Pharmacotherapeutic group: Centrally Acting Sympathomimetics, ATC code: N06 BA12.
Mechanism of action
Lisdexamfetamine dimesylate is a pharmacologically inactive prodrug. After oral administration, lisdexamfetamine is rapidly absorbed from the gastrointestinal tract and hydrolysed primarily by red blood cells to dexamfetamine, which is responsible for the drug's activity.
Amfetamines are non-catecholamine sympathomimetic amines with CNS stimulant activity. The mode of therapeutic action of amfetamine in ADHD is not fully established, however it is thought to be due to its ability to block the reuptake of norepinephrine and dopamine into the presynaptic neuron and increase the release of these monoamines into the extraneuronal space. The prodrug, lisdexamfetamine, does not bind to the sites responsible for the reuptake of norepinephrine and dopamine in vitro.
Clinical efficacy and safety
The effects of lisdexamfetamine dimesylate in the treatment of ADHD has been demonstrated in three controlled trials in children aged 6 to 12 years, three controlled studies in adolescents aged 13 to 17 years, three controlled studies in children and adolescents (6 to 17 years), and four controlled trials in adults who met the DSM‑IV‑TR criteria for ADHD.
In clinical studies conducted in children and adults, the effects of lisdexamfetamine dimesylate were ongoing at 13 hours after dosing in children and at 14 hours in adults when the product was taken once daily in the morning.
Paediatric population
Three hundred and thirty-six patients aged 6‑17 years were evaluated in the pivotal Phase 3 European Study SPD489‑325. In this seven-week randomised double-blind, dose-optimised, placebo- and active-controlled study, lisdexamfetamine dimesylate showed significantly greater efficacy than placebo.
The ADHD Rating Scale is a measure of the core symptoms of ADHD. The placebo-adjusted mean reduction from baseline in patients treated with lisdexamfetamine dimesylate on the ADHD-RS-IV Total Score was 18.6 (p < 0.001). At every on-treatment visit and at Endpoint the percentages of subjects who met pre-defined response criteria (a ≥ 30% reduction from Baseline in ADHD-RS-IV Total Score and a CGI-I value of 1 or 2) was significantly higher (p < 0.001) for lisdexamfetamine dimesylate when compared to placebo. The endpoint of this study is defined in Table 1. The results were also significantly higher for lisdexamfetamine dimesylate when compared to placebo when the individual components of the response criteria were evaluated. In addition, mean scores for ADHD symptoms following treatment discontinuation did not exceed baseline scores prior to treatment, indicating there was no rebound effect.
In addition to a reduction in symptoms, clinical studies have demonstrated that lisdexamfetamine dimesylate significantly improves functional outcomes. Specifically, in Study SPD489‑325, 75.0% of subjects on lisdexamfetamine dimesylate showed Improvement (defined as “very much improved” or “much improved”) on the Clinical Global Impression-Improvement (CGI-I) rating scale compared to 14.2% on placebo (p < 0.001).
Lisdexamfetamine dimesylate showed significant improvement in child achievement in academic performance, as measured by the Health Related Quality of life instrument, Parent Report Form of the Child Health and Illness Profile-Child Edition (CHIP-CE:PRF) Achievement Domain. Lisdexamfetamine dimesylate demonstrated a significant improvement from baseline compared to placebo (lisdexamfetamine dimesylate: 9.4 versus Placebo -1.1) with a mean difference between the two treatment groups of 10.5 (p < 0.001).
