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858 Therapeutics is developing a tablet that blocks PARG, a protein cancer cells use to repair damaged DNA, aiming at tumours that are already weak at DNA repair, such as some ovarian and breast cancers with BRCA changes. It is in its first human trial.
858 Therapeutics is a San Diego biotechnology company (3115 Merryfield Row) developing small molecules against DNA damage response targets in cancer. Its lead programme ETX-19477 is an oral, selective inhibitor of poly(ADP-ribose) glycohydrolase (PARG), designed to exploit replication stress and defects in replication fork protection; it is in an open-label phase 1/2 study in advanced solid tumours (NCT06395519), with initial data presented at ASCO 2026, and received FDA Fast Track designations in January 2026 for BRCA-mutated platinum-resistant ovarian cancer and in August 2026 for BRCA-mutated HR-positive, HER2-negative metastatic breast cancer. The company exited stealth in September 2021 with a USD 60 million Series A led by Versant Ventures with NEA, Cormorant Asset Management and Logos Capital, and acquired Gotham Therapeutics at launch; in September 2024 it raised a USD 50 million Series B led by Avidity Partners with Insight Partners, Mirae Asset Capital and Alexandria Venture Investments. Its first registered cancer trial, NCT06395519, was posted on ClinicalTrials.gov in May 2024.
| Round | Year | Amount | Source |
|---|---|---|---|
| Series B · Led by Avidity Partners with Insight Partners, Mirae Asset Capital and Alexandria Venture Investments, and existing investors Versant Ventures, NEA and Logos Capital. | 2024 | $50M | 8five8tx.com |
| Series A · Led by Versant Ventures with NEA, Cormorant Asset Management and Logos Capital. | 2021 | $60M | 8five8tx.com |
Amounts only where the cited source states them. Rounds without a public source are not listed.
Shares Versant Ventures, Cormorant Asset Management, Alexandria Venture Investments.
Shares Synthetic lethality approaches, Ovarian cancer, Breast cancer (all types).
Shares Cormorant Asset Management, Alexandria Venture Investments, Synthetic lethality approaches.
Shares Logos Capital, Cormorant Asset Management.
Shares Synthetic lethality approaches, Ovarian cancer, Breast cancer (all types).
Shares Logos Capital, Cormorant Asset Management, Synthetic lethality approaches.
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