GlaxoSmithKline plc / Sirtris Pharmaceuticals, Inc.

Type 2 Diabetes / Aging-related metabolic disease (sirtuin platform)

Disease Overview

Sirtris was a platform deal targeting sirtuins — a family of seven NAD+-dependent enzymes (SIRT1–SIRT7) thought to mimic the metabolic benefits of caloric restriction and modulate aging-related disease. Lead clinical applications at deal time were Type 2 diabetes (SRT501 + metformin Phase 2a), MELAS mitochondrial syndrome (SRT501 Phase 1b) and preclinical Huntington's disease.

Competitive Landscape

GSK's April 2008 acquisition of Sirtris for ~$720M ($22.50/share, an ~82–84% premium) was a platform bet on sirtuin biology, not a competitive entry into an established therapeutic class. Lead candidate SRT501 was a proprietary resveratrol formulation; backup compound SRT2104 was a structurally distinct novel SIRT1 activator. The competitive context: in Type 2 diabetes, the standard-of-care was metformin, with sulfonylureas, TZDs (Actos, Avandia — the latter under cardiovascular safety scrutiny by 2008) and the newly approved DPP-4 inhibitor Januvia (sitagliptin, Merck). Sirtuins promised a differentiated mechanism with a cleaner safety profile than glitazones. The deal unraveled progressively: 2009–2010 Pfizer and Amgen papers showed resveratrol's apparent SIRT1 activation was an assay artifact; SRT501 was halted in late 2010 over GI tolerability and lack of SIRT1 specificity; and GSK shut the Cambridge Sirtris site in 2013, absorbing remaining compounds into corporate R&D. The transaction is now a canonical example of platform M&A risk when underlying biology is contested.