GlaxoSmithKline’s pazopanib pill for renal cell carcinoma showed similar efficacy to Pfizer Inc.’s sunitinib with fewer side effects in a late-stage study.

For both drugs, the average progression-free survival was slightly more than 10 months, according to a study of 1,100 patients. The study, dubbed COMPARZ and funded by London-based drug maker Glaxo (NYSE: GSK), was released Monday at the European Society for Medical Oncology meeting in Vienna.

“The COMPARZ trial allows us to define a standard option in the front line treatment of renal cell carcinoma, because it was proven that pazopanib is non-inferior to sunitinib,” Maria De Santis of Kaiser Franz Josef-Spital in Vienna said in a statement. “In addition, being treated with pazopanib, patients experienced fewer troublesome side-effects and an increased quality of life.”

Renal cell carcinoma is a type of kidney cancer that starts in the lining of tubes in the kidney. While both drugs resulted in side effects, some, such as fatigue and skin sores, occurred with less frequency for pazopanib than with sunitinib, which is marketed as Sutent, the researchers found.

Pazopanib was approved for use in the U.S. in 2009 for advanced renal cell carcinoma and is marketed as Votrient. An estimated 64,770 new cases of kidney cancer will probably be diagnosed in the U.S. this year, and about 13,570 people will die of the disease, according to the American Cancer Society. Many patients don’t know they have cancer until it has reached an advanced stage because small tumors can’t be felt and aren’t easily detected.

“We anticipate that the COMPARZ data with Votrient will likely enable Glaxo to take market share from Pfizer’s Sutent in renal cancer,” Andrew Baum, an analyst for Citigroup Inc. in London, said in a note to investors last week.

Sutent had global sales of $1.2 billion in 2011.

GSK operates its U.S. headquarters in Research Triangle Park, N.C.

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