Tessera Therapeutics confirmed it will start the first‑in‑human trial of its in vivo gene‑writing platform next month, filing clinical steps to test the technology in adults with a rare genetic disease. The company’s approach programs DNA directly in patients’ tissues without permanent viral insertion at the target locus. Tessera’s entry into the clinic marks a pivotal moment for 'gene writing' approaches that aim to install or rewrite genomic sequences in situ rather than delivering a corrective gene via a conventional vector. The trial is being watched for safety, on‑target editing rates, and biomarkers of functional benefit. Regulatory interest and rigorous monitoring of off‑target edits will shape trial design; success could open a new class of in vivo genetic medicines aimed at conditions now out of reach for standard gene replacement or editing strategies.