Table 1: Outcome Results for Study SPD489-325 at Endpoint1 (Full Analysis Set)
| | Lisdexamfetamine dimesylate | Placebo | Methylphenidate hydrochloride |
| Change in ADHD-RS IV Total Score | | | |
| Least Square Mean | -24.3 | -5.7 | -18.7 |
| Effect size (versus Placebo) | 1.804 | N/A | 1.263 |
| P-value (versus Placebo) | < 0.001 | N/A | < 0.001 |
| ADHD-RS-IV Responders | | | |
| Patients Showing a response2 | 83.7% (87/104) | 22.6% (24/106) | 68.2% (73/107) |
| Difference in response from placebo | 61.0 | N/A | 45.6 |
| P-value (versus Placebo) | < 0.001 | N/A | < 0.001 |
| CGI-I Responders | | | |
| Patients Showing Improvement3 | 75.0% (78/104) | 14.2% (15/106) | 58.9 % (63/107) |
| Difference in improvement from placebo | 60.8 | N/A | 44.7 |
| P-value (versus Placebo) | < 0.001 | N/A | < 0.001 |
| Change in CHIP-CE: PRF Achievement Domain | | | |
| Least Square Mean | 9.4 | -1.1 | 6.4 |
| Effect size (versus Placebo) | 1.280 | N/A | 0.912 |
| P-value (versus Placebo) | < 0.001 | N/A | < 0.001 |
1 Endpoint = the last on-treatment post-Baseline visit of the dose optimisation or dose maintenance Period (Visits 1‑7) with a valid value
2 Response is defined as percentage reduction from Baseline in the ADHD-RS-IV Total Score of ≥ 30%
3Improvement (“very much improved” or “much improved”)
Similar results for ADHD‑RS and CGI‑I have been shown in two placebo-controlled studies, one in children (n=297) and the other in adolescents (n=314), both conducted in the United States.
A double-blind, randomised, active-controlled, dose-optimisation study was conducted in children and adolescents aged 6 to 17 years (n=267) who met DSM-IV criteria for ADHD. In this nine-week study, patients were randomised (1:1) to a daily morning dose of lisdexamfetamine dimesylate (30, 50 or 70 mg/day), or atomoxetine (dosed as appropriate for the subject's weight up to 100 mg). During a 4-week Dose Optimisation Period, patients were titrated until an optimal dose, based on treatment emergent adverse events and clinical judgement, was reached. Patients treated with lisdexamfetamine dimesylate had a shorter time to first response compared to patients treated with atomoxetine (median 13.0 vs 21.0 days, respectively; p=0.003), where response was defined as having a CGI-I score of 1 (very much improved) or 2 (much improved) at any of the double-blind treatment visits. Across all of the double-blind treatment visits, the proportion of responders in the lisdexamfetamine dimesylate group was consistently higher than the proportion of responders in the atomoxetine group. The difference ranged from 16-24 percentage points. At the study endpoint the least square mean changes from baseline in ADHD-RS-IV Total Score for lisdexamfetamine dimesylate and atomoxetine were -26.1 and -19.7, respectively, with a between-group difference of ‑6.4.
Two double-blind, parallel-group, active-controlled (OROS-MPH [Concerta]) studies have been conducted in adolescents aged 13 to 17 years with ADHD. Both studies also included a placebo reference arm. The 8-week dose-optimisation study (SPD489-405) had a 5-week dose-optimisation period and a 3-week dose-maintenance period. During the dose-optimisation period, subjects were titrated once weekly based on treatment emergent adverse events (TEAEs) and clinical response to an optimal dose of 30, 50, or 70 mg/day (for SPD489 subjects) or 18, 36, 54, or 72 mg/day (for OROS-MPH subjects), which was maintained throughout a 3-week dose-maintenance period. The mean doses at endpoint were 57.9 mg and 55.8 mg for SPD489 and OROS-MPH, respectively. In this study, neither SPD489 nor OROS-MPH was found to be statistically superior to the other product at Week 8. The 6-week fixed-dose study (SPD489-406) had a 4-week forced-dose titration period and a 2-week dose-maintenance period. At the highest doses of SPD489 (70 mg) and OROS-MPH (72 mg), SPD489 treatment was found to be superior to OROS-MPH as measured by both the primary efficacy analysis (change from baseline at Week 6 on the ADHD-RS Total score) and the key secondary efficacy analysis (at last study visit on the CGI-I) (see Table 2).
