June 16 (Reuters) - A drug approved to prevent rejection of transplanted kidneys significantly reduced relapses of multiple sclerosis in a late stage-trial sponsored by Biogen Idec and AbbVie Inc, but serious infections and potential liver toxicity continued to cloud the drug's future.
The mixed results were seen in a Phase III international study of the medicine, called daclizumab, that involved more than 1,800 patients with relapsing-remitting multiple sclerosis - the most common form of MS which can lead to disability and paralysis.
The companies disclosed partial results from the new trial on Monday. Shares of both Biogen and AbbVie were little changed in morning trading.
In the study, called DECIDE, once-monthly injections of daclizumab were tested against once-weekly injections of Biogen's blockbuster Avonex (interferon beta-1a) treatment for MS.
Patients taking daclizumab, which is meant to tame the immune system by blocking a protein called the CD25 receptor, had 45 percent fewer annual relapses than those receiving Avonex. Moreover, patients taking daclizumab had 54 percent fewer new or enlarging brain and spinal lesions at week 96 of the study, compared to those taking Avonex, thereby meeting a secondary goal of the study.
The overall incidence of side effects was similar in both patient groups. But there was a two-fold higher incidence of serious infections among those taking daclizumab, at 4 percent, as well as a two-fold higher incidence of elevated liver enzymes - a potential marker for liver toxicity.
Daclizumab would be a new approach to treating MS, if it is approved for the condition.
Biogen and AbbVie said they would discuss with health regulators timing for potential marketing applications for the drug.
MS is believed to be caused by overactive immune system cells, called t-cells, that attack and destroy the protective covering of nerves.
(Reporting by Ransdell Pierson; Editing by Nick Zieminski)