Eli Lilly (NYSE: LLY) has committed up to USD 1.9 billion to access Boston-based Ascidian Therapeutics' RNA exon editing platform for inherited kidney diseases, in a deal that underscores large pharma's accelerating appetite for next-generation RNA modalities beyond siRNA and antisense. Under the global research collaboration and licensing agreement, Lilly receives exclusive, target-specific rights to Ascidian's technology for undisclosed monogenic kidney disease targets, with an option to expand to additional targets. The specific upfront payment was not disclosed, with the USD 1.9 billion ceiling encompassing upfront, development and commercial milestones, and tiered royalties on worldwide sales.
Under the division of labor, Ascidian leads discovery and selected preclinical activities, while Lilly assumes responsibility for additional preclinical work, clinical development, manufacturing, and commercialization. Ascidian retains the right to pursue other kidney targets independently or with additional partners.
Deal context
Ascidian's platform uses pre-mRNA trans-splicing to correct disease-causing mutations at the RNA level without altering genomic DNA. An engineered RNA exon editor molecule — delivered via a viral vector — binds to an intronic region of the endogenous pre-mRNA target; the cell's own spliceosome then performs a trans-splicing reaction, replacing mutated exons with correct, wild-type sequence carried by the editor molecule. The result is a corrected, full-length mRNA encoding functional protein. Critically, the approach can replace multiple contiguous exons in a single reaction, addressing a mutation landscape inaccessible to base editors, single-exon skipping antisense oligonucleotides, or standard AAV gene replacement constrained by packaging capacity.
Inherited kidney diseases represent an increasingly attractive target class for genetic medicines because many are monogenic, lack disease-modifying therapies, and can potentially be addressed through a single genetic intervention. More than 60 genetic diseases are known to affect the kidneys, and many are caused by mutations in large genes or genes with high mutational variance — precisely the profile where RNA exon editing holds a mechanistic advantage over existing tools.
The programs covered by the Lilly deal are at the discovery stage; no named clinical candidates for kidney disease have been identified. Ascidian's most advanced asset remains ACDN-01, an RNA exon editor targeting the ABCA4 gene in Stargardt disease, which completed dose escalation in its Phase I/II STELLAR trial in May 2026. The molecule's entry into the clinic in January 2024 marked the US FDA's first-ever IND approval for an RNA exon editor, and was accompanied by Fast Track designation, providing a degree of validation of the platform's clinical viability ahead of any partnering discussions.