A randomized, double-blind, crossover comparison of MK-0929 and placebo in the treatment of adults with ADHD

Improved Executive Function in Adults Diagnosed With Attention-Deficit/ Hyperactivity Disorder as Measured by the Brown Attention-Deficit Disorder Scale Following Treatment With SHP465 Mixed Amphetamine Salts Extended-Release: Post Hoc Analyses From 2 Randomized, Placebo-Controlled Studies

OBJECTIVE

Assess executive function (EF) improvement with SHP465 mixed amphetamine salts (MAS) extended-release in adults with attention-deficit/hyperactivity disorder (ADHD) using responder analyses of the Brown Attention-Deficit Disorder Scale (BADDS).

METHODS

Post hoc analyses examined data from placebo-controlled SHP465 MAS dose-optimization (12.5-75 mg) and fixed-dose (25-75 mg) studies. Treatment response was assessed using two definitions (BADDS total score at endpoint <50 [no EF impairment] vs. ≥50 [impaired]; BADDS total score at endpoint relative to the in-treatment 90% CI range for baseline total score [below the range = improved]).

RESULTS

Response rates (SHP465 MAS vs. placebo) favored SHP465 MAS (all nominal p < .0001) in the dose-optimization (BADDS <50: 41.9% vs. 19.2%; below 90% CI range: 57.4% vs. 29.6%) and fixed-dose (BADDS <50: 51.9% vs. 16.7%; below 90% CI range: 70.6% vs. 32.3%) studies.

CONCLUSION

Improvement in EF measured by BADDS response rates was approximately 2-fold greater with SHP465 MAS than placebo.

Functional and pharmacological role of the dopamine D4 receptor and its polymorphic variants

The functional and pharmacological significance of the dopamine D₄ receptor (D₄R) has remained the least well understood of all the dopamine receptor subtypes. Even more enigmatic has been the role of the very prevalent human DRD4 gene polymorphisms in the region that encodes the third intracellular loop of the receptor. The most common polymorphisms encode a D₄R with 4 or 7 repeats of a proline-rich sequence of 16 amino acids (D_4.4R and D_4.7R). DRD4 polymorphisms have been associated with individual differences linked to impulse control-related neuropsychiatric disorders, with the most consistent associations established between the gene encoding D_4.7R and attention-deficit hyperactivity disorder (ADHD) and substance use disorders. The function of D₄R and its polymorphic variants is being revealed by addressing the role of receptor heteromerization and the relatively avidity of norepinephrine for D₄R. We review the evidence conveying a significant and differential role of D_4.4R and D_4.7R in the dopaminergic and noradrenergic modulation of the frontal cortico-striatal pyramidal neuron, with implications for the moderation of constructs of impulsivity as personality traits. This differential role depends on their ability to confer different properties to adrenergic α_2A receptor (α_2AR)-D₄R heteromers and dopamine D₂ receptor (D₂R)-D₄R heteromers, preferentially localized in the perisomatic region of the frontal cortical pyramidal neuron and its striatal terminals, respectively. We also review the evidence to support the D₄R as a therapeutic target for ADHD and other impulse-control disorders, as well as for restless legs syndrome.

Emerging drugs for the treatment of attention-deficit hyperactivity disorder (ADHD)

INTRODUCTION

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder affecting up to 5.3% of children and 2.5% of adults depending on the country considered. Current pharmacological treatments for ADHD are based on stimulant or non-stimulant medications, targeting dopaminergic and noradrenergic systems in the frontal cortex and dopaminergic system in the basal ganglia. These drugs are effective and safe for the majority of patients, whereas about 20% of treated patients do not tolerate current therapies or experience insufficient efficacy. The adequate treatment of ADHD is necessary to allow a proper social placement and prevent the acquisition of additional, more severe, comorbidities.

AREAS COVERED

We conducted a review of the scientific literature and of unpublished/ongoing clinical trials to summarize the advances made in the last 10 years (2010-2020) for the pharmacological treatment of ADHD. We found many pharmacological mechanisms beyond dopaminergic and noradrenergic ones have been investigated in patients.

EXPERT OPINION

Some emerging drugs for ADHD may be promising as add-on treatment especially in children, amantadine to enhance cognitive functions and tipepidine for hyperactivity/impulsivity. Stand-alone emerging treatments for ADHD include viloxazine and dasotraline, which will soon have more clinical data available to support market access requests.