Exelixis Inc said a late-stage trial of its experimental thyroid cancer drug met the main goal of improving survival of patients without disease progression, compared with a dummy drug.

The drug cabozantinib significantly improved median progression-free survival (PFS) by 7.2 months compared with a placebo. The median PFS for patients taking cabozantinib was 11.2 months versus 4 months for those on placebo.

The trial, named EXAM, is being conducted under a special protocol assessment (SPA) agreement with the U.S. Food and Drug Administration.

SPA provides a company with a written agreement that the design and analysis of the trial are adequate to support a marketing application submission with the FDA.

Exelixis said it was requesting permission to begin a rolling submission of the new drug application for cabozantinib in advanced medullary thyroid cancer and expects the filing will be completed in the first half of 2012.