BRP

What is BRP?

BRP (BRINP2-related peptide) is a 12-amino-acid endogenous hypothalamic peptide discovered at Stanford University by the Svensson laboratory and published in Nature on March 5, 2025. It is derived from the prohormone BRINP2 (Bone Morphogenetic Protein/Retinoic Acid Inducible Neural-specific 2), with the bioactive sequence corresponding to BRINP2 residues 386-397: THRILRRLFNLC.

BRP is mechanistically distinct from the GLP-1 / amylin / GIP families that dominate current obesity pharmacology. It is one of the most-watched preclinical-stage anti-obesity peptides because of two distinguishing features:

Strong appetite suppression and weight loss in mouse and minipig models — comparable to liraglutide
No GLP-1-class adverse events — no nausea, no muscle loss, no gastric emptying delay in animal studies

Merrifield Therapeutics, co-founded by Stanford's Dr. Katrin Svensson, is advancing BRP toward IND filing.

Discovery and Origin

The BRP discovery used a novel AI-assisted prohormone cleavage prediction workflow. Computational analysis of human prohormones identified BRINP2 as a candidate prohormone with a likely cleaved bioactive peptide. Synthesis and screening of the predicted cleavage products against mouse hypothalamic neurons revealed BRP's strong anorexigenic activity.

This methodology — computational prediction → synthesis → screening — represents a new approach to discovering endogenous bioactive peptides that may have been missed by classical biochemistry, and BRP is the lead validation case.

Mechanism of Action

BRP suppresses appetite via a novel non-incretin pathway in hypothalamic neurons:

Activation of cAMP-PKA-CREB-FOS signaling in ventral tegmental area and arcuate nucleus neurons
No GLP-1 receptor binding — distinct from the entire incretin class
No amylin or melanocortin receptor activity — distinct from cagrilintide and setmelanotide
No effect on gastric emptying — explaining the absence of nausea
Reduces food intake without altering metabolic rate or causing muscle loss in animal studies

The receptor mediating BRP's effects has not been definitively identified as of mid-2026; this is an active area of investigation.

Preclinical Evidence

Mouse studies (Nature 2025):

Acute IP administration produced dose-dependent reduction in food intake comparable to liraglutide
Chronic dosing produced significant body weight reduction
No effect on lean mass — preserved skeletal muscle (a key differentiator from GLP-1 class)
No nausea / aversion — measured by conditioned taste aversion
Effects abolished by hypothalamic-targeted disruption of cAMP signaling

Minipig studies:

Confirmed weight-loss effect at translatable doses
Pharmacokinetic profile supporting potential once-daily or weekly dosing
Tolerability consistent with mouse data

Pipeline Status

Preclinical — IND-enabling studies underway
Sponsor: Merrifield Therapeutics (founded by Svensson lab principals)
IND filing target: 2026-2027
Phase 1 first-in-human studies anticipated: 2027

Place in Future Therapy

If BRP advances successfully through clinical development, it would represent:

A non-incretin alternative or complement to GLP-1, GLP-1/GIP, and GLP-1/amylin/glucagon classes
Potentially better-tolerated weight management therapy — particularly attractive for the substantial subset of GLP-1 patients who discontinue due to nausea
Lean-mass preservation — a major concern with chronic GLP-1 use, especially in older adults

These advantages would position BRP as a meaningful addition to obesity pharmacology rather than a direct competitor to existing approved drugs.

Important Caveats

BRP is preclinical as of mid-2026. Many factors may attenuate or change its profile in human studies:

Pharmacokinetic differences in humans
Receptor identity and tissue distribution may differ
Adverse events not seen in mice/minipigs may emerge
Efficacy magnitude in humans is unproven

The animal data are encouraging, but BRP must complete Phase 1, 2, and 3 trials before any of its current promise translates into approved therapy. Realistic approval timing (if successful) is 2030-2032.

Why It Matters

BRP represents two important advances in peptide drug discovery:

AI-assisted prohormone discovery — successfully identifying a bioactive endogenous peptide from computational prediction, validating a methodology that may yield additional drug candidates from the human prohormone-derived peptidome
Non-incretin obesity mechanism — moving beyond GLP-1 / GIP / glucagon biology to explore a novel hypothalamic appetite circuit

Even if BRP itself does not advance to approval, the discovery methodology and the new mechanism are scientifically significant and may catalyze a wave of related discovery efforts.