Phase II win for Silence's divesiran in PV lifts bar for Takeda's rusfertide

Silence Therapeutics' siRNA divesiran achieved an 88% clinical response rate in its Phase II SANRECO trial for polycythemia vera (PV), compared with 19% on placebo. The primary endpoint—a combination of maintaining hematocrit below 45% and avoiding phlebotomy between weeks 18 and 36—was met with a placebo-adjusted response difference of about 69 percentage points (p<0.0001). Mean phlebotomies were 0.2 per patient with divesiran versus 2.1 with placebo.

Both dosing regimens performed well:
93.8% response with every‑6‑week administration and 81.3% with every‑12‑week (quarterly) dosing. The drug was well tolerated, with no new safety signals, supporting an upcoming Phase III trial planned around the every‑12‑week schedule.

This Phase II win raises the bar for the PV field, particularly for Takeda/Protagonist’s rusfertide, a hepcidin mimetic that previously showed a 60% response rate versus 17% on placebo in its Phase 2 trial. Rusfertide has advanced to a Phase 3 (VERIFY) and has already had its NDA accepted with Priority Review.

The strong efficacy and convenient quarterly dosing of divesiran position siRNA‑based therapy as a potential best‑in‑class option for PV, challenging the nearer‑term commercial positioning of rusfertide and intensifying competitive pressure on Takeda