Threshold Pharmaceutical Inc's experimental cancer drug received orphan status from U.S. health regulators, sending the biotechnology company's stock up as much as 6 percent in premarket trade. The orphan status, which is granted in the United States to drugs that treat diseases affecting fewer than 200,000 people, can provide a seven-year marketing exclusivity for the drug from the date of approval. The experimental drug, which was licensed to a unit of Germany's Merck KGaA in February, had received orphan status from European health regulators early this month.
