Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library
PN-943: what the evidence says
At a glance
What it is: an oral peptide from Protagonist Therapeutics that blocks α4β7 integrin, a gut-homing signal, and is designed to stay in the gut. R1, R2 Protagonist stopped putting resources into it in Nov 2022. R3
What the evidence says: Human in the IDEAL phase 2 trial in ulcerative colitis, the lower dose gave 27.5% clinical remission vs 14.5% on placebo (not statistically significant overall), and the higher dose did no better than placebo. These figures come from a company press release, not a journal. R2, R4
Biggest risks: human safety data are limited to small healthy-volunteer studies and one phase 2 trial; long-term risks are unknown. R1, R2
Rating
| Human Human evidence | Very limited: one phase 2 RCT, company-reported only R2 |
| Animal Animal / lab evidence | Not reviewed |
| Regulatory | Never approved; development stopped R3 · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page R5, R6, R7 · not named on WADA's 2026 list; as a drug not approved anywhere for human use it falls under S0 (non-approved substances) R8 |
| Established human dose | No (trial amounts only; see Study details) |
Evidence verdict: Ulcerative colitis: Very limited (one phase 2 RCT; the high dose failed and results were only company-reported) · Other uses: No human data
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
About the evidence: there is no peer-reviewed efficacy result. The positive framing in the press release rests on the lower dose; the higher dose missed the main goal.
What is it?
Related pages: icotrokinra, rusfertide.
Does it work?
- Human IDEAL (phase 2, 12 weeks, 159 analyzed): clinical remission 27.5% on the lower dose vs 14.5% on placebo (p = 0.08); 15.1% on the higher dose. The company highlighted a subgroup without prior biologic treatment (p = 0.04). R2, R4
- Human Healthy volunteers: very little drug reached the blood, consistent with a gut-restricted design. R1
- Unknown No CT.gov results posted and no journal publication of IDEAL found. UNVERIFIED R4
Is it safe?
- Human Reported as well tolerated in healthy-volunteer studies. R1
- Unknown IDEAL safety details are company-reported only. R2
- No ongoing safety monitoring because development stopped. R3
Pipeline status (investigational)
- Sponsor: Protagonist Therapeutics. R2
- Status: after IDEAL, the company said it would spend no further internal resources on clinical development or manufacturing. R3 No phase 3 was registered. UNVERIFIED later partnering.
- Expected readouts: none.
Gray-market vials: extra risks
A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.
Is it legal?
- US: not FDA-approved; no Drugs@FDA application found (openFDA searched Oct 27, 2026).
- Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. R5, R6, R7
- Sport: not named on WADA's 2026 list; as a drug not approved anywhere for human use it falls under S0 (non-approved substances) R8.
Study details
Study details
These are amounts researchers used, not recommendations.
| Study | People / model | Route | Amount used | Follow-up | Reported | Citation |
|---|---|---|---|---|---|---|
| First-in-human and crossover studies | 107 healthy men in total | Oral | 100 to 1,400 mg single doses; 100 to 1,000 mg repeated doses | Short-term | Minimal blood exposure; generally well tolerated | PMID 33942566 |
| IDEAL (phase 2) | 159 adults with ulcerative colitis analyzed | Oral | 150 or 450 mg twice daily | 12 weeks | Remission 27.5% (150 mg) and 15.1% (450 mg) vs 14.5% | R2 |
Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)
- R1 Modi NB, et al. Clin Pharmacol Drug Dev. 2021. PMID 33942566
- R2 Protagonist Therapeutics, Protagonist Therapeutics Announces Topline Data from Phase 2 IDEAL Study of PN-943 in Ulcerative Colitis (press release, SEC exhibit 99.1), Apr 25, 2022. https://www.sec.gov/Archives/edgar/data/1377121/000110465922049856/tm2213399d1_ex99-1.htm
- R3 Protagonist Therapeutics, Protagonist Reports Third Quarter 2022 Financial Results and Provides Corporate Update (SEC exhibit 99.1), Nov 2022. https://www.sec.gov/Archives/edgar/data/1377121/000110465922115933/tm2229956d1_ex99-1.htm
- R4 ClinicalTrials.gov NCT04504383, IDEAL, phase 2 in ulcerative colitis, Protagonist, completed, 169 enrolled; no results posted (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT04504383
- R5 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
- R6 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
- R7 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- R8 WADA. The 2026 Prohibited List, S0 Non-approved substances; full list checked, compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
Disclaimer
This page is for education and harm reduction, not medical advice or a recommendation to use PN-943. This drug was never approved and its development has stopped. Products sold online under this name are unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).