Wells Fargo analyst Jim Birchenough believes shares of Bluebird Bio (BLUE) have been under pressure on concerns regarding potential competitive risk to BCMA CAR T therapeutic bb2121 from Amgen's (AMGN) bispecific T cell engager AMG420. The analyst highlights that AMGN420 is a continuous IV infusion and in his opinion not a viable competitor to a single bb2121 cell therapy dose, particularly given long-term durability of response with bb2121. Further, he notes that Amgen's approved first generation CD19 bispecific engager, BLINCYTO, is dosed as a continuous IV for 4 weeks out of every 6 and achieved only $175M in sales in 2017 following 2015 approval. He does not view this dose schedule for first generation bispecific T cell engagers as commercially viable in a more chronic cancer. Additionally, the analyst points out that Affimed (AFMD) also has a preclinical BCMA engager AFM26, established proof-of-concept data for CD30 bispecific AFM13, and upcoming proof-of-concept data for CD19 bispecific AFM11.