RESEARCH PEPTIDE FUNDAMENTALS / MATRIX
Five Compounds, One Evidence Ladder
How mechanism, evidence maturity, and regulatory status actually differ across the five research peptides covered on this desk.
The short version
This page lines up BPC-157, KPV, NAD+, retatrutide, and tirzepatide on the dimensions that actually matter when reading research-peptide claims: what each targets mechanistically, how much human evidence backs it, its regulatory status, and the one caution worth knowing before reading anything else about it. The blunt summary: these five sit at very different points on the same evidence ladder. Tirzepatide is FDA-approved with a deep multi-trial record. Retatrutide has strong Phase 2 numbers but no approval anywhere. NAD+ has solid human dosing data but unproven downstream benefit. BPC-157 has one two-person human safety pilot and decades of rat data. KPV has no human trial data at all. None of this is medical advice, and no dose appears anywhere on this page as a recommendation.
The comparison matrix
| Dimension | BPC-157 | KPV | NAD+ | Retatrutide | Tirzepatide |
|---|---|---|---|---|---|
| What it targets | Angiogenesis / tissue-repair signaling (VEGFR2-Akt-eNOS) | Anti-inflammatory signaling (NF-kB, MAPK) via PepT1 uptake | Cellular redox metabolism + sirtuin/PARP/CD38 signaling | GLP-1, GIP, and glucagon receptors (triple agonist) | GIP and GLP-1 receptors (dual agonist) |
| Human evidence | One 2-person IV safety pilot; no efficacy trial [1] | None published — cells and mice only [6][7][8][9] | Multiple placebo-controlled dosing trials (NMN, NR) [12][13][15] | Phase 2 only (Phase 3 ongoing) [19][20] | Large multi-trial Phase 3 program; FDA-approved [21][24][25] |
| Regulatory status | Not approved; research chemical; WADA-banned in sport | Not approved; research chemical | Marketed as a dietary supplement / compounded IV therapy | Investigational; not approved anywhere as of mid-2026 | FDA-approved (T2D, weight management, sleep apnea) |
| Evidence maturity | Thin — mostly rodent, one human safety pilot | Lowest of the five — zero human data | Moderate — dosing/safety proven, efficacy unproven | Growing — Phase 2 complete, Phase 3 pending | Highest — full approval, years of post-market data |
| Key caution | Human evidence extremely thin; unregulated sourcing | No human safety or dosing data exists at all | IV form carries real contamination risk (FDA Class I recall) | Unapproved; gray-market supply, unverified identity/purity | GI intolerance and a real gallbladder-disease signal [23] |
What each one targets
The five split into two mechanistic families. BPC-157 and KPV work through tissue-level signaling — BPC-157 by driving new blood-vessel growth via VEGFR2 activation [4], KPV by damping inflammatory signaling through NF-kB and MAP-kinase suppression after entering cells via the PepT1 transporter [8]. NAD+ is different again: it's not a signaling molecule that binds a receptor, it's a metabolic coenzyme the body already runs on, with supplementation aimed at restoring an age-declining pool [14]. Retatrutide and tirzepatide belong to the incretin-receptor family — tirzepatide engages two receptors (GIP, GLP-1) [26], retatrutide engages three (adding glucagon) [17]. Same family, different reach.
Evidence maturity — where each actually stands
This is the sharpest dividing line on this desk. Tirzepatide has the deepest record: multiple large Phase 3 trials, a head-to-head win over semaglutide, years of post-marketing safety data, and full FDA approval across three indications [21][22][24][25]. Retatrutide is one tier behind — genuine Phase 2 trials with strong numbers, but no Phase 3 results published and no approval anywhere [19][20]. NAD+ occupies a strange middle position: several well-run, placebo-controlled human dosing trials confirm it's safe and reliably raises blood NAD+ [12][15], but a 2025 review is blunt that proof of a downstream clinical benefit is still limited [11]. BPC-157 has a single two-person human safety pilot layered on top of a large rodent literature [1][2]. KPV has no human trial data whatsoever — every finding cited on its page comes from mice or cultured human cells, never from a person [6][7][8][9].
Regulatory and approval status
Only tirzepatide is an approved medicine — available strictly by prescription. Retatrutide is investigational, studied only inside registered clinical trials, and the FDA issued over 50 warning letters to vendors selling it outside that context in 2025. BPC-157 and KPV are both sold as research chemicals for laboratory use only, with no approved drug or supplement status anywhere; BPC-157 is additionally banned in competitive sport under WADA's non-approved-substances category. NAD+ sits in its own lane — it and its precursors are legally sold as dietary supplements, and NAD+ itself is also offered as a compounded IV product, a category the FDA does not treat as approved and has flagged for at least one contamination-related recall.
The single biggest caution for each
For BPC-157, it's that the human evidence is genuinely almost nonexistent — a two-person safety pilot is not proof of anything, and sourcing is entirely unregulated [1][2]. For KPV, it's starker still: there is no human data of any kind to weigh a caution against, so any human use is, by definition, unstudied. For NAD+, it's the gap between well-proven blood-level changes and unproven clinical benefit, plus a documented contamination risk in the IV/injectable form specifically. For retatrutide, it's the combination of investigational status with a documented gray-market identity/purity problem, on top of a real dose-dependent heart-rate signal from the trials themselves [19]. For tirzepatide, the most consistently documented issue across pooled trial data is an increased risk of gallbladder or biliary disease [23] — a real, quantified signal even within an otherwise well-characterized drug. Reading the five together, the pattern holds: more human evidence generally means more precisely known risks, not fewer risks — it just means the risks are actually documented instead of guessed at.