Shares in Sangamo lost 50% of their value in after-hours trading following the announcement, which came just before the close on 30 December. Credit: jayk7 via Getty Images.

Sangamo Therapeutics’ stock has plummeted by 50% in premarket trading after Pfizer ended the companies’ partnership to co-develop a gene therapy for haemophilia A. 

Sangamo announced it will regain the development and commercialisation rights to giroctocogene fitelparvovec, an investigational gene therapy for adults with moderately severe to severe haemophilia A.  

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This follows Pfizer’s decision to terminate their global collaboration and license agreement, effective 21 April 2025. Sangamo plans to explore options to advance the programme, including seeking a new collaboration partner. Shares in Sangamo – which had been set to receive up to $220m in milestone payments under the agreement – lost 50% of their value in after-hours trading following the announcement, which came just before the close on 30 December. 

The decision comes despite positive results from the Phase III AFFINE clinical trial (NCT04370054), which demonstrated that the therapy met its primary goal by reducing the total annualised bleeding rate (ABR) compared to routine Factor VIII (FVIII) replacement prophylaxis. Pfizer previously indicated plans to submit biologics license application (BLA) and marketing authorisation application filings in early 2025 but has now opted not to proceed. 

Pfizer said in a statement that a slow uptake of haemophilia A gene therapy in patients with moderate to severe disease and “limited interest” in another gene therapy option for the specified patient population prompted its decision.  

The development of gene therapies for rare diseases is a resource-intensive process that requires advanced technologies, large-scale clinical trials, and navigation of complex regulatory pathways. This has led several pharmaceutical companies to reevaluate or halt gene therapy programmes due to high costs and questions about commercial viability.  

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Gene therapies, especially for conditions with small patient populations like haemophilia A, pose unique financial challenges. While these treatments can potentially provide long-term or curative outcomes, their high development costs and production complexities result in significant price tags. For instance, BioMarin’s US Food and Drug Administration (FDA)-approved haemophilia A gene therapy, Roctavian (valoctocogene roxaparvovec-rvox), launched in 2023 with a $2.9m price point, sparking ongoing debate about the cost-effectiveness of such therapies. 

Sandy Macrae, CEO of Sangamo Therapeutics, said the therapy has the potential to be life-changing for haemophilia A patients and is well-positioned for regulatory submissions and commercialisation. Macrae expressed disappointment at Pfizer’s decision, particularly given the strong Phase III data, but acknowledged Pfizer’s role in advancing the programme to this stage. Pfizer will continue to monitor trial participants during the transition period. 

Cell & Gene Therapy coverage on Pharmaceutical Technology is supported by Cytiva.

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