Silence Therapeutics this week presented updated follow-up data from the Phase 1 SANRECO study of its investigational siRNA therapy, divesiran, at the 2026 European Hematology Association Annual Meeting.
The data indicate that the drug demonstrates durable efficacy in patients with polycythemia vera, maintaining control of hematocrit levels after treatment cessation and significantly improving disease-related symptoms and quality of life.
Study Design and Patient Population
The Phase 1 study enrolled 21 patients with polycythemia vera who were dependent on phlebotomy treatment. In the six months prior to treatment, these patients underwent a total of 80 phlebotomy procedures.
During the 34-week active treatment period, only five phlebotomies were required, all of which occurred in patients with baseline hematocrit levels above 45%. Notably, during the 16-week follow-up period after the last dose, only four phlebotomy events were recorded.
Among 14 patients with longer-term follow-up data, the median time to first post-treatment phlebotomy was 287 days.
Key Efficacy and Safety Outcomes
Beyond the significant reduction in phlebotomy needs, most patients showed improvement in their MPN-10 Total Symptom Score from baseline to week 34, indicating enhanced management of disease-related symptoms and overall quality of life.
Regarding safety, divesiran was well-tolerated, with no dose-limiting toxicities observed. The most common treatment-emergent adverse events were mild and transient injection site reactions.
No treatment-related serious adverse events or treatment discontinuations due to adverse events were reported.
Management Commentary and Future Development
Dr. Curtis Rambaran, Chief Medical Officer of Silence Therapeutics, stated that the sustained hematocrit control, symptom improvement, and significant, durable reduction in phlebotomy burden observed in the Phase 1 study further support the potential for low-frequency dosing.
The ongoing Phase 2 SANRECO study is currently evaluating two dosing regimens—every six weeks and every twelve weeks—in 48 phlebotomy-dependent patients. Topline data from this study is anticipated in August 2026.
Disease Background and Drug Profile
Polycythemia vera is a rare blood cancer characterized by the overproduction of red blood cells. Current standard treatments include repeated phlebotomy and cytoreductive agents, but there are no approved therapies specifically targeting red blood cells and hematocrit.
Divesiran is a first-in-class siRNA therapy targeting TMPRSS6, designed to reduce excessive red blood cell production by modulating iron metabolism. It has received Fast Track designation and Orphan Drug designation from the U.S. Food and Drug Administration for the treatment of polycythemia vera.
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