Abrupt end of Pfizer's hemophilia A gene therapy deal with Sangamo is the latest in a line of flip-flops between the big drug maker and smaller Bay Area partners.

Sangamo Therapeutics Inc.’s stock tumbled 56% on Tuesday for its second-biggest one-day percentage decline ever, after Pfizer Inc. terminated a hemophilia A gene-therapy partnership.

Sangamo, a gene therapy pioneer, loses a financial lifeline as Pfizer drops a gene therapy program for hemophilia.

Sangamo Therapeutics said on Monday that partner Pfizer has terminated their hemophilia A gene therapy co-development agreement, sending its shares down nearly 64% in extended trade. Sangamo added that it has now regained the rights to the therapy's development and would explore all options to advance the program,

Sangamo Therapeutics shares lost more than half their value when Pfizer pulled out of a collaboration agreement.

Sangamo Therapeutics (SGMO) stock plunged as Pfizer (PFE) ends collaboration on hemophilia A gene therapy. Find out the reasons for the selloff.

Sangamo Therapeutics, Inc. (NASDAQ:SGMO) regained the development and commercialization rights to giroctocogene fitelparvovec, an investigational gene therapy product candidate for moderately severe to severe hemophilia A that it has co-developed with and licensed to Pfizer Inc (NYSE:PFE).

The biotech company intends to explore ways to move ahead with developing the treatment, including seeking a new collaborator.