Key Takeaways
Aktis Oncology Inc. (NASDAQ: AKTS) reported first-in-human data showing its B7-H3-targeted radiopharmaceutical, AKY-2519, achieves high tumor concentration with limited impact on healthy tissue, positioning it as a potential new option for cancers including prostate, lung, and colorectal. The results provide an early proof-of-concept for the company's miniprotein-based approach to delivering radioisotopes.
"The robust tumor uptake and retention and low normal tissue uptake consistently seen... gives us an initial understanding of its potential to kill cancer cells while minimizing normal-tissue radiation exposure," Akos Czibere, Chief Medical Officer at Aktis, said in a statement.
The data, from two separate assessments to be presented at the 2026 ASCO Annual Meeting, showed a median SUVmax of 40.4 in bone metastases and 31.0 in visceral metastases for prostate cancer patients (n=7) 120 minutes after infusion. Predicted absorbed radiation doses in critical normal tissues were low, particularly in the salivary glands (4.2 GyRBE=5), a key potential advantage over PSMA-targeting agents which can cause significant toxicity there.
The positive imaging and dosimetry results have prompted Aktis to advance a broad clinical program, including an ongoing Phase 1b trial in metastatic castration-resistant prostate cancer (mCRPC) and a planned second Phase 1b for other solid tumors starting in the second half of 2026. With preliminary efficacy data for AKY-2519 expected in 2027, the results provide early validation for the company's platform.
AKY-2519 is a miniprotein radioconjugate, a class of drugs designed to combine the precision of targeted therapies with the potent cell-killing power of radiation. Aktis' proprietary platform creates small, engineered proteins that deliver a radioactive payload—in this case, actinium-225 for therapy—directly to cancer cells. The target, B7-H3, is a protein highly expressed on a variety of solid tumors, including prostate, lung, and colorectal cancer, but has limited presence in healthy tissues, making it an attractive target for minimizing side effects.
The first-in-human studies evaluated an imaging version of the drug, using gallium-68 and lutetium-177, in a total of 34 patients across two assessments. One study focused on 16 patients with mCRPC, while the other evaluated 18 patients with a variety of advanced solid tumors. Across both, the drug was reported as well-tolerated with no infusion-related reactions.
The data provides a boost for Aktis, a clinical-stage company looking to carve out a niche in the competitive radiopharmaceutical space. The field is dominated by larger players, and positive early data is crucial for smaller biotechs. The company's lead program, AKY-1189, targets Nectin-4 and is also in a Phase 1b trial, with data expected in the first quarter of 2027. Aktis also has a discovery collaboration with Eli Lilly and Company to develop other radioconjugates.
The low salivary gland dose for AKY-2519 is a specific point of emphasis, as it contrasts with a known side effect of PSMA-targeted radioligand therapies like Pluvicto. If this safety advantage holds up in larger trials, it could make AKY-2519 a compelling alternative or complementary treatment for mCRPC and other cancers. The company is currently enrolling both Pluvicto-naïve and -experienced patients in its mCRPC trial, directly addressing this clinical need.
This article is for informational purposes only and does not constitute investment advice.
