July 16 (Reuters) - The U.S. Food and Drug

Administration's reviewers on Wednesday raised efficacy concerns

over the use of Otsuka Pharma's drug in combination

with Viatris' ( VTRS ) Zoloft for the treatment of adults with

PTSD.

The FDA staff's assessment comes ahead of a meeting of its

independent experts on Friday, who will make recommendations on

whether the regulator should approve the use of the drug,

brexpiprazole, in combination with Zoloft for treating PTSD.

The FDA staff cited inconsistent trial results and a modest

treatment effect that may not be clinically meaningful as

reasons for the efficacy concerns.

Otsuka's application was based on the data from one

mid-stage and two late-stage studies testing the combination of

brexpiprazole and Zoloft in PTSD patients compared to sertraline

monotherapy.

The reviewers, however, noted that one of the late-stage

studies failed to show statistically significant differences in

treatment response between the two groups.

They also added that the mid-stage study had statistical

and methodological concerns.

PTSD is a mental health condition that can develop after a

traumatic event, causing symptoms including flashbacks,

nightmares and severe anxiety.

Brexpiprazole, sold under the brand name of Rexulti, is

approved in the U.S. to treat agitation in patients with

Alzheimer's disease as well as for adults with major depressive

disorder and schizophrenia.

The drug is being co-developed by Otsuka and Danish

drugmaker Lundbeck.

Otsuka had said earlier this year the FDA, which was

originally set to decide on the company's treatment by February

8, delayed its decision to seek the advisory panel's input on

certain issues related to the marketing application.

The agency has not set a new action date for the drug.

If approved, the combination drug would be the first

PTSD treatment to gain U.S. approval in over 30 years after

Zoloft and GSK's Paxil.