SHP465 Mixed Amphetamine Salts in the Treatment of Attention-Deficit/Hyperactivity Disorder in Children and Adolescents: Results of a Randomized, Double-Blind Placebo-Controlled Study

An updated safety review of the current drugs for managing ADHD in children

INTRODUCTION

Attention-Deficit/Hyperactivity Disorder (ADHD) is a highly prevalent condition that causes persistent problems with attention and/or hyperactivity-impulsivity and often results in significant impairment when left untreated. Medications for this disorder continue to evolve and provide new treatment options. Ongoing review of related medication safety and tolerability remains an important task for prescribers.

AREAS COVERED

This manuscript provides an updated safety review of medications used to treat ADHD in children and adolescents. PubMed and OneSearch online databases were utilized to search for literature relevant to the topic of ADHD medications and safety. Clinical trials of medications used to treat ADHD, systematic reviews and meta-analyses, and articles covering specific safety issues (adverse or unfavorable events) such as cardiovascular effects, seizures, impact on growth, depression, suicidal ideation, substance use disorders, psychosis, and tics are described.

EXPERT OPINION

Available pharmacologic treatments for ADHD have favorable efficacy, safety and tolerability and allow many patients to achieve significant improvement of their symptoms. Despite the availability of multiple stimulant and non-stimulant formulations, some individuals with ADHD may not tolerate available medications or attain satisfactory improvement. To satisfy unmet clinical needs, ADHD pharmaceutical research with stimulant and nonstimulant formulations targeting dopamine, norepinephrine, and novel receptors is ongoing.

Pharmacokinetics, Safety, and Tolerability of SHP465 Mixed Amphetamine Salts After Administration of Multiple Daily Doses in Children Aged 4-5 Years with Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Given the limited treatment options for younger children with attention-deficit/hyperactivity disorder (ADHD), a clinical study for SHP465 treatment was warranted.

OBJECTIVES

We aimed to evaluate the pharmacokinetics, safety, and tolerability of SHP465 mixed amphetamine salts (MAS) 6.25 mg after multiple once-daily doses in children aged 4-5 years with ADHD.

METHODS

In this open-label multicenter study, SHP465 MAS 6.25 mg once daily was administered for 28 days to children aged 4-5 years with ADHD; baseline ADHD Rating Scale-5 total score ≥ 28 (boys) or ≥ 24 (girls) and Clinical Global Impression-Severity scale score ≥ 4. Blood samples were collected in the pharmacokinetic-rich group predose on day 1 week 1 and day 7 week 4 (predose, postdose at 2, 5, 8, 12, 16, 24, and 48 hours); and in the pharmacokinetic-sparse group predose on day 1 weeks 1, 2, and 3 and 24 hours postdose on day 7 week 4 . Key pharmacokinetic parameters included maximum plasma drug concentration (C_max), plasma trough drug concentration, time to C_max during a dosing interval (t_max), area under the concentration-time curve from time 0 to time of last collected sample, area under the concentration-time curve over the dosing interval (24 h) at steady state (AUC_tau,ss), first-order rate constant associated with the terminal phase of elimination, terminal half-life (t_1/2), total clearance of drug from plasma after oral administration, and apparent volume of distribution at steady state. Safety endpoints included treatment-emergent adverse events and vital signs.

RESULTS

Mean ± standard deviation age and body mass index of 24 participants (66.7% male) were 4.8 ± 0.41 years and 17.2 ± 3.18 kg/m², respectively. The most common ADHD was the combined presentation (91.7%); ratings were 50% markedly ill and 45.8% moderately ill on the Clinical Global Impression-Severity scale. Plasma d-amphetamine and l-amphetamine steady state was attained by predose on treatment day 8, consistent with the half-life. Peak steady-state plasma concentration (median t_max) for both d-amphetamine and l-amphetamine occurred at 7.92 h postdose on day 7 week 4 and thereafter declined monoexponentially, with a geometric mean t_1/2 of 10.4 and 12.3 h for d-amphetamine and l-amphetamine, respectively. For both d-amphetamine and l-amphetamine, C_max and AUC_tau,ss were comparable between children aged 4 years (n = 3) and children aged 5 years (n = 8) regardless of sex. In total, 14 treatment-emergent adverse events were reported by 45.8% (11/24) of participants. Five treatment-emergent adverse events, reported for four (16.7%) participants, were considered treatment related; affect lability occurred in two (8.3%) participants, and insomnia, accidental overdose, and increased blood pressure each occurred in one (4.2%) participant.

