Aripiprazole Lauroxil: A Review in Schizophrenia

Recent Advances in representative small-molecule DRD2 inhibitors: Synthetic Routes and clinical applications

The dopamine D2 receptor (DRD2) represents a pivotal target for therapeutic intervention in the treatment of neuropsychiatric disorders, including schizophrenia, bipolar disorder, and Parkinson's disease. The successful discovery of numerous effective DRD2 inhibitors has led to their clinical application and ongoing evaluation in various clinical trials. This review explores the synthetic approaches and clinical applications of prototypical small-molecule DRD2 inhibitors that have received approval or are currently undergoing clinical trials, highlighting their therapeutic potential and challenges. The synthesis of these inhibitors employs various chemical strategies, including modifications of phenothiazine and butyrophenone structures, which have yielded significant antipsychotic agents like chlorpromazine and haloperidol. Additionally, newer classes of inhibitors, such as aripiprazole, exhibit partial agonist activity at DRD2, offering a unique therapeutic profile. Clinically, DRD2 inhibitors demonstrate efficacy in managing positive symptoms of schizophrenia, manic episodes in bipolar disorder, and dopaminergic imbalance in Parkinson's disease. However, the emergence of adverse effects, including tardive dyskinesia, extrapyramidal symptoms and metabolic syndrome, presents substantial challenges. Advances in the development of second-generation antipsychotics aim to balance efficacy with a better side effect profile by targeting additional neurotransmitter receptors. This review aims to deliver an overview of the synthesis and clinical applications of representative small-molecule DRD2 inhibitors across various clinical phases, thereby offering strategic insights for the advancement of DRD2 inhibitor development.

Prodrugs as empowering tools in drug discovery and development: recent strategic applications of drug delivery solutions to mitigate challenges associated with lead compounds and drug candidates

The delivery of a drug to a specific organ or tissue at an efficacious concentration is the pharmacokinetic (PK) hallmark of promoting effective pharmacological action at a target site with an acceptable safety profile. Sub-optimal pharmaceutical or ADME profiles of drug candidates, which can often be a function of inherently poor physicochemical properties, pose significant challenges to drug discovery and development teams and may contribute to high compound attrition rates. Medicinal chemists have exploited prodrugs as an informed strategy to productively enhance the profiles of new chemical entities by optimizing the physicochemical, biopharmaceutical, and pharmacokinetic properties as well as selectively delivering a molecule to the site of action as a means of addressing a range of limitations. While discovery scientists have traditionally employed prodrugs to improve solubility and membrane permeability, the growing sophistication of prodrug technologies has enabled a significant expansion of their scope and applications as an empowering tool to mitigate a broad range of drug delivery challenges. Prodrugs have emerged as successful solutions to resolve non-linear exposure, inadequate exposure to support toxicological studies, pH-dependent absorption, high pill burden, formulation challenges, lack of feasibility of developing solid and liquid dosage forms, first-pass metabolism, high dosing frequency translating to reduced patient compliance and poor site-specific drug delivery. During the period 2012-2022, the US Food and Drug Administration (FDA) approved 50 prodrugs, which amounts to 13% of approved small molecule drugs, reflecting both the importance and success of implementing prodrug approaches in the pursuit of developing safe and effective drugs to address unmet medical needs.

Advancements in Drug Repurposing: Examples in Psychiatric Medications

Because there are a limited number of animal models for psychiatric diseases that can be extrapolated to humans, drug repurposing has been actively pursued. This study was aimed at uncovering recent trends in drug repurposing approaches and new technologies that can predict efficacy on humans based on animal models used in psychiatric drug development. Psychiatric drugs that were approved by the FDA between 2002 and 2022 were listed, and the method of how the drug repurposing has been applied was analyzed. Drug repurposing has been increasingly applied to recently approved psychiatric drugs. The development concepts of psychiatric drugs that have been developed through drug repurposing over the past 20 years were found to be divided into six categories: new application exploration, reduction of side effects, improvement of symptom control, improvement of medication compliance, enhancement of drug efficacy, and reduction of drug-drug interactions. All repurposed drugs approved before 2016 used either prodrugs or active metabolites, while all drugs approved in 2021 and beyond used fixed-dose combinations with sophisticated ideas. SmartCube^®, which uses artificial intelligence to predict human drug efficacy from animal phenotypes, was developed and produced novel drugs that show clinical efficacy. Well-designed drug repurposing approaches and new technologies for predicting human drug efficacy based off of animal models would contribute to novel psychiatric drug development.

