 Shares of Blueprint Medicines Corp. BPMC, -2.00 tumbled 11.7 in premarket trading on Tuesday 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. 