Alpha-9 Oncology has begun a clinical program that could eventually tell the radiopharmaceutical industry something more interesting than whether another experimental drug works.
The company announced Tuesday that it has dosed the first patient with 225Ac-A9-0642 in a Phase 1 study evaluating two GRPR-targeted radiotherapeutics: the actinium-225 compound and 177Lu-A9-0631, a separate lutetium-177 therapy. Alpha-9 is also using its 68Ga-A9-6217 imaging agent to identify patients with GRPR-positive tumors for enrollment. The study is evaluating patients with advanced or metastatic solid tumors, including breast, prostate and colorectal cancers, with initial data expected in late 2027.
On its face, this is another first-patient-dosed announcement from a radiopharma company with an early-stage pipeline. The more interesting part is that Alpha-9 is advancing alpha- and beta-emitting approaches against the same biological target at the same time.
Gastrin-releasing peptide receptor, or GRPR, has attracted radiopharmaceutical interest be
cause it is expressed across several solid tumors while offering a potentially favorable expression profile in normal organs. Alpha-9's Phase 1 study is expected to enroll approximately 115 patients and includes patients with prostate cancer, HR-positive/HER2-negative breast cancer, colorectal cancer and other GRPR-positive solid tumors.
That makes the program worth watching because it could push radiopharmaceutical therapy deeper into tumor types beyond the prostate and neuroendocrine cancers that have driven much of the industry's commercial development. But Alpha-9's isotope strategy makes it more unusual.
The company isn't simply attaching two different isotopes to an otherwise identical drug and calling it a comparison. Alpha-9's development platform is designed to optimize the binder, linker, chelator and radioisotope as components of a fit-for-purpose molecule. That means 225Ac-A9-0642 and 177Lu-A9-0631 are distinct compounds built around the same target rather than interchangeable versions of a single drug.
"Running both 225Ac and 177Lu programs in parallel allows us to efficiently generate data and validate our modular optimization platform," CEO Paul Blanchfield said in announcing the first patient dosing.
Actinium-225 has become one of the most sought-after isotopes in radiopharmaceutical development. Its alpha particles deliver high-energy radiation across a very short path length, creating the potential to inflict severe damage on targeted cancer cells while limiting exposure beyond them. That promise has driven substantial investment into Ac-225 drug development, isotope production and manufacturing infrastructure.
Lutetium-177, however, already has something actinium-225 does not: a mature commercial ecosystem. Lu-177 therapies have demonstrated that radioligand treatment can become a major pharmaceutical business, while isotope production, manufacturing, logistics and treatment-center experience have expanded around commercial products such as Pluvicto and Lutathera.
That makes the alpha-versus-beta question more complicated than simply asking which isotope delivers more powerful radiation. Developers ultimately have to determine whether the clinical benefit of an alpha-emitting therapy is large enough to outweigh differences in isotope availability, manufacturing, handling, dosimetry, supply-chain maturity and cost.
For some tumors and targets, that answer may eventually be obvious. An Ac-225 therapy that produces substantially better responses, longer durability or activity after resistance to Lu-177 could justify considerable additional complexity. In other settings, a beta emitter with strong efficacy and an established supply chain could remain the more commercially practical choice. The industry doesn't yet have enough clinical evidence to know where that line falls.
Alpha-9's study will not provide a clean head-to-head comparison of Ac-225 and Lu-177. The molecules are independently optimized, and Phase 1 studies are designed primarily to establish safety, tolerability, dosimetry and dosing rather than determine which isotope wins.
Still, developing both programs around GRPR creates an unusually useful opportunity to observe how alpha- and beta-emitting strategies behave against the same target and within overlapping tumor populations. Alpha-9 says imaging with 68Ga-A9-6217 demonstrated tumor targeting with limited healthy-organ uptake, while early compassionate-use experience with 177Lu-A9-0631 showed the therapy was well tolerated in GRPR-positive patients. Those observations remain preliminary, but the clinical program can now begin generating more systematic evidence.
Alpha-9 also already has another actinium program in the clinic. In December 2025, the company began Phase 1 dosing of A9-3408, an Ac-225 radiotherapeutic targeting MC1R in melanoma, giving the company clinical exposure to targeted alpha therapy beyond the new GRPR program.
The supply side has not been ignored either. Alpha-9 entered an agreement with ITM in April 2025 for therapeutic Ac-225 supply, an increasingly important consideration as developers try to move alpha programs from promising molecules into clinical and eventually commercial products.
Radiopharma's first commercial wave was largely organized around whether a targeting molecule could successfully deliver radiation to a tumor. The next generation of development is becoming considerably more sophisticated. Companies can increasingly choose among targeting molecules, linkers, chelators and isotopes, and those choices affect much more than efficacy. They influence dosimetry, toxicity, manufacturing, isotope sourcing, logistics, treatment-center requirements and ultimately the economics of the finished product.
That means the most powerful isotope will not automatically produce the most valuable drug. The winner will be the combination that delivers enough clinical advantage while still being manufacturable, available and commercially scalable.
Alpha-9 is now developing two different answers to that problem against GRPR. It will be years before the industry knows whether either becomes a successful drug, but the program could begin answering a question that will matter across dozens of radiopharmaceutical pipelines: as actinium-225 development accelerates, radiopharma will eventually have to demonstrate not simply that alpha therapy works, but where it works well enough to be worth choosing over the alternatives.
