GlaxoSmithKline PLC (GSK), of London, announced on April 22 that it would acquire Sirtris Pharmaceuticals of Cambridge, Massachusetts, for $720 million, making the month one of the busiest for biotech mergers and acquisitions in recent years, and certainly the best for Boston-area biotech (see “Millennium ends Takeda's US shopping spree”). The deal centers on Sirtris' stronghold position in sirtuins, a family of proteins implicated in the aging process in many species, for access to which GSK agreed to pay an 84% premium on Sirtris' outstanding shares.

Sirtris' lead compound, SRT501, is a molecule reported to target the sirtuin enzyme SIRT1 and thereby activate mitochondria. The drug cleared its phase 1 trial and is now in a phase 2a study used in combination with metformin for the treatment of type 2 diabetes. In announcing the deal, GSK chairman of R&D Moncef Slaoui said that modulation of the sirtuin enzymes was “potentially transformative science,” with potential applications in a wide range of metabolic and degenerative disorders.

“From GSK's perspective, it's a significant but certainly not a large deal,” notes David Seemungal, managing director for pharmaceutical research at ING Wholesale Banking in London. “And it's very much in line with a longer-term plan to develop their metabolic control portfolio, particularly following the Avandia setback.”

But the offer was not without its critics, who point out that Sirtris currently has only a single compound in an early-stage clinical trial and that there is still scant evidence for efficacy in humans to back up the considerable hype that has surrounded the sirtuins since their discovery in budding yeast nearly 20 years ago.

GSK plans to maintain Sirtris as an autonomous drug-discovery unit with current Sirtris CEO Christoph Westphal and his management team at the helm, making this the latest in a number of recent deals in which big pharma has made efforts to structure buyouts so as to acquire people in addition to pipelines. DS