The deal includes a drug approved in the U.S. and the EU for systemic mastocytosis, a rare immunology disease, as well as an early-stage immunology pipeline, the companies said.

French drugmaker Sanofi said Monday it has agreed to acquire Blueprint Medicines for $9.5 billion, sending shares of the Cambridge, Mass.-based biopharma firm soaring in premarket trading.

The acquisition includes a rare immunology disease medicine and an advanced and early-stage immunology pipeline.