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Zenas BioPharma this week closed an upsized $200 million Series C financing. The company’s lead product candidate, obexelimab, is a bifunctional monoclonal antibody designed to bind both CD19 and FcγRIIb to inhibit the activity of B cells, plasmablasts, and CD19-expressing plasma cells to treat autoimmune diseases.

The financing round was led by SR One along with NEA, Norwest Venture Partners, and Delos Capital with significant participation from Enavate Sciences and Longitude Capital. 

Zenas is advancing a portfolio of autoimmune therapeutics for conditions such as IgG4-related disease, multiple sclerosis, systemic lupus erythematosus, and warm autoimmune hemolytic anemia (wAIHA). 

According to one recent study, autoimmune diseases affect approximately one in ten individuals in the U.K. alone, and the health effects of these conditions continues to increase over time. The world market for autoimmune diseases is currently estimated at over $14B.

“We are excited to support Zenas’ continued progress toward its goal of becoming a global leader in innovative immunology-based therapies, and we are confident in the capabilities of this exceptional team to advance the comprehensive development program for obexelimab across multiple potential indications,” said Jake Nunn, venture partner at SR One.

Proceeds will support ongoing mid- to late-stage clinical development programs for obexelimab. By simultaneous binding to CD19 and FcγRIIB, obexelimab mimics a natural antigen-antibody complex and down-regulates B-cell activity. Clinical programs for this drug include an ongoing Phase III registration-directed trial in IgG4-Related Disease, two planned Phase II randomized controlled trials in multiple sclerosis and systemic lupus erythematosus, and an ongoing open label Phase II trial in warm autoimmune hemolytic anemia (wAIHA). 

Additional new investors included, the Federated Hermes Kaufmann Funds, and Arrowmark Partners, along with existing investors, Fairmount, Wellington Management, Rock Springs Capital, Pivotal bioVenture Partners, Vivo Capital, Quan Venture Fund, and Superstring Capital participated in the financing. In conjunction with the financing, Jake Nunn, venture partner at SR One, and Tim Xiao, Partner at Delos Capital, joined Zenas’ board of directors.

“We are pleased and appreciative of the support we have received from this group of tremendous life sciences investors as we advance the ongoing obexelimab development program across multiple auto-immune diseases,” said Lonnie Moulder, Zenas founder and chief executive officer. 

Obexelimab has demonstrated clinical activity and was well-tolerated in five clinical trials, including in several autoimmune diseases, in which 198 subjects were dosed. In these clinical studies, obexelimab demonstrated inhibition of B cell function without depleting the cells, resulting in encouraging treatment effect in patients with various autoimmune diseases. 

More information on the Phase 3 (INDIGO) study of obexelimabfor the treatment of IgG4-Related Disease is available at NCT05662241. More information on the Phase II/III (SApHiAre) study for the treatment of wAIHA is available at NCT05786573. 

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