Table 2: Change from Baseline on ADHD-RS-IV Total Score and Endpoint on CGI-I (Full Analysis Set)
| SPD489-405 | Primary at Week 8 ADHD-RS-IV | Placebo | SPD489 | OROS-MPH |
| Baseline Total Score | N Mean (SE) | 89 38.2 (0.73) | 179 36.6 (0.48) | 184 37.8 (0.45) |
| Change from baseline at Week 8 | N LS Mean (SE) [a] | 67 -13.4 (1.19) | 139 -25.6 (0.82) | 152 -23.5 (0.80) |
| Lisdexamfetamine vs OROS-MPH difference | LS Mean (SE) [a] (95% CI) [a] Effect size [b] p-value | NA | -2.1 (1.15) -4.3, 0.2 0.2 0.0717 | NA |
| Active vs Placebo difference | LS Mean (SE) [a] (95% CI) [a] Effect size [b] p-value | NA | -12.2 (1.45) -15.1, -9.4 1.16 < 0.0001 | -10.1 (1.43) -13.0, -7.3 0.97 < 0.0001 |
| Key Secondary Endpoint CGI-I |
| Subjects analysed (n) | 89 | 178 | 184 |
| Improved (%) [c] Not improved (%) [d] | 31 (34.8) 58 (65.2) | 148 (83.1) 30 (16.9) | 149 (81.0) 35 (19.0) |
| Lisdexamfetamine vs OROS-MPH [e] Active treatment vs Placebo [e] | NA NA | 0.6165 < 0.0001 | NA < 0.0001 |
| SPD489-406 | Primary at Week 6 ADHD-RS-IV | Placebo | SPD489 | OROS-MPH |
| Baseline Total Score | N Mean (SE) | 106 36.1 (0.58) | 210 37.3 (0.44) | 216 37.0 (0.44) |
| Change from baseline at Week 6 | N LS Mean (SE) [a] | 93 -17.0 (1.03) | 175 -25.4 (0.74) | 181 -22.1 (0.73) |
| Lisdexamfetamine vs OROS-MPH difference | LS Mean (SE) [a] (95% CI) [a] Effect size [b] p-value | NA | -3.4 (1.04) -5.4, -1.3 0.33 0.0013 | NA |
| Active vs Placebo difference | LS Mean (SE) [a] (95% CI) [a] Effect size [b] p-value | NA | -8.5 (1.27) -11.0, -6.0 0.82 < 0.0001 | -5.1 (1.27) -7.6, -2.6 0.50 < 0.0001 |
| Key Secondary Endpoint CGI-I |
| Subjects analysed (n) | 106 | 210 | 216 |
| Improved (%) [c] Not improved (%) [d] | 53 (50.0) 53 (50.0) | 171 (81.4) 39 (18.6) | 154 (71.3) 62 (28.7) |
| Lisdexamfetamine vs OROS-MPH [e] Active treatment vs Placebo [e] | NA NA | 0.0188 < 0.0001 | NA 0.0002 |
[a] From a mixed effects model for repeated measures (MMRM) that includes treatment group, nominal visit, interaction of the treatment group with the visit as factors, baseline ADHD-RS-IV total score as a covariate, and an adjustment for the interaction of the baseline ADHD-RS-IV total score with the visit. The model is based on a REML method of estimation and utilizes an unstructured covariance type.
[b] The effect size is the difference in LS mean divided by the estimated standard deviation from the unstructured covariance matrix.
[c] The 'Improved' category includes responses of 'Very much improved' and 'Much improved'.
[d] The 'Not improved' category includes responses of 'Minimally improved', 'No change', 'Minimally worse', 'Much worse' and 'Very much worse'.
[e] From a CMH test stratified by baseline CGI-S.
Note: N = number of subjects in each treatment group, n = number of subjects analysed.
A 2-year open label safety study conducted in children and adolescents (ages 6 to 17) with ADHD enrolled 314 patients. Of these, 191 patients completed the study.
