Overview
Tome Biosciences sought to turn a genome-editing technique from MIT into treatments for genetic and immune diseases. It emerged publicly in December 2023 with $213 million raised across two funding rounds. Eight months later it scaled back and announced layoffs affecting 131 people. Forbes reported in February 2026 that Tome was no longer operating. The exact closure date is not established. [1][2][3]
The company remained preclinical. Its laboratory research and financing did not establish that its platform could safely treat patients. [2]
Founding Story
Researchers Omar Abudayyeh and Jonathan Gootenberg founded Tome around work licensed from MIT. Their research on programmable insertion of DNA sought to expand what genome editing could do beyond cutting or making small changes. Rahul Kakkar, previously CEO of Pandion Therapeutics, led the company. The a16z investment account described the scientific founders and management team; it is an investor's view of the opportunity. [4][5]
The company disclosed $213 million in Series A and B funding at its December 2023 launch. Its investors included a16z Bio + Health, ARCH Venture Partners, GV, Longwood, and Polaris. The announcement described a platform and pipeline under development, not a marketed product. [1]
Timeline
- 2022: MIT researchers published work on PASTE, a method for inserting larger DNA sequences without double-strand DNA cleavage. [6]
- December 2023: Tome launched publicly and disclosed $213 million raised. [1]
- January 2024: Tome announced its acquisition of Replace Therapeutics and its small-sequence editing technology. [7]
- August 2024: Tome said it was operating at reduced capacity and exploring strategic options; a notice described 131 layoffs by November. [2]
- February 2026: Forbes reported Tome was no longer operating, without specifying a closure date. [3]
What They Built
Tome called its approach programmable genomic integration. The underlying MIT work, called PASTE, used CRISPR-directed machinery and an integrase to insert DNA at targeted locations without requiring a double-strand cut. A 2022 paper and MIT's account reported laboratory experiments, including work in cells and a mouse model containing human liver cells. These were early experimental results, not evidence of safety or efficacy in patients. [6][8]
Tome intended to develop treatments both inside the body and by editing cells outside it. Its launch plans included liver disease and B-cell-driven autoimmune disease. In January 2024 it acquired Replace Therapeutics, whose ligase-based approach was designed for smaller edits. Tome announced $65 million in upfront and near-term milestones and up to $185 million in total deal value, through stock and cash. The maximum was contingent; it was not established as cash paid at closing. [4][7]
Market Position
Target Customers
Tome aimed to develop genetic medicines for patients, with clinicians and regulators determining the suitability and approval of future therapies. Its programs were preclinical when funding pressures became public. [2]
Market Size
A technology that might apply to several diseases did not establish an addressable market or approved treatment. Each proposed use still required delivery, safety, clinical, and regulatory work. [5]
Competition
Tome entered a field with multiple approaches to gene editing, including companies using CRISPR and prime editing. Its proposed distinction was inserting larger sequences at targeted sites. The research was promising but did not prove superiority or a clinical outcome. [5][6]
Business Model
Tome raised venture funding to develop technology and candidate medicines. It also pursued collaborations: in 2024 it arranged to combine its editing technology with Genevant's lipid nanoparticle delivery work for a liver-disease program. The deal's reported maximum included potential future payments. Public sources reviewed do not establish product revenue or the company's complete spending. [9]
Traction
The scientific paper, $213 million financing, and Replace transaction showed access to research, capital, and additional technology. None was a clinical approval. The company reported scientific progress while also seeking strategic options in 2024. [1][2][7]
Post-Mortem
Funding and time
BioPharma Dive reported that Tome had unsuccessfully sought a Series C. Kakkar attributed the pressure to a shift in investor sentiment toward preclinical gene-editing companies. That account explains a funding challenge, but the public record reviewed does not establish the full budget, each investor's decision, or a definitive breakdown of why the company stopped. [2]
Scale-back and later status
In August 2024 Tome described reduced operations and confidential discussions with potential partners. A regulatory notice projected 131 layoffs by November, roughly the size of its reported workforce. That announcement did not itself confirm an immediate shutdown. Forbes reported in February 2026 that the company was no longer operating; it did not supply the exact date or establish an asset buyer. [2][3]
The structural problem was timing: an early platform needed years of delivery and clinical work, while continuing that work depended on financing before a product could earn revenue. The exact contribution of company decisions and market conditions cannot be separated from the available evidence. [2][5]
Key Lessons
- Separate experimental capability from a medicine. Tome's PASTE research demonstrated laboratory methods, while the company remained preclinical. [6][2]
- Distinguish headline deal value from cash spent. Replace's $185 million maximum included future milestones and a mix of stock and cash. [7]
- Track status over time. Tome described reduced operations in 2024; the later report of no operations came in 2026. [2][3]
Sources
- Tome launch announcement
- BioPharma Dive on layoffs and funding
- Forbes on later operating status
- Andreessen Horowitz investment announcement
- BioPharma Dive on launch and technology
- Nature Biotechnology PASTE paper
- Tome acquisition of Replace Therapeutics
- MIT McGovern Institute on PASTE experiments
- Fierce Biotech on scale-back and Genevant collaboration