Researchers at the Arc Institute and Stanford reported that supplementation with β‑hydroxybutyrate (BHB) enhanced metabolic fitness and antitumor activity of CAR‑T cells in mouse models, and human trials are now underway to test the approach. The team showed BHB supported CAR‑T persistence and function in hostile tumor microenvironments, improving response rates in preclinical systems. BHB is a naturally occurring ketone body produced during fasting or ketogenic states; the findings suggest metabolic modulation can be used to increase the therapeutic window for adoptive cell therapies. Investigators have initiated early‑phase human studies to assess safety, dosing, and whether the metabolic effects translate to durable clinical responses. If validated in patients, BHB or related metabolic adjuvants could become low‑cost adjuncts to cell therapy regimens and broaden CAR‑T applicability beyond hematologic malignancies into solid tumors.