Dren Bio has significantly expanded its strategic collaboration with Sanofi, extending a relationship that already delivered one of 2025’s most closely watched autoimmune asset acquisitions. Under the new agreement, Sanofi and the privately held biotech will jointly develop next-generation B-cell depletion therapies aimed at achieving deeper, more durable remission across a range of autoimmune diseases.
The deal includes a $100 million upfront payment to Dren Bio, with the biotech eligible for up to $1.7 billion in development, regulatory, and commercial milestones, underscoring Sanofi’s growing conviction in deep B-cell depletion as a differentiated therapeutic strategy. Beyond headline economics, the structure gives Dren Bio a long-term participation option, including potential U.S. co-promotion rights and a 50/50 profit-and-loss split.
The collaboration builds directly on Sanofi’s May 2025 acquisition of DR-0201, Dren Bio’s lead B-cell–depleting program, now renamed SAR448501. That asset is currently being evaluated in two phase 1 studies and has demonstrated robust and sustained B-cell depletion, an effect Sanofi believes could translate into treatment-free remission, a long-standing goal in diseases such as lupus, multiple sclerosis, and other antibody-driven autoimmune disorders.
Under the expanded agreement, the companies will work together on discovery and preclinical development using Dren Bio’s proprietary Targeted Myeloid Engager and Phagocytosis Platform, a multispecific antibody technology designed to selectively activate myeloid-cell–mediated phagocytosis only in the presence of disease targets. The approach will deliver potent immune-cell depletion while avoiding the off-target immune activation that has limited earlier immunomodulatory strategies.
Once a development candidate is selected, Sanofi will assume responsibility for global development, manufacturing, regulatory filings, and commercialization, leveraging its scale and immunology infrastructure. However, Dren Bio retains a meaningful strategic lever, the option to co-fund 40% of global development costs in exchange for U.S. co-promotion rights and an equal share of U.S. profits and losses. Outside the U.S., Dren Bio would receive milestones and tiered royalties on net sales.
The deal reinforces an increasingly aggressive push to redefine autoimmune treatment around immune reset and remission, rather than chronic disease suppression. The company has been assembling a portfolio of differentiated immunology assets that go beyond traditional B-cell depletion, and Dren Bio’s platform offers a mechanistically distinct way to engage the innate immune system.
The collaboration also marks a strategic inflection point. The structure of the agreement allowed Dren to evolve beyond a discovery-focused biotech into a commercially aligned partner with exposure to U.S. profit economics, an uncommon position for companies at this stage. Management has framed the deal as a step toward becoming a fully integrated biopharmaceutical company rather than a pipeline seller.
If SAR448501 continues to validate deep B-cell depletion in the clinic, the newly expanded collaboration positions Sanofi and Dren Bio to move quickly into next-generation follow-on programs, potentially reshaping expectations for remission in autoimmune disease.