Pfizer is voluntarily withdrawing Thelin (sitaxentan) for the treatment of pulmonary arterial hypertension (PAH) in the EU, Canada and Australia, where the drug is approved. The company will also discontinue clinical studies of Thelin worldwide. The decision was based on emerging safety information from clinical trials and post-marketing reports that a new potentially life-threatening risk of liver injury with Thelin has been observed. While liver toxicity is a known complication of the class...