CONCLUSIONS

In children aged 4-5 years with ADHD, following multiple once-daily administrations of SHP465 MAS 6.25 mg, the pharmacokinetic profile of plasma d-amphetamine and l-amphetamine was generally consistent among participants. Between-individual variability of plasma d-amphetamine and l-amphetamine steady-state exposure was low to moderate. SHP465 MAS was generally well tolerated in this study.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03327402 (31 October, 2017).

Efficacy and Safety of a Long-Acting Multilayer-Release Methylphenidate Formulation (PRC-063) in the Treatment of Adolescent Attention-Deficit/Hyperactivity Disorder: A Randomized, Double-Blind Clinical Trial with a 6-Month Open-Label Extension

Objectives: To study the safety and efficacy of the long-acting methylphenidate formulation PRC-063 in adolescents with attention-deficit/hyperactivity disorder (ADHD). Methods: Adolescents 12 to ≤17 years who met Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 criteria for ADHD and had a baseline ADHD Rating Scale DSM-5 (ADHD-5-RS) score ≥24 participated in a randomized, double-blind, placebo-controlled, fixed-dose, parallel-group study. Participants were randomized 1:1:1:1:1 to receive placebo or one of four doses of PRC-063 once daily for 4 weeks. The primary endpoint was change from baseline in least-squares mean clinician-rated ADHD-5-RS total score for PRC-063 (all doses combined) versus placebo. Other efficacy assessments included Conners third Edition: Self-Report (C3SR) and Clinical Global Impression-Improvement (CGI-I). A subset of double-blind study participants entered a subsequent open-label, dose-optimized study. Safety outcomes in both studies included treatment-emergent adverse events (TEAEs). Results: Three hundred fifty-four participants were included in the primary analysis. The least-squares mean change from baseline in ADHD-5-RS total score was -15.17 for PRC-063 versus -10.98 for placebo (least-squares mean difference -4.2, p = 0.0067). For individual PRC-063 doses, improvements in ADHD-5-RS total score versus placebo were significant for 45 mg (p = 0.0155) and 70 mg (p = 0.0401), but not for 25 or 85 mg. A significant improvement for PRC-063 versus placebo was recorded for C3SR Inattention (p = 0.0168), but not for the other C3SR subscales. About 52.7% of participants randomized to PRC-063 were responders based on CGI-I versus 32.4% of those randomized to placebo (p = 0.0004). Further improvements in ADHD symptoms based on ADHD-5-RS were observed from 1 month through 6 months of open-label treatment (p < 0.0001). There were two serious adverse events (both during the open-label study), one of which (aggressive behavior) was assessed as related to study drug. The only TEAEs that occurred in >10% of participants during double-blind treatment were decreased appetite (20.1%) and headache (15.0%). Most TEAEs were of mild or moderate severity. Conclusion: PRC-063 significantly improved ADHD symptomatology in adolescents. It was generally well tolerated, with an AE profile consistent with other long-acting stimulants. NCT02139111 and NCT02168127.

A Phase 3, Randomized Double-Blind Study of the Efficacy and Safety of Low-Dose SHP465 Mixed Amphetamine Salts Extended-Release in Children with Attention-Deficit/Hyperactivity Disorder

