Seamless Therapeutics Secures Up to $1.1B Eli Lilly Partnership to Develop Next-Generation Gene Therapies for Genetic Hearing Loss

 January 28, 2026-Dresden-based Seamless Therapeutics has entered a global research and licensing collaboration with Eli Lilly and Company worth up to $1.1 billion, positioning its programmable recombinase platform as a potential next wave of gene therapy innovation for genetically caused hearing loss, alongside established AAV-based gene therapy approaches.

Seamless Therapeutics GmbH, with a U.S. subsidiary in the Boston area, announced the worldwide strategic agreement with Lilly to develop and commercialize recombinase-based gene therapies for selected inherited hearing loss indications. Under the deal, Seamless will apply its proprietary sequence-precise recombinase technology to enable large and accurate DNA insertions—an approach designed to overcome limitations associated with conventional AAV gene therapy, such as payload size constraints and reliance on episomal gene expression.

The collaboration combines Seamless’s expertise in engineering site-specific recombinases with Lilly’s extensive capabilities in genetics, translational development, and clinical programs in hearing disorders. While many current hearing loss gene therapy programs rely on AAV vectors to deliver functional gene copies, Seamless’s platform enables direct correction or replacement of disease-causing mutations at defined genomic loci, independent of cellular DNA repair pathways and without the size limitations typical of AAV-mediated delivery.

Under the agreement, Seamless will design and optimize recombinases capable of precise DNA cutting and insertion of long genetic sequences, potentially addressing mutations that exceed the packaging capacity of standard AAV vectors. Lilly will receive an exclusive license in the hearing loss field to advance selected candidates through preclinical and clinical development and eventual commercialization. Although the program remains at an early preclinical stage, the deal includes an upfront payment, committed R&D funding, and development and commercial milestones totaling up to $1.1 billion. No tiered sales royalties were disclosed.

Albert Seymour, CEO of Seamless Therapeutics, said the partnership validates the company’s technology and strategic direction. He noted that while AAV-based gene therapy remains the most clinically established modality for inner ear disorders, recombinase-driven gene editing could complement or, in some cases, surpass AAV approaches by enabling permanent, sequence-precise correction of pathogenic mutations.

Recombinases have long been used in basic research, but Seamless has applied directed evolution and protein engineering to transform them into programmable tools capable of insertion, deletion, or exchange of DNA at predefined genomic sites. According to Seymour, preclinical animal data demonstrating functional correction were central to Lilly’s decision to commit to the collaboration, marking a transition from platform development toward clinical translation.

The deal also highlights growing pharmaceutical interest in genetic hearing loss, a field historically dominated by AAV gene therapy programs. This momentum is underscored by recent activity from other players, including Sanofi’s strategic investment in Sensorion to advance AAV-based gene therapies for hearing loss into clinical development.

While Seamless continues to collaborate with large pharmaceutical partners, the company also plans to advance at least one internal recombinase program independently, with additional data expected later this year. Together, recombinase-based editing and established AAV gene therapy platforms signal a rapidly expanding and increasingly competitive landscape for genetic medicines targeting hearing loss.