WN561
Class APLNR biased agonist peptide (G-protein selective)
Status Pre-clinical / Pre-IND — published Cell (March 2024); estimated 2–3 years from human trials
TL;DR
WN561 is the first G-protein-biased apelin receptor (APLNR) agonist to solve the core failure of all prior apelin therapeutics: balanced agonism caused receptor desensitization and cardiac hypertrophy (killing AMG986 and BGE-102). WN561 achieves zero β-arrestin recruitment via structural modifications (D-Met at position 11, C1-C6 disulfide cyclization, glycine insertion), delivering sustained cardioprotection, inotropy, and AMPK activation without receptor burnout. Exercise mimetic via AMPK/GLUT4/mitochondrial biogenesis. Not available outside research settings.
Why it matters for Vitals
WN561 is the structural solution to a pharmacological paradox: apelin is the most potent endogenous positive inotrope (increases cardiac output without raising heart rate or myocardial oxygen demand), but prior agonists couldn’t sustain the benefit. If it reaches humans, the combination of chronic cardioprotection, exercise mimetic signaling, and AMPK activation would be highly relevant to Vitals’ cardiovascular and metabolic monitoring layers. Human safety is entirely unknown at this stage.
Key Facts
| Mechanism | G-protein biased APLNR agonism; zero β-arrestin recruitment; dimer stabilization |
| Preclinical | 14-day TAC/isoproterenol mouse models; blocked pathological hypertrophy; improved EF and fractional shortening |
| Exercise mimetic | AMPK activation; GLUT4 translocation; mitochondrial biogenesis; brown adipocyte differentiation; UCP1 thermogenesis |
| Human equivalent dose | ~32–65 mg SubQ (projected from 0.4–0.8 mg/kg in mice) |
| Structural key | D-Methionine at position 11; glycine insertion after D-M11; C1-C6 disulfide cyclization |
| Evidence | Preclinical only; cryo-EM structural basis (Cell 2024); no human data |
The β-Arrestin Problem — Why Prior Programs Failed
Native apelin signaling:
- G-protein pathway → good: cardioprotection, vasodilation, inotropy, AMPK
- β-arrestin pathway → bad: receptor desensitization, cardiac hypertrophy with chronic use
AMG986 (Amgen): Balanced agonist → monomer dissociation → β-arrestin hyperactivation → Phase 1/2 failed (NCT03276728), terminated for heart failure.
BGE-102 (BioAge): Acquired azelaprag; tried as exercise mimetic + tirzepatide adjunct → Phase 2 terminated December 2024 (transaminitis from off-target balanced signaling).
WN561 solution: Zero β-arrestin recruitment. Cryo-EM identified the molecular switch — D75²·⁵⁰ residue displacement of 0.1 nm dictates G-protein vs. β-arrestin. WN561 binds at a shallower depth, stabilizing the receptor dimer, avoiding the monomerization that triggers β-arrestin signaling.
Mechanism Summary
G-protein signaling (preserved):
- Gq/Gi activation → PLC/IP3/DAG cascade
- Sarcolemma-level acute hemodynamic effects: vasodilation, positive inotropy
- AMPK activation → GLUT4 translocation (insulin-independent glucose uptake) -完整 fatty acid oxidation; prevents acylcarnitine buildup
Exercise mimetic axis:
- PGC-1α upregulation via AMPK
- Mitochondrial biogenesis
- Brown adipocyte differentiation; WAT browning → UCP1 thermogenesis
- Sarcopenia: reactivates dormant muscle stem cells; clears senescent mitochondria via autophagy
ACE2 counter-regulation (broken by WN561):
- Apelin ↑ → ACE2 ↑ → Ang II → Ang 1-7 (protective)
- ACE2 also cleaves and inactivates apelin-13
- In heart failure: apelin collapses → ACE2 collapses → Ang II runs unchecked
- WN561 sustains apelin benefits without triggering this destructive cycle
Synergies
| Stack | Rationale |
|---|---|
| + SLU-PP-332 | WN561: acute hemodynamic + sarcolemma AMPK activation; SLU-PP-332: nuclear PGC-1α/ERR → maximum mitochondrial biogenesis infrastructure |
| + BPC-157 | WN561: vasodilation + SDF-1α/CXCR-4 progenitor mobilization; BPC-157: VEGFR2 upregulation + endothelial repair + antiarrhythmic → post-MI healing |
| + MOTS-c | WN561: extracellular AMPK via APLNR; MOTS-c: direct mitochondrial AMPK → dual-axis AMPK activation mimicking extreme endurance |
Risks and Uncertainty
- Human safety: completely unknown — do not use outside formal development settings
- Hypotension risk (vasodilation) — contraindicated in unstable cardiac physiology
- Pre-IND stage; 2–3 year minimum to Phase 1
- Translation from mouse TAC model to human heart failure is not guaranteed
- Optimal cycling/human dose not established
Links
- Exercise Mimetics — umbrella mechanism note; WN561 links here
- SLU-PP-332 — mitochondrial biogenesis stack
- BPC-157 — vascular healing stack
- MOTS-c — AMPK stack
- Peptides MOC
Source: Cell 2024 (Zhejiang/Peking University) · Amgen NCT03276728 · BioAge Phase 2 (terminated Dec 2024) · Gemini Deep Research 2026-03-12