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Ratio Therapeutics
Ratio Therapeutics, of Boston, designs small molecules that carry a radioactive isotope to fibroblast activation protein, a protein on the supporting tissue of sarcomas and other solid tumours, so radiation is delivered from inside the body. Its lead, an actinium-225 radioligand, is in the ATLAS phase 1/2 trial in advanced sarcomas.
Overview
Ratio Therapeutics is a clinical-stage Boston radiopharmaceutical company whose Trillium targeting scaffold combines pharmacokinetic modulation with chelation chemistry to create small-molecule radioligands that can be paired with imaging or therapeutic isotopes (theranostics). The lead programme [Ac-225]RTX-2358 is a fibroblast activation protein (FAP)-targeted actinium-225 therapeutic in the ATLAS phase 1/2 trial in advanced sarcomas; the pipeline also includes a next-generation GRPR programme and additional mono- and bispecific radioligands, with a fifth IND filing in preparation. In July 2026 Ratio closed a USD 70 million Series C with Duquesne Family Office, Bristol Myers Squibb, Catalio Capital, Eli Lilly and Wasatch Group, taking total capital raised above USD 240 million. It has manufacturing collaborations with PharmaLogic, an actinium-225 supply agreement with PanTera (June 2026) and, in September 2026, a research collaboration and licence agreement with RayzeBio.
Headquarters
Boston, MA, US
Funding
All startupsGrowth stage
Investors not recorded; see the round sources.
Rounds on record
| Round | Year | Amount | Source |
|---|---|---|---|
| Series C · Brings total capital raised to over USD 240 million | 2026 | $70M | ratiotx.com |
Amounts only where the cited source states them. Rounds without a public source are not listed.
Stage
Growth stage
Website
Notes
top- Earlier rounds (Series A and B) not fetched and omitted.
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