British biotech Silence Therapeutics has been making noise on the stock markets by posting 30% growth in its share price after the company’s first-in-class polycythaemia vera (PV) drug, divesiran, met all its key endpoints in a mid-stage study.
During the Phase II SANRECO trial (NCT05499013), Silence pitted a once-six-weekly and once-twelve-weekly subcutaneous dose of its short interfering RNA (siRNA)-based divesiran against placebo in patients with PV who were dependent on phlebotomy, or bloodletting, for 36 weeks.
Go deeper with GlobalData
Discover B2B Marketing That Performs
Combine business intelligence and editorial excellence to reach engaged professionals across 36 leading media platforms.
As per a topline readout, 88% of patients in the divesiran arm across both dosing regimens had a clinical response versus 19% in the placebo arm, meeting the trial’s primary endpoint. In this study, a patient was considered to have had a clinical response if they did not require a phlebotomy and maintained red blood cell concentrations below 45% of the total blood volume between weeks 18 and 36.
Alongside its primary endpoint win, divesiran also demonstrated significant benefit through its key secondary endpoint of phlebotomy rate up to week 36, with the average number of procedures in the divesiran group at 0.2 compared with 2.1 in the placebo arm.
Patients also tolerated this drug well in the study, and researchers observed no new safety signals linked to its use in PV treatment.
Divesiran piques industry interest
These mid-stage results appear to have garnered positive investor attention, as the London-based biotech’s stock value grew from $11.95 at market close on 7 August to $16.70 at open on 10 August, before settling at a near 30% increase to $15.43 at 10 August close.
William Blair analysts were also impressed with this outcome, noting they have interpreted the results as a “home run”, while viewing these data as “superior” to that from the Phase III VERIFY study on Protagonist Therapeutics and Takeda’s rusfertide – potentially differentiating Silence’s offering from its late-stage pipeline peers.
With these positive results in hand, Silence is looking to begin a Phase III trial on divesiran in PV, which will further evaluate the drug’s potential versus placebo when dosed once every twelve weeks, after the drug exhibited a clinical response rate of 81.3% at this dosing frequency. The biotech anticipates this trial will begin in the first half of 2027.
PV is a rare, slow-growing blood cancer that causes the bone marrow to produce too many red blood cells. This can have an impact on the speed of circulation, increasing an impacted individual’s risk of cardiovascular events such as blood clots, heart attacks and strokes.
Currently, US regulators have only given Incyte and Novartis’ Janus kinase (JAK) inhibitor, Jakafi (ruxolitinib), and PharmaEssentia’s Besremi (repeginterferon alfa) the greenlight in PV.
If divesiran were to secure approval, William Blair analysts note it would join a blockbuster total addressable market (TAM). According to a GlobalData report, the key targets currently under exploration in PV include interferon receptors, Bcl-2-like proteins, hepcidin and histone deacetylase 1.
GlobalData is the parent company of Clinical Trials Arena.
