Dr. Clackson brings three decades of experience building oncology companies, including three drug approvals. Dr. Clackson was most recently Chief Executive Officer of Theseus Pharmaceuticals, a clinical stage biotechnology company focused on development of targeted oncology therapies, where he led the Company through its initial public offering and early clinical development for its lead product candidate for the treatment of GIST. Prior to Theseus, Dr. Clackson served as President at Xilio Therapeutics, a privately held oncology company developing tumor-selective immunotherapies, where he led the development of the company's technology and product strategy.

From 1994 to 2018, Dr. Clackson was with ARIAD Pharmaceuticals, where he was most recently President of Research & Development and Chief Scientific Officer. He played a key role in the company's evolution from early research to a global commercial oncology company, and its subsequent acquisition by Takeda. He led the multi-disciplinary R&D team that internally discovered and developed five clinical-stage product candidates, including ICLUSIG® (ponatinib), approved for patients with treatment-resistant Ph+ leukemias; ALUNBRIG® (brigatinib), approved for ALK+ non-small cell lung cancer (NSCLC); and EXKIVITY™, approved for Exon20 insertion+ NSCLC. Prior to ARIAD, Dr. Clackson was a postdoctoral research fellow at Genentech.

He received his Ph.D. in Biology from the University of Cambridge, and his B.A. in Biochemistry from the University of Oxford. Dr. Clackson serves as a Director on the Board of Elevation Oncology and previously served as a Director on the Boards of Forma Therapeutics (acquired by Novo Nordisk), Spring Bank Pharmaceuticals, and the Massachusetts Biotechnology Council (MassBio).