However CD38 therapy for MM is now a crowded space:
Because of this, it was entirely possible that Sanofi was sitting on development until the economics became more attractive as initial results were available even 5 years ago. Cutting such a deal with Immunogen may have been the kicker that spurred development, and it may have been a win-win arrangement.
Some of the price movement in IMGN post FORWARD I may have been due to misplaced enthusiasm for next gen ADC plays like DS-1062 or compounds based on ZYME's technology. Recent developments indicate that the safety\efficacy profiles of existing therapies like MS and IMMU132 are harder to achieve than expected and the promise of better theoretical based rationale in pre-clinical models don't pan out in practice.