JPMorgan analyst Jessica Fye downgraded ImmunoGen (IMGN) to Underweight from Neutral without a price target. The failure of Forward I is a "meaningful setback" for the mirvetuximab development program, Fye tells investors in a research note. The analyst sees an "encouraging profile emerging" for IMGN632, but notes the program remains relatively early-stage. Further, she sees much of the economics going to Jazz Pharmaceuticals (JAZZ) should the company opt-in, likely after pivotal data. Substantially more data will likely be needed for "credit to come back into the stock" for mirvetuximab despite the Forward II readouts expected over 2019, Fye contends. As a result, the analyst expects ImmunoGen shares will be a relative underperformer.