Third Arc Bio, launched in 2022, focuses on creating multispecific antibodies that form immune synapses to either activate or inhibit T cells with high precision. Its lead program, ARC101, is a bispecific T-cell engager targeting CLDN6 and is currently in Phase 1 dose-escalation studies for patients with advanced solid tumors. The company’s solid-tumor ARCStim platform and immunology-focused ARCTag (Tethered Agonist) platform underpin a broader pipeline aimed at both cancer and immune-mediated disorders. By localizing immune modulation to sites of disease, Third Arc seeks to improve both efficacy and safety over conventional systemic therapies. The management team includes executives with prior drug-development track records, and a16z General Partner Jorge Conde recently joined the board. Financially, Third Arc Bio has secured at least $217 million in Series A funding (an initial $165 million plus a $52 million extension) in addition to earlier seed capital. Proceeds are earmarked to accelerate its immunology portfolio and advance additional oncology programs into the clinic.

Total raised

$217M

Funding rounds

2

Latest round

Series A

Latest activity

Feb 2026