Aug 12 (Reuters) - AbbVie Inc on Wednesday said its experimental treatment for a form of leukemia associated with a gene mutation met its primary goal in a mid-stage trial and that the company would seek U.S. approval of the medicine, which analysts have said has blockbuster sales potential.

AbbVie, which is developing the drug venetoclax with Switzerland's Roche Holding AG, said it would unveil data from the Phase II trial at an upcoming medical meeting and will seek U.S. marketing approval for the product before the end of 2015.

The drug was tested in patients with chronic lymphocytic leukemia (CLL) who had a so-called 17p gene deletion that has been associated with aggressive cancer and survival of less than 2 to 3 years after diagnosis. The trial included patients with relapsed or advanced CLL, or those who had previously been untreated.

Brokerage Cowen and Co has predicted the medicine, if approved, could capture annual sales of $2 billion by 2020. It works by blocking BCL-2, a protein that prevents self-destruction of defective or cancerous cells in the body.

(Reporting by Ransdell Pierson; Editing by Nick Zieminski)