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(This Oct 31 story corrects paragraph one to say targeted therapy, not immunotherapy)

(Reuters) - AbbVie Inc and Roche Holding AG said on Wednesday their targeted therapy delayed the progression of a type of blood and bone marrow cancer when used in combination with the Swiss drugmaker’s cancer drug in a late-stage trial.

The drug, Venclexta, when used with Roche’s Gazyva, showed a statistically significant reduction in the risk of disease worsening or death in patients with chronic lymphocytic leukemia (CLL), when compared to the standard of care, Roche said.

The results demonstrate the potential of Venclexta as a treatment with a fixed duration for patients with CLL, and may serve as the basis to expand into first-line treatment, AbbVie Chief Scientific Officer Michael Severino said in a statement.

It is estimated that more than 20,000 patients in the United States will be diagnosed with CLL in 2018, Roche said.