Paul Weiss Rifkind Wharton & Garrison has advised Big Pharma giants on two major deals this week: Merck’s acquisition of drugmaker Prometheus Biosciences for almost $11bn and today's £1.6bn acquisition by GSK of Canadian drugmaker Bellus.

Also cashing in on what is being dubbed a revival of the pharma sector is Latham & Watkins, which is advising Prometheus Biosciences, and Skadden Arps Slate Meagher & Flom, which is advising Bellus. 

Merck's deal for San Diego-based Prometheus, which develops treatments for autoimmune diseases, comes as Merck moves to diversify its pipeline ahead of the expiration of key patents related to its blockbuster cancer drug Keytruda later this decade. 

Merck said on Sunday that the two companies had entered into a definitive agreement under which Merck, through a subsidiary, has agreed to acquire Prometheus for $200.00 per share in cash for a total equity value of approximately $10.8bn.

The company said the deal would boost its position in the fast-growing field of immunology, where there is significant unmet patient need. 

“This transaction adds diversity to our overall portfolio and is an important building block as we strengthen the sustainable innovation engine that will drive our growth well into the next decade,” said Robert Davis, Merck’s chair and chief executive.

A Paul Weiss team led by corporate partners Laura Turano and Scott Barshay and associate Jennifer Wang advised Merck on the matter. Corporate partner Christodoulos Kaoutzanis also acted on the deal along with intellectual property partner Jonathan Ashtor and counsel Bonnie Chen, executive compensation partner Jarrett Hoffman, real estate partner Peter Fisch, tax counsel Alyssa Wolpin and environmental counsel William O’Brien.

The Latham team representing Prometheus comprised a corporate deal team led by partners Daniel Rees, Matthew Bush and Cheston Larson. Partners Holly Bauer (benefits and compensation), Ben Haas (regulatory), Betty Pang (regulatory), Josh Holian (antitrust), Chris Hazuka (intellectual property), Samuel Weiner (tax) and Heather Deixler (data privacy) also worked on the deal alongside a supporting cast of counsel and associates. 

Meanwhile, GSK's deal to buy late-stage biopharmaceutical company Bellus Health, which is priced at $14.75-per share, is being interpreted as a tonic for London's stock market. Today's deal will provide the UK pharma giant with ‘potential best-in-class treatment for refractory chronic cough’ via camlipixant, which is in phase III clinical development with anticipated regulatory approval and launch in 2026.

Canadian law firm Stikeman Elliott is also acting for GSK on the deal, while Toronto-based Davies Ward Phillips & Vineberg is advising Bellus alongside Skadden. 

The deals are the latest sign of a thaw in mergers and acquisitions in the pharmaceuticals sector following a dip in activity last year after a record-breaking year for M&A globally in 2021. 

In March, Pfizer announced it was buying Seagen for a total enterprise value of $43bn, in a deal that saw M&A powerhouse Wachtell Lipton Rosen & Katz called in to advise longtime client Pfizer and a team from Sullivan & Cromwell act for Seagen. The acquisition was the largest in the pharma sector since AbbVie agreed to buy Allergan in 2019, according to the Financial Times.