SAN FRANCISCO — In a widely anticipated report, researchers reported that a phase 3 study showed statistically significant improvements in patients with agitation related to Alzheimer’s disease (AD) who took the atypical antipsychotic brexpiprazole (Rexulti).

Members of a panel of dementia specialists here at the 15th Clinical Trials on Alzheimer’s Disease (CTAD) Conference said that the results were encouraging. But they also noted that the available data make it difficult to understand the impact of the drug on the day-to-day life on patients.

“I’d like to be able to translate that into something else to understand the risk benefit calculus,” said neurologist and neuroscientist Alireza Atri, MD, PhD, of Banner Sun Health Research Institute in Phoenix, Arizona. “How does it affect the patients themselves, their quality of life, and the family members and their burden?”

Currently, there’s no US Food and Drug Administration (FDA) approved treatment for agitation in AD.

In 2015, the FDA approved brexpiprazole, an oral medication, as a treatment for schizophrenia and an adjunctive treatment for major depressive disorder (MDD). It is an expensive drug with an average retail price per GoodRx is $1582 per month, and no generic is available.

Researchers released the results of a trio of phase 3 clinical trials at CTAD that examined various doses of brexpiprazole. The results of the first 2 trials had been released earlier in 2018.

Three Trials

All trials were multicenter, 12-week, randomized, double-blind and placebo-controlled.

Study participants were aged 55-90 years, had probable AD diagnoses, and had agitation per various scales. The average age in the groups was 74 years, 56.0%-61.7% were women, and 94.3%-98.1% were White.

The first trial examined two fixed doses (1 mg/d, n = 137; and 2 mg/d, n = 140) or placebo (n = 136). “The study initially included a 0.5 mg/day arm,” the researchers reported, “which was removed in a protocol amendment, and patients randomized to that arm were not included in efficacy analyses.”

The second trial looked at a flexible dose (0.5-2 mg/d, n = 133) or placebo (n = 137).

In a CTAD presentation, Nanco Hefting, MSc, of Lundberg, a co-developer of the drug, said that the researchers learned from the first two trials that 2 mg/d might be an appropriate dose, and the FDA recommended they also examine 3 mg/day. As a result, the third trial examined two fixed doses (2 mg/d, n = 75; 3 mg/d, n = 153; or placebo, n = 117).

In the third trial, both the placebo and drug groups improved per a measurement of agitation; those in the drug group improved somewhat more.

The mean change in baseline on the Cohen-Mansfield Agitation Inventory scale — the primary endpoint — was -5.32 for the 2 mg/d and 3 mg/d groups vs placebo (P = .0026); the score in the placebo group fell by about 18 and by about 22 in the drug group.

The key secondary endpoint was an improvement from baseline to week 12 in the Clinical Global Impression-Severity (CGI-S) score related to agitation. Compared with the placebo group, this score was -0.27 in the drug group (P = .0078). Both scores hovered around -1.0.

Safety data show the percentage of treatment-emergent events ranged from 45.9% in the placebo group to 49.0%-56.8% for brexpiprazole in the three trials. The percentage of these events leading to discontinuation was 6.3% among those receiving the drug and 3.4% in the placebo group.

University of Exeter dementia researcher Clive Ballard, MD, MB ChB, one of the panelists who discussed the research after the CTAD presentation, praised the trials as “well-conducted” and said that he was pleased that subjects in institutions were included. “It’s not an easy environment to do trials in. They should be really commended for doing for doing that.”

But he echoed fellow panelist Atri by noting that more data are needed to understand how well the drug works. “I would like to see the effect sizes and a little bit more detail to understand the clinical meaningfulness of that level of benefit.”

What’s next? A spokeswoman for Otsuka, a co-developer of brexpiprazole, said that it hopes to hear in 2023 about a supplemental new drug application that was filed in November 2022.

Otsuka and Lundbeck funded the research. Hefting is an employee of Lundbeck, and several other authors work for Lundbeck or Otsuka. The single non-employee author reports various disclosures. Disclosures for Atri and Ballard were not provided.

15th Clinical Trials on Alzheimer’s Disease (CTAD) Conference. Presented December 1, 2022.

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