Addition Therapeutics to Present Preclinical Data from PRINT™ Programs at the European Society of Gene & Cell Therapy’s (ESGCT) 33rd Annual Congress

• Addition continues to progress a novel pipeline of non-viral, LNP-delivered, RNA-only gene-addition therapies for severe, lifelong genetic and non-genetic diseases
• Company to present an oral presentation on the PRINT platform and posters reporting new preclinical data on its lead programs in Fabry disease/hypothalamic obesity

SOUTH SAN FRANCISCO, Calif., Oct. 27, 2026 (GLOBE NEWSWIRE) -- Addition Therapeutics, a genetic medicines company aiming to deliver functional cures for patients with severe, lifelong acquired and inherited diseases, today announced it will present new preclinical data supporting its lead programs targeting Fabry disease and hypothalamic obesity (poster presentations) and demonstrating the progress of its PRINT platform (oral presentation) at the European Society of Gene & Cell Therapy (ESGCT) Annual Congress taking place October 27–30, 2026, in Hamburg, Germany.

Addition is combining the efficacy, safety, and scalability of RNA therapeutics with the multi-year durability of gene therapies. This “best of both modalities” approach – enabled by Addition’s all-RNA, LNP-based PRINT technology – could unlock the potential of genetic medicines for a much broader number of patients impacted by genetic and non-genetic diseases. Addition’s portfolio strategy is focused initially on rare patient populations, with the goal of also addressing larger, related patient populations over time.

“We’re pleased to share with the scientific community at ESGCT 2026 our continued progress advancing our novel non-viral, LNP-delivered, RNA-only, gene-addition therapies for patients with severe, lifelong acquired and inherited diseases,” said Ron Park, MD, MBA, President and CEO of Addition. “We aim to transform the treatment paradigm for Fabry disease and hypothalamic obesity, our lead programs, both of which are suboptimally addressed with current therapeutic options. We believe these programs will also create opportunities to expand into a range of diseases currently treated with enzyme replacement therapies and broader metabolic indications.”

Oral presentation details:

Title: Precise, RNA-mediated insertion of transgenes using an R2 retrotransposase yields stable, durable, and therapeutic hepatic protein expression, from mice to NHPs
Date & Time: Thursday, October 29, 10:00 am CEST
Presenter: Gregory J. Cost, PhD, Addition Therapeutics, Vice President, Distinguished Scientific Fellow, Addition Therapeutics
Abstract #: OR045

Data Highlights:

• This abstract is embargoed until 8:00 am CEST on Thursday, October 29, 2026.
• Presentation will include an overview of improvements to the PRINT platform, a demonstration of the tunability (both up and down) of PRINTed transgene expression in mice and NHPs, and a view into the specificity and biological transparency of PRINT.

Pipeline-related Poster Presentation Details

Title: Preclinical proof-of-concept of treatment for Fabry disease via precise RNA-mediated insertion of a GLA transgene
Date & Time: Thursday, October 29, 2:00-4:00 pm CEST
Presenter: Francine Gregoire, Chief Scientific Officer, Addition Therapeutics
Abstract #: P0746

Data Highlights:

• Single dose of PRINTed GLA encapsulated in LNP delivered to GLA knock-out mice demonstrated functional α-Gal A expression and lyso-Gb3 reduction in liver.
• Sustained, supra-physiological levels of α-Gal A activity were detected in plasma through week 16 (end of study),
• Achieved a corresponding dramatic and sustained reduction (~80%) in plasma, liver, kidney, and heart lyso-Gb3 levels, demonstrating that the PRINTed a-Gal A was not only secreted into the circulation but also penetrated key organs affected in Fabry disease.
• Comparable levels of α-Gal A were achieved in NHPs, suggesting translation of the approach to larger species.
• Further optimization of the PRINT platform yielded ~10x greater α-Gal A activity in mice. Addition is testing these platform enhancements in NHPs.
  

Significance:

• Fabry disease is caused by GLA mutations, leading to deficient α-Gal A activity and progressive Gb3/lyso-Gb3 accumulation in the kidney, heart, and nervous system.
• The current standard of care, enzyme replacement therapy (ERT), requires life-long biweekly infusions and fails to prevent progressive renal/cardiac disease.
• Fundings demonstrate that Addition’s non-viral, LNP-delivered, RNA-only gene-addition approach, with the additional potential for re-dosing, may address key limitations of ERTs in Fabry disease (treatment burden, limited tissue exposure, and neutralizing anti-drug antibodies), as well as emerging AAV-based gene therapies for the disease (eligibility constraints and re-dosing barriers).
  

Title: Durable in vivo expression of engineered incretin agonists using PRINT
Date & Time: Thursday, October 29, 2:00-4:00 pm CEST
Presenter: Lander Foquet, Principal Scientist, Addition Therapeutics
Abstract #: P0220

Data Highlights:

• Single-doses of two separate PRINT reagents encoding engineered incretins both gave exposure-dependent, physiologically active incretin activity in mice.
• Sustained expression in juvenile mice produced up to 30% body weight suppression compared to controls.
• Comparable circulating protein expression was achieved in non-human primates (NHPs), suggesting translation of the approach to larger species.
• PRINTing was well-tolerated by both mice and NHPs, with only very mild, transient, and self-resolving elevations in liver enzymes.
• To improve control over transgene activity, Addition PRINTed a transgene containing a small-molecule-inducible “off switch”. Administration of the inducer resulted in an approximately 90% reduction in PRINTed protein levels, demonstrating post-treatment regulation of established transgene expression in vivo.
  

Significance:

• Hypothalamic obesity is a rare disease caused by damage or injury to the hypothalamus, the part of the brain that regulates appetite, how calories are burned, and how fat is stored. Currently approved and off-label therapies to treat hypothalamic obesity are associated with serious side effects and frequent administration challenges.
• The new findings demonstrate PRINT’s potential to deliver durable therapeutic expression of an incretin, tunable transgene output, and sustained systemic protein exposure, potentially avoiding the peak-and-trough pharmacokinetics associated with repeated protein dosing. The data support Addition’s program for hypothalamic obesity as well as future metabolic disease programs.

For more information on these and other abstracts, please visit the ESGCT Annual Congress website.

About Addition Therapeutics

Addition Therapeutics is a privately held genetic medicines company aiming to deliver functional cures for patients with severe, lifelong acquired and inherited diseases. We are pursuing a “best of both modalities” approach, combining the efficacy, safety, and scalability of RNA therapeutics with the multi-year durability of gene therapies. Our portfolio strategy is focused initially on rare patient populations, with the goal of also addressing larger, related patient populations over time.

Our lead programs focus on Fabry disease and hypothalamic obesity. Through research initiatives with two top 10 pharmaceutical companies, we are advancing CAR-T and obesity programs. In addition, the Gates Foundation has provided a grant award for a program focused on HIV.

Our investor syndicate includes SR One, Pivotal Life Sciences, Abingworth, Osage University Partners, the Gates Foundation, and BEVC.

To learn more, visit us at additiontx.com and follow us on LinkedIn.

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