Mosaic Taps Oncology Veteran to Lead Precision Cancer Therapy Push

CAMBRIDGE, England – April 01, 2026 – Mosaic Therapeutics, a clinical-stage company at the forefront of developing next-generation cancer treatments, has announced a significant addition to its leadership team with the appointment of Dr. Vince O'Neill as Head of Research and Development. The move signals a strategic acceleration for the Cambridge-based firm as it prepares to advance its innovative pipeline of combination therapies into the clinic.

Dr. O'Neill, a board-certified medical oncologist with over two decades of experience steering drugs from initial discovery to market approval, joins Mosaic at a critical juncture. The company, which is built on a foundation of world-class genomics research, is transitioning from a platform-focused entity into a clinical development powerhouse.

“We are delighted to welcome Vince to the Mosaic leadership team at this pivotal stage of the company’s evolution,” said Thomas Fuchs, CEO of Mosaic Therapeutics. “His deep expertise in targeted oncology drug development and diagnostics will be instrumental as we advance our pipeline to bring transformative therapies to patients in need.”

A Veteran Strategist for a New Era of Oncology

Dr. O'Neill’s track record is a roster of successes in both large pharmaceutical corporations and agile biotechnology startups. His leadership has been instrumental in the development and commercialization of some of modern oncology’s most impactful therapeutics, including Avastin, Venclexta, and Tarceva. His experience spans senior roles at industry giants like Genentech, Roche, Sanofi-Aventis, and GlaxoSmithKline (GSK).

Notably, during his tenure at GSK, Dr. O'Neill led the first investigational new drug (IND) application and clinical trial for the MEK inhibitor Mekinist®. This experience is particularly relevant to Mosaic's current pipeline, which includes an ERK1/2 inhibitor targeting the same frequently hyperactive cancer pathway. More recently, at BioXcel Therapeutics, he was a key figure in the development and FDA approval of IGALMI™ and led its immuno-oncology program.

Beyond his scientific and clinical acumen, Dr. O'Neill brings a proven ability to secure significant capital, having played a central role in executive teams that raised over $480 million through public and private financing rounds. This dual expertise in both R&D and strategic finance makes him a uniquely qualified leader to guide Mosaic through its next phase of growth, which will involve complex clinical trials and significant capital investment.

Synergistic Precision: The Core of Mosaic's Pipeline

Mosaic is pioneering an approach it calls “Synergistic Precision Oncology.” The strategy moves beyond single-drug treatments to identify and develop combinations of therapies that work together to deliver a more powerful and durable anti-cancer effect. This approach relies on an advanced computational and experimental platform to pinpoint these synergistic pairs and the specific biomarker-defined patient populations most likely to benefit.

The company’s pipeline was significantly advanced in April 2025 when it in-licensed two clinical-stage assets from Astex Pharmaceuticals. The deal, which gave Astex a 19% equity stake in Mosaic, is built around two promising small molecules:

• ASTX295: A potent MDM2 antagonist designed to reactivate the body's own p53 tumor suppressor protein. After completing a Phase 1 study in over 100 patients, the drug demonstrated a highly differentiated safety profile, notably avoiding the severe blood-related toxicities that have challenged other drugs in its class. This makes it an ideal backbone for combination therapies.

• ASTX029: An ERK1/2 inhibitor that targets a critical cancer growth pathway. Having completed a Phase 2 study, this asset provides a mature clinical candidate for Mosaic to combine with its other programs.

Mosaic’s lead program, designated MOS101, exemplifies its strategy. It combines ASTX295 with olaparib, an already-approved PARP inhibitor, to create a novel treatment for solid tumors with a specific genetic profile (BRCA2 mutant and TP53 wild-type). The company is finalizing plans for a Phase 1b/2a study of this combination, expected to commence in early 2027, with initial preclinical data set to be unveiled at the upcoming American Association for Cancer Research (AACR) Annual Meeting.

From World-Class Research to Clinical Reality

Mosaic’s scientific credibility is rooted in its origins, spinning out of 15 years of pioneering research at two of the world’s leading cancer research institutions: the Wellcome Sanger Institute (WSI) in the UK and the Netherlands Cancer Institute (NKI). This academic lineage provides the company with a unique competitive advantage, including ongoing access to cutting-edge expertise, data, and experimental models.

The company’s platform is directly based on the work of co-founder Dr. Mathew Garnett at the WSI, a renowned leader in cancer genomics and therapeutics. This foundation allows Mosaic to leverage genome-scale CRISPR screening and a vast library of patient-derived tumor organoids—miniature tumors grown in the lab from patient biopsies—to test and validate drug combinations with unprecedented precision and scale. This approach aims to de-risk clinical development by better predicting which patients will respond to which treatments.

This robust scientific engine is complemented by the clinical translation expertise brought by co-founder Professor Emile Voest of the NKI, ensuring that discoveries made in the lab are designed from the outset with a clear path to patient benefit. The company's $28 million Series A financing in 2023, led by Syncona and Cambridge Innovation Capital, has provided the fuel to translate this powerful research into tangible clinical programs.

With Dr. O'Neill now at the R&D helm, Mosaic is poised to integrate its powerful discovery engine with a seasoned clinical and regulatory strategy. His appointment is a clear statement of intent to not only discover the next generation of cancer therapies but to successfully navigate the complex path to approval and deliver them to patients with substantial unmet needs.

“I look forward to working closely with the Board and the team to advance our programs into the clinic and for the opportunity to develop novel combination therapies for cancer patients,” Dr. O'Neill commented, “utilising innovative biomarker strategies to maximise patient benefit.”