June 03, 2026 —
Eli Lilly has entered into a partnership with Ascidian Therapeutics to develop RNA exon editing therapies for inherited kidney diseases. The deal could be worth up to $1.9 billion, including an undisclosed upfront payment and future milestones.
Ascidian is developing a novel RNA editing approach called exon editing, which uses the natural RNA splicing process to replace defective sections of RNA. Instead of permanently altering DNA, the technology edits RNA transcripts, allowing correction of large or complex genetic regions at the RNA level. This could be particularly useful for diseases caused by genes that are too large or complex for traditional gene replacement strategies.
The deal builds on momentum from Ascidian’s lead retinal program, ACDN-01, which is being developed for Stargardt disease. ACDN-01 uses a single AAV vector to perform in vivo RNA exon editing and restore full-length ABCA4 protein, which is deficient in Stargardt patients. ABCA4 is too large to fit into standard AAV-based full-gene replacement approaches, making it a strong example of where exon editing may offer an advantage. Ascidian has reported that ACDN-01 has demonstrated durable and efficient editing in both non-human primate and human retinal models.
Ascidian became the first company to receive FDA clearance to test an exon editing therapy in the clinic in 2024. At ASGCT 2026, the company presented early clinical data from its Stargardt program, reporting that the therapy appeared safe in the first 10 treated patients, with no dose-limiting toxicities. The company also noted that visual acuity appeared stable in treated eyes compared with untreated eyes after three months, although Stargardt disease is slow-progressing and longer follow-up will be needed to evaluate clinical benefit.
Through the Lilly collaboration, Ascidian will apply its exon editing platform to inherited kidney diseases, an area that remains difficult for genetic medicine delivery. Kidney-directed gene therapy has historically been challenging because of barriers to efficient and cell-type-specific delivery. While Ascidian does not position itself as a delivery company, its leadership has noted that advances in kidney delivery technologies could make renal genetic medicines increasingly feasible.
The partnership reflects Lilly’s continued investment in genetic medicine, including RNA editing, gene editing, in vivo CAR-T, and other emerging therapeutic platforms. For Ascidian, the collaboration represents external validation of its exon editing strategy beyond the eye and into organs that have been harder to reach with genetic medicines.
If successful, the approach could support a new class of RNA exon editing therapies designed to address the root genetic causes of inherited diseases while avoiding permanent DNA modification. For large, complex genes such as ABCA4 and potentially for selected kidney disease targets, exon editing may provide a flexible alternative to conventional gene replacement or DNA editing strategies.
