Opinion vs. Evidence: Reading a Clinician's Peptide Tier List

In October 2026, Dr. Jason Pencek, a clinician who shares peptide content on Instagram (@dr.jasonpencek), posted a peptide tier list. He ranks compounds from S (game-changing) to D (limited benefit, better alternatives exist), and says the rankings come from his clinical experience, self-experimentation and the outcomes he has observed. He is not affiliated with Youthful Peptide. We summarize his public post here for academic discussion, and we would welcome his perspective on a future Pep Talk.

Tier lists measure belief and experience. Our evidence grades measure published human data and FDA status. Both are useful. They answer different questions.

S tier in his list

• Retatrutide: our Grade B. Strong phase 3 weight-loss data; not yet FDA-approved.

• BPC-157: our Grade C. Popular, but controlled human trials are scarce.

• GHK-Cu: our Grade C. Best evidence is for topical skin use.

• MOTS-c: our Grade D. Mostly animal and cell data.

• Tesamorelin: our Grade B. FDA-approved for HIV-associated abdominal fat.

• Selank: our Grade C. Small Russian studies, not independently replicated.

• Epitalon: our Grade C. Data largely from one research group.

• NAD+: our Grade C. Raises NAD+ levels; clinical outcome data are limited.

• Also listed: HGH and HMG, prescription hormones we do not cover as peptides.

A tier in his list

• Tirzepatide: our Grade A. FDA-approved, large outcome trials.

• PT-141: our Grade A. FDA-approved (Vyleesi) for a specific indication.

• hCG: our Grade B.

• SS-31: our Grade C, with an FDA accelerated approval in a rare disease.

• TB-500, CJC-1295, Semax: our Grade C to D.

• Also listed: SLU-PP-332, Pinealon and Melanotan-2, which we do not cover. FDA has warned consumers about unapproved melanotan products.

B, C and D tiers

• B tier: KPV, AOD-9604, DSIP, Thymosin Alpha-1, Ipamorelin, plus IGF-1 LR3, 5-Amino-1MQ and LL-37.

• C tier: Semaglutide, Sermorelin, Kisspeptin-10, ARA-290 and Cagrilintide.

• D tier: Hexarelin, PEG-MGF, GHRP-2, GHRP-6, Follistatin-344 and ACE-031.

Where opinion and evidence part ways

The biggest gap is semaglutide. It sits in his C tier, yet it has some of the strongest evidence of any peptide, including a large cardiovascular outcomes trial. His view may reflect preference for newer agents rather than doubt about the data. On the other side, BPC-157, MOTS-c and Epitalon rank at the top of his list while human evidence remains thin.

Where they agree

Tirzepatide, tesamorelin and PT-141 rank well in both systems. Hexarelin and MGF rank low in both. ACE-031 sits in his D tier, and its human trial was stopped early over safety concerns.

How to use a tier list

• Treat it as a conversation starter, not a prescription.

• Ask what kind of evidence sits behind each ranking.

• Remember that “works for me” and “works in a trial” are different claims.

• Bring questions to a licensed clinician who knows your history.

Academic discussion for education only. Not medical advice, not a recommendation to use any product, and no dosing is discussed. Opinions belong to the speakers. Talk with your own licensed clinician.