Bristol Myers Squibb Co.’s Orencia on Wednesday became the first drug to win U.S. approval for the prevention of acute Graft versus Host Disease (aGvHD), a potentially fatal complication that could occur after a stem cell transplant. The Food and Drug Administration (FDA) has cleared the drug in combination with certain immunosuppressants for use in adults and children aged two and older who are undergoing stem cell transplantation from an unrelated donor. The disease, in which the immune cells of the donor attack the recipient’s body, can be acute or chronic. The former could affect the gastrointestinal tract, skin and liver, with symptoms likely appearing within weeks of the transplant. In 2019, Incyte’s Jakafi had won the first U.S. approval for the treatment of aGvHD patients 12 years and older. Orencia’s approval was based on real-world clinical evidence of the drug’s efficacy and results from a mid-stage study showing a …