The Phase IIa lure of sirtuins drew GlaxoSmithKline to snatch up Sirtris Pharmaceuticals in a cash tender offer of $22.50 per share, valuing the deal - expected to close in the second quarter - at about $720 million.

"It's an over 80 percent premium for our shareholders," said Michelle Dipp, Sirtris' director of corporate development, an architect of the GSK deal.

News of the merger broke after the market closed April 22. Sirtris' shares ended trading that day at $12.23.

London-based GSK is "committed to diseases of aging, so we share a common vision," she told "The Pink Sheet" DAILY.

Sirtris, of Cambridge, Mass., will operate as an independent unit of GSK, with no loss of employees or management.

SRT501, Sirtris' lead candidate, is designed to mimic the beneficial effects of calorie restriction by activating sirtuin-1, an enzyme that regulates aging.

The ongoing trial is testing SRT501 with and without metformin in type 2 diabetics with inadequate HbA1c control on metformin alone.

Formulated from resveratrol, a phytoalexin found in red wine, SRT501 boosts the number of mitochrondria, and thus "goes to the grass roots of what causes diabetes," Dipp said.

Oppenheimer analyst Bret Holley, in an April 17 research note, "cited a good probability of positive data" from the trial in the second half of this year.

Sirtris had been shopping for a partner, but Dipp would not say whether the takeover by GSK grew out of such talks (¹ Also see "Fourth Quarter R&D Costly For Sirtris, But Partner Could Be Near" - Pink Sheet, 27 February, 2008.).

Paperwork to be filed within a week with the Securities and Exchange Commission will provide more details, Dipp said.

SRT501 also is undergoing Phase Ib testing in a three-month study to evaluate the compound in a syndrome called MELAS (Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes).

Progressive and fatal, MELAS strikes between ages 3 and 40, bringing muscle weakness, fatigue, headaches and seizures. About a third of patients also have type 2 diabetes. FDA granted SRT501 orphan drug status in MELAS.

Mitochondria, Dipp noted, are the only organelles with their own DNA that can undergo point mutations, potentially leading to any of about 200 disorders.

Sirtris also is looking into using sirtuins against cancer. Last year, Pharmion and MethylGene added sirtuins to their pact for developing histone deacetylase enzyme inhibitors (² Also see "Pharmion and MethylGene Collaborate On Sirtuin Inhibitors To Treat Cancer" - Pink Sheet, 20 August, 2007.).

- Randall Osborne (r.osborne@elsevier.com)

GSK To Pay $720 Million For Sirtris

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