Silence Therapeutics reported positive Phase II trial results for divesiran, an siRNA therapy targeting TMPRSS6 in polycythemia vera (PV). In the SANRECO study (NCT05499013), the company said divesiran met its primary endpoint with an 88% response rate versus 19% in placebo-controlled groups. PV therapies aim to control elevated hematocrit to reduce thrombotic risk, and Silence framed divesiran as enabling more consistent control without frequent phlebotomies that can be burdensome and poorly tolerated. The company stated that divesiran kept hematocrit under control in nearly 90% of treated patients and reduced the need for phlebotomy, with patients going a total of 36 weeks without requiring phlebotomy. Mechanistically, the company said divesiran works by silencing TMPRSS6, a gene involved in iron balance and red blood cell production. In Silence’s description, the siRNA effect acts like a controlled, reversible “dimmer switch,” aiming to slow overproduction of red blood cells. For PV and other hematology applications of RNAi, the result is a potential validation of gene-silencing approaches that may offer durable dosing intervals while targeting upstream biology tied to thrombosis risk.