A Cambridge- and Oslo-based biotech designing radioligands that stay on the tumor and leave the rest of the body alone.
Radiation has treated cancer for more than a century. The hard part was never the radiation - it was the aiming. Actithera, founded in 2021 by medicinal chemist Andreas Goutopoulos, is built around that single idea. The company designs radioligand therapies: drugs that clip a radioactive isotope onto a small, carefully engineered molecule, then send that molecule to hunt down a tumor and deliver its dose from the inside.
Most companies in the field compete on the isotope. Actithera competes on the molecule. Its proprietary platform uses covalent chemistry - the kind of bond that does not easily let go - so a radioligand can lodge inside a tumor and stay there while the surrounding healthy tissue clears the drug quickly. The pitch is deceptively simple: keep the radiation on the cancer, keep it off the kidneys, and make the dosing math work in the patient's favor.
It is a chemistry-first answer to a field that often reaches for physics first. "We engineer our radioconjugates for extended retention within tumors, making them suitable for longer-lived radionuclides," founder Andreas Goutopoulos has said - a sentence that captures the whole thesis in one line.
Harnessing the power of chemistry in the fight against cancer.
Actithera's discovery engine combines rational drug design with radiochemistry. Three ideas hold it together.
First-in-class covalent-binding strategies designed to optimize how long a radioligand stays inside the tumor while the body clears it elsewhere.
Chemistry approaches that enhance tumor retention and reduce off-target uptake - the difference between a treated tumor and an irradiated kidney.
One molecular design compatible with different radionuclides - alpha or beta emitters - so the platform can adapt as the science and supply evolve.
A simplified view of what a covalent, isotope-agnostic radioligand is designed to do inside the body.
Engineer a small molecule or modified peptide that recognizes a tumor-specific protein such as FAP.
Link a radioactive isotope to the molecule - the payload that delivers the therapeutic dose.
The radioligand travels to the tumor and binds covalently, lodging in place rather than washing out.
Unbound drug clears rapidly from healthy tissue, concentrating radiation where it is needed.
Radioligand therapy works, but two problems limit it. Some radioligands leave the tumor before they finish their job, wasting dose and exposing healthy organs. And a molecule designed around one isotope can be stranded when supply or half-life needs change. Actithera's covalent, isotope-agnostic design attacks both: better retention on the tumor, and freedom to swap the radioactive payload.
The near-term target is Fibroblast Activation Protein (FAP), which appears on the surface of many solid tumors and is largely absent from healthy adult tissue - a clean address for radiation to be delivered to.
The ultimate beneficiaries are cancer patients. In the near term, Actithera's stakeholders are oncologists, clinical-trial partners, and the pharmaceutical collaborators who could one day help develop or commercialize its therapies.
The company sits inside one of biotech's hottest arenas. Radioligand therapy has drawn multibillion-dollar acquisitions from Novartis, Bristol Myers Squibb, Eli Lilly and AstraZeneca. Actithera's wager is that in a crowded field, a differentiated chemistry platform - not just a novel isotope - is what earns a lasting place.
A founder with 25+ years in medicinal chemistry set the direction: design the molecule first, then choose the isotope.
Radioligands built to lodge in the tumor, not wash through it - potentially enabling longer-lived radionuclides and fewer cycles.
Designs that can carry alpha or beta emitters, keeping the pipeline adaptable as the radiopharma supply chain matures.
Actithera's founder and CEO spent more than 25 years in pharmaceutical and biotech chemistry, including a leadership role in medicinal chemistry at EMD Serono, the biopharma arm of Merck KGaA. Before founding the company, he served as an Entrepreneur-in-Residence at M Ventures - the venture arm that would go on to become Actithera's founding investor and Series A co-lead. In 2025, the company appointed Dr. Darshan Dalal as Chief Medical Officer to lead its move into the clinic. M Ventures' Hakan Goker chairs the board.
Actithera is a venture-backed, clinical-stage biotech. It funds research through equity financing and invests in a proprietary discovery platform plus a pipeline of radioligand assets. Value is created by advancing programs toward the clinic - with eventual paths through partnerships, licensing, or commercialization of approved therapies. The $75.5M Series A is earmarked to push the lead FAP asset into clinical development across multiple indications while continuing to build out the platform.
Medicinal chemist Andreas Goutopoulos starts the company to build chemistry-led radioligand therapies.
The covalent, isotope-agnostic discovery platform matures and a lead FAP asset moves forward.
Dr. Darshan Dalal is appointed CMO to lead clinical development.
An oversubscribed round co-led by M Ventures, Sofinnova, Hadean and 4BIO funds the push toward the clinic.
It develops radioligand therapies - drugs that link radioactive isotopes to targeting molecules to deliver radiation directly to tumors while sparing healthy tissue.
Andreas Goutopoulos, a medicinal chemist and former chemistry leader at EMD Serono, founded the company in 2021.
An oversubscribed $75.5 million Series A in July 2025, co-led by M Ventures, Hadean Ventures, Sofinnova Partners and 4BIO Capital.
A radioligand targeting Fibroblast Activation Protein (FAP), found across many solid tumors, being prepared for clinical trials in multiple indications.
Its chemistry-led, covalent, isotope-agnostic platform keeps radioligands in the tumor longer while clearing healthy tissue quickly, and works with either alpha or beta emitters.
Sources: Actithera company website; PR Newswire Series A release (July 2025); BioPharma Dive; Sofinnova Partners; Nature; Drug Discovery News. Figures such as employee count and funding reflect publicly reported information and may be approximate. Investor bar chart is illustrative of the syndicate composition, not disclosed allocations.