What happened Shares of the clinical-stage biotech Synthorx (NASDAQ: THOR) jumped by an eye-popping 169% right out of the gate Monday morning. What's behind this enormous spike? Synthorx's stock is on fire today in response to an all-cash buyout agreement with French pharma giant Sanofi (NASDAQ: SNY) for $68 per share. On a fully diluted basis, the total equity value of this buyout works out to a hefty $2.5 billion. Image source: Getty Images. So what This latest biotech buyout is noteworthy for two reasons. First off, Sanofi CEO Paul Hudson has only been on the job for a little over three months. That's an unusually short amount of time for a newly minted pharma CEO to start engaging in mergers and acquisitions. So Hudson seems to have a clear vision of where he plans to take the French drugmaker. Secondly, Sanofi is paying an extremely steep price for Synthorx. The biotech's novel cancer and autoimmune disease platform -- centering around the creation of synthetic proteins -- has yet to be validated in human trials after all. That's not to say that this unique drug development platform won't prove to be worth the price of admission, but it's a risky move nonetheless. Now what Synthorx and Sanofi said that the deal should close in the first quarter of 2020. Meanwhile, investors shouldn't be surprised if Sanofi continues to be aggressive on the M&A scene with Hudson at the helm, especially in the areas of cancer and autoimmune diseases. 10 stocks we like better than SanofiWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Sanofi wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of December 1, 2019 George Budwell has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source