Lundbeck and Otsuka start phase III for Rexulti in bipolar

Otsuka and co-development partner Lundbeck have started two phase III trials of their atypical antipsychotic Rexulti in bipolar disorder, potentially adding a third indication for the drug.

The two companies have started enrolling patients into the two studies, which will evaluate Rexulti (brexpiprazole) as a treatment for manic episodes in bipolar patients that are accompanied by depressive symptoms and require hospitalisation.

First approved in 2015, Rexulti is currently available as an adjunctive therapy for adults with major depressive disorder as well as for schizophrenia and after a slow start, has seen its sales growth accelerate, with Lundbeck reporting turnover of the drug up 85% to $91m in the first half of the year.

It has a long way to go however before it can reach the heights of its predecessor - Abilify (aripiprazole) - which was a mainstay for both Lundbeck and Otsuka but has fallen off the patent cliff in recent years and seen steep sales decline as a result, although a long-acting depot formulation (Abilify Maintena) is still making gains.

To date Rexulti has only been launched in the US, Canada and Australia, although it was filed for approval in Europe in schizophrenia earlier this year.

The partners recently suffered a big setback in their plans for brexpiprazole after the drug posted mixed results in agitation in Alzheimer’s disease patients, a condition that affects millions of people worldwide. They were hoping brexpiprazole could become the first antipsychotic to be approved in that indication, but while one trial was positive, a second failed to hit the mark, leaving the future of the programme in doubt. They also were unable to convince the FDA that the drug improved cognitive function in patients with depression.

Approval for bipolar patients would not have the same large-scale opportunity but could still add momentum to the new drug as it would mean brexpiprazole would match the indications of Abilify. Lundbeck and Otsuka are also evaluating the drug in a phase II trial involving patients with post-traumatic stress disorder (PTSD).

The bipolar trials are comparing brexpiprazole to placebo on their ability to improve Young-Mania Rating Scale (YMRS) scores, a widely-used clinician rating scale.

Rexulti is one of a string of new drugs at Lundbeck - along with Abilify and antidepressant Brintellix (vortioxetine) - which it is banking on to help it weather the loss of patent protection for Abilify and former blockbuster antidepressant Lexapro/Celexa (escitalopram).