Peptide Head-to-Head Comparisons

Semaglutide is a single-pathway GLP-1 receptor agonist with ~7-day half-life. Tirzepatide is a dual GIP and GLP-1 agonist with ~5-day half-life and meaningfully larger magnitude on both weight and HbA1c endpoints. Both are weekly-administered research peptides; the tradeoff is potency vs tolerability and cost.

Tirzepatide is a dual GIP / GLP-1 agonist with mature clinical data. Retatrutide is a triple agonist adding glucagon receptor activation, producing larger weight-loss signals in Phase 2 research but with less long-term safety data and a steeper side-effect curve.

Liraglutide is the first-generation GLP-1 receptor agonist — daily injection, ~13-hour half-life. Semaglutide is the second-generation version — weekly injection, ~7-day half-life, stronger magnitude on weight and HbA1c endpoints. The research question is rarely which to pick, it's why someone would still pick Liraglutide.

BPC-157 is a pentadecapeptide derived from gastric juice with strong localized healing signals, especially in GI and tendon research. TB-500 is a fragment of Thymosin Beta-4 with systemic actin-binding activity driving cell migration, angiogenesis, and broad tissue recovery. Half-lives and delivery profiles are very different; so are their niches.

GHK-Cu and 'copper tripeptide' are the same molecule: a glycyl-L-histidyl-L-lysine tripeptide bound to a copper-2 ion. The terminology overlap confuses newcomers. The meaningful research question isn't which molecule — it's topical vs injectable delivery, because the two routes produce very different biological profiles.

Ipamorelin mimics ghrelin and triggers a GH pulse via the growth hormone secretagogue receptor. CJC-1295 is a GHRH analog that extends and amplifies the natural GH pulse window. They hit different receptors and produce a bigger, cleaner GH pulse when stacked than either does alone.

Ipamorelin is a selective ghrelin-receptor agonist (GHS class). Sermorelin is a GHRH (1-29) analog and the oldest research-grade GHRH tool. They act on different receptors in the GH axis — Ipamorelin triggers a new pulse, Sermorelin extends the natural GHRH-driven pulse. Stacking them is more common than comparing them.

CJC-1295 without DAC (also called Mod GRF 1-29) has a ~30-minute half-life and preserves the natural pulsatile GH rhythm. CJC-1295 with DAC attaches a Drug Affinity Complex that extends the half-life to ~8 days, producing a flat elevated GH baseline instead of pulses. The choice is pulsatility vs steady-state — and pulsatility is what you usually want.

NAD+ is the whole molecule — the cellular cofactor every sirtuin and PARP needs. NMN (nicotinamide mononucleotide) is the direct biosynthetic precursor, one step upstream of NAD+. Oral NAD+ is poorly absorbed; injectable NAD+ bypasses the gut. Oral NMN is reasonably absorbed and converts to NAD+ intracellularly. Both pathways elevate intracellular NAD+ — the tradeoff is delivery practicality.

MOTS-c is a mitochondrial-derived peptide that signals systemically — it activates AMPK, improves insulin sensitivity, and enhances exercise capacity. SS-31 (elamipretide) is a mitochondrial-targeting peptide that binds cardiolipin on the inner mitochondrial membrane, preserving electron-transport-chain function and reducing oxidative damage. Same organelle, completely different mechanism.

Epitalon (also called Epithalon) is a synthetic tetrapeptide developed from pineal-gland extract. Thymalin is a polypeptide complex from thymus tissue. Both emerged from the Khavinson longevity research program in Soviet/Russian gerontology. Different organ sources, different mechanisms — pineal / circadian for Epitalon, thymic / immune for Thymalin.

Both are synthetic melanocortin-receptor agonists derived from alpha-MSH analogs. PT-141 (bremelanotide) is MC4R-selective, developed specifically for sexual-response research. Melanotan II is a broader MC1R/MC3R/MC4R/MC5R agonist — tanning is its strongest effect, sexual response is a cross-effect. Different target selectivity, dramatically different side-effect load.