Aktis Oncology NASDAQ: AKTS outlined its clinical development strategy for AKY-2519, a B7-H3 targeted miniprotein radioconjugate, emphasizing a two-trial approach intended to generate indication-specific data in metastatic castration-resistant prostate cancer (mCRPC) while also exploring broader potential in other B7-H3–expressing solid tumors.
Two Phase 1b studies: prostate-specific lead-in plus a broader basket trial
President and CEO Matthew Roden said the company has initiated a dedicated Phase 1b trial of AKY-2519 in mCRPC and plans to follow with a separate Phase 1b basket trial in other tumor types. Roden described B7-H3 as highly expressed across multiple solid tumors and associated with poor prognosis when overexpressed.
Chief Medical Officer Akos Czibere said the mCRPC Phase 1b trial will enroll patients in two cohorts: those who are PLUVICTO-naïve and those previously treated with PLUVICTO. Czibere said the study will be run under an IND in the U.S. and will use a mix of prostate-specific radioligand therapy centers and academic sites.
The basket Phase 1b trial—planned for the second half of 2026—will also be conducted under IND in the U.S. and will focus on lung cancers, colorectal cancer, and other solid tumors with high B7-H3 expression. Czibere said the basket protocol has been finalized and is under regulatory review.
Why B7-H3, and why separate trials?
Czibere said Aktis views B7-H3 as an “ideal target” for radiopharmaceutical development due to high expression across tumor types and low expression in normal tissues. In prostate cancer, he argued B7-H3 may offer differentiation versus PSMA-directed approaches, citing variability and heterogeneity in PSMA expression and noting that PSMA expression in salivary glands can be challenging, particularly for higher-energy modalities. Czibere added that B7-H3 is not expected to be expressed on salivary glands.
He also said B7-H3 is expressed “very consistently in about 90%” of patients with metastatic cancers and prostate cancer, with low expression in normal tissues.
On the rationale for splitting prostate cancer into a dedicated protocol rather than including it solely in a basket study, Czibere pointed to the established and rapidly evolving radiopharmaceutical treatment landscape in prostate cancer and the presence of specialized U.S. radioligand therapy centers. He said the dedicated design enables parallel evaluation of PLUVICTO-naïve and PLUVICTO-experienced patients and could help optimize patient selection and trial execution in that population.
Prostate Phase 1b design and dose escalation approach
Czibere said the mCRPC study will run parallel dose escalation in cohorts A and B using a BOIN design. The trial includes three planned dose levels, starting at 6 megabecquerel and escalating in 3 megabecquerel increments to 9 and then 12 megabecquerels, with the option for intermediate doses if needed. He said two of the three dose levels may be expanded for additional dose optimization work across both cohorts.
In Q&A, Czibere said the protocol does not require PSMA expression assessment by imaging for enrollment of PLUVICTO-naïve patients. He added that patients may enter the study “in lieu of receiving PLUVICTO,” do not need prior chemotherapy, and must have mCRPC with documented progression after “at least 2 ARPIs.”
Addressing why both PLUVICTO-naïve and PLUVICTO-experienced cohorts are included, management said the decision was driven primarily by potential differences in tolerance due to prior radiation exposure. Czibere said patients who have received radioligand therapy may tolerate a different dose because of cumulative radiation to normal tissues, and separating cohorts could help “dial the right dose” for each population. He also said the company believes the larger opportunities may be in earlier disease settings rather than only after PLUVICTO.
Preclinical foundation and upcoming ASCO presentations
Czibere highlighted preclinical findings supporting AKY-2519, stating the program has shown internalization in vitro and durable tumor retention in vivo with limited normal tissue biodistribution. He said these properties translated into robust anti-tumor effects and dose-dependent survival benefit in a non-small cell lung cancer xenograft model after a single administration.
He also discussed AKY-3212, described as a “sister molecule” and tool compound, saying that when chelated to actinium-225 it demonstrated superior efficacy compared with PSMA-617 chelated to lutetium-177 in an mCRPC patient-derived xenograft model engineered to be resistant to PSMA-617 lutetium-177.
Roden said Aktis plans to present clinical imaging and dosimetry analyses for AKY-2519 in two posters at the upcoming ASCO Annual Meeting. Czibere said one poster will cover imaging and dosimetry in mCRPC, including predicted absorbed doses to key organs such as salivary glands and kidneys as well as tumor dosimetry, based on 16 patients. He said the second poster will focus on tumor uptake and normal tissue biodistribution across multiple tumor types, including non-small cell lung cancer and colorectal cancer, using SUV-based measurements (such as SUVmean and SUVmax) without dosimetry.
Other milestones: manufacturing scale-up and AKY-1189 timeline
Roden also reiterated timelines for the company’s other lead clinical program, AKY-1189, a Nectin-4 targeted radioconjugate that is currently enrolling in a Phase 1b trial and has FDA Fast Track designation. He said Aktis expects to present preliminary dose escalation data for AKY-1189 in the first quarter of 2027.
On operations, Roden said the company expects its in-house GMP manufacturing facility to be operational in the second half of 2026 as part of a “hybrid manufacturing strategy.” In response to an analyst question about actinium supply and manufacturing capacity, Roden said the company has been focused on ensuring its supply chain can scale with growing clinical trial demand and noted what he described as an acceleration versus plans discussed during the IPO process.
Looking ahead for AKY-2519, Roden said the company expects to commence the basket Phase 1b study in the second half of 2026 and anticipates reporting preliminary data from the prostate Phase 1b study in 2027.
About Aktis Oncology NASDAQ: AKTS
Aktis Oncology NASDAQ: AKTS is a biotechnology company focused on the discovery and development of new therapies for cancer. The firm concentrates on advancing oncology candidates through research and development with the goal of addressing unmet medical needs in oncology. Its work emphasizes targeted and precision approaches intended to improve the safety and efficacy profiles of cancer treatments.
The company's activities include laboratory research, preclinical studies and clinical development as it advances its pipeline programs toward regulatory milestones.
Further Reading
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