On September 14, 2026 Perspective Therapeutics, Inc. ("Perspective," the "Company," "we," "us," and "our") (NYSE AMERICAN: CATX), a radiopharmaceutical development company pioneering advanced treatments for cancers throughout the body, reported a clinical trial collaboration agreement with Merck (NYSE: MRK), known as MSD outside of the United States and Canada.
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The agreement supports the evaluation of Perspective’s targeted alpha-particle therapy [212Pb]PSV359 in combination with Keytruda (pembrolizumab), Merck’s anti-PD-1 therapy. This combination will be evaluated under an amendment to the Company’s ongoing Phase 1/2a study of [212Pb]PSV359 in patients with certain types of non-small cell lung cancer and colorectal cancer that express fibroblast activation protein alpha (FAP-α) (clinicaltrials.gov identifier NCT06710756). The study has completed enrollment in the first three monotherapy dose cohorts.
Perspective is sponsoring the study, and Merck is providing pembrolizumab at no cost.
"FAP-α is associated with the majority of solid tumors and with a tumor microenvironment historically characterized by poor drug penetration and immune suppression or exclusion," said Markus Puhlmann, Perspective’s Chief Medical Officer. "By combining targeted radiopharmaceutical treatment with a well-established immune checkpoint inhibitor, we aim to evaluate whether this approach can reshape the tumor environment and potentially improve treatment outcomes for patients with advanced FAP-α-positive solid tumors."
About FAP-α
FAP-α is a protein abundantly expressed on the surface of cancer-associated fibroblasts (CAFs) in the stroma, a part of the tumor microenvironment (TME) in the majority of epithelial cancers. In addition to expression on CAFs, FAP-α is expressed on certain cancer cells themselves, including sarcomas and mesotheliomas.1,2,3,4 Higher FAP-α expression has been found to be associated with poor prognosis in a number of solid tumors such as non-small cell lung cancer, colorectal cancer, pancreatic cancer, stomach cancer, mesothelioma, head and neck cancer, esophageal cancer, and ovarian cancer.5,6,7,8,9,10 Expression of FAP-α in healthy tissues is usually low.3,4
About PSV359
PSV359 was designed to target and deliver 212Pb to tumor sites expressing FAP-α, associated with multiple highly prevalent solid tumors, with patients in need of additional treatment options. The targeting moiety may also be radiolabeled with 203Pb or 68Ga (known as PSV377) to detect FAP-α expression in individual patients. Preclinical imaging and therapy as well as human imaging results suggest Perspective’s proprietary targeting ligand has improved levels of target engagement and uptake in tumors, as well as reduced retention in healthy tissues, which may result in a desirable therapeutic index.
Perspective is conducting a multi-center, open-label, dose-finding and dose-expansion study (clinicaltrials.gov identifier NCT06710756) of [212Pb]PSV359 in patients with advanced solid tumors that express FAP-α as determined by imaging with [203Pb]PSV359. The primary objective of the dose finding phase of the study is to assess the safety and tolerability of various doses of [212Pb]PSV359 in order to determine the recommended Phase 2 dose to be used in the expansion phase of the study, where anti-tumor activities may be an additional primary outcome measure.
(Press release, Perspective Therapeutics, SEP 14, 2026, View Source [SID1234670852])