The FDA granted “priority review” status to Roche/Genentech’s Phase III chronic lymphocytic leukemia drug obinutuzumab, or GA101, Wednesday. It comes after the agent earned Breakthrough Therapy designation from the regulator in May. The FDA is set to make a thumbs-up/thumbs-down decision by December 20, according to a company statement.

The timing of the drug’s approval would be great news for the Swiss company, because it would allow the drug maker to add a branded biologic to the therapy mix as its branded Rituxan loses its patent protection in the next two years. Rituxan added close to $6 billion in sales to the firm’s 2012 balance sheet.

Priority review shortens the review window to six months from the standard 10. Breakthrough therapy designations help expedite review and can be applied to drugs that are substantially better than what is already available on clinically significant endpoints, such as morbidity or mortality or disease symptoms.

The FDA provided the priority review status based on the first set of data from a Phase III clinical trial the drug maker says “demonstrated a statistically significant 86% reduction in the risk of disease worsening or death” when combined with chlorambucil chemotherapy, as opposed to a chemotherapy-only approach.

Chronic lymphocytic leukemia (CLL) results from an overproduction of B lymphocytes, and is generally diagnosed in adults 60 and older—men more frequently than women.