Nov 1 (Reuters) - U.S. regulators said on Friday they approved a new treatment from Roche Holding AG for patients with chronic lymphocytic leukemia who have not previously been treated for the blood and bone marrow disease.

The U.S. Food and Drug Administration said the new drug, Gazyva (obinutuzumab), works by helping certain immune system cells to attack cancer cells, and is meant to be used with a standard treatment for the disease called chlorambucil.

It is the first drug having a "breakthrough therapy" designation to win FDA approval, the agency said. The new designation indicates the medicine may offer substantial improvement over standard treatments for patients with serious or life-threatening diseases.