US-based Zenas BioPharma has raised $200m in a Series C round to support the clinical development of its lead candidate, obexelimab.

The investors included multiple US-based venture capital companies such as SR One, New Enterprise Associates (NEA), Norwest Venture Partners, Delos Capital, and others. The Series C funds will go towards supporting the “mid to late stage” clinical development programmes of obexelimab, a bispecific antibody that targets CD19 and FcγRIIb. Zenas acquired the rights to the antibody from Xencor in 2021.

In September 2023, Bristol Myers Squibb (BMS) acquired the developmental and marketing rights to obexelimab in several Asia Pacific regions, including Australia, Hong Kong, Japan, Singapore, South Korea and Taiwan. BMS made an equity investment in and paid $50m upfront to Zenas, which is also eligible for additional milestone-based payments.

Zenas is evaluating obexelimab in a placebo-controlled Phase III INDIGO trial (NCT05662241) as a subcutaneous treatment for IgG4-related disease (IgG4-RD), a chronic fibroinflammatory disease. The study is expected to enrol approximately 200 participants with IgG4-RD.

An open-label Phase II/III SApHiAre trial (NCT05786573) is also evaluating obexelimab as a treatment for warm autoimmune haemolytic anaemia (wAIHA). Both the IgG4-RD and wAIHA trials are expected to conclude in late 2025 or early 2026.

Zenas also plans to start Phase II trials investigating the bifunctional antibody as a treatment for multiple sclerosis and systemic lupus erythematosus (SLE), for which obexelimab has previously shown mixed results as a treatment. In 2018, it failed to meet the primary endpoint of maintenance of improvement in SLE in a Phase II trial (NCT02725515). Additionally, the Xencor-sponsored trial did meet the secondary endpoint, with treated patients taking a median of 76% longer to show losses in improvement.

The current Series C funds add to the $118m in a Series B round that Zenas raised in 2022. Other autoimmune candidates in the company’s portfolio include ZB002, an anti-TNFα therapy, and ZB004, a cytotoxic T lymphocyte-associated antigen-4 immunoglobulin (CTLA-4-Ig) fusion protein. The two therapies were also acquired from Xencor.