The Fusion Pipeline


We are leveraging our proprietary Targeted Alpha Therapies platform and Fast-ClearTM linker technology to advance a pipeline of alpha-based therapeutic programs to treat various cancers.

[225Ac]-FPI-1434 is our lead clinical candidate  engineered to deliver alpha particles to cancer cells. The new drug was created by combining an antibody for an established cancer biomarker, IGF-1R, with our Fast-Clear™ linker technology to create a Targeted Alpha Therapy that has the potential to be used across multiple tumor types. IGF-1R is a well-established tumor target found on numerous types of cancer cells. We rely on IGF-1R simply as a way to identify and target the tumor to deliver our alpha emitting payload.

The first human trial of [225Ac]-FPI-1434 is actively recruiting. For more information or questions about trial eligibility, please contact Fusion.

Contact Us

Trial Overview

FPI-1434 Monotherapy

Fusion is currently conducting a Phase 1, non-randomized, multi-center, open-label clinical trial in patients with solid tumors expressing IGF-1R to investigate the safety, tolerability and pharmacokinetics of FPI-1434 as well as to establish the maximum tolerated dose and potentially the recommended Phase 2 dose. FPI-1434 is a targeted alpha radioimmunoconjugate that consists of a humanized monoclonal antibody targeting the insulin-like growth factor-1 receptor 1 (IGF-1R), our Fast-Clear™ linker technology, a bifunctional chelate, and actinium-225 (225Ac).

As part of the screening process for the trial, all patients are administered a single injection of 185 megabecquerel, or MBq, of FPI-1547, the imaging analogue of FPI-1434 which contains 111In instead of 225Ac, and SPECT and planar imaging is used to evaluate tumor uptake of the imaging isotope. In accordance with the trial protocol, patients that meet predefined uptake and dosimetry criteria for FPI-1547 are advanced into the trial and administered a single dose of FPI-1434 within approximately fourteen days of receiving the imaging analogue.

FPI-1434 Combination


Based on the mechanisms of action of FPI-1434 and data from preclinical studies, Fusion is also evaluating the combination potential of FPI-1434 with checkpoint inhibitors as well as DNA damage repair inhibitors (DDRi’s), which include poly (ADP-ribose) polymerase, or PARP, inhibitors.

Fusion is progressing an earlier-stage product candidate, FPI-1966, into clinical development. FPI-1966 is designed to target and deliver 225Ac to tumor sites expressing FGFR3, a protein that is overexpressed in head and neck and bladder cancers. FPI-1966 utilizes our Fast-Clear linker to connect a human monoclonal antibody that targets FGFR3 with 225Ac. Fusion plans to submit an investigational new drug application to the FDA.