Aktis completes first biotech IPO of 2026, raising $318 million to expand radiopharmaceutical coverage
Despite the many benefits of radiopharmaceuticals, these treatments currently only target a limited number of cancer targets. Aktis Oncology has technology that could expand the scope of such therapies, potentially addressing more targets to help more patients. The clinical-stage company currently has $318 million in IPO cash to support the development of its pipeline.
After a slump with limited biotech IPO activity in 2025, Aktis found enough investor interest to increase the size of its deal to 17.65 million shares from the 11.77 million shares it planned to offer in preliminary financial terms set earlier this week. Late Thursday, Aktis priced the shares at $18 a share, the upper end of the company's expected price range. The Boston-based company's shares will trade on Nasdaq under the ticker symbol “AKTS.”
Radiopharmaceuticals reach their tumor destination by exploiting the targeting capabilities of another molecule, such as a peptide or antibody. But these targeting molecules have their limitations. The large size of the antibody makes it difficult to penetrate tumors. In addition, their long circulating half-life means that the treatment remains in the body longer, thereby risking radiation exposure of healthy organs and tissues. At the same time, the peptide's small size makes it difficult to hit certain cancer targets.
Aktis’ approach is somewhere between antibodies and peptides. Its radiopharmaceutical uses a targeting molecule called a “miniprotein,” which is composed of chains of amino acids, making the targeting molecule smaller than an antibody but larger than a peptide. These miniature proteins are derived from Aktis' proprietary technology platform. Aktis said in its IPO filing that its mini-protein radiopharmaceutical has the potential for potent anti-tumor activity and better safety and tolerability.
“The small size of the microproteins allows them to penetrate tumors quickly,” Aktis said. “In addition, our small protein radioconjugates are able to internalize into cancer cells, which we believe results in prolonged retention. We have reproducibly generated high-affinity small protein binders for specific tumor targets. Tumor killing is achieved through the delivery of absorbed radiation doses, and tumor killing is enhanced by high tumor penetration, high binding affinity for the tumor target, and prolonged retention of the drug in the tumor.”
Aktis' lead drug candidate, AKY-1189, is being developed to treat solid tumors that express the nectin-4 protein. This target has been drugged with Padcev, an antibody-drug conjugate (ADC) marketed by Pfizer and Astellas Pharmaceuticals to treat urothelial cancer. Aktis said in the filing that while the product sells well, its use in other cancers may be limited by the need to develop companion diagnostics for tissue testing when using the ADC.
Aktis plans to use imaging radioisotopes combined with AKY-1189 to select patients most likely to benefit from radiopharmaceuticals. The company also sees potential in expanding the therapy to more tumor types, such as breast and lung cancer. AKY-1189 is currently in Phase 1b testing against urothelial carcinoma and other nectin-4-expressing solid tumors. Preliminary data from the dose-escalation portion of the study are expected in the first quarter of 2027.
The next program in Aktis' pipeline is AKY-2519, a radiopharmaceutical targeting B7-H3. This protein is highly expressed in a range of solid tumors, including prostate cancer cells. The program has the potential to expand the reach of radiopharmaceuticals beyond PSMA, which is the target of targeted radiation therapies being developed by Novatis' Pluvicto and others. Documents show that Aktis plans to submit an investigational new drug application for AKY-2519 in the first half of this year.
Under a 2024 collaboration with Eli Lilly, Aktis is leveraging its technology to discover radiopharmaceuticals for multiple cancer targets selected by the pharma giant. The targets have not been disclosed, but Aktis said they are separate from its wholly-owned pipeline. Eli Lilly will take over the partners' development projects once they reach the clinic. Eli Lilly kicked off the alliance with a $60 million upfront payment and an additional equity investment in Aktis. The radiopharmaceutical developer has been paid $1 million for achieving milestones and may receive additional milestone payments of up to $1.2 billion, documents show.
Aktis was founded in 2020 and was founded and incubated by MPM Capital. The startup emerged from stealth in 2021, backed by a Series A round that included participation from Novartis and Bristol Myers Squibb. Prior to its IPO, Aktis had raised $345.5 million since its inception, most recently completing a $175 million Series B round in 2024. MPM is Aktis' largest shareholder with a 17.4% stake in the company, followed by Vida Ventures with a 9.5% stake, the filing shows.
Aktis has the opportunity to further increase its cash earnings. Aktis said in an updated prospectus that Eli Lilly has expressed interest in buying about $100 million worth of company stock at the IPO price. As of the end of the third quarter of 2025, Aktis reported a cash position of $246.2 million. Aktis said that combined with IPO proceeds, the company plans to spend $140 million to $150 million on ongoing Phase 1b testing of AKY-1189 against nectin-4-expressing tumors. Another $70 million to $80 million will be used to advance Ac-AKY-2519 into a Phase 1b clinical trial targeting B7-H3-expressing tumors. Aktis expects its capital to last until the first half of 2028.
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