Addition Therapeutics Presents Preclinical Proof-of-Concept Data at American Society of Gene & Cell Therapy (ASGCT) 29th Annual Meeting

Platform non-human primate (NHP) data demonstrate stable, durable protein expression enabled by all-RNA, LNP-based PRINT technology
Preclinical proof-of-concept rodent data being presented in multiple disease areas, including obesity, Fabry, HIV and ocular disease
Breadth of data demonstrate PRINT’s potential to address both acquired and genetic diseases

SOUTH SAN FRANCISCO, Calif., May 12, 2026 (GLOBE NEWSWIRE) -- Addition Therapeutics, a genetic medicines company aiming to deliver functional cures for patients with severe, lifelong acquired and inherited diseases, today will present preclinical proof-of-concept NHP data validating the stability and durability of therapeutic protein expression enabled by its all-RNA, LNP-based PRINT™ technology at the American Society of Gene & Cell Therapy (ASGCT) Annual Meeting in Boston, MA. At ASGCT, Addition is also presenting in vivo PoC data demonstrating how the PRINT technology potentially can be leveraged to deliver novel treatments for obesity, Fabry disease, HIV and ocular disease.

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 is enabled by the PRINT (Precise, RNA-Mediated, Insertion of Transgenes) technology. Addition’s lead programs are PRINTed therapeutic candidates for a rare, undisclosed obesity indication and Fabry disease. The company’s portfolio strategy is focused initially on rare patient populations, with the goal of also addressing larger, related patient populations over time.

“The current treatment paradigm for most lifelong diseases involves perpetual repeat-dose therapies, which lead to peaks and troughs in therapeutic serum levels that adversely impact safety and efficacy, in addition to being extremely difficult to take for an entire lifetime. The proof-of-concept data we’re presenting at ASGCT demonstrate our PRINT technology’s potential to create medicines that hold transformative potential for patients suffering with a spectrum of severe, lifelong non-genetic and genetic diseases,” said Ron Park, M.D., President and CEO of Addition.

Summary of Addition’s Preclinical PoC Data at ASGCT
All Addition Therapeutics presentations and posters will be available on Friday, May 15, 2026, on the Presentations & Publications page of Addition’s website at https://additiontx.com/publications-presentations/.

PRINT Platform & Lead Internal Programs

Title: PRINT: Precise, RNA-mediated insertion of transgenes using an R2 retrotransposase yields stable, durable, and therapeutic hepatic protein expression, from mice to NHPs
Oral Presentation / Date & Time: May 12 at 3:30 p.m. ET; Abstract #: 103
Highlights:

Demonstrated, with a single dose, durable liver-based expression of proteins for >1 year in mice (luciferase) and >6 months in NHPs (EPO), with flat pharmacokinetics and pharmacodynamics (PK/PD) profile

Title: Turning hepatocytes into incretin factors with PRINT, an RNA-based genomic medicine platform
Oral Presentation / Date & Time: May 15 at 4:15 p.m. ET; Abstract #: 511
Highlights (from abstract only):

Single dose of PRINTed incretin mimetics demonstrated sustained serum levels for ≥6 weeks in rodents
Incretin-PRINTed rodents, whether maintained on standard chow or a high-fat diet, demonstrated that sustained GLP-1 receptor agonist exposure correlated with favorable PD effects, including reductions in weight gain comparable to reported benchmarks for these molecules as well as biomarker shifts consistent with incretin activity.

Significance:

The current challenges of incretin-based therapeutics, including perpetual repeat dosing and tolerability challenges, render them a difficult treatment paradigm for patients with severe, lifelong obesity indications.
A stable, durable PRINTed incretin therapy would be a novel option for patients with severe, life-threatening obesity conditions.

Title: Preclinical proof of concept of treatment for Fabry disease via precise RNA-mediated insertion of a GLA transgene
Poster Presentation / Date & Time: May 12 at 5:00 – 6:30 p.m. ET; Abstract #: 1085
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 in plasma; and durable systemic lyso-Gb3 reduction, as well as significant lyso-Gb3 reduction in kidney and heart

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, requires life-long biweekly infusions and fails to prevent progressive renal/cardiac disease.
A PRINTed GLA medicine that addresses the multi-organ impact of Fabry and deliver multi-year durability without the challenges of frequent dosing or viral vector-based delivery would be transformative for patients.

Other Programs

Title: Establishment of an in vivo antibody-production platform via precise, RNA-mediated insertion of a broadly neutralizing anti-HIV transgene
Poster Presentation / Date & Time: May 12 at 5:00 – 6:30 p.m. ET; Abstract #: 1347
Highlights:

Single dose of LNP-delivered eCD4-Ig (an HIV-neutralizing biologic) PRINT reagents demonstrated substantial expression of bioactive eCD4-Ig from primary human hepatocytes and durable eCD4-Ig expression in both mice and rats

Significance:

A single PRINT administration could enable continuous HIV suppression for the potential prevention, control and possible eradication of HIV infection

**This poster presentation is based on research funded by the Gates Foundation. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Gates Foundation.

Title: Establishing PRINT-mediated protein expression in the retinal pigment epithelium for treatment of ocular diseases
Poster Presentation / Date & Time: May 14 at 5:00 – 6:30 p.m. ET; Abstract #: 3441
Highlights:

In vitro PRINT of two distinct anti-VEGF biologics demonstrated functional expression of a therapeutically relevant payload with target-binding activity in RPE cells

Significance:

Anti-VEGFs are efficacious for neovascular age-related macular degeneration but rely on frequent intravitreal injections.
PRINT’s steady, localized protein production potentially could avoid the need for frequent dosing and the resulting patient compliance issues of current intravitreal therapies.

**Currently seeking partner with ocular expertise to further advance program

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 are focused on an undisclosed rare obesity indication and Fabry disease. Through research initiatives with two top ten pharmaceutical companies, we are advancing in vivo 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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media@additiontx.com

Investor Inquiries:
investors@additiontx.com

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