# 858 Therapeutics

> 858 Therapeutics is a clinical-stage biotechnology company in San Diego building small-molecule cancer drugs aimed at novel targets in DNA damage response, RNA modulation, and innate immunity. Its lead candidate, the oral PARG inhibitor ETX-19477, is in a first-in-human Phase 1/2 trial for advanced solid tumors and has won FDA Fast Track designation for BRCA-mutated, platinum-resistant ovarian cancer. Founded in 2019 by a serial team of San Diego drug developers, the company has raised $110 million across Series A and B financings.

- **Founded:** 2019
- **Headquarters:** San Diego, California, United States
- **Founders:** Jeffrey A. Stafford (Co-Founder & CEO), James Veal (Co-Founder & Chief Scientific Officer), Gretchen Bain (Co-Founder & VP of Biology)
- **Team size:** ~21 employees (11-50 range)
- **Products:** ETX-19477, RNA modulation programs, Innate immunity programs
- **Notable:** Raised $110 million total across Series A ($60M, 2021) and Series B ($50M, 2024)., Advanced lead PARG inhibitor ETX-19477 into a first-in-human Phase 1/2 clinical trial., Received FDA Fast Track designation for ETX-19477 in BRCA-mutated, platinum-resistant ovarian cancer.

## Products & services

- **ETX-19477** — An oral, potent, selective small-molecule inhibitor of PARG (poly(ADP-ribose) glycohydrolase), a DNA repair enzyme. Inhibition drives hyperPARylation and kills cancer cells undergoing replication stress. In a first-in-human Phase 1/2 trial for advanced solid tumors; FDA Fast Track designated for BRCA-mutated, platinum-resistant high-grade serous ovarian cancer.
- **RNA modulation programs** — Discovery-stage small molecules targeting RNA-modifying proteins implicated in cancer.
- **Innate immunity programs** — Small-molecule programs targeting innate immune pathways in oncology.

## Achievements

- Raised $110 million total across Series A ($60M, 2021) and Series B ($50M, 2024).
- Advanced lead PARG inhibitor ETX-19477 into a first-in-human Phase 1/2 clinical trial.
- Received FDA Fast Track designation for ETX-19477 in BRCA-mutated, platinum-resistant ovarian cancer.
- Reported a 57% objective response rate in early Phase 1/2 data presented at ASCO 2026.
- Founded by a team with a track record of building San Diego biotechs (Quanticel, Amira, PharmAkea, Jecure).

## Latest updates

- **2026-05** — Announced initial first-in-human Phase 1/2 data for ETX-19477 - including a 57% objective response rate in BRCA-mutated platinum-resistant ovarian cancer and a favorable safety profile - to be presented at the 2026 ASCO Annual Meeting.
- **2024-09** — Closed $50 million Series B financing led by Avidity Partners to advance ETX-19477 and the broader pipeline.
- **2024-04** — Presented preclinical data on ETX-19477 at the AACR 2024 Annual Meeting.
- **2021-09** — Launched publicly with $60 million Series A led by Versant Ventures.

## Links

- Website: https://8five8tx.com
- LinkedIn: https://www.linkedin.com/company/858-therapeutics

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Profile page: https://yespress.io/858-therapeutics
Published by YesPress — https://yespress.io
Last updated: 2026-06-16