Nat. Biotechnol. 34, 1019–1024 (2016); published online 11 October 2016; corrected after print 2 November 2016

In the version of this article initially published, on p.1024, middle column, the quote, “We have ipilimumab....” should have read, “We have tremelimumab....” The error has been corrected in the HTML and PDF versions of the article.