Tessera Therapeutics

Tessera is the leading non-CRISPR bet in genome engineering, and its Gene Writing platform targets the two capabilities the field most needs: writing entire genes and doing it in vivo without cutting DNA. Built inside Flagship Pioneering and founded in 2018, Gene Writing re-engineers mobile genetic elements — nature's own systems for relocating DNA and RNA — into programmable tools that span single-base corrections, short insertions and deletions, and whole-gene insertion, paired with lipid-nanoparticle delivery for systemic administration. The lead sickle cell program is the showcase: in non-human primates, a single intravenous dose achieved an average of 24% rewriting of the HBB gene in long-term hematopoietic stem cells — a level meeting therapeutic thresholds and, crucially, delivered in vivo without the toxic chemotherapy conditioning or lymphodepletion that ex-vivo cell therapies require. That is a genuinely differentiated approach to a disease where approved therapies still demand brutal conditioning. The Bill & Melinda Gates Foundation's commitment of up to $50M to jointly fund the in-vivo sickle cell program toward the clinic is a strong non-dilutive validation of both the science and its global-health reach. With over $300M raised in its 2022 Series C (Flagship, ADIA, Alaska Permanent Fund) and $530M total, Tessera holds a well-capitalized, scientifically distinct platform aimed squarely at the whole-gene-insertion prize that CRISPR nucleases struggle to reach.