Alkermes PLC has raised its offer to acquire Avadel Pharmaceuticals PLC to as much as $22.50 a share, valuing the deal at about $2.37 billion. The revised terms include $21 in cash and a contingent value right worth up to $1.50 a share, tied to U.S. Food and Drug Administration approval of Avadel’s LUMRYZ treatment for idiopathic hypersomnia by the end of 2028. The companies signed an amended agreement on Nov. 18, following Avadel’s disclosure last week of an unsolicited bid from Denmark’s H....