Regeneron Pharmaceuticals and Tessera Therapeutics struck a collaboration valued at $150 million to develop and commercialize TSRA‑196, Tessera’s in‑vivo gene‑writing candidate for alpha‑1 antitrypsin deficiency (AATD). The deal combines Regeneron’s development and commercialization infrastructure with Tessera’s gene writing platform, a newer approach that writes corrective sequences directly into genomic DNA rather than editing existing bases. TSRA‑196 is described as one of Tessera’s near‑clinic programs; Regeneron will advance clinical development under the agreement. Company announcements characterize the pact as a strategic expansion of Regeneron’s genetic medicine investments and a validation of gene writing as a complementary modality to established gene editing and gene therapy approaches. Gene writing refers to technologies that insert or replace DNA sequences at target loci without relying on double‑strand breaks typical of nuclease editing; proponents say it can enable durable correction for monogenic diseases. The collaboration signals increased Big Pharma appetite for platform bets in rare genetic disorders and surfaces questions about regulatory and manufacturing pathways for in‑vivo sequence‑insertion technologies.