The U.S. Food and Drug Administration placed a partial hold on all trials evaluating AbbVie Inc. and Roche Holding AG's medicine Venclexta to treat a type of blood cancer called multiple myeloma, following several deaths.

North Chicago, Ill.-based AbbVie said a higher proportion of deaths was reported in patients receiving Venclexta, or venetoclax, compared to the control arm of a phase 3 trial dubbed Bellini, even though the study met its primary objective at an earlier date.

The study was evaluating the drug in patients whose cancer returned or was resistant to treatment. The trial evaluated Venclexta against placebo in combination with the drugs bortezomib and dexamethasone.

The trial met its main goal of prolonging patients lives without the disease getting worse. Patients receiving the medicine lived on average 22.4 months without their disease worsening compared to about 11.5 months for patients on placebo.

However, out of the 194 patients receiving Venclexta, 41 deaths were observed, of which 13 were treatment-related. In the placebo group of 97 patients, 11 deaths were reported, of which one was related to treatment. The deaths were flagged in a pre-planned analysis of the results from the Bellini trial.

AbbVie said no new patients will be enrolled in any trials of Venclexta for treating multiple myeloma until further analysis of the Bellini data was completed. The company, however, added that enrolled patients who are benefiting from the drug may continue with treatment after consulting their doctor.

AbbVie President and Vice Chairman Michael Severino said the company will work with the FDA and worldwide regulatory authorities to determine the next steps for the multiple myeloma program.

The company noted in its March 19 press release that the action does not impact any of the approved uses of Venclexta.

Venclexta, also known as Venclyxto, is developed by AbbVie and Roche's unit Genentech Inc.The medicine is approved in combination with Roche's Rituxan to treat patients with chronic lymphocytic leukemia and small lymphocytic lymphoma who have received at least one prior therapy and also to treat acute myeloid leukemia.