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 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.

Blueprint, based in Cambridge, has an approved drug called Ayvakit that treats a rare immunological condition.