858 Therapeutics Announces $50 Million Series B Financing

-- Round led by Avidity Partners with participation from Insight Capital, Mirae Asset Capital, and Alexandria Venture Investments, alongside participation from existing investors --

-- Investment will support ongoing clinical development of PARG inhibitor ETX-19477 and further advancement of pipeline --

858 Therapeutics today announced it raised $50 million in a Series B financing led by Avidity Partners with participation from Insight Partners, Mirae Asset Capital, and Alexandria Venture Investments, as well as existing investors Versant Ventures, NEA, and Logos Capital. As part of the financing, Monal Mehta, Ph.D., Managing Director at Avidity Partners, will join the company’s Board of Directors.

“We are pleased to have strong backing from an elite group of life science investors,” said Jeffrey Stafford, Ph.D., CEO of 858 Therapeutics. “The Series B financing is a testament to the 858 team and the progress we’ve made across our portfolio, including the advancement of our PARG inhibitor ETX-19477 into the clinic.”

858 Therapeutics plans to use the proceeds to advance its pipeline of small molecule therapeutics. The company’s lead asset, ETX-19477, is a potent and selective inhibitor of the DNA repair protein PARG and is currently being evaluated in patients with advanced solid tumors. Data from the ongoing clinical trial will provide insights for advancing ETX-19477 through clinical development and for understanding the patients who may benefit most from PARG inhibition.

The Phase 1 trial for ETX-19477 is a multi-center, open-label, dose escalation and expansion study designed to evaluate safety, tolerability, dose, pharmacokinetics, pharmacodynamics, and preliminary efficacy. The dose escalation portion of the study is preferentially enrolling patients with specific tumor types and genetic alterations that are likely to confer sensitivity to PARG inhibition. Once a recommended dose for expansion is identified, the company will initiate tumor- and biomarker-focused Phase 2 cohorts. For more information, visit www.clinicaltrials.gov (NCT06395519).

“858 Therapeutics has a seasoned management team with a track record of drugging challenging targets,” said Dr. Mehta. “We are excited to partner with the company to help address unmet needs across a variety of disease types in an effort to bring transformative medicines to patients.”

About ETX-19477

The company’s lead asset, ETX-19477, is a novel and potent small molecule inhibitor of PARG, a glycohydrolase that plays a pivotal role in the regulation of DNA repair mechanisms. Pharmacological inhibition of PARG results in hyperPARylation, which leads to the death of cancer cells undergoing replication stress. In multiple animal models, ETX-19477 shows potent tumor growth inhibition, which is associated with specific genetic biomarkers. 858 Therapeutics is evaluating ETX-19477 in a Phase 1 study in patients with advanced solid tumors at multiple sites in the U.S. For more information on the Phase 1 study, please visit: https://clinicaltrials.gov/study/NCT06395519.

About 858 Therapeutics

858 Therapeutics is a biotechnology and drug discovery company developing a portfolio of small molecule therapeutics directed against novel oncology and immunology targets. Its lead programs focus on important nodes in cancer biology, including DNA damage repair, innate immunity, and RNA epigenetics, and expands on decades of drug discovery experience by the founders. 858 is headquartered in the biotech hub of San Diego, CA. For more information, please visit www.8five8tx.com.

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