GlaxoSmithKline (GSK) has agreed to buy US biopharmaceutical firm Sirtris Pharmaceuticals for $720 million (£362 million) for its research.

GSK will pay $22.50 (£11.13) per share for the company and is hoping to close the deal in the second quarter of 2008.

Cambridge, Massachusetts-based Sirtris is developing a class of enzymes called sirtuins, which are believed to be involved in the ageing process.

According to GSK, Sirtris has established a drug discovery capability to exploit sirtuin modulation for treatments and has so far focussed on developing a drug for Type 2 diabetes.

“Modulation of this family of enzymes is a potentially transformative science that could address diseases associated with metabolism and ageing such as diabetes, muscle wasting, and neurodegeneration,” said Moncef Slaoui, chairman of GSK R&D.

“This acquisition continues GSK’s strategy of pursuing the best new science, externally or internally, to bring new medicines to patients and value to the GSK pipeline. Our intent is to retain all Sirtris employees and continue the entrepreneurial and innovative culture they created.”

Sirtris will become part of GSK’s drug discovery organisation, the company said, while continuing to operate from laboratories in Cambridge, Massachusetts as an autonomous drug discovery unit.

Christoph Westphal, CEO and vice chair of Sirtris and the management team will continue to lead the unit.