Astra and Fusion’s actinium bet is on

Seven weeks after AstraZeneca paid $2bn for Fusion Pharmaceuticals the target company’s lead asset, FPI-2265, has been confirmed as having started pivotal development. That might not seem surprising – except that the phase 2/3 trial in question actually started recruitment two weeks before Astra pulled the acquisition trigger, according to its just revealed clinicaltrials.gov entry. Indeed, at the time of the deal’s 20 March announcement FPI-2265 was said to be in phase 2, a reference to its Tatcist trial, later presented at AACR; phase 2/3 start, presumably a reference to actual patient dosing, was a second-quarter catalyst. Such minutiae aside, the phase 2/3 Alphabreak study, in PSMA-positive metastatic castration-resistant prostate cancer, is notable for enrolling patients who have already been treated with a PSMA-directed radioligand that uses lutetium-177. As such it will show whether patients who progress on Novartis’s Pluvicto or Lilly’s PNT2002 can be rescued by FPI-2265, which targets PSMA but uses the radioisotope actinium-225. For now the clinicaltrials.gov entry reveals only the phase 2 dose-finding part, in 60 patients, but Fusion earlier said the phase 3 portion would enrol 550 subjects and compare FPI-2265 against alternative androgen receptor-targeting therapy.

FPI-2265 in the clinic

Note: *AR-targeted therapy switch, meaning Zytiga, Xtandi or similar, whichever not previously received. Source: OncologyPipeline & AACR.