- Presented new data in non-human primates (NHP) for sickle cell disease (SCD), where RNA Gene Writer achieved approximately 40% and 60% of long-term hematopoietic stem cells (LT-HSCs) with at least one edited allele after 1 or 2 doses, respectively, exceeding the anticipated curative threshold
- Evidence in NHP that T cell directed lipid nanoparticles (LNP) produced functional chimeric antigen receptor (CAR)-T cells in vivo, with significant B cell clearance observed in blood and lymph nodes
SOMERVILLE, Mass., Dec. 08, 2025 (GLOBE NEWSWIRE) -- Tessera Therapeutics, the biotechnology company pioneering a new approach in genetic medicine known as Gene Writing™, is presenting updates across its in vivo genetic medicine programs for SCD and T cell therapies, including its proprietary delivery platform that enables extra-hepatic LNP delivery to hematopoietic stem cells (HSCs) and T cells. These data were shared across three poster presentations at the American Society of Hematology (ASH) Annual Meeting taking place in Orlando, Florida, December 6 – 9, 2025.
“These latest data highlight meaningful progress towards a potentially curative, non-viral approach for treating sickle cell disease (SCD), with our Gene Writers achieving in vivo editing levels in long-term stem cells that exceed the established efficacy thresholds for transformative clinical benefit, without the use of stem cell mobilization, toxic myeloablative pre-conditioning, or transplantation,” said Michael Severino, M.D., CEO of Tessera Therapeutics. “We are also encouraged by our T cell engineering results, which demonstrate the ability to generate functional CAR-T cells in NHPs in vivo. Together, these findings underscore the broad potential of our Gene Writing and delivery platforms to pioneer a new generation of in vivo therapies for patients.”
In Vivo SCD Data
SCD is the most common lethal monogenic disease globally, arising from a mutation in the hemoglobin beta-globin (HBB) gene that results in hemoglobin S, which can cause red blood cell sickling, acute and chronic pain, and widespread organ damage.
- Based on single cell analysis of LT-HSCs collected from NHPs treated with an optimized Gene Writer formulated in LNP, approximately 40% and 60% of cells after 1 or 2 doses, respectively, had at least one edited HBB gene. This data improves upon earlier data presented at the American Society of Gene and Cell Therapy 28th Annual Meeting, where 35-50% of cells had mono or bi-allelic HBB editing after 2 doses of Gene Writer administered.
- This level of % edited cells exceeds the observed efficacy threshold of 20-30% edited HSCs associated with significant clinical benefit, including resolution of vaso-occlusive crises (VOCs) and improved anemia1-4.
- Edited LT-HSCs continue to demonstrate durability in NHP, including out to 15 months with beta-2 microglobulin (B2M) surrogate editing and out to approximately 14 months with HBB editing. These cells showed intact HSC function, with editing seen in multiple hematopoietic lineages with continued follow-up.
- RNA Gene Writers achieved efficient levels of in vivo HBB editing with a single intravenous administration, including ~35% correction to wild type in humanized mice engrafted with mobilized peripheral blood cells across SCD donors, and >50% editing across multiple healthy donors.
- HSC targeted LNPs demonstrated favorable pharmacokinetics in NHP, including higher early plasma concentrations and slower initial clearance compared to liver LNP, resulting in improved systemic persistence after intravenous dosing.
Advances Towards In Vivo T-Cell Therapies
Tessera is applying its Gene Writing and proprietary LNP delivery platforms to develop in vivo cell therapies for potential oncology and autoimmune disease applications.
- For the first time, demonstrated proof-of-concept in NHP that T cell directed LNP with CD20 targeted CAR cargo successfully delivered to T cells in vivo, which enabled robust and rapid CAR-T cell expansion and B cell clearance was observed in peripheral blood and immunohistochemistry (IHC) further confirmed significant B cell clearance in lymph nodes.
- Proof-of-concept in a naïve humanized mouse model, with a single intravenous infusion of RNA Gene Writer delivered in a proprietary LNP, successfully generated functional CAR-T cells in vivo targeting CD20, resulting in the elimination of circulating human B cells.
- Further, we highlighted the ability to multiplex different edits in a single step, including two different CARs, CD19 and CD20, with these dual edited CAR-T cells demonstrating superior cancer cell killing in vitro.
1 Lenoard A, et al., Blood Advances. 2024
2 Magnani A, et al., Haematologica. 2020
3 Fitzhugh CD, et al., Blood. 2017
4 Kanter J, et al. Am J Hematol. 2023
About Tessera Therapeutics
Tessera Therapeutics is pioneering a new approach to genome engineering through the development of its Gene Writing™ and delivery platforms, with the aim to unlock broad new therapeutic frontiers. Our Gene Writing platform is designed to write therapeutic messages into the genome by efficiently changing single or multiple DNA base pairs, precisely correcting insertions and deletions, or adding exon-length sequences and whole genes. Our proprietary lipid nanoparticle delivery platform is designed to enable the in vivo delivery of RNA to targeted cell types. We believe our Gene Writing and delivery platforms will enable transformative genetic medicines to not only cure diseases that arise from errors in a single gene, but also modify inherited risk factors for common diseases and create engineered cells to treat cancer and potentially autoimmune and other diseases. Tessera Therapeutics was founded in 2018 by Flagship Pioneering, a life sciences innovation enterprise that conceives, creates, resources, and develops first-in-category bioplatform companies to transform human health and sustainability.
For more information about Tessera, please visit www.tesseratherapeutics.com.
Contact
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LifeSci Communications, LLC
jpappas@lifescicomms.com
