Johnson & Johnson moved deeper into in vivo cell therapy by paying $785 million upfront to partner with Sail Biomedicines on autoimmune programs, with an option to acquire Sail for $2.58 billion. The collaboration includes a $465 million equity investment and up to $140 million in development milestones, targeting immune “reset” by delivering circular RNA intended to drive durable CD19 CAR expression in vivo. The deal positions J&J to compete in a growing field of in vivo CAR-T bets, where multiple large pharma players have already committed capital. Sail’s vanguard program centers on SAIL-0839, designed to target CD4 and CD8 T cells, with preclinical results described in mouse models showing B-cell depletion after short dosing cycles. The announcement underscores that in vivo approaches are increasingly treated as platform plays—expanding across targets after validating a lead disease program—rather than as single-asset, single-indication bets.