In addition, maintenance of effect was demonstrated in a double-blind, placebo-controlled, randomised withdrawal study conducted in children and adolescents ages 6 to 17 (n=157) who met the diagnosis of ADHD (DSM-IV criteria). Patients were optimised to open-label lisdexamfetamine dimesylate for an extended period (at least 26 weeks) prior to entry into the 6-week randomised withdrawal period. Eligible patients were randomised to continue receiving their optimised dose of lisdexamfetamine dimesylate or to switch to placebo. Patients were observed for relapse (treatment failure) during the 6-week double-blind phase. Treatment failure was defined as a ≥ 50% increase (worsening) in the ADHD-RS Total Score and a ≥ 2-point increase in the CGI-S score compared to scores at entry into the double-blind randomised withdrawal phase. Treatment failure was significantly lower (p < 0.001) for the lisdexamfetamine dimesylate subjects (15.8%) compared to placebo (67.5%). For the majority of subjects (70.3%) who were treatment failures regardless of treatment, ADHD symptoms worsened at or before the Week 2 visit following randomisation.
A fixed-dose safety and efficacy study was conducted in preschool children aged 4 to 5 years with ADHD. Subjects were randomised in a 5:5:5:5:6 ratio to lisdexamfetamine dimesylate (5, 10, 20, 30 mg dose strength) or placebo (see also section 5.2). The duration of the double-blind evaluation period was 6 weeks. In this study, the most commonly reported TEAEs for subjects receiving Elvanse were decreased appetite (13.7% of subjects), irritability (9.6% of subjects), and affect lability and cough (4.8% subjects each). In a 52-week open-label study, the most common TEAE was decreased appetite (15.9%) (see section 4.8).
Adult population
The efficacy of lisdexamfetamine dimesylate in the treatment of adults who met DSM-IV-TR criteria for ADHD has been demonstrated in four controlled trials in which 846 patients were enrolled.
Adult Study 1 was a double-blind, randomised, placebo-controlled, parallel-group study conducted in adults (n=420). In this 4-week study, patients were randomised to fixed dose treatment groups receiving final doses of 30, 50, or 70 mg of lisdexamfetamine dimesylate or placebo. All subjects receiving lisdexamfetamine dimesylate were initiated on 30 mg for the first week of treatment. Subjects assigned to the 50 and 70 mg dose groups were titrated by 20 mg per week until they achieved their assigned dose. Significant improvements in ADHD symptoms, based upon investigator ratings on the ADHD Rating Scale with adult prompts total score (ADHD-RS), were observed at endpoint for all lisdexamfetamine dimesylate doses compared to placebo (see Table 1). Treatment with lisdexamfetamine dimesylate significantly reduced the degree of functional impairment as measured by improvement on the Clinical Global Impression-Improvement (CGI-I) rating scale compared to placebo.
Table 3: Change from Baseline to Endpoint in ADHD-RS with Adult Prompts Total Score at Endpoint1 (Full Analysis Set)
| | Placebo | 30 mg | 50 mg | 70 mg |
| Baseline Total Score | N Mean (SD) | 62 39.4 (6.42) | 115 40.5 (6.21) | 117 40.8 (7.30) | 120 41.0 (6.02) |
| Change from baseline at Endpoint | N LS Mean (SE) | 62 -8.2 (1.43) | 115 -16.2 (1.06) | 117 -17.4 (1.05) | 120 -18.6 (1.03) |
| Placebo-adjusted difference | LS Mean (95% CI) p-value | NA | -8.04 (-12.14, -3.95) < 0.0001 | -9.16 (-13.25, -5.08) < 0.0001 | -10.41 (-14.49, -6.33) < 0.0001 |
1 Endpoint is the last post-randomisation treatment week for which a valid ADHD-RS-IV Total Score is obtained.
Note: Dunnett's test was used for the construction of Cis and p-values; p-values are the adjusted p-values and should be compared to a critical alpha of 0.05.
LS=least squares; SD= standard deviation; SE=standard error.
