Study DAR-312 did not meet its primary co-endpoints.

This is a double-blind, active-controlled, long-term study of a new experimental drug called darusentan. Darusentan in not currently approved by the United States Food and Drug Administration (FDA), which means that a doctor cannot prescribe this drug. The purpose of this study is to evaluate the long-term safety of darusentan (optimized dose) as compared to an active control, administered orally.

SELECTED INCLUSION CRITERIA:

1. Subjects must be competent to provide written informed consent;
2. Subjects must have completed the Maintenance Period of the DAR-312 study.

SELECTED EXCLUSION CRITERIA:

1. Subjects who discontinue treatment with study drug prior to the end of the Maintenance Period in DAR-312 due to a study drug-related AE;
2. Subjects who experience a study drug-related serious adverse event (SAE) during the DAR-312 study.