On December 10, 2020 Fusion Pharmaceuticals Inc. (Nasdaq: FUSN), a clinical-stage oncology company focused on developing next-generation radiopharmaceuticals as precision medicines, reported that the first patient has been dosed in the multi-dose portion of the Phase 1 study evaluating [225Ac]-FPI-1434 (FPI-1434) in patients with advanced solid tumors (Press release, Fusion Pharmaceuticals, DEC 10, 2020, View Source [SID1234572635]). FPI-1434 is a radioimmunoconjugate that utilizes Fusion’s proprietary Fast-Clear linker to connect a humanized monoclonal antibody targeting the insulin-like growth factor 1 receptor (IGF-1R), with the alpha-emitting isotope actinium-225, creating a targeted alpha therapy (TAT).

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The Phase 1, multi-center, open-label clinical trial is designed to investigate the safety, tolerability and pharmacokinetics of FPI-1434 in patients with solid tumors expressing IGF-1R. The trial is also designed to establish the maximum tolerated dose for FPI-1434 and the recommended Phase 2 dose. As part of the precision medicine approach, prior to receiving the therapeutic injection of FPI-1434, patients are administered an indium-111 imaging analogue, [111In]-FPI-1547 (FPI-1547). The images collected are used to confirm the presence of tumor uptake and to ensure that estimated radiation doses to organs and tissues are below protocol-specified safety limits.

The multi-dose study follows completion of the single-dose portion of the Phase 1 study, which showed that FPI-1434 was generally well tolerated with no dose limiting toxicities or treatment-related serious adverse events reported to date. The multi-dose portion of the study is expected to enroll patients at sites in Canada, the United States and Australia. The initial patient cohort is being dosed with FPI-1434 at 75kBq/kg with repeat cycles every six weeks up to allowable limits.

"We are pleased with the results of the single-dose portion of our Phase 1 study of FPI-1434 which, following the evaluation of the Safety Review Committee, support initiating the multi-dosing portion of the study," said Chief Executive Officer John Valliant, Ph.D. "This is a critical next step in the FPI-1434 development program as data from the multi-dose portion of the study may provide important insights on potential anti-tumor activity. The multi-dosing trial will also inform the design of the Phase 2 program and assist in the selection of tumor indications to be pursued in planned expansion cohorts. This is especially important given the broad expression of IGF-1R across multiple tumor types."

For additional detail about the study, please visit View Source

About FPI-1434

FPI-1434 is a radioimmunoconjugate designed to target and deliver alpha emitting medical isotopes to cancer cells expressing IGF-1R, a receptor that is overexpressed on many tumor types. FPI-1434 utilizes Fusion’s Fast-Clear linker to connect a human monoclonal antibody that targets IGF-1R with actinium-225, a powerful alpha-emitting isotope with desirable half-life and decay chain properties.

Acknowledgement of US DOE and Actiunium-225 Supply

The actinium-225 used in this research was supplied by the United States Department of Energy Office of Science by the Isotope Program in the Office of Nuclear Physics.