Fusion Pharmaceuticals Inc., a clinical-stage oncology company focused on developing next-generation radiopharmaceuticals as precision medicines, today announced that the U.S. Food and Drug Administration (FDA) has cleared the Company's Investigational New Drug (IND) applications for [225Ac]-FPI-1966 (FPI-1966) and imaging agent [111In]-FPI-1967 (FPI-1967). FPI-1966 is a targeted alpha therapy (TAT) designed to use vofatamab, a human monoclonal antibody, to target and deliver actinium-225 to tumor sites expressing fibroblast growth factor 3 (FGFR3), a protein that is overexpressed in multiple tumor types, particularly head and neck and bladder cancers. FPI-1966 utilizes Fusion's Fast-Clear™ linker to connect vofatamab to actinium-225.

"Leveraging Fusion's platform and expertise developing targeted alpha therapies, we are excited to begin our second clinical program," said Chief Executive Officer John Valliant, Ph.D. "FGFR3 is an established and validated cancer target which is found in multiple tumor types with substantial unmet need, notably head and neck and bladder cancers. We have an opportunity to selectively deliver alpha particles to these tumors and use precision radiation therapy as a new treatment paradigm. While the currently approved pan-FGFR inhibitor for bladder cancer requires the presence of a specific mutation, our approach requires only over-expression of FGFR3. If successful, this could provide an opportunity to treat a larger population of patients."

Fusion plans to initiate a Phase 1, non-randomized, open-label clinical trial in patients with solid tumors expressing FGFR3 intended to investigate the safety, tolerability, and pharmacokinetics and to establish the recommended Phase 2 dose. The study employs a 3 + 3 dose-escalation design to evaluate multiple ascending doses of FPI-1966. The first cohort will comprise four sub-groups in which various doses of non-radiolabeled vofatamab ("cold antibody") will be evaluated to assess the impact of pre-dosing on tumor uptake. As part of the screening process, patients will be administered an imaging analogue of FPI-1966, FPI-1967, and only those who meet predefined tumor uptake and safety criteria will go on to receive FPI-1966.

About FPI-1966
[225Ac]-FPI-1966 is a targeted alpha therapy designed to target and deliver an alpha-emitting medical isotope, actinium-225, to cancer cells expressing FGFR3; a receptor that is overexpressed on several tumor types, including head and neck and bladder cancers. FPI-1966 utilizes Fusion's Fast-Clea linker to connect vofatamab, the human monoclonal antibody that targets FGFR3, with actinium-225. Vofatamab was previously evaluated as a therapeutic agent in a Phase 1b/2 trial and was reportedly well-tolerated.