Item 8.01 Other Events.

On January 25, 2013, Threshold Pharmaceuticals, Inc. issued a press release announcing that Threshold's partner Merck KGaA, Darmstadt, Germany, through its division Merck Serono, initiated the global Phase 3 MAESTRO (MetastAtic or unrESectable pancreaTic adenocaRcinOma) study assessing the efficacy and safety of investigational hypoxia-targeted drug TH-302 in combination with gemcitabine in patients with previously untreated, locally advanced unresectable or metastatic pancreatic adenocarcinoma. The initiation of the Phase 3 MAESTRO study resulted in Threshold earning a $30 million milestone payment from Merck KGaA pursuant to the terms of Threshold's license and co-development agreement with Merck KGaA, which includes an option for Threshold to co-commercialize in the U.S. The press release is attached as Exhibit 99.1 to this Form 8-K.