Tessera Therapeutics has unveiled significant preclinical progress for its in vivo genetic medicine platforms, demonstrating editing levels that surpass established curative thresholds for sickle cell disease (SCD) and successfully generating functional Chimeric Antigen Receptor (CAR) T cells directly within animal models.

The data, presented at the 67th American Society of Hematology (ASH) Annual Meeting, taking place from December 6-9, 2025, in Florida, underscores the company’s bid to pioneer a new class of single-dose, non-viral therapies.

SCD Editing Surpasses Curative Benchmark

A key highlight from the ASH presentations involves Tessera’s RNA Gene Writer for sickle cell disease. In non-human primates (NHPs), the therapy achieved approximately 40% editing of long-term hematopoietic stem cells (LT-HSCs) after one dose, climbing to about 60% after a second dose. Crucially, these levels exceed the 20-30% editing threshold in HSCs associated with significant clinical benefit, including resolution of painful vaso-occlusive crises.

The company reported durability of edited cells out to approximately 14 months for HBB editing in NHPs, with edited cells showing intact function across multiple blood lineages. This builds on earlier data presented in May 2025 at the American Society of Gene and Cell Therapy (ASGCT) meeting, where 35-50% of NHP stem cells showed editing after two doses. The latest results represent a measurable step forward in efficiency.

Breakthrough in In Vivo CAR-T Cell Generation

Separately, Tessera showcased advances in creating CAR-T cells inside the body, bypassing the complex ex vivo manufacturing process used in current therapies. For the first time in NHPs, T cell-directed lipid nanoparticles (LNPs) delivered a CD20-targeted CAR cargo, leading to robust CAR-T cell expansion and significant clearance of B cells in blood and lymph nodes.

Proof-of-concept was also reinforced in humanized mouse models, where a single intravenous infusion generated functional CD20-targeted CAR-T cells that eliminated circulating human B cells. The platform also demonstrated the ability to multiplex, creating T cells edited with two different CARs (CD19 and CD20) in a single step, which showed superior cancer cell killing in vitro.

Building on a Foundation of Preclinical Validation

The new data expands upon a solid foundation of preclinical results Tessera has accumulated over the past year. At the American Society of Gene & Cell Therapy (ASGCT) meeting in May 2025, the company reported high-efficiency editing in liver diseases, achieving an estimated 76% editing in hepatocytes for Alpha-1 Antitrypsin Deficiency and 70% for Phenylketonuria in NHPs. Those studies also reinforced the safety and liver-specificity of its proprietary LNP delivery system.

For SCD, the earlier 2025 data had already demonstrated greater than 20% editing in LT-HSCs—meeting the potential curative threshold—and durability of edits out to several months in NHPs. The consistent progression from these earlier results to the higher efficiencies now reported validates the iterative improvement of the platform.

This momentum is further supported by external validation and funding. In October 2025, Tessera was awarded up to $41.3 million from the Advanced Research Projects Agency for Health (ARPA-H) as part of its EMBODY program, which aims to engineer immune cells inside the body. This grant is specifically directed toward advancing Tessera’s in vivo CAR-T therapy efforts, leveraging the same LNP delivery platform highlighted in the new data.

Earlier this month, the company signed a global collaboration agreement with Regeneron Pharmaceuticals, potentially worth up to $275 million. Under the agreement, the companies will split worldwide development costs and future profits for TSRA-196 equally. Tessera will receive $150 million from Regeneron, comprising an upfront cash payment and an equity investment, with up to $125 million in additional development milestone payments.