Merck to develop mAb through $10.8b acquisition

Merck & Co. Inc has agreed to acquire Prometheus Biosciences for $10.8 billion. The agreement is set to help advance PRA023, a novel humanised monoclonal antibody (mAb), developed by Prometheus. Its chosen indications are ulcerative colitis (UC) and Crohn’s disease (CD) and other autoimmune conditions.

Prometheus is a clinical-stage biotechnology company. “I look forward to working with the Prometheus team to establish a new paradigm of precision treatment for immune diseases,” commented Dr Dean Y Li, President of Merck Research Laboratories. 

According to Merck’s Chairman and Chief Executive Officer, Robert M Davis, the agreement will “accelerate [the company’s] growing presence in immunology.” 

Anti-TL1A monoclonal antibody for autoimmune conditions

PRA023 is directed to tumour necrosis factor (TNF)-like ligand 1A (TL1A), a target associated with both intestinal inflammation and fibrosis. It binds both soluble and membrane associated human TL1A with high affinity and specificity.

“By applying a portfolio of powerful analytic tools to a comprehensive collection of IBD samples, Prometheus identified important disease insights that have now yielded a promising late-stage candidate,” added Dr Dean Y Li.

In December 2022, Prometheus announced positive results for PRA023 from two studies of the monoclonal antibody:

• ARTEMIS-UC, a Phase II study evaluating safety and efficacy in patients with moderate to severely active UC
• APOLLO-CD, a Phase IIA study evaluating safety and efficacy in patients with moderate to severe CD. The findings were recently presented at the 18th Congress of European Crohn’s and Colitis Organisation (ECCO).

Further details of the transaction

Under the agreement, Merck, through a subsidiary, will acquire all of the outstanding shares of Prometheus. The acquisition is subject to Prometheus Biosciences shareholder approval.

Closing of the proposed transaction is expected in the third quarter of 2023 and is subject to certain conditions. This includes the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions.