On November 17, 2025 Mosaic Therapeutics, Ltd, (‘Mosaic’, or ‘the Company’) an oncology therapeutics company building the category leader in Synergistic Precision Oncology, reported the appointment of Dr Stephen Shuttleworth as Chief Scientific Officer (CSO).

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Stephen has over 30 years’ experience as a pharmaceutical scientist, senior executive, entrepreneur and investor. He has been a Venture Partner at Samsara BioCapital, Palo Alto, US since 2019, where his responsibilities include R&D due diligence, new company creation and C-suite level company leadership. He also previously served as CSO, COO and Executive Director for over 10 years at Karus Therapeutics, where he was the founding scientist and R&D director of the company’s two small molecule oncology programmes, and raised blue-chip VC investment. Prior to Karus, Stephen held scientific leadership positions in the UK, US and Canadian biotech industries, notably at Piramed Pharma, Tularik, BioChem Pharma and CRUK. He began his industrial career in Cambridge, UK, at Chiroscience.

Stephen brings to Mosaic significant scientific expertise in small molecule cancer therapeutics R&D and medicinal chemistry. He has directed multiple small molecule therapeutics research programmes, primarily in cancer, and also in immunology and inflammation, metabolic disorders and infectious diseases. Of note, he led the design, research and preclinical development of three small molecule cancer therapeutics, all completing phase I clinical studies: Pictilisib (pan-class I PI3K), KA2237/CVL-237 (selective PI3K-b/d), and KA2507 (HDAC6). Stephen holds a PhD in Chemistry from the University of Liverpool, and is a Fellow of the Royal Society of Chemistry.

Stephen succeeds Dr Barry Davies, who is retiring as CSO at the end of November.

Stephen Shuttleworth, CSO, Mosaic Therapeutics, commented: "I am delighted to be joining Mosaic, and for the opportunity to work with this world-class team in its pursuit of cutting-edge, precision combination therapies for the treatment of patients with cancer. Mosaic’s Synergistic Precision approach to the discovery of biomarker-defined, targeted therapies is truly innovative and I look forward to working alongside the team to realise the full potential of the Company’s discovery platform and capabilities."

"We are excited to welcome Stephen to the Mosaic leadership team," said Thomas Fuchs, CEO, Mosaic Therapeutics. "He is a seasoned scientific leader and biotech investor, and I look forward to working with him as we bring our lead products into the clinic and work to build out our pipeline of precision oncology programmes. We also thank Barry for his leadership and significant contributions to the Mosaic team, in particular guiding our platform and pipeline development, and wish him all the best in his well-deserved retirement."

Mosaic is applying its advanced experimental and computational platform to identify oncology combinations that have synergistic activity in biomarker-defined patient populations. The Company’s pipeline of combination programmes is anchored by ASTX029, an ERK1/2 inhibitor, and ASTX295, an MDM2 antagonist, both in-licensed from Astex Pharmaceuticals in April 20251. Mosaic’s first clinical combination study is expected to commence in 2026.

Learn more about Mosaic’s molecularly-guided approach to oncology medicine: View Source

(Press release, Mosaic Therapeutics, NOV 17, 2025, View Source [SID1234660044])