor activity and produced up to 22.6% mean weight loss at 80 weeks in TRIUMPH-3.
• BPC-157 vs TB-500Neither BPC-157 nor TB-500 is FDA-approved; both were recommended for compounding by an 8–6 FDA advisory vote on July 23, 2026 that the FDA has not adopted, and both rest mainly on animal research.
• Semaglutide vs LiraglutideBoth are FDA-approved GLP-1 receptor agonists from Novo Nordisk. Semaglutide is injected once weekly; liraglutide once daily. In the head-to-head STEP 8 trial, semaglutide 2.4 mg weekly produced −15.8% mean weight change at 68 weeks versus −6.4% with liraglutide 3.0 mg daily.
• Tirzepatide vs LiraglutideBoth are FDA-approved for weight management. Tirzepatide (Zepbound) is a once-weekly GIP and GLP-1 receptor agonist; liraglutide (Saxenda) is a once-daily GLP-1 receptor agonist. In separate pivotal trials tirzepatide 15 mg produced −20.9% at 72 weeks and liraglutide 3.0 mg −8.0% at 56 weeks.
• Sermorelin vs CJC-1295 + ipamorelinSermorelin is the first 29 amino acids of growth hormone-releasing hormone and was once FDA-approved (Geref) before being discontinued. CJC-1295 plus ipamorelin pairs an investigational long-acting GHRH analog with an investigational ghrelin-receptor agonist; neither component has ever been FDA-approved.
• Ipamorelin vs GHRP-2Both are synthetic ghrelin-receptor agonists that trigger growth-hormone release. Animal studies described ipamorelin as more selective, with little effect on cortisol or prolactin, while GHRP-2 (pralmorelin) raised both. Neither is FDA-approved; GHRP-2 is approved in Japan as a diagnostic agent.
• PT-141 vs Melanotan IIPT-141 (bremelanotide) is FDA-approved as Vyleesi for low sexual desire (HSDD) in premenopausal women. Melanotan II is an unapproved, related melanocortin peptide sold as a tanning agent; regulators have warned against it.
• GHK-Cu vs BPC-157GHK-Cu is a naturally occurring copper tripeptide used mainly in topical cosmetics; BPC-157 is a synthetic 15-amino-acid peptide studied almost entirely in animals. Neither is FDA-approved as a drug, and both are sold as "research" injectables.
• Thymosin alpha-1 vs TB-500Despite similar names they are unrelated peptides. Thymosin alpha-1 (thymalfasin, Zadaxin) is a 28-amino-acid immune peptide approved in a number of countries outside the US for hepatitis B and as an immune adjuvant; TB-500 is a synthetic version or fragment of thymosin beta-4, studied for tissue repair and never approved.
• Semax vs SelankSemax and Selank are short synthetic peptides developed in Russia and approved there, Semax for stroke and cognitive disorders and Selank as an anti-anxiety medicine; neither is approved by the FDA.