Cambridge, Massachusetts-based Typewriter Therapeutics, Inc. has emerged from stealth with a USD 56 million Series A financing round to advance a non-viral, RNA-based platform designed to insert full-length therapeutic genes into a defined genomic safe harbor — an approach the company said could make in vivo chimeric antigen receptor T cell (CAR T) therapy accessible to a far broader patient population than current ex vivo manufacturing allows.

AN Venture Partners and RA Capital Management co-led the round, with participation from ANRI, Gemseki, and SBI US Gateway Fund. AN Venture Partners and RA Capital also led the company's USD 5 million seed round in February 2024, with ANRI having backed the company from its earliest stage following its founding in February 2022. Typewriter said proceeds will be used to identify its first in vivo CAR T development candidate and to initiate non-human primate studies planned for late 2026. The company has also received up to USD 30 million in non-dilutive funding through Japan's Agency for Medical Research and Development program to strengthen the country's pharmaceutical startup ecosystem.

The platform is built on the R2 retrotransposon, a natural gene-insertion system studied for decades by the company's academic co-founders — Professor Emeritus Haruhiko Fujiwara of the University of Tokyo and Thomas Eickbush of the University of Rochester. Using a two-component all-RNA system delivered by lipid nanoparticles (LNPs), the R2 protein inserts a therapeutic gene into the 28S ribosomal DNA locus via target-primed reverse transcription (TPRT) — a sequential single-strand nicking process that avoids the double-strand DNA breaks associated with CRISPR-based editing. The R2 machinery then degrades, leaving only the inserted gene. Because the system uses no viral vectors, it is designed to be re-dosable, overcoming a limitation that has constrained AAV-based gene therapies.

Typewriter's two initial programs target in vivo CAR T therapy across oncology and autoimmune indications, and severe genetic liver diseases. Proof-of-concept has been established in humanized mouse models for the CAR T program. Matthew Stanton, previously chief scientific officer at Generation Bio and before that head of chemistry at Moderna Therapeutics, has been appointed chief executive officer. Leanne Peiser, formerly executive director of translational research for cellular therapy at Bristol Myers Squibb, joins as chief scientific officer. Mikael Dolsten, former chief scientific officer at Pfizer, joins the board as an independent director. Stanley R. Riddell, a pioneer in adoptive T cell therapy at Fred Hutchinson Cancer Center whose CAR T work was licensed to Juno Therapeutics, has joined the scientific advisory board.

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