(Reuters) – The U.S. health regulator said on Monday companies will be required to add a serious warning on the prescribing information for cancer therapies known as CAR-T, made by Gilead Sciences, Johnson & Johnson, Novartis and others. Last November, the U.S Food and Drug Administration said it had received reports of patients developing a type of T-cell blood cancer after being treated with genetically modified cells known as chimeric antigen receptor T-cell therapies or CAR-T. The other cancer therapies include Bristol Myers Squibb’s Breyanzi and its partnered therapy, Abecma, with 2sevent…