French biopharmaceutical company Sanofi has agreed to buy California-headquartered biotechnology firm Synthorx in a cash deal worth about $2.5 billion.

Sanofi said the deal would bolster its immuno-oncology pipeline.

It said Synthorx is a clinical-stage biotechnology company “focused on prolonging and improving the lives of people suffering from cancer and autoimmune disorders.”

Sanofi has offered to buy the outstanding shares of Synthorx common stock for $68 per share in cash — a 172% premium to Synthorx’s closing price on December 6.

“This acquisition fits perfectly with our strategy to build a portfolio of high-quality assets and to lead with innovation …” said Sanofi CEO Paul Hudson.

“Additionally, it is aligned with our goal to build our oncology franchise with potentially practice-changing medicines and novel combinations.”

Liberum analysts said in a note: “The acquisition price is full at a 172% premium to Synthorx Dec. 6 close price and is a lot to pay for an early stage pipeline (lead drug THOR-707 is in phase 1 trial.”

The transaction has been unanimously approved by both the Sanofi and Synthorx boards of directors.

John Reed, global head of research & development at Sanofi, said: “Synthorx’s exceptionally novel discovery platform has already produced a molecule that has the potential to become a foundation of the next generation of immuno-oncology combination therapies.

“By selectively expanding the numbers of effector T-cells and natural killer cells in the body, THOR-707 can be combined with our current oncology medicines and our emerging pipeline of immuno-modulatory agents for treating cancer.

“Moreover, Synthorx’s pipeline of engineered lymphokines has great promise not only for oncology but also for addressing many autoimmune and inflammatory diseases. ”

Synthorx CEO Laura Shawver said: “We are grateful that Sanofi has acknowledged the value of our Expanded Genetic Alphabet platform and the potential of our pipeline of optimized therapeutics for cancer and autoimmune disorder.

“Importantly, Sanofi has a portfolio of therapeutics that holds incredible promise for combining with our cytokine Synthorins to benefit patients around the world.

“I want to thank our employees and the Sanofi organization for their relentless efforts on behalf of patients.”