Adult Study 2 was a 10-week, double-blind, placebo-controlled study conducted to evaluate change in executive function behaviours, key quality of life outcomes, and ADHD symptoms in adults with ADHD and a clinically significant impairment in executive function. The study enrolled adults aged 18 to 55 years (n=161) who met DSM-IV criteria for ADHD as assessed by a total score of ≥ 65 on the Behaviour Rating Inventory of Executive Function – Adult Version (BRIEF‑A) Global Executive Composite (GEC) T-score by subject-report and a score of ≥ 28 using the Adult ADHD‑RS with prompts at the Baseline visit. At Week 10 the mean subject-reported BRIEF-A GEC T-score was 68.3 for the placebo group and 57.2 for the SPD489 group, representing LS mean changes from baseline of -11.1 and -22.3, respectively. The effect size was 0.74 in favour of the SPD489 group. The difference in LS mean change from baseline to Week 10 (-11.2) was significantly better in the lisdexamfetamine dimesylate group compared with placebo (p < 0.0001). Secondary efficacy measures of Adult ADHD Impact Module (AIM-A), ADHD-RS with adult prompts, CGI-I and the ADHD Index T-score of the Conners' Adult ADHD Rating Scale – Observer: Short Version (CAARS-O:S) were all significantly better in the lisdexamfetamine dimesylate group compared with placebo.
Adult Study 3 was a multi-centre, randomised, double-blind, placebo-controlled, crossover study. This study of lisdexamfetamine dimesylate was designed to simulate a workplace environment and enrolled 142 adults. Following a 4-week open-label, dose optimisation phase with lisdexamfetamine dimesylate (30, 50, or 70 mg/day in the morning), subjects were randomised to one of two treatment sequences: 1) lisdexamfetamine dimesylate (optimised dose) followed by placebo, each for one week, or 2) placebo followed by lisdexamfetamine dimesylate each for one week. Efficacy assessments occurred at the end of each week, using the Permanent Product Measure of Performance (PERMP). The PERMP is a skill-adjusted maths test that measures attention in ADHD. Lisdexamfetamine dimesylate treatment, compared to placebo, resulted in a statistically significant improvement in attention across all post-dose time points, as measured by average PERMP total scores over the course of one assessment day, as well as at each time point measured. The PERMP assessments were administered at pre-dose (-0.5 hours) and at 2, 4, 8, 10, 12, and 14 hours post-dose.
Adult Study 4 examined maintenance of efficacy. This study was a double-blind, placebo-controlled, randomised withdrawal design study was conducted in adults aged 18 to 55 (n=123) who met DSM-IV criteria for ADHD. At study entry, subjects must have had documentation of treatment with lisdexamfetamine dimesylate for a minimum of 6 months and had to demonstrate treatment response as defined by CGI-S ≤ 3 and Total Score on the ADHD-RS with adult prompts < 22. ADHD-RS with adult prompts Total Score is a measure of core symptoms of ADHD. Subjects that maintained treatment response at Week 3 of open label treatment phase (n=116) were eligible to enter the double-blind randomised withdrawal phase, and received their entry dose of lisdexamfetamine dimesylate (n=56) or placebo (n=60). Maintenance of efficacy for subjects treated with lisdexamfetamine dimesylate was demonstrated by the significantly lower proportion of treatment failure (< 9%) compared to subjects receiving placebo (75%) in the double-blind randomised withdrawal phase. Treatment failure was defined as a ≥ 50% increase (worsening) in the ADHD-RS with adult prompts Total Score and ≥ 2-point increase in the CGI-S score compared to scores at entry into the double-blind randomised withdrawal phase.
Abuse liability studies
In a human abuse liability study, when equivalent oral doses of 100 mg lisdexamfetamine dimesylate and 40 mg immediate-release dexamfetamine sulphate were administered to individuals with a history of drug abuse, lisdexamfetamine dimesylate 100 mg produced subjective responses on a scale of “Drug Liking Effects” (primary endpoint) that were significantly less than dexamfetamine immediate‑release 40 mg. However, oral administration of 150 mg lisdexamfetamine dimesylate produced increases in positive subjective responses on this scale that were comparable to the positive subjective responses produced by 40 mg of oral immediate-release dexamfetamine and 200 mg of diethylpropion.
Intravenous administration of 50 mg lisdexamfetamine dimesylate to individuals with a history of drug abuse produced positive subjective responses on scales measuring “Drug Liking”, “Euphoria”, “Amfetamine Effects”, and "Benzedrine Effects" that were greater than placebo but less than those produced by an equivalent dose (20 mg) of intravenous dexamfetamine.