Silence Therapeutics said its Phase II SANRECO trial met the primary endpoint for divesiran, an siRNA targeting TMPRSS6 in polycythemia vera. The company reported an 88% response rate versus 19% in placebo-controlled groups, alongside an ability to maintain hematocrit control with fewer phlebotomy needs. The mechanism centers on silencing TMPRSS6, a regulator of iron balance and red blood cell production. The company characterized the pharmacology as a “dimmer switch,” aiming for controlled and reversible modulation at the message level. For the field, a robust hematocrit-control signal can translate into fewer thrombotic events for PV patients, given the linkage between hematocrit thresholds and clotting risk. SANRECO’s results also strengthen the case for siRNA platforms targeting hepatic or systemic gene drivers in chronic hematologic disease.