12:20 PM EST, 12/31/2024 (MT Newswires) -- Sangamo Therapeutics' ( SGMO ) shares were sinking intraday Tuesday after the company said its partner Pfizer ( PFE ) decided not to proceed with further development of a new gene therapy to treat hemophilia A, a bleeding disorder.

The companies developed giroctocogene fitelparvovec as part of their collaboration for the global development and commercialization of gene therapies for hemophilia A. Sangamo transferred the manufacturing technology and the investigational new drug application to Pfizer ( PFE ) in late 2019, the genomic medicine company said in a late-Monday statement.

Pfizer ( PFE ) will not proceed with the biologics license application and marketing authorization application submissions for, or to explore commercialization of, the experimental treatment, Sangamo said. The companies' collaboration and license agreement will terminate effective April 21, according to Sangamo.

Sangamo's shares were down 54% in Tuesday trade, while Pfizer's ( PFE ) rose 0.5%.

Sangamo Chief Executive Sandy Macrae said the company was "surprised and extremely disappointed" by Pfizer's ( PFE ) decision. "We are committed to exploring the optimal path forward for this important treatment, including seeking the right partner."

"After extensive analysis of clinical trial results, key opinion leader feedback and the slow uptake of hemophilia A gene therapy in patients with moderate to severe disease, we believe there is limited interest in an additional gene therapy option in this patient population at this time," Pfizer ( PFE ) said in a statement e-mailed to MT Newswires Tuesday. "Our responsible course of action now is to re-dedicate our time and resources to those assets and treatments that will have the greatest impact on patients and the greatest chance of commercial success."

In July, Pfizer ( PFE ) announced that a phase 3 trial of giroctocogene fitelparvovec met its primary and key secondary objectives of superiority compared with prophylaxis, Sangamo said in the Monday statement. Pfizer ( PFE ) in the past told Sangamo that the biologics license application and marketing authorization application submissions were expected early next year, according to the statement.

Sangamo said it expects to begin patient enrollment in a phase 1/2 study of ST-503 for idiopathic small fiber neuropathy in the middle of 2025 and to file a clinical trial authorization submission for its prion disease program in the fourth quarter, each subject to obtaining additional funding.

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