SLN Divesiran: 88% Response in Phase 2 PV Trial

Silence Therapeutics (SLN) reported Monday that its siRNA drug divesiran crushed the primary endpoint in the Phase 2 SANRECO trial of phlebotomy-dependent polycythemia vera. The stock jumped 42% intraday to $16.95, adding roughly $235 million in market value.

The numbers: 88% of divesiran-treated patients achieved phlebotomy-free hematocrit control versus 19% on placebo, a 69-point placebo-adjusted gap (p<0.0001). Both dosing arms cleared independently: 93.8% at every-six-week dosing and 81.3% at every-twelve-week dosing. Divesiran also cut phlebotomies to 0.2 per patient versus 2.1 for placebo (p<0.0001). No new safety signals emerged in the 48-patient trial.

How divesiran works. The drug is a short interfering RNA that silences TMPRSS6, a gene in the liver that suppresses the iron-regulating hormone hepcidin. Removing that suppression raises hepcidin levels, which restricts iron delivery to the bone marrow and slows the red blood cell overproduction that drives PV. The mechanism targets the disease upstream of current treatments. The dosing advantage, one subcutaneous shot every twelve weeks, is a genuine differentiator for a chronic condition where patients already endure regular phlebotomies. PV is a rare blood cancer where elevated hematocrit above 45% is associated with a four-times higher risk of death from cardiovascular and thrombotic events, and divesiran holds FDA Fast Track and Orphan Drug designations.

The rusfertide overhang. Takeda and Protagonist’s rusfertide, a hepcidin mimetic peptide, was approved by the FDA on August 28, 2026 as MIMRYLO for erythrocytosis in polycythemia vera — the first FDA-approved hepcidin-targeted PV drug (see our MIMRYLO coverage). In the Phase 3 VERIFY trial, rusfertide achieved a 76.9% response rate. Divesiran’s 88% looks stronger on paper, but cross-trial comparisons carry the usual caveats: different patient populations, different endpoints, and only 48 patients in SANRECO. The dosing gap is clearer. Rusfertide requires weekly injections. Quarterly dosing, if confirmed in Phase 3, matters for real-world adherence.

What to watch. Silence plans to start Phase 3 in the first half of 2027, putting any approval no earlier than 2029. Between now and then, the company needs to fund a registrational program. With roughly $70 million in cash at last report, a financing raise is coming, and the post-data stock rally gives management an opportune window. Rusfertide will have a two-to-three-year commercial head start by the time divesiran could reach market. The Phase 3 will need to prove that infrequent dosing, four shots a year instead of fifty-two, closes that lead.

For investors learning to parse these readouts, the guide to clinical trial press releases covers what endpoints matter and why placebo-adjusted rates matter more than raw percentages.

Source: Silence Therapeutics press release, August 10, 2026 · SANRECO Phase 2 on ClinicalTrials.gov (NCT05499013)