Data From Blueprint Medicines' Blood Disorder Trial Fails To Lift Shares

Blueprint Medicines Corporation BPMC announced topline results from the registrational Part 2 of the PIONEER trial of Ayvakit (avapritinib) for non-advanced systemic mastocytosis (SM). 

• SM is a rare disorder that results in too many mast cells (type of mast cells) building up in the body.
• Blueprint Medicines plans to submit a supplemental marketing application to the FDA for Ayvakitin in Q4 of 2022, with European submission in 2023.
• Related: This Analyst Thinks Blueprint Medicines' Non-Dilutive Funding 'Deflates M&A Speculation'
• The Ayvakit arm had a reduction of 15.6 points in mean symptom severity score at 24 weeks, which continued to deepen to 20.2 points at 48 weeks in patients who rolled over to the Part 3 open-label extension study. 
• At 24 weeks, the control arm had a reduction of 9.2 points in the mean score.
• In addition, the PIONEER trial met all key secondary endpoints, including significant improvements across all measures of mast cell burden. More than half of Ayvakit-treated patients had over 50% reduction of serum tryptase, compared to no patients in the control arm.
• Ayvakit had a favorable safety profile compared to the control arm. 
• The rate of adverse events was 90.8% in the Ayvakit arm and 93.0% in the control arm. 
• Overall, 0.7% of patients in the Ayvakit arm and no patients in the control arm were discontinued due to treatment-related adverse events.
• Price Action: BPMC shares are down 24.1% at $52.04 on the last check Wednesday.