CAMBRIDGE, Mass. — Serif Biomedicines said new preclinical data presented at the American Society of Gene and Cell Therapy Annual Meeting support the potential of Modified DNA as a new class of genetic medicines.
The Cambridge-based company, a Flagship Pioneering company, said the data show early progress in addressing two barriers that have historically limited DNA as a therapeutic modality: innate immune activation and inefficient access to the cell nucleus.
Serif’s platform is designed to use Modified DNA forms that reduce innate immune activation and co-delivered mRNA co-factors that increase Modified DNA activity. The company said the approach could create a therapeutic space between mRNA and gene therapy, allowing DNA to express genes for longer than RNA without relying on permanent genome integration or engineering.
“DNA has always had extraordinary therapeutic potential, but it has remained just out of reach because of immunogenicity and nuclear access challenges,” said Jacob Rubens, Ph.D., Co-Founder and Chief Executive Officer of Serif Biomedicines and Origination Partner at Flagship Pioneering. “These data show that we are making meaningful progress against both barriers and beginning to define a new space between mRNA and gene therapy, where DNA can express genes for longer than RNA without relying on permanent genome integration or engineering.”
In studies presented at ASGCT 2026, Serif said its Modified DNA showed minimal to undetectable activation of cGAS/STING and innate immunogenicity compared with unmodified DNA, while maintaining high levels of gene expression. The company also said LNP-formulated Modified DNA was well-tolerated after intravenous administration in non-human primates, with limited inflammation.
Serif said its proprietary mRNA co-factors significantly increased gene expression from Modified DNA in hepatocytes and T cells in both in vitro and in vivo studies.
The company also presented preclinical proof-of-concept data in rare disease and immune cell programming models. In a liver-directed rat model, Modified DNA achieved sustained expression of therapeutic levels of human Factor IX for more than six weeks after a single dose, supporting potential use in rare diseases.
In a humanized mouse model of immune cell programming, a single dose of T cell-targeted lipid nanoparticles carrying Modified DNA encoding a CD19 CAR led to CAR expression for more than a week and complete B-cell depletion in peripheral blood and spleen.
“These results reflect the core elements we believe are required to support the development Modified DNA as a new therapeutic modality, including reduction of innate immune activation, sustained expression, and demonstration of functional activity in vivo,” said Matt Kennedy, Ph.D., SVP, Head of Platform at Serif Biomedicines. “Together, they highlight Modified DNA’s potential to enable multiple categories of medicines for diseases where longer expression, cell-specific control, and the ability to dose again could create advantages over existing genetic medicine approaches.”
The data were presented by Kennedy in an oral presentation titled, “Modified DNA: a new therapeutic modality for scalable, programmable, durable, and redosable genetic medicines,” at the ASGCT Annual Meeting 2026.
