Stockholm-based Affibody announced the Trial Review Committee recommended advancing the Phase 1 clinical study of ABY-271 following favorable safety and biodistribution data from initial patients
Affibody announced that the Trial Review Committee has recommended advancing the Phase 1 clinical study with radioligand therapy candidate ABY-271 in HER2-positive metastatic breast cancer to its second part, where higher radioactivity levels will be evaluated. The recommendation follows safety, tolerability, dosimetry and biodistribution data from the first enrolled patient cohort, demonstrating tumor targeting and a favorable safety profile with low uptake in kidneys and other critical organs.
The initial data from the ABY-271 study are very promising, said Oscar Wiklander, assistant professor at Karolinska University Hospital and coordinating investigator. We observed a favorable safety profile and encouraging biodistribution data, supporting progression of the study to the next stage. These results offer important insight into how the therapy behaves in patients, and we are eager to advance the study to deepen our understanding of its clinical potential.
Platform validation
Early findings align with preclinical dosimetry predictions, strengthening confidence in both ABY-271 and the broader platform. CEO David Bejker expressed enthusiasm that early clinical results mirror preclinical findings remarkably well, with particular excitement about low kidney uptake. The positive outcome marks an important milestone not only for this program but also for the Affibody platform as a powerful technology for developing next-generation targeted radiotherapeutics.
Treatment mechanism
ABY-271 is an Affibody molecule targeting HER2-expressing tumors and labeled with radioisotope lutetium-177, which emits cytotoxic beta radiation exerting irreversible damage to tumor cells. The company is evaluating ABY-271 in a first-in-human, open-label, two-stage, randomized Phase 1 clinical study to assess safety, tolerability and biodistribution in tumors and critical organs in subjects with HER2-positive metastatic breast cancer. The study is conducted at sites specialized in breast cancer and nuclear medicine in Sweden and Germany.
Trial progression plan
The Trial Review Committee, including principal investigators, medical monitor, dosimetry and nuclear medicine specialists, reviewed safety, tolerability, dosimetry and biodistribution data from a pre-specified number of enrolled patients. The committee confirmed favorable safety and biodistribution, with low uptake in kidneys and other critical organs. Following this recommendation, Affibody will submit a protocol amendment to the European Medicines Agency to accelerate transition to the second part, expected to start in the first half of 2026 with first results anticipated in the second half of 2026.
Study design details
The clinical study consists of two parts. Part A evaluates uptake of ABY-271 in tumors and critical organs in up to six sequentially enrolled patients. Part B will evaluate higher radioactivity levels and additional protein mass doses for subsequent clinical trials in a total of 15 randomized patients. Patients receive a single intravenous infusion of ABY-271 in both parts.
Target indication
Metastatic breast cancer is cancer that has spread beyond the breast and nearby lymph nodes to other body parts, such as bones, liver, lungs or brain. It carries a poor prognosis and cannot be treated curatively with surgery or systemic therapies. Instead, treatment goals shift to delaying disease progression, controlling symptoms and improving quality of life. Approximately 6% to 10% of women are diagnosed with metastatic breast cancer at initial diagnosis. However, nearly 30% of women initially diagnosed with early-stage breast cancer will experience metastatic recurrence during their lifetime.
HER2 targeting approach
HER2 is a protein involved in cell growth. HER2 is overexpressed by some cancer types, including breast, stomach, esophageal, ovarian, bladder and pancreatic cancers. HER2 may cause cancer cells to grow more quickly and spread to other body parts, making HER2-positive cancers more aggressive than HER2-negative cancers. However, they are much more likely to respond to treatments targeting the HER2 protein. HER2-targeted therapies can remain effective even after multiple treatment lines.
Technology platform
Affibody molecules represent a novel drug class of small therapeutic proteins with characteristics surpassing monoclonal antibodies and antibody fragments. The company created a large library consisting of more than ten billion Affibody molecules, all with unique binding sites, from which binders to given targets are selected. Affibody molecules are only 6 kilodaltons in size.