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.

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

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

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, 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.