Two independent research teams reported advances toward generating CAR‑T cells in vivo, demonstrating programmable, site‑specific integration or dual‑vector approaches that reprogram T cells inside living hosts. In preclinical models researchers achieved stable transgene integration, durable antitumor responses and activity against solid tumors—outcomes that, if reproduced clinically, would bypass centralized ex‑vivo cell manufacturing. The work showcases a range of delivery modalities—from targeted vectors to lipid nanoparticles—paired with genome‑editing or integrase systems to insert CAR constructs into defined loci. For readers: in‑vivo CAR‑T refers to methods that genetically modify circulating T cells inside the patient, rather than extracting and engineering cells in specialized facilities. Teams caution that specificity, off‑target integration and immunogenicity are key obstacles before clinical translation. If solved, in‑vivo CAR‑T could radically lower costs, shorten treatment timelines and expand global access to engineered cell therapies.