AbbVie Inc. said a combination treatment with its drug Venclexta and Roche Holding AG's Gazyva showed promise in a phase 3 trial with chronic lymphocytic leukemia.

Results from the CLL14 study showed the drugs worked better for previously untreated patients than the standard treatment of Gazyva and chlorambucil, a chemotherapy drug.

The combo treatment showed that after two years — one year of treatment and one year after treatment — 88.2% of patients exhibited no sign of disease progression, compared to 64.1% of the standard treatment, according to a June 4 statement from Roche.

AbbVie said the Venclexta-Gazyva combination reduced the risk of disease worsening or death by 65% compared to Gazyva plus chlorambucil.

Chronic lymphocytic leukemia, or CLL, is when too many white blood cells are found in the bone marrow, according to the National Cancer Institute. CLL is the most common form of adult leukemia, and there will be an estimated 20,000 new cases diagnosed in the U.S. in 2019, according to the Roche statement.

The U.S. Food and Drug Administration approved the drug treatment May 15 through its breakthrough therapy pathway, which speeds up the approval process to two months after submission. The approval was based on results from the CLL14 trial.

The trial results also showed success for the combo treatment in regards to minimal residual disease-negativity, or MRD-negativity. The test is highly sensitive and measures the prevalence of the disease at the blood level, defined as less than one CLL cell in 10,000 white blood cells, according to the Roche statement.

The combo treatment showed MRD-negativity in the bone marrow of 56.9% of patients and in the peripheral bloodstream of 75.5% of patients. The standard treatment showed MRD-negativity in the bone marrow of 17.1% of patients and in the peripheral bloodstream of 35.2% of patients.

Side effects and safety issues were consistent with the individual effects of both Venclexta and Gazyva, and no new safety issues were exhibited with the drug combination, according to the Roche statement.

The 2019 American Society of Clinical Oncology meeting is expected to bring together more than 32,000 professionals from around the world, with more than 2,400 study abstracts to be presented on site and an additional 3,200 abstracts to be published online.