Objectives: In a previous pivotal study of children and adolescents (aged 6-17 years) with attention-deficit/hyperactivity disorder (ADHD), dose-optimized SHP465 mixed amphetamine salts (MAS) extended-release (12.5-25 mg once daily) was superior to placebo in reducing ADHD symptoms. This study evaluated the efficacy, tolerability, and safety of 6.25 mg SHP465 MAS once daily (one-half the lowest approved dose for adolescents and adults) versus placebo in children aged 6-12 years with ADHD. Methods: Children (aged 6-12 years) with Diagnostic and Statistical Manual of Mental Disorders, Fifth edition-defined ADHD; baseline ADHD-Rating Scale, Fifth Edition, Child, Home Version total scores (ADHD-RS-5-HV-TS) ≥28; and baseline Clinical Global Impressions-Severity scores ≥4 were eligible. Participants received 6.25 mg SHP465 MAS once daily or placebo for 4 weeks. The primary (ADHD-RS-5-HV-TS change from baseline at week 4) and key secondary (Clinical Global Impressions-Improvement [CGI-I] score at week 4) efficacy end points were assessed using linear mixed-effects models for repeated measures. Safety and tolerability assessments included treatment-emergent adverse events (TEAEs) and vital sign changes. Results: Of 89 randomized participants, 83 completed the study (placebo, n = 41; SHP465 MAS, n = 42). At week 4, the least squares mean (95% confidence interval) treatment differences (SHP465 MAS-placebo) were not statistically significant for ADHD-RS-5-HV-TS change (-1.9 [-6.8 to 3.1], p = 0.451; effect size [ES] = 0.17) or CGI-I score (-0.1 [-0.5 to 0.3], nominal p = 0.597; ES = 0.12). The percentage of participants reporting TEAEs was 16.3% with placebo and 24.4% with SHP465 MAS. The most frequently reported TEAEs (placebo; SHP465 MAS) were headache (7.0%; 4.4%) and decreased appetite (4.7%; 2.2%). Minimal increases in blood pressure were observed with SHP465 MAS at the final on-treatment assessment. Conclusions: SHP465 MAS 6.25 mg once daily (one-half the lowest dose approved for adolescents and adults) was well tolerated in children aged 6-12 years but was not superior to placebo in reducing ADHD symptoms, suggesting that this dose of SHP465 MAS was subtherapeutic in this age group. The Clinical Trial Registration number: NCT03325881.

New Formulations of Stimulants: An Update for Clinicians

In the last 15 years, there has been a marked increase in the number of available stimulant formulations with the emphasis on long-acting formulations, and the introduction of several novel delivery systems such as orally dissolving tablets, chewable tablets, extended-release liquid formulations, transdermal patches, and novel "beaded" technology. All of these formulations involve changes to the pharmaceutical delivery systems of the two existing compounds most commonly employed to treat attention-deficit/hyperactivity disorder (ADHD), amphetamine (AMP) and methylphenidate (MPH). In addition to these new formulations, our knowledge about the individual differences in response has advanced and contributes to a more nuanced approach to treatment. The clinician can now make increasingly informed choices about these formulations and more effectively individualize treatment in a way that had not been possible before. In the absence of reliable biomarkers that can predict individualized response to ADHD treatment, clinical knowledge about differences in MPH and AMP pharmacodynamics, pharmacokinetics, and metabolism can be utilized to personalize treatment and optimize response. Different properties of these new formulations (delivery modality, onset of action, duration of response, safety, and tolerability) will most likely weigh heavily into the clinician's choice of formulation. To manage the broad range of options that are now available, clinicians should familiarize themselves in each of these categories for both stimulant compounds. This review is meant to serve as an update and a guide to newer stimulant formulations and includes a brief review of ADHD and stimulant properties.

Diagnosis and Treatment of Attention-Deficit/Hyperactivity Disorder in Preschool-Aged Children

OBJECTIVES

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder defined as a persistent pattern of inactivity and/or hyperactivity that interferes with behavioral function or development. Diagnosis and treatment of ADHD in the preschool-aged population (children 3-5 years old) is more complicated compared with older children because of developmental and physiological differences. This article reviews the available literature regarding the challenges associated with ADHD diagnosis and treatment in preschool-aged children, as well as the unmet needs of preschool-aged children with ADHD.

METHODS

Key considerations for ADHD diagnosis and treatment patterns in preschool-aged children are summarized in this review, including the need for early intervention, the association with comorbidities, and the differences in pharmacokinetic profiles between preschool-aged children and older children.

RESULTS

Efficacy and safety data are lacking, as clinical trial design and execution pose unique challenges in this population. Preschool-aged children often have difficulty with pill swallowing and tolerating phlebotomy necessary for the collection of pharmacokinetic and safety data. However, early diagnosis and treatment are essential to mitigate ADHD symptoms and comorbidities that may develop during childhood and adolescence in patients with persistent ADHD.

