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

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.

Sanofi has agreed to acquire US-based Blueprint Medicines for an equity value of $9.1bn to bolster its immunology pipeline with rare disease treatments. The acquisition includes Ayvakit/Ayvakyt (avapritinib),