William Blair analyst Raju Prasad downgraded Bluebird Bio to Market Perform from Outperform saying he's taking a conservative view on the company's transition from a development-stage company to a commercial-stage company. Based on the reimbursement model, the analyst believes that the Zynteglo launch is likely to be a "slow mover." Further, Prasad altered his model for bb2121-bb21217 to reflect the increased BCMA competition from both autologous and allogeneic cell therapy approaches that he says are moving faster through the clinic than he initially anticipated.