The FDA has granted accelerated approval to Pfizer's Elrexfio, a therapy for adult patients with relapsed or refractory multiple myeloma who have received at least four prior lines of therapy. The approval is based on Phase 2 trial results and is contingent upon verification of clinical benefit in confirmatory trials. Pfizer expects the therapy to generate more than $4 billion in potential peak revenue. Pfizer's shares are down 0.42% in premarket trading.