Potential beneficial effects of masupirdine (SUVN-502) on agitation/aggression and psychosis in patients with moderate Alzheimer's disease: Exploratory post hoc analyses

Emerging therapies for treatment of agitation, psychosis, or apathy in Alzheimer's disease

INTRODUCTION

Agitation, psychosis, and apathy are prevalent and highly distressing neuropsychiatric symptoms (NPS) of Alzheimer's disease (AD) that have been linked to numerous negative outcomes, including increased mortality, worsened cognitive decline, and caregiver burden. Current treatments for AD-associated agitation, namely atypical antipsychotics, provide some benefits but may increase the risk of serious adverse events and death. Meanwhile, no pharmacotherapies have been approved by regulatory agencies for the treatment of psychosis or apathy in AD. Over the past decade, many new and repurposed drugs have emerged as potential therapeutic options for managing these challenging NPS.

AREAS COVERED

This review aims to provide a comprehensive summary of pharmacotherapies that have recently been investigated in phase 2 and 3 clinical trials for the treatment of agitation, psychosis, or apathy in AD.

EXPERT OPINION

Novel atypical antipsychotics, serotonergic antidepressants, cannabinoids, and dextromethorphan combination drugs have shown promising results for alleviating agitation. Pimavanserin appears to be the most effective emerging therapy for psychosis, while methylphenidate has demonstrated good efficacy for apathy. Further research on biomarkers of NPS severity and treatment response, as well as continued improvements in methodological approaches are needed to advance the field.

Alzheimer's disease approaches - Focusing on pathology, biomarkers and clinical trial candidates

The strategy for the development of new drugs for Alzheimer's disease (AD) recognizes that an effective therapy requires early therapeutic intervention and a multifactorial approach that considers the individual initiators of AD development. Current knowledge of AD includes the understanding of pathophysiology, risk factors, biomarkers, and the evolving patterns of biomarker abnormalities. This knowledge is essential in identifying potential molecular targets for new drug development. This review summarizes promising AD drug candidates, many of which are currently in phase 2 or 3 clinical trials. New agents are classified according to the Common Alzheimer's Disease Research Ontology (CADRO). The main targets of new drugs for AD are processes related to amyloid beta and tau neurotoxicity, neurotransmission, inflammation, metabolism and bioenergetics, synaptic plasticity, and oxidative stress. These interventions are aimed at preventing disease onset and slowing or eliminating disease progression. The efficacy of pharmacotherapy may be enhanced by combining these drugs with other treatments, antioxidants, and dietary supplements. Ongoing research into AD pathophysiology, risk factors, biomarkers, and the dynamics of biomarker abnormalities may contribute to the understanding of AD and offer hope for effective therapeutic strategies in the near future.

Recent applications of positron emission tomographic (PET) imaging in psychiatric drug discovery

INTRODUCTION

Psychiatry is one of the medical disciplines that suffers most from a lack of innovation in its therapeutic arsenal. Many failures in drug candidate trials can be explained by pharmacological properties that have been poorly assessed upstream, in terms of brain passage, brain target binding and clinical outcomes. Positron emission tomography can provide pharmacokinetic and pharmacodynamic data to help select candidate-molecules for further clinical trials.

AREAS COVERED

This review aims to explain and discuss the various methods using positron-emitting radiolabeled molecules to trace the cerebral distribution of the drug-candidate or indirectly measure binding to its therapeutic target. More than an exhaustive review of PET studies in psychopharmacology, this article highlights the contributions this technology can make in drug discovery applied to psychiatry.

EXPERT OPINION

PET neuroimaging is the only technological approach that can, in vivo in humans, measure cerebral delivery of a drug candidate, percentage and duration of target binding, and even the pharmacological effects. PET studies in a small number of subjects in the early stages of the development of a psychotropic drug can therefore provide the pharmacokinetic/pharmacodynamic data required for subsequent clinical evaluation. While PET technology is demanding in terms of radiochemical, radiopharmacological and nuclear medicine expertise, its integration into the development process of new drugs for psychiatry has great added value.

