Ropes & Gray Advised Sanofi in Dren Bio Collaboration to Develop Autoimmune Disease Therapies in Deal Worth Up to $1.7 Billion

Ropes & Gray represented Sanofi in a strategic collaboration with Dren Bio to develop a next-generation B-cell depleting therapy for autoimmune diseases in a deal worth up to $1.7 billion. The transaction was announced on December 15.

The collaboration builds on Sanofi’s March 2025 acquisition of Dren Bio’s biospecific antibody-based immunology program, which has shown strong B-cell depletion with potential for sustained treatment-free remission in patients with autoimmune diseases.

Under the collaboration agreement, Dren Bio will receive a $100 million upfront payment and is eligible for up to $1.7 billion in development, regulatory and commercial milestones. The companies will collaborate on discovery and preclinical research, after which Sanofi will lead development, manufacturing, regulatory and commercialization.

Dren Bio has the option to enter a U.S. market profit and loss sharing arrangement, co-funding 40 percent of development costs for U.S. co-promotion rights and an equal share of U.S. profits and losses. Outside of the U.S., Dren will remain eligible for milestones and tiered royalties.

The Ropes & Gray team was led by life sciences licensing partner Abby Gregor, IP transactions counsel Joshua Talicska and IP transactions associate James Gould and included tax partners Scott Pinarchick and Zhen Zhang.