Shares of Pfizer (PFE - Get Report)  were falling slightly in trading after the drugmaker announced it has agreed to pay up to $636 million for the rights to a portfolio of gene therapies under development at French company Vivet Therapeutics. 

Pfizer acquired a 15% equity interest in Vivet up front for $51 million and secured an exclusive option to acquire all of the private company's outstanding shares. The two companies will collaborate on Vivet's propriety treatment for the chronic, life-threatening liver disorder Wilson disease. 

"Pfizer strives to provide meaningful enhancements to the lives of patients with rare diseases. Our partnership with Vivet offers an important expansion of Pfizer's commitment to collaborate with the scientific community and to accelerate our leading AAV-directed gene therapy portfolio," Pfizer Chief Scientific Officer and President Mikael Dolsten said. 

The biotech industry has made a push into gene therapy in recent years, with rivals Novartis and Roche acquiring gene therapy developers, while Pfizer has been partnering with gene therapy companies without acquiring them outright. 

"We welcome Pfizer as a shareholder and partner that can help us advance our efforts to develop therapies for patients burdened with inherited liver disorders. This investment demonstrates the clear value of Vivet's innovative approaches to gene therapy," Vivet CEO Jean-Phillippe Combal said. 

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