Inaccurate ads on Facebook regarding Truvada. More than 50 people and advocacy organizations sent a letter to Facebook chief executive officer Mark Zuckerberg late last year, demanding that Facebook and its subsidiary, Instagram, cease accepting advertisements with false or misleading warnings about Truvada, a once-a-day pill for HIV preexposure prophylaxis (PrEP) that research shows is 99% effective at preventing HIV transmission. The ads, which appeared to target LGBTQ people, sought plaintiffs for class action lawsuits against the drug's manufacturer, Gilead Sciences. The advocates asserted that because the ads included misleading claims that Truvada caused bone and kidney damage, they were having a "chilling" effect on users and potential users of the drug. Initially, Facebook claimed that the ads did not violate company policy and weren't rated as false by third-party fact-checkers. The advocates insisted that Facebook review and update "current advertising policies to prevent false or misleading public health statements from reaching users." In January, Facebook began limiting the visibility of some of the ads, a response that advocates, health experts, and regulators said is unsatisfactory and raised questions about how Facebook will handle such ads in the future. To read the letter, go to http://www.glaad.org/blog/open-letter-facebook.