8-K: Silence Therapeutics Completes Divesiran Phase 2 Enrollment

Silence Therapeutics has completed patient enrollment in its SANRECO Phase 2 study of divesiran for polycythemia vera, with topline results expected in Q3 2026.

Summary

• Completed patient enrollment in the SANRECO Phase 2 study of divesiran for the treatment of polycythemia vera (PV).
• Divesiran is a first-in-class siRNA (short interfering RNA) therapy targeting TMPRSS6.
• The SANRECO Phase 2 study is a global, randomized, double-blind, placebo-controlled trial that enrolled 48 phlebotomy-dependent PV patients.
• The primary endpoint is the proportion of patients receiving divesiran compared to placebo who maintain hematocrit (HCT) levels below 45% without phlebotomies between weeks 18 and 36.
• Secondary endpoints include safety and tolerability, pharmacokinetics, and quality of life changes.
• Initial topline results from the SANRECO Phase 2 study are anticipated in the third quarter of 2026.
• Results from the Phase 1 portion of the SANRECO study showed divesiran's potential to maintain HCT to target levels with infrequent dosing (every six weeks) without phlebotomies.
• The Phase 2 study includes a second, longer dosing interval of every 12 weeks, based on the sustained duration of effect observed in Phase 1.
• PV is a rare myeloproliferative neoplasm (blood cancer) characterized by excessive red blood cell production, leading to elevated hematocrit levels.
• Elevated hematocrit above 45% is associated with a four-times higher rate of death from cardiovascular or thrombotic events.
• Divesiran aims to selectively target and silence production of the TMPRSS6 protein, increasing hepcidin levels to redirect iron delivery away from the bone marrow, thereby lowering red blood cell production.
• Divesiran has received FDA Fast Track and Orphan Drug designations for PV.

Sentiment

Score: 7

Explanation: The completion of enrollment is a positive operational milestone, advancing the clinical program for a first-in-class therapy with Fast Track and Orphan Drug designations. However, the lack of immediate clinical data and the distant timeline for topline results (Q3 2026) temper immediate enthusiasm.

Positives

• Completion of patient enrollment in the SANRECO Phase 2 study is a significant operational milestone, advancing the clinical development of divesiran.
• The rapid completion of Phase 2 enrollment highlights growing enthusiasm for divesiran and novel treatment options for the significant unmet need in PV.
• Divesiran is positioned as a first-in-class siRNA for PV, offering a novel mechanism of action.
• Phase 1 results demonstrated divesiran's potential to maintain HCT to target levels with infrequent dosing (every six weeks) without the need for phlebotomies.
• The inclusion of a longer dosing interval (every 12 weeks) in Phase 2 suggests confidence in the sustained duration of effect observed in Phase 1.
• Divesiran has been granted FDA Fast Track and Orphan Drug designations for PV, which can expedite development and review processes.

Negatives

• No immediate clinical data or financial results were announced in this filing.
• Topline results from the Phase 2 study are not anticipated until the third quarter of 2026, indicating a significant waiting period for key data.
• Polycythemia vera is a serious condition associated with high risks of thrombotic events, cardiovascular death, and potential transformation to myelofibrosis and Acute Myeloid Leukemia.

Risks

• The company has a history of net operating losses.
• Ability to obtain necessary capital to fund clinical programs.
• Product candidates are in early stages of clinical development.
• Ability to obtain regulatory approval of and successfully commercialize product candidates.
• Potential for undesirable side effects or other properties of product candidates.
• Reliance on third-party suppliers and manufacturers.
• Outcomes of any future collaboration agreements.
• Ability to adequately maintain intellectual property rights for product candidates.

Future Outlook

The company anticipates initial topline results from the SANRECO Phase 2 study of divesiran in the third quarter of 2026. Management believes divesiran has the potential to address significant unmet needs in polycythemia vera by offering continuous hematocrit and symptom control, improved quality of life, and more convenient dosing as a first-in-class siRNA.

Management Comments

• "The rapid completion of Phase 2 enrollment highlights the growing enthusiasm for divesiran and novel treatment options to address the significant unmet need in PV." Craig Tooman, President and Chief Executive Officer.
• "Despite currently approved treatment options, a serious unmet need exists for patients seeking continuous hematocrit and symptom control, improved quality of life, and more convenient dosing, which we believe divesiran has the potential to address as a first-in-class siRNA." Craig Tooman.
• "We extend our sincerest thanks to the patients, investigators, and collaborative partners who made the achievement of this important milestone possible." Craig Tooman.

Industry Context

The completion of enrollment for a first-in-class siRNA targeting a rare blood cancer like Polycythemia Vera aligns with the broader biotechnology industry trend of developing highly specific, targeted therapies for diseases with significant unmet medical needs. The siRNA modality is gaining traction for its precision in gene silencing, offering potential advantages over traditional treatments, especially in chronic conditions requiring long-term management. The focus on improving quality of life and convenient dosing also reflects patient-centric drug development trends.

Comparison to Industry Standards

• The filing highlights that current standard of care for PV involves repeated phlebotomies and/or cytoreductive agents, and notes there are no currently approved therapies specifically targeting red blood cells and hematocrit.
• Divesiran, as a first-in-class siRNA targeting TMPRSS6, aims to offer a novel mechanism of action by increasing hepcidin levels to redirect iron delivery away from bone marrow, potentially reducing red blood cell production.
• This positions divesiran as a potentially differentiated treatment compared to existing options, though no specific competitor drugs or companies are named for direct comparison within the filing.

Stakeholder Impact

• Shareholders: Potential for increased valuation if divesiran demonstrates positive results, but also risk associated with clinical trial failures and funding needs.
• Patients (Polycythemia Vera): Potential for a novel, more convenient, and effective treatment option to manage hematocrit levels, reduce thrombotic events, and improve quality of life.
• Investigators and Collaborative Partners: Successful completion of enrollment reflects effective collaboration and progress in clinical research.

Next Steps

• Continue the SANRECO Phase 2 study, which includes a 36-week, placebo-controlled, double-blind period followed by a double-blind extension period and then an open-label extension period.
• Anticipate initial topline results from the SANRECO Phase 2 study in the third quarter of 2026.

Key Dates

Recommendation

While the completion of Phase 2 enrollment for a first-in-class therapy with FDA Fast Track and Orphan Drug designations is a positive operational milestone, the absence of immediate clinical data and the distant timeline for topline results (Q3 2026) suggest a 'hold' recommendation. Investors should await further clinical data to assess the drug's efficacy and safety profile before making significant investment decisions, especially given the inherent risks of clinical-stage biotechnology companies, including funding requirements and potential trial outcomes.

Keywords

Silence Therapeutics, Divesiran, Polycythemia Vera, PV, siRNA, TMPRSS6, Phase 2 Study, Clinical Trial, Hematology, Rare Disease, Biotechnology, Drug Development, FDA Fast Track, Orphan Drug