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FDA staff focus on Onyx cancer drug's side effects
June 18, 2012 / 1:01 PM / in 5 years

FDA staff focus on Onyx cancer drug's side effects

WASHINGTON (Reuters) - U.S. drug reviewers said the serious heart, lung and liver side effects of Onyx Pharmaceuticals Inc’s carfilzomib drug may outweigh the experimental drug’s benefits for patients with a type of blood cancer.

The Food and Drug Administration staff said about 22 percent of people taking the drug during a key clinical trial responded to the medicine, and many had severe side effects, meaning carfilzomib may not be better than older treatments for multiple myeloma.

“FDA is very concerned with the severe toxicities, including deaths that are associated with the use of this agent,” the reviewers said in documents posted online on Monday. They added it was not clear whether the drug caused the side effects.

“Considering these factors, the risks of carfilzomib may not outweigh its benefits,” they said.

The FDA staff review comes ahead of an advisory panel, which will vote on whether to recommend the drug on Wednesday. The FDA will make a final decision later, taking into account the panel’s recommendations.

Multiple myeloma, a type of cancer that affects plasma cells, is relatively rare in the United States but often deadly. In 2012, about 21,700 new cases of multiple myeloma will be diagnosed in the United States, and about 10,710 people will die from the disease, according to the American Cancer Society.

Analysts expect the multiple myeloma market to reach $5.4 billion by 2016, with carfilzomib garnering about $570 million if it is approved, according to Thomson Reuters forecasts.

Onyx wants to obtain approval of its drug, to be sold as Kyprolis, for people who have not had success with at least two other treatments for multiple myeloma, or cannot tolerate the older drugs.

The older treatments must include Takeda Pharmaceutical Co Ltd’s Velcade and Celgene Corp’s Revlimid or Thalomid, known chemically as thalidomide.

But the FDA staff said Onyx did not prove that people taking Kyprolis in clinical trials had already failed with all of the seven drugs approved for multiple myeloma.

They also said Revlimid and Thalomid, among others, did not have the same serious side effects as Kyprolis.

The FDA staff said seven people taking the drug during a clinical trial died from cardiac-related issues, and these issues may have also contributed to another three deaths. Another 6 percent of the 266 patients enrolled in the clinical trial stopped taking the drug because of cardiac issues.

The FDA said it was hard to figure out if people died because of the drug, since carfilzomib was tested only in a single-arm study, meaning it was not compared with placebo or any other treatment.

However, some analysts viewed the FDA staff documents as positive for Onyx, since they had expected the FDA staff to have stronger disagreements with the company about the drug’s effectiveness.

Geoff Porges, analyst at Sanford Bernstein, said he expects Wednesday’s panel to decide that the drug’s risks could be managed with a post-approval safety program.

“We expect a positive split vote in favor of (the) drug’s approval,” he said in a research note.

Shares of San Francisco-based Onyx were down 0.5 percent at $45.74 on Monday morning. Shares of Ligand Pharmaceuticals Inc - a small biotech that contributed to Kyprolis and would receive royalties from its sales - were down 2.8 percent at $12.96.

Reporting by Anna Yukhananov; Editing by Gerald E. McCormick and Matthew Lewis

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