# Third Arc Bio

Source: https://onco.cc/companies/third-arc-bio/  
OnCo record `third-arc-bio` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Third Arc Bio builds antibodies that link the immune system's T cells to cancer cells. Its first medicine, aimed at tumours carrying the protein Claudin 6, entered its first human trial in 2025.

## Summary

Third Arc Bio was launched in 2022 with seed funding from Omega Funds and came into public view on 23 July 2024 with an oversubscribed USD 165 million Series A led by Vida Ventures and co-led by Cormorant Asset Management and Hillhouse Investment, under chief executive Peter Lebowitz, formerly head of oncology R&D at Johnson & Johnson. It designs multifunctional antibodies optimised for T cell engagement in solid tumours (its ARCStim platform) and in immunology and inflammation (ARCTag). The lead asset ARC101, a bispecific T cell engager against Claudin 6 (CLDN6), dosed its first patient in a phase 1 dose-escalation trial in CLDN6-expressing advanced solid tumours in March 2025. In November 2025 Adagene licensed it two masked CD3 T cell engagers built on its SAFEbody technology, and on 4 February 2026 the company added a USD 52 million Series A extension led by a16z with Omega Funds.

## Fields

- Kind: Company
- Last checked: 2026-10-29
- HQ: Spring House, PA
- Type: biotech
- Website: https://www.thirdarcbio.com/

## Notes

- The phase 1 trial of ARC101 is registered as NCT06672185 per the company's March 2025 release; that trial has no record in the corpus, so it is not linked. Headquarters follows the dateline of the company's 2025 and 2026 releases; the 2024 launch release was datelined Boston.

## Sources

- Official website: https://www.thirdarcbio.com/
- Launch and USD 165 million Series A, July 2024: https://www.biospace.com/third-arc-bio-launches-with-oversubscribed-165-million-series-a-financing-to-deliver-superior-biologics-for-solid-tumors-and-inflammatory-immunology-i-i-diseases
- First patient dosed with ARC101, March 2025: https://www.thirdarcbio.com/news/third-arc-bio-announces-first-patient-dosed-in-phase-1-clinical-trial-of-lead-t-cell-engager-arc101-to-treat-cldn6-positive-cancers/
- USD 52 million Series A extension, February 2026: https://www.thirdarcbio.com/news/third-arc-bio-announces-$52m-series-a-extension-to-expand-oncology-and-immunology-&-inflammation-portfolio/

## Connected records

- fronts: [Immunotherapy](https://onco.cc/fronts/immunotherapy/)
- technologies: [Bispecific antibodies](https://onco.cc/technologies/bispecific-antibody/), [T-cell engagers (bispecific)](https://onco.cc/technologies/t-cell-engager/)
- targets: [CD3](https://onco.cc/targets/cd3/), [Claudin 6](https://onco.cc/targets/cldn6/)
- companies: [AbbVie Ventures](https://onco.cc/companies/abbvie-ventures/), [Andreessen Horowitz Bio + Health](https://onco.cc/companies/a16z-bio-health/), [Cormorant Asset Management](https://onco.cc/companies/cormorant-asset-management/), [Foresite Capital](https://onco.cc/companies/foresite-capital/), [Logos Capital](https://onco.cc/companies/logos-capital/), [Omega Funds](https://onco.cc/companies/omega-funds/), [Vida Ventures](https://onco.cc/companies/vida-ventures/)

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