Piper Jaffray analyst Danielle Brill said Acceleron's (XLRN) detailed data from luspatercept's Phase 2 myelofibrosis, or MF, trial was "mixed," though the drug did "hit the mark" in the two cohorts of patients on background ruxolitib, which she notes is the largest MF subpopulation. While she still expects partner Celgene (CELG) to initiate Phase 3 development based on these data, the opportunity now appears to be less than $1B, Brill said. The analyst, who said she plans to update her model and thoughts following the company's Q3 earnings call, has an Overweight rating and $71 price target on Acceleron shares ahead of the call.