Nat. Med. 10, 262–267 (2004); published online 22 February 2004

We wish to alert our readers that VX-680, the compound originally reported in the above study, is no longer available from the authors at Vertex Pharmaceuticals due to a post-publication licensing agreement with Merck. However, the compound (referred to by Merck as MK-0457) is being made available through Merck's Investigator-Initiated Studies Program (https://www.merckiisp.com).