CONCLUSION

This review describes the established diagnostic and treatment modalities, along with the unmet needs of preschool-aged children with ADHD.

Comparative efficacy and tolerability of medications for attention-deficit hyperactivity disorder in children, adolescents, and adults: a systematic review and network meta-analysis

BACKGROUND

The benefits and safety of medications for attention-deficit hyperactivity disorder (ADHD) remain controversial, and guidelines are inconsistent on which medications are preferred across different age groups. We aimed to estimate the comparative efficacy and tolerability of oral medications for ADHD in children, adolescents, and adults.

METHODS

We did a literature search for published and unpublished double-blind randomised controlled trials comparing amphetamines (including lisdexamfetamine), atomoxetine, bupropion, clonidine, guanfacine, methylphenidate, and modafinil with each other or placebo. We systematically contacted study authors and drug manufacturers for additional information. Primary outcomes were efficacy (change in severity of ADHD core symptoms based on teachers' and clinicians' ratings) and tolerability (proportion of patients who dropped out of studies because of side-effects) at timepoints closest to 12 weeks, 26 weeks, and 52 weeks. We estimated summary odds ratios (ORs) and standardised mean differences (SMDs) using pairwise and network meta-analysis with random effects. We assessed the risk of bias of individual studies with the Cochrane risk of bias tool and confidence of estimates with the Grading of Recommendations Assessment, Development, and Evaluation approach for network meta-analyses. This study is registered with PROSPERO, number CRD42014008976.

FINDINGS

133 double-blind randomised controlled trials (81 in children and adolescents, 51 in adults, and one in both) were included. The analysis of efficacy closest to 12 weeks was based on 10 068 children and adolescents and 8131 adults; the analysis of tolerability was based on 11 018 children and adolescents and 5362 adults. The confidence of estimates varied from high or moderate (for some comparisons) to low or very low (for most indirect comparisons). For ADHD core symptoms rated by clinicians in children and adolescents closest to 12 weeks, all included drugs were superior to placebo (eg, SMD -1·02, 95% CI -1·19 to -0·85 for amphetamines, -0·78, -0·93 to -0·62 for methylphenidate, -0·56, -0·66 to -0·45 for atomoxetine). By contrast, for available comparisons based on teachers' ratings, only methylphenidate (SMD -0·82, 95% CI -1·16 to -0·48) and modafinil (-0·76, -1·15 to -0·37) were more efficacious than placebo. In adults (clinicians' ratings), amphetamines (SMD -0·79, 95% CI -0·99 to -0·58), methylphenidate (-0·49, -0·64 to -0·35), bupropion (-0·46, -0·85 to -0·07), and atomoxetine (-0·45, -0·58 to -0·32), but not modafinil (0·16, -0·28 to 0·59), were better than placebo. With respect to tolerability, amphetamines were inferior to placebo in both children and adolescents (odds ratio [OR] 2·30, 95% CI 1·36-3·89) and adults (3·26, 1·54-6·92); guanfacine was inferior to placebo in children and adolescents only (2·64, 1·20-5·81); and atomoxetine (2·33, 1·28-4·25), methylphenidate (2·39, 1·40-4·08), and modafinil (4·01, 1·42-11·33) were less well tolerated than placebo in adults only. In head-to-head comparisons, only differences in efficacy (clinicians' ratings) were found, favouring amphetamines over modafinil, atomoxetine, and methylphenidate in both children and adolescents (SMDs -0·46 to -0·24) and adults (-0·94 to -0·29). We did not find sufficient data for the 26-week and 52-week timepoints.

INTERPRETATION

Our findings represent the most comprehensive available evidence base to inform patients, families, clinicians, guideline developers, and policymakers on the choice of ADHD medications across age groups. Taking into account both efficacy and safety, evidence from this meta-analysis supports methylphenidate in children and adolescents, and amphetamines in adults, as preferred first-choice medications for the short-term treatment of ADHD. New research should be funded urgently to assess long-term effects of these drugs.

FUNDING

Stichting Eunethydis (European Network for Hyperkinetic Disorders), and the UK National Institute for Health Research Oxford Health Biomedical Research Centre.