On July 27, 2005, WLF wrote to DDMAC, calling on DDMAC to withdraw a warning letter sent to Actelion Pharmaceuticals US, Inc. on July 20, 2005 regarding Actelion’s allegedly improper promotion of Tracleer on Actelion’s web site. Tracleer is a drug used to treat pulmonary arterial hypertension. DDMAC alleged that Actelion’s web site failed to include sufficient information regarding risks associated with use of Tracleer. WLF’s letter to DDMAC stated that DDMAC’s actions were unwarranted because FDA has never issued any guidance on Internet promotion of prescription drugs, despite its promises to do so. WLF also took issue with DDMAC’s assertion that Actelion should have submitted the promotional material to FDA before posting it on the Internet; WLF argued that DDMAC lacks statutory authority to impose that requirement, and that it constitutes an unconstitutional prior restraint on speech.