225Ac-FPI-1434 (225Ac-FPX-01) is an alpha labeled antibody under development for the treatment of solid tumors. 225Ac-FPI-1434 is a targeted alpha radioimmuno-therapeutic agent that consists of FPI-1175, an insulin-like growth factor-1 receptor (IGF-1R)-targeting humanized monoclonal antibody, a bifunctional chelate (FPI-1397), and Actinium-225.

IGF-1R is up-regulated in numerous chemo-resistant cancers of unmet medical need. 225Ac-FPI-1434 has a potential to target and destroy most of the solid tumors including lung, colorectal, hepatic, gastric, prostate, breast, ovarian, endometrial and head neck. The primary target for 225Ac-FPI-1434 is not known yet.

225Ac-FPI-1434 has completed preclinical development under the name 225Ac-FPX-01. Biodistribution in animal with 124I-FPX-01 on different types of solid tumors has shown high selectivity. Additional preclinical studies comparing biodistribution of 111In, 177Lu and 225Ac analogues have been published in 2018.

Clinical Phase I/II study with 225Ac-FPI-1434 using the indium analogue for SPECT imaging and selection of patients, 111In-FPI-1547 was initiated in January 2019. No specific cancer was targeted and patient recruitment is based on advanced solid tumors refractory to all standard treatment, for which no standard treatment is available or the patient refuses standard therapy. This study is expected to be completed by January 2021.