Tessera Therapeutics, backed by Flagship Pioneering, confirmed plans to start the first human trial of its in vivo gene‑writing platform next month in adults with a rare genetic disease. The Phase 1 entry marks one of the earliest clinical tests of a gene‑writing approach designed to install or rewrite multiple bases in genomic DNA without using viral replacement. The company will evaluate safety, delivery and initial biomarker signals as it transitions from preclinical to human testing.