CREATE Medicines Unveils All-RNA T-Cell Engineering Platform: RetroT Enables Site-Specific, Durable CAR integration In Vivo

• All-RNA gene writing for T cells (RetroT): Utilizes human LINE-1 machinery to drive programmable, site-specific integration of multi-kb payloads, without DSBs, supporting a superior genomic safety profile.
• Successful genetic delivery of CART constructs to T cells

CAMBRIDGE, Mass., Oct. 29, 2025 /PRNewswire/ -- CREATE Medicines, Inc. (formerly Myeloid Therapeutics) today announced new preclinical data for RetroT, the company's fully RNA-encoded, site-specific gene-integration system, presented at the Cold Spring Harbor Laboratory Meeting on Immune Engineering & Cellular Immunotherapy. The results highlight precise integration of therapeutic payloads without double-strand DNA breaks, viral vectors, or DNA templates, supporting a path to safer, scalable in vivo cell engineering. 

"RetroT reframes what's possible, a purely RNA-based system that programs T cells in vivo with site-specific, durable gene insertion while maintaining the flexibility to re-dose," said Robert Hofmeister, PhD, Chief Scientific Officer of CREATE Medicines. "When combined with our targeted LNP delivery and human-validated mRNA platform, RetroT provides a direct and scalable path to clinical proof of concept."

By harnessing the natural mobility of the LINE-1 retrotransposon and a CRISPR-based nickase, the results demonstrate that RetroT achieves site-specific integration of genetic payloads into immune cells. This approach has the potential to transform precision in vivo gene editing by reducing off-target effects and genotoxicity associated with traditional CRISPR/Cas9 methods.

In the presented study, CREATE Medicines used RetroT to successfully insert a CD19-CAR transgene into human T cells. RetroT uses the LINE-1 retrotransposon, the only active "jumping gene" in the human genome, to integrate genetic payloads without double-strand DNA breaks, viral vectors, or DNA payloads. RetroT engineered T cells show full functionality and target-specific cytotoxicity while preserving cell fitness and phenotype. Sequencing confirmed precise integration with no detectable off-target effects, partial insertions, or genomic scars.

Additional background on RetroT is available in the peer-reviewed publication "CRISPR-Enabled Autonomous Transposable Element (CREATE) for RNA-based gene editing and delivery," published in EMBO Reports in January (Wang et al., EMBO Rep (2025)26:1062–1083).

CREATE Medicines continues to advance its multi-immune programming platform, which enables selective programming of T cells, myeloid cells, and NK cells directly within the body. The company's pipeline includes next-generation in vivo CAR therapies for solid tumors and autoimmune diseases, supported by a validated LNP delivery platform and proprietary RNA engineering.

Presentation Details

• Title: CRISPR Enabled Autonomous Transposable Element (CREATE), an All-RNA Platform to Engineer T Cells
• Authors: Meghan Harris, Bianca Lavayen, Yuxiao Wang, Daniel Getts, Robert Hofmeister, Philippe Kieffer-Kwon
• Meeting: Cold Spring Harbor Laboratory Meeting on Immune Engineering & Cellular Immunotherapy
• Poster date and time: October 29, 2025, 7:30 – 10:30 PM, Poster #57
• Location: Cold Spring Harbor, New York
• Meeting program: https://meetings.cshl.edu/meetings.aspx?meet=IMMENG

About CREATE Medicines

CREATE Medicines (formerly Myeloid Therapeutics) is a clinical-stage biotech pioneering in vivo multi-immune programming. Its proprietary mRNA-LNP platform directly programs immune cells inside the body to deliver scalable, repeat-dose, off-the-shelf immunotherapies. With proven human validation and next-generation RNA technology, CREATE is advancing a pipeline of in vivo CAR therapies to transform outcomes in cancer, autoimmunity, and fibrosis.
For more, visit createmedicines.com. Follow us on LinkedIn and X (Twitter).

Business Development: partnering@createmedicines.com

Media Contact: Susan Roberts, sr@roberts-communications.com | +1 (202) 779-0929

Investor Contact: Brian Korb, brian.korb@astrpartners.com | +1 (917) 653-5122

SOURCE CREATE Medicines, Inc.