ASP Isotopes' Alpa Theranostics to Advance Nanobody-Powered Radiopharmaceuticals into Clinical Trials Within 12 Months
Key Insights
ASP Isotopes' wholly owned subsidiary Alpa Theranostics (search) expects to advance its first nanobody-based targeted radionuclide therapeutic candidates into human clinical trials within the next 12 months, with initial results anticipated during the first half of 2027.
The preclinical pipeline uses Terbium-161 (search) and Actinium-225 (search) as radionuclides and targets cancers including gliomas, colorectal cancer (search), triple-negative and HER2-positive breast cancer (search), and osteosarcoma (search).
Alpa Theranostics (search)' approach leverages nanobodies' small size for superior solid tumor penetration and their ability to recognize cryptic epitopes inaccessible to traditional monoclonal antibodies.
ASP Isotopes Inc. (search) (NASDAQ: ASPI) has announced that its wholly owned biotechnology subsidiary, Alpa Theranostics (search), is poised to enter human clinical trials with its first nanobody-powered targeted radionuclide therapeutic candidates within the next 12 months, with initial results expected during the first half of 2027. The disclosure came in a shareholder letter from Executive Chairman and CEO Paul Mann, released ahead of the company's second-quarter 2026 financial results.
The clinical advancement marks a significant milestone for a program that has been incubating within ASP Isotopes for the past 24 months. According to the company, preclinical studies have already demonstrated efficacy using novel nanobodies conjugated to radioisotopes produced by the company's PET Labs division.
Nanobody Platform and Therapeutic Rationale
Alpa Theranostics (search)' pipeline is built on nanobody technology, which the company believes offers distinct advantages over traditional monoclonal antibody (mAb)-based radiopharmaceutical delivery. "In our opinion, the short biological half-life of Nanobodies makes them the best tracer for carrying short-lived radionuclides and owing to their small size, Nanobodies also have a higher solid tumor penetration than monoclonal antibodies (mAb), which have traditionally been used to deliver radionuclides," the company stated in its shareholder letter.
The company further noted that, unlike mAbs, fragments, and peptides, nanobodies "usually recognize hidden, cryptic and inaccessible epitopes in the antigen" and do not compete with regular antibodies for antigen binding. Additionally, despite being much larger than the blood-brain barrier free diffusion limit of 400 Da, nanobodies have been shown to transmigrate across the blood-brain barrier—a characteristic the company describes as important for treating brain tumors and brain metastasis.
Radionuclide Selection: Terbium-161 (search) and Actinium-225 (search)
The therapeutic candidates will employ two radionuclides: Terbium-161 (search) and Actinium-225 (search). Terbium-161 is highlighted as a particularly promising candidate for clinical translation because it emits short-ranged conversion and Auger electrons in addition to β⁻-particles and γ-radiation. This multi-modal emission profile, the company explained, "may effectively eliminate microscopic metastases that are not even visible on a PET image but are responsible for relapse and metastatic spread."
Target Indications and Unmet Need
Alpa Theranostics (search) is developing multiple nanobodies targeting a range of tumor types. The research programs encompass gliomas, colorectal cancer (search), and both triple-negative and HER2-positive breast cancer (search). Notably, the company is also pursuing therapeutic candidates for cancers affecting younger populations where no approved therapies currently exist, specifically triple-negative breast cancer (search) and osteosarcoma (search).
"The successful development of treatments for these diseases would represent a significant scientific breakthrough, improving the survival outcomes for thousands of young people annually," the company stated.
Leadership and Scientific Partnerships
The research efforts at Alpa Theranostics (search) are led by Martin Magwaza, a biotech entrepreneur with a focus on medical biotechnology and cancer theranostics, in partnership with the South African Nuclear Medicine Research Infrastructure (NuMeRI) under the leadership of Professor Mike Sathekge.
Magwaza brings experience from a career spanning several multinational pharmaceutical corporations before founding multiple biotech ventures. Professor Sathekge serves as Professor and Head of the Nuclear Medicine Department at the University of Pretoria and Steve Biko Academic Hospital, and is described as "a clinical innovator and researcher with a significant track record in developing Theranostics based on Lutetium 177, Actinium 225, Rhenium 188 (and many others)."
Broader Context: PET Labs Growth and Radiopharmaceutical Supply
The clinical development program at Alpa Theranostics (search) is supported by ASP Isotopes' PET Labs division, which demonstrated organic revenue growth of over 50% during the first half of 2026 compared to the same period in 2025. The company forecasts PET Labs will deliver full-year 2026 revenues of approximately $14 million, up from $6 million in 2025. Globally, the company now operates four radiopharmacies that delivered tens of thousands of radiopharmaceutical doses during the first half of 2026.
"We are in the early innings of a new therapeutic product cycle whereby we harness radioisotopes to cure fatal diseases, such as cancer," the company noted, adding that while only a handful of radiopharmaceutical drugs are currently approved, hundreds are in clinical trials with many showing great promise.