Preliminary results from a phase 2 trial studying bezuclastinib in systemic mastocytosis (SM) patients show the therapy is on track to yield positive results, according to data recently published in Blood.
The data was published after researchers obtained preliminary results from part 1 of phase 2 of the Apex trial evaluating bezuclastinib as a treatment for SM. The Apex study is a randomized phase 2, open-label, multicenter study designed to determine the optimal dosage and effect of bezuclastinib in adult patients.
The study included 33 participants divided into four groups according to the dosage received: 50 mg twice daily, 100 mg twice daily, 200 mg twice daily, or 400 mg once daily. All patients had a confirmed SM diagnosis based on World Health Organization (WHO) criteria.
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The primary endpoint was the overall response rate, which includes the complete response, complete response with incomplete hematologic recovery, partial response, and clinical improvement, as determined by a single review committee that based their assessment on the standardized response criteria (mIWG-MRT-ECNM).
The authors wrote that the patient cohort reflected the typical SM characteristics, with 64% men and 46% women, of which over 90% were carriers of the KIT D816V mutation.
Patients were divided into two groups: one including those who had previously received tyrosine kinase inhibitors (TKIs) and one of patients without a history of TKI use. Among the first group, 33% had tried midostaurin, and 15% avapritinib.
Baseline disease markers showed variable disease severity among patients. Notably, 61% of patients harbored additional mutations in SRSF2, ASXL1, or RUNX1, which are associated with poorer survival outcomes in SM.
The results suggested that bezuclastinib has clinical efficacy in patients with SM, even those previously treated with other TKIs. However, further research will establish the safety profile and efficacy.
