July 25, 2023 — Ratio Therapeutics Inc. (Ratio), a pharmaceutical company that employs a suite of innovative technologies to develop best-in-class radiopharmaceuticals for the monitoring and treatment of cancers today announced, in partnership with Lantheus, a company committed to improving patient outcomes through diagnostics, radiotherapeutics and artificial intelligence solutions that enable clinicians to Find, Fight and Follow disease, and in collaboration with PharmaLogic, a world-class contract development and manufacturing organization (CDMO) specializing in radiopharmaceuticals, that it has initiated dosing in a Phase I study evaluating the pharmacokinetics, biodistribution and radiation dosimetry of a novel fibroblast activation protein-alpha (FAP)-targeted radiopharmaceutical, Copper-64[Cu-64]-labeled RTX-1363S, for PET imaging in adult healthy volunteers.
FAP is a membrane-bound dipeptidyl peptidase that is specifically expressed in activated fibroblasts. The ubiquitous expression of FAP in cancer-associated fibroblasts across nearly all epithelial-derived cancers paired with the low abundance in normal tissues, makes it a unique target to exploit for tumor imaging for a wide variety of cancers such as breast, pancreatic, lung and stomach cancer.
"Today marks a major milestone for Ratio as we take a crucial step forward in the development of our FAP-targeted imaging agent," said Dr. John Babich, Ratio's President and Chief Scientific Officer. "Cancer-associated fibroblasts selectively expressing FAP comprise up to 90% of the tumor mass in highly desmoplastic cancers, including pancreatic, breast, and colorectal. RTX-1363S has the potential to transform the way we detect and monitor various epithelial-derived cancers."
"We are delighted by our collaboration with Ratio Therapeutics in advancing the clinical development of RTX-1363S as a FAP-targeted diagnostic to the clinic," stated Etienne Montagut, Lantheus' Chief Business Officer. "By leveraging our expertise in radiopharmaceuticals, we aim to contribute to the early detection and accurate monitoring of epithelial-derived cancers. This partnership exemplifies our commitment to Find, Fight and Follow disease by delivering innovative solutions to improve cancer care, ultimately leading to better patient outcomes."
"PharmaLogic is honored to contribute its manufacturing expertise in radiopharmaceuticals to this clinical trial, advancing diagnostics for epithelial-derived cancers," said Scott Holbrook, Chief Strategy Officer, General Manager PET & Precision Medicine at PharmaLogic, the manufacturing partner involved in the trial. "This further strengthens our commitment to production and development of novel radiopharmaceuticals to advance cancer treatments and quality of life for cancer patients."
Ratio's clinical candidate, RTX-1363S, is a highly selective, high affinity FAP inhibitor that will be radiolabeled with copper-64 (Cu-64), a positron-emitting radionuclide with a half-life of 12.7 hr. In the first study, biodistribution and pharmacokinetics will be evaluated following a single injection of [Cu-64]-labeled RTX-1363S in a small subset of adult healthy volunteers. Study subjects will be screened within 28 days of administration and up to 6 eligible subjects will be enrolled, including 3 female and 3 male subjects. Results from the study will inform further development of [Cu-64]-labeled RTX-1363S as a FAP-targeted tumor imaging agent.
About Trillium and Macropa
Ratio Therapeutics' fully integrated proprietary R&D platforms, Trillium and Macropa, harness the tumor-killing power of alpha particles. The tunable nature of the platforms enables the efficient and timely development of numerous novel radiopharmaceuticals for a broad range of high unmet need in solid tumors, while addressing the trifecta of typical challenges seen with most radiopharmaceuticals: delivery, safety and efficacy. Trillium is a pharmacokinetic modulation platform that can be altered to bind to any antigen-specific target, while Macropa is a best-in-class Actinium-225 chelator. The combination of these platforms enables the tumor-killing power of alpha particles with potential for first- and best-in-class radiopharmaceuticals.
For more information: www.ratiotx.com
November 18, 2025 
