Third Arc Bio announced it has closed a $52 million Series A extension financing, adding to a previously announced $165 million Series A as the company looks to broaden and accelerate its oncology and immunology and inflammation pipeline. The financing was led by new investor Andreessen Horowitz (a16z) alongside founding investor Omega Funds. The round also included participation from Life Sciences at Goldman Sachs Alternatives, BVF Partners LP, funds managed by abrdn. Inc., accounts advised by T. Rowe Price Associates, Inc., Marshall Wace, Hillhouse Investment, Galapagos NV, AbbVie Ventures, and Alderline Group. As part of the transaction, a16z General Partner Jorge Conde is joining Third Arc Bio’s board.
The clinical-stage biotech is developing multifunctional antibodies that generate immune synapses to precisely activate or inhibit T cells, with an emphasis on improved control of immune activity and the potential to enhance both efficacy and safety.
The company said it will use proceeds to accelerate its immunology and inflammation portfolio while continuing to move additional oncology programs into the clinic. Third Arc Bio’s lead asset, ARC101, is a bispecific T-cell engager targeting CLDN6 and is currently in a Phase 1 dose-escalation study in patients with advanced solid tumors.
In immunology and inflammation, the company is emphasizing its ARCTag (Tethered Agonist) Platform, which uses multispecific antibodies to localize immune modulation to sites of disease. Third Arc Bio positioned the approach as a step beyond conventional systemic autoimmune therapies, arguing that targeted activity could improve the therapeutic index by concentrating biological effects where they are needed.
Third Arc Bio launched in 2022 with seed financing from Omega Funds and said it has since built an experienced team spanning drug discovery and development. The company also highlighted its platform portfolio, including the solid tumor ARCStim Platform and the immunology and inflammation ARCTag Platform, as the foundation for a pipeline it describes as focused on high-value therapeutics optimized for best-in-class T cell engagement.
KEY QUOTES
“Third Arc represents a shift toward more precise immune modulation—moving beyond systemic exposure to therapies designed to deliver highly controlled biological effects at sites of disease. The company’s platforms, combined with a team that has repeatedly translated complex immunology into approved medicines, reflect a rigorous, patient-driven approach to building biologics that can improve both efficacy and safety across oncology and immune-mediated disease.”
Jorge Conde, General Partner, Andreessen Horowitz (a16z)
“This financing allows us to maintain momentum across our expanding oncology portfolio while rapidly advancing our next-generation I&I assets into first-in-human studies. By parallel-tracking programs, we can more efficiently validate the full potential of our platforms, rapidly generate proof-of-concept data, and deliver innovative therapies for patients with significant unmet need.”
Peter F. Lebowitz, MD, PhD, Chief Executive Officer, Third Arc Bio
