Onyx Pharmaceuticals, Inc. : Bayer’s Stivarga® (regorafenib) Tablets Approved in Europe

Whippany, NJ, and South San Francisco, CA. - Aug. 30, 2013

Bayer HealthCare and Onyx Pharmaceuticals, Inc. (NASDAQ: ONXX) announced today that the European Commission has approved Stivarga® (regorafenib) tablets for the treatment of adult patients with metastatic colorectal cancer (mCRC).

In September 2012, Stivarga was approved by the U.S. Food and Drug Administration (FDA) for the treatment of patients with mCRC who have been previously treated with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy, an anti-VEGF therapy, and, if KRAS wild type, an
anti-EGFR therapy.

The approval of Stivarga was based on data from the pivotal Phase III CORRECT (Colorectal cancer treated with regorafenib or placebo after failure of standard therapy) trial. Full results from the CORRECT study were presented at the 48th Annual Meeting of the American Society of Clinical Oncology in June 2012 and published online on November 22, 2012 in The Lancet.

In the United States, Stivarga is indicated for the treatment of patients with mCRC who have been previously treated with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy, an anti-VEGF therapy, and, if KRAS wild type, an anti-EGFR therapy. It is also indicated for the treatment of patients with locally advanced, unresectable or metastatic GIST who have been previously treated with imatinib mesylate and sunitinib malate.

Stivarga is an inhibitor of multiple kinases involved in normal cellular functions and in pathologic processes such as oncogenesis, tumor angiogenesis, and maintenance of the tumor microenvironment.

Stivarga is a Bayer compound developed by Bayer and jointly promoted by Bayer and Onyx in the
United States. In 2011, Bayer entered into an agreement with Onyx, under which Onyx receives a
royalty on all global net sales of Stivarga in oncology.

For full prescribing information, including BOXED WARNING, visit www.stivarga-us.com.

• Severe and sometimes fatal hepatotoxicity has been observed in clinical trials.
• Monitor hepatic function prior to and during treatment.
• Interrupt and then reduce or discontinue Stivarga for hepatotoxicity as manifested by elevated liver function tests or hepatocellular necrosis, depending upon severity and persistence.

Severe drug-induced liver injury with fatal outcome occurred in 0.3% of 1200 Stivarga-treated patients across all clinical trials. In metastatic colorectal cancer (mCRC), fatal hepatic failure occurred in 1.6% of patients in the Stivarga arm and in 0.4% of patients in the placebo arm; all the patients with hepatic failure had metastatic disease in the liver. In gastrointestinal stromal tumor (GIST), fatal hepatic failure occurred in 0.8% of patients in the Stivarga arm.

Obtain liver function tests (ALT, AST, and bilirubin) before initiation of Stivarga and monitor at least every 2 weeks during the first 2 months of treatment. Thereafter, monitor monthly or more frequently as clinically indicated. Monitor liver function tests weekly in patients experiencing elevated liver function tests until improvement to less than 3 times the upper limit of normal (ULN) or baseline values. Temporarily hold and then reduce or permanently discontinue Stivarga, depending on the severity and persistence of hepatotoxicity as manifested by elevated liver function tests or hepatocellular necrosis.

Stivarga caused an increased incidence of hemorrhage. The overall incidence (Grades 1-5) was 21% and 11% with Stivarga vs 8% and 3% with placebo in mCRC and GIST patients, respectively. Fatal hemorrhage occurred in 4 of 632 (0.6%) Stivarga-treated patients and involved the respiratory, gastrointestinal, or genitourinary tracts. Permanently discontinue Stivarga in patients with severe or life-threatening hemorrhage and monitor INR levels more frequently in patients receiving warfarin.

Stivarga caused an increased incidence of hand-foot skin reaction (HFSR) (also known as palmar-plantar erythrodysesthesia [PPE]) and severe rash, frequently requiring dose modification. The overall incidence was 45% and 67% with Stivarga vs 7% and 12% with placebo in mCRC and GIST patients, respectively. Incidence of Grade 3 HFSR (17% vs 0% in mCRC and 22% vs 0% in GIST), Grade 3 rash (6% vs <1% in mCRC and 7% vs 0% in GIST), serious adverse reactions of erythema multiforme (0.2% vs 0% in mCRC), and Stevens-Johnson syndrome (0.2% vs 0% in mCRC) was higher in Stivarga-treated patients. Toxic epidermal necrolysis occurred in 0.17% of 1200 Stivarga -treated patients across all clinical trials. Withhold Stivarga, reduce the dose, or permanently discontinue depending on the severity and persistence of dermatologic toxicity.

Stivarga caused an increased incidence of hypertension (30% vs 8% in mCRC and 59% vs 27% in GIST with Stivarga vs placebo, respectively). Hypertensive crisis occurred in 0.25% of 1200 Stivarga-treated patients across all clinical trials. Do not initiate Stivarga until blood pressure is adequately controlled. Monitor blood pressure weekly for the first 6 weeks of treatment and then every cycle, or more frequently, as clinically indicated. Temporarily or permanently withhold Stivarga for severe or uncontrolled hypertension.

Stivarga increased the incidence of myocardial ischemia and infarction in mCRC (1.2% with Stivarga vs 0.4% with placebo). Withhold Stivarga in patients who develop new or acute cardiac ischemia or infarction, and resume only after resolution of acute cardiac ischemic events if the potential benefits outweigh the risks of further cardiac ischemia.

Reversible Posterior Leukoencephalopathy Syndrome (RPLS) occurred in 1 of 1200 Stivarga-treated patients across all clinical trials. Perform an evaluation for RPLS in any patient presenting with seizures, headache, visual disturbances, confusion, or altered mental function. Confirm the diagnosis of RPLS with MRI and discontinue Stivarga in patients who develop RPLS.

Gastrointestinal perforation or fistula occurred in 0.6% of 1200 patients treated with Stivarga across clinical trials. In GIST, 2.1% (4/188) of Stivarga-treated patients developed gastrointestinal fistula or perforation: of these, 2 cases of gastrointestinal perforation were fatal. Permanently discontinue Stivarga in patients who develop gastrointestinal perforation or fistula.

Treatment with Stivarga should be stopped at least 2 weeks prior to scheduled surgery. Resuming treatment after surgery should be based on clinical judgment of adequate wound healing. Stivarga should be discontinued in patients with wound dehiscence.

Stivarga can cause fetal harm when administered to a pregnant woman. Use effective contraception during treatment and up to 2 months after completion of therapy. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.

Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from Stivarga, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

The most frequently observed adverse drug reactions (