Evaluating parameters affecting drug fate at the intramuscular injection site

Intramuscular (IM) injections are a well-established method of delivering a variety of therapeutics formulated for parenteral administration. While the wide range of commercial IM pharmaceuticals provide a wealth of pharmacokinetic (PK) information following injection, there remains an inadequate understanding of drug fate at the IM injection site that could dictate these PK outcomes. An improved understanding of injection site events could improve approaches taken by formulation scientists to identify therapeutically effective and consistent drug PK outcomes. Interplay between the typically non-physiological aspects of drug formulations and the homeostatic IM environment may provide insights into the fate of drugs at the IM injection site, leading to predictions of how a drug will behave post-injection in vivo. Immune responses occur by design after e.g. vaccine administration, however immune responses post-injection are not in the scope of this article. Taking cues from existing in vitro modelling technologies, the purpose of this article is to propose "critical parameters" of the IM environment that could be examined in hypothesis-driven studies. Outcomes of such studies might ultimately be useful in predicting and improving in vivo PK performance of IM injected drugs.

Translation-Focused Approaches to GPCR Drug Discovery for Cognitive Impairments Associated with Schizophrenia

There are no effective therapeutics for cognitive impairments associated with schizophrenia (CIAS), which includes deficits in executive functions (working memory and cognitive flexibility) and episodic memory. Compounds that have entered clinical trials are inadequate in terms of efficacy and/or tolerability, highlighting a clear translational bottleneck and a need for a cohesive preclinical drug development strategy. In this review we propose hippocampal-prefrontal-cortical (HPC-PFC) circuitry underlying CIAS-relevant cognitive processes across mammalian species as a target source to guide the translation-focused discovery and development of novel, procognitive agents. We highlight several G protein-coupled receptors (GPCRs) enriched within HPC-PFC circuitry as therapeutic targets of interest, including noncanonical approaches (biased agonism and allosteric modulation) to conventional clinical targets, such as dopamine and muscarinic acetylcholine receptors, along with prospective novel targets, including the orphan receptors GPR52 and GPR139. We also describe the translational limitations of popular preclinical cognition tests and suggest touchscreen-based assays that probe cognitive functions reliant on HPC-PFC circuitry and reflect tests used in the clinic, as tests of greater translational relevance. Combining pharmacological and behavioral testing strategies based in HPC-PFC circuit function creates a cohesive, translation-focused approach to preclinical drug development that may improve the translational bottleneck currently hindering the development of treatments for CIAS.

Newly Developed Prodrugs and Prodrugs in Development; an Insight of the Recent Years

BACKGROUND

The design and development of prodrugs is the most common and effective strategy to overcome pharmacokinetic and pharmacodynamic drawbacks of active drugs. A respected number of prodrugs have been reached the drugs market throughout history and the recent years have witnessed a significant increase in the use of prodrugs as a replacement of their parent drugs for an efficient treatment of various ailment.

METHODS

A Scan conducted to find recent approved prodrugs and prodrugs in development.

RESULTS

Selected prodrugs were reported and categorized in accordance to their target systems.

CONCLUSIONS

the prodrug approach has shown many successes and still remains a viable and effective approach to deliver new active agents. This conclusion is supported by the recent approved prodrugs and the scan of clinical trials conducted between 2013-2018.

In vivo 5-HT6 and 5-HT2A receptor availability in antipsychotic treated schizophrenia patients vs. unmedicated healthy humans measured with [11C]GSK215083 PET

While 5-HT₆ receptor is a potential therapeutic target for cognitive impairment in schizophrenia (SCZ), in vivo 5-HT₆ receptor availability following antipsychotic treatment has not been examined to-date. We examined the availability of 5-HT₆ and 5-HT_2A receptors following treatment with olanzapine, risperidone, aripiprazole and quetiapine in male patients with SCZ vs unmedicated age-matched healthy male controls (HC) using positron emission tomography (PET) imaging with [¹¹C]GSK215083. [¹¹C]GSK215083 has been shown to have selectivity for 5-HT₆ in the striatum and 5-HT_2A in the cortex. Patients with SCZ (n = 9) were scanned with [¹¹C]GSK215083 on HR+ PET scanner at presumed steady-state trough and peak serum levels following 7 days of confirmed inpatient antipsychotic treatment. Time-activity curves in regions-of-interest were fitted with multilinear analysis-1 (MA1). Regional nondisplaceable binding potential (BP_ND) values were calculated using cerebellum as the reference region and corrected for partial volume effects. Compared to HCs (n = 9), olanzapine was associated with significantly lower BP_ND (range: 53%-95%) in ventral striatum, putamen, caudate and frontal cortex at both trough and peak scans. Risperidone was associated with significantly lower BP_ND in frontal cortex at both trough and peak scans. The study provides preliminary evidence that treatment with different second-generation antipsychotics results in differing profiles of 5-HT_2A and 5-HT₆ availability.