On 16 April 2023, Merck & Co. announced its intention to acquire Prometheus Biosciences, pending board and regulatory approval, at $200.00 per share in cash price, a 75% premium, and a total equity value of $10.8bn. With a relatively high purchase price for a set of early to mid-stage assets, the deal would be the second largest acquisition so far this year, only behind Pfizer’s $43bn offer for Seagen, and the third highest compared to last year. Central to this transaction is ownership of Prometheus’s lead drug, PRA023, an anti-TL1A monoclonal antibody currently being evaluated in ulcerative colitis (UC) and Crohn’s disease (CD). At the time of the announcement, PRA023 had completed a Phase II trial in UC and a Phase IIa study in CD. In addition to this agent, a companion diagnostic test (CDx) for PRA023 is being assessed alongside PRA023. This is another bold step by Merck within the inflammatory bowel disease (IBD) market and a crowded immunology field.