Thelin is sold in the Australia, Canada and the European Union as an oral treatment for severe pulmonary arterial hypertension.
Pfizer has said that two patients enrolled in a clinical trial of Thelin have died during the trial. Further, a review of data from clinical studies and post-marketing reports showed a new link to liver injury. While liver damage was a known side effect of Thelin and similar agents, the data review revealed a new link to liver damage that was not related to identifiable risk factors. Pfizer noted that it was unlikely routine monitoring would detect any problem and that in some cases, the related health problems did not stop after the patients had stopped taking the drug.
Pfizer also said that it has withdrawn its filing for marketing approval of the drug in the US.