Long-term safety findings from the phase III Shorespan-017 extension study of bomedemstat in patients with ET

At the European Hematology Association (EHA) 2026 Congress, June 11–14, 2026, Stockholm, SE, Francesca Palandri presented results from Shorespan-017 (NCT06351631), a nonrandomized, single-arm, open-label, phase III extension study evaluating the long-term safety of continued bomedemstat in adults with myeloproliferative neoplasms (MPN) who had received it in prior clinical studies (N = 56), with a focus on those with essential thrombocythemia (ET; n = 40). The primary objective was safety and tolerability, including the incidence and discontinuation of treatment due to adverse events (AEs). 

Key data: At data cutoff (April 2025), after a median treatment duration of 8.1 months, 39/40 patients with ET remained on treatment; one patient had discontinued due to Grade 4 anemia. In patients with ET, any-grade AEs occurred in 88%, most commonly diarrhea (23%), contusion (13%), abdominal pain (10%), and upper respiratory tract infection (10%). Grade 3/4 AEs occurred in 20% of patients with ET, most commonly diarrhea, anemia, and gastroenteritis; no Grade 5 AEs were reported. In addition, dose modification due to AEs were required in 23% of patients, while serious AEs occurred in 18%. Any-grade treatment-related AEs occurred in 18%, with no treatment-related Grade 3/4 events, discontinuations, or deaths; one serious treatment-related AE of Grade 2 constipation occurred. 

Key learning: Continued bomedemstat demonstrated a manageable safety profile in patients with MPN, including those with ET, supporting further follow-up to characterize the long-term efficacy of bomedemstat in this population.