Blueprint's stock falls 11% after sharing new Phase 2 data for its rare-disease therapy

Shares of Blueprint Medicines Corp. /zigman2/quotes/209215354/composite BPMC +3.50% tumbled 11.7% in premarket trading on Wednesday after the company said a Phase 2 clinical trial evaluating Ayvakit in patients with non-advanced systemic mastocytosis, a rare disorder, met the primary and secondary endpoints. However, one Wall Street analyst said he is concerned about the change in the symptom score in the Phase 2 study, compared with the Phase 1 trial. "While we think these data are approvable, they do represent a deterioration in the absolute improvement in the symptom score, which was 15.6 points in this trial versus 19.7 in the Phase 1" trial, SVB Securities analyst Andrew Berens told investors on Tuesday morning. He also noted that "some physicians, payers, and patients may balk at the anticipated cost given that Ayvakit appears to add about a 10% improvement in symptoms versus best supportive care," adding that the therapy is expected to cost more than $350,000 per year. Blueprint said it plans to submit an application to the Food and Drug Administration for approval in the fourth quarter of this year. The company's stock is down 36.0% this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -0.38% has declined 9.6%.