Clinical trials of new drugs for Alzheimer disease: a 2020-2023 update

Alzheimer's disease (AD) is the leading cause of dementia, presenting a significant unmet medical need worldwide. The pathogenesis of AD involves various pathophysiological events, including the accumulation of amyloid and tau, neuro-inflammation, and neuronal injury. Clinical trials focusing on new drugs for AD were documented in 2020, but subsequent developments have emerged since then. Notably, the US-FDA has approved Aducanumab and Lecanemab, both antibodies targeting amyloid, marking the end of a nearly two-decade period without new AD drugs. In this comprehensive report, we review all trials listed in clinicaltrials.gov, elucidating their underlying mechanisms and study designs. Ongoing clinical trials are investigating numerous promising new drugs for AD. The main trends in these trials involve pathophysiology-based, disease-modifying therapies and the recruitment of participants in earlier stages of the disease. These trends underscore the significance of conducting fundamental research on pathophysiology, prevention, and intervention prior to the occurrence of brain damage caused by AD.

A 2023 update on the advancements in the treatment of agitation in Alzheimer's disease

INTRODUCTION

Neuropsychiatric symptoms (NPS) in Alzheimer's Disease (AD) are associated with negative outcomes for patients and their care partners. Agitation is one of the most common and distressing NPS, yet we lack safe and effective treatment options. While nonpharmacologic interventions are considered first line treatment, these may not be effective or appropriate for every patient. Our current approaches to the pharmacologic treatment of agitation in AD consist of the off-label use of antipsychotics, sedative/hypnotics, anxiolytics, mood-stabilizing anticonvulsants, acetylcholinesterase inhibitors, NMDA receptor antagonists, and antidepressants. Despite their prevalent use, they have questionable efficacy and significant safety concerns.

AREAS COVERED

Advances in the understanding of neurobiological mechanisms of agitation have fueled recent clinical trials. This article is an update to our 2017 review. A comprehensive search of ClinicalTrials.gov was completed from January 2017 to June 2022 using the search terms "Alzheimer's Disease" and "Agitation". A subsequent scoping review was completed in PubMed and Google Scholar. Several agents were identified for promise in treating agitation, including: brexpiprazole, cannabinoids, dexmedetomidine, dextromethorphan, escitalopram, masupirdine, and prazosin.

EXPERT OPINION

Clinical trials remain underway utilizing both novel and repurposed agents to address symptoms of agitation in AD. With increasing understanding of the neurobiological mechanisms that fuel the development of agitation in AD, the use of enhanced trial design and conduct, advanced statistical approaches, and accelerated pathways for regulatory approval, we are advancing closer to having safe and efficacious treatment options for agitation in AD.

Progress in Investigational Agents Targeting Serotonin-6 Receptors for the Treatment of Brain Disorders

Serotonin (5-HT) plays an important role in the regulation of several basic functions of the central and peripheral nervous system. Among the 5-HT receptors, serotonin-6 (5-HT6) receptor has been an area of substantial research. 5-HT6 receptor is a G-protein-coupled receptor mediating its effects through diverse signaling pathways. Exceptional features of the receptors fueling drug discovery efforts include unique localization and specific distribution in the brain regions having a role in learning, memory, mood, and behavior, and the affinity of several clinically used psychotropic agents. Although non-clinical data suggest that both agonist and antagonist may have similar behavioral effects, most of the agents that entered clinical evaluation were antagonists. Schizophrenia was the initial target; more recently, cognitive deficits associated with Alzheimer's disease (AD) or other neurological disorders has been the target for clinically evaluated 5-HT6 receptor antagonists. Several 5-HT6 receptor antagonists (idalopirdine, intepirdine and latrepirdine) showed efficacy in alleviating cognitive deficits associated with AD in the proof-of-concept clinical studies; however, the outcomes of the subsequent phase 3 studies were largely disappointing. The observations from both non-clinical and clinical studies suggest that 5-HT6 receptor antagonists may have a role in the management of neuropsychiatric symptoms in dementia. Masupirdine, a selective 5-HT6 receptor antagonist, reduced agitation/aggression-like behaviors in animal models, and a post hoc analysis of a phase 2 trial suggested potential beneficial effects on agitation/aggression and psychosis in AD. This agent will be assessed in additional trials, and the outcome of the trials will inform the use of 5-HT6 receptor antagonists in the treatment of agitation in dementia of the Alzheimer's type.