BTK Inhibitor Rilzabrutinib Shows Efficacy in Immune Thrombocytopenia

California-based biopharmaceutical company Principia Biopharma (Nasdaq: PRNB) has announced in a press release preliminary phase 1/2 clinical trial data indicating the utility of oral Bruton’s tyrosine kinase (BTK) inhibitor rilzabrutinib for the treatment of Immune thrombocytopenia (ITP). The results were presented at the 2020 virtual conference of the European Hematology Association (EHA).

ITP involves the immune-mediated destruction of platelets, which are important for blood clotting, and can lead to the risk of severe bleeding and a decreased quality of life. While the precise immunological mechanisms underlying this autoimmune disorder are not fully characterized, B cell activity is known to play a role, suggesting the utility of a BTK inhibitor for treating the disease.

“Rilzabrutinib treatment at 400 mg twice daily led to both a rapid response detectable at the first platelet measurement (day eight), and a durable response. These results are significant not only for the speed of onset and sustainability of response, but also for the heavily pretreated nature of the population in which these results were seen,” stated Dr. David Kuter, MD, Principal Investigator of the clinical trial.

“It is also important to note that rilzabrutinib continues to be well tolerated and achieved significant reliable responses across subgroups at all doses and treatment times,” Dr. Kuter continued.

Principia Biopharma’s Chief Medical Officer Dr. Dolca Thomas, MD, stated, “We are very pleased with the consistency of responses and durability of effect observed among the patient responders. This data provides confidence to move forward to a pivotal Phase 3 trial, and assuming no future COVID-19 related impact, our goal is to initiate the trial by the end of 2020.”

The study involved 47 patients with a prior history of treatment and had a primary endpoint of “the proportion of patients able to achieve two or more consecutive platelet counts, separated by at least 5 days, of ≥ 50,000/μL and an increase of platelet count of ≥20,000/μL from baseline, without use of rescue medication.”

Regardless of treatment dose or duration, 43 percent of the patients met the primary endpoint. Among patients treated with 400 mg rilzabrutinib twice daily for at least 12 weeks, 50% achieved the primary endpoint. 21 patients experienced grade 1 or 2 treatment emergent adverse events (TEAEs). Bleeding or thrombotic events related to the treatment were not reported. Additional data from the study are available in the press release.

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