Ratio Therapeutics Closes $70M Series C for Radiopharma

Ratio Therapeutics has closed a $70M Series C financing, bringing company-reported total capital raised to more than $240M. The Boston biotechnology company plans to use the capital to advance its lead cancer program, move another radioligand candidate toward the clinic, broaden its oncology pipeline, and expand manufacturing capacity.

The round included returning investors Duquesne Family Office and Bristol Myers Squibb, plus new investors Catalio Capital Management, Eli Lilly and Company, and Wasatch Group. Ratio did not identify a lead investor or disclose a valuation, which keeps the useful part of the announcement centered on execution rather than financing theater.

This matters because radiopharmaceutical development asks a company to solve several difficult problems at once. A promising molecule still needs clinical evidence, reliable isotope access, specialized manufacturing, and a distribution model that respects the short working life of radioactive materials.

What Happened in Ratio Therapeutics' Series C

Ratio Therapeutics announced the financing on July 31, 2026. The $70M Series C follows a publicly announced financing history that includes more than $20M in seed capital at launch, a Series A extension that brought total financing above $40M in February 2023, and a $50M Series B that brought the total above $90M in January 2024.

The company now reports more than $240M in total capital raised. Its public round announcements do not fully reconcile that figure, so the responsible reading is to use the company-reported total without inventing undisclosed rounds, amounts, or financing structures.

The proceeds have 5 stated jobs: advance the ATLAS clinical study, move a next-generation radioligand therapy candidate into the clinic, expand discovery into additional oncology targets, strengthen Ratio's proprietary technology, and scale manufacturing. That is less a spending list than an operating blueprint for moving a radiopharmaceutical platform from early clinical development toward a more mature pipeline.

The Clinical Test Behind the Funding

Ratio's lead therapeutic candidate, [Ac-225]RTX-2358, is a fibroblast activation protein, or FAP, targeted radiopharmaceutical for cancer. The candidate is being evaluated in the Phase 1/2 ATLAS trial for patients with relapsed or refractory soft tissue sarcoma, with ClinicalTrials.gov listing the study as recruiting and sponsored by Ratio Therapeutics.

ATLAS is designed to evaluate safety, tolerability, dosimetry, biodistribution, pharmacokinetics, and anti-tumor activity. Ratio completed dosing of the first cohort in December 2025, but no trial results are posted on ClinicalTrials.gov, so the Series C should be viewed as capital for clinical execution rather than evidence of efficacy.

That distinction is important. Private financing can validate investor conviction, strategic fit, and a company's ability to fund the next stage, but only clinical data can answer whether an investigational therapy is safe and useful for patients.

How Ratio Is Engineering Radiopharmaceuticals

Ratio was founded in 2021 by Jack Hoppin and John Babich and launched from stealth in June 2022. Hoppin serves as Chairman and CEO, while Babich is Director, President and Chief Scientific Officer; the current leadership team also includes CTO Matthias Friebe and CMO Colin Hayward.

The company's technology strategy centers on Trillium and Macropa. Trillium is designed to tune pharmacokinetic properties such as plasma clearance and target affinity, while Macropa provides chelation technology for working with therapeutic and imaging radioisotopes.

In plain English, Ratio is trying to improve the amount of radiation that reaches and remains in a tumor while limiting exposure to healthy tissue. The broader pipeline includes a next-generation GRPR program, additional mono- and bispecific radioligand therapies, and imaging assets, giving the company more than a single clinical shot on goal without removing the risk attached to each program.

Ratio also has partnered programs with Novartis, Lantheus, and Merck. Its SSTR2 radioligand therapy collaboration with Novartis offers external validation of the platform, but the Series C remains primarily a test of Ratio's ability to turn its internal technology into repeatable clinical progress.

Why Manufacturing Is Part of the Drug Story

Radiopharmaceutical manufacturing is not a back-office detail. The material has to be produced to strict standards, delivered on time, and supported by a dependable supply of isotopes such as actinium-225.

Ratio has been building a hybrid approach that combines internal infrastructure with external manufacturing and isotope partners. In May 2026, the company expanded its collaboration with PharmaLogic to increase clinical-supply capacity for [Ac-225]RTX-2358 and support later-stage development planning.

That work explains why manufacturing appears beside clinical development in the Series C announcement. If ATLAS advances and the pipeline widens, Ratio will need capacity, redundancy, and isotope access to grow with the science rather than chase it after the fact.

The investor group adds another layer to the signal. Participation from Bristol Myers Squibb and Eli Lilly shows strategic pharmaceutical interest in a company working across clinical assets, platform technology, and manufacturing, but it does not imply a future partnership, acquisition, or successful trial outcome.

What the Series C Signals for Radiopharma

The Series C reflects a broader shift in radiopharmaceutical investing from pure platform enthusiasm toward execution. Ratio is being financed to produce clinical data, prepare another candidate for human testing, expand discovery, and build the operational systems that later-stage development requires.

That combination creates a harder standard than a conventional software growth round. Ratio must prove that its engineered compounds can help patients while also showing that specialized production and supply can scale around them.

For operators and investors, the takeaway is direct: radiopharma value is created where biology, chemistry, clinical development, isotope supply, and manufacturing meet. Ratio Therapeutics now has $70M more to make those pieces work as one system, and the next meaningful evidence will come from clinical progress and execution rather than another headline.