Model-based comparison of subcutaneous versus sublingual apomorphine administration in the treatment of motor fluctuations in Parkinson's disease.

The objective of this study was to compare the effectiveness of subcutaneous (SC) and sublingual (SL) formulations of apomorphine for the treatment of motor fluctuations in Parkinson's disease using a pharmacokinetics (PK)/pharmacodynamics (PD) modeling approach. The PK of SC and SL apomorphine are best described by a one-compartment model with first-order absorption and a two-compartment model with delayed absorption, respectively. The PK/PD model relating apomorphine plasma concentrations to the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores was described by a sigmoidal Emax model assuming effective concentration = drug concentration in an effect compartment. Apomorphine concentrations and UPDRS motor scores were simulated from the PK/PD models using 500 hypothetical subjects. UPDRS motor score change from baseline was evaluated using time to clinically relevant response, response duration, area under the curve, maximal response, and time to maximal response. Higher doses of each apomorphine formulation were associated with shorter time to response, longer response duration, and greater maximal response. Although the mean maximal responses to SC and SL apomorphine were comparable, the time to response was four times shorter (7 vs. 31 min) and time to maximal response was two times shorter (27 vs. 61 min) for 4 mg SC vs. 50 mg SL. Thus, faster onset of action was observed for the SC formulation compared to SL. These data may be useful for physicians when selecting "on demand" therapy for patients with Parkinson's disease experiencing motor fluctuations.

Advanced Model-based Approach to Evaluate Human Plasma, Cerebrospinal Fluid, and Neuronal mTORC1 Activation Biomarkers After NV-5138 Administration in Healthy Volunteers.

PURPOSE: NV-5138 ([S]-2-amino-5,5-difluoro-4,4-dimethylpentanoic acid) is an orally bioavailable, small-molecule activator of the mechanistic target of rapamycin complex 1 (mTORC1) pathway in development for treatment-resistant depression. The authors established a model to describe the relationship between plasma and cerebrospinal fluid (CSF) concentrations of NV-5138 and between CSF concentrations and potential biomarkers thought to be associated with mTORC1 activity (ie, orotic acid, N-acetylmethionine, and N-formylmethionine). METHODS: Data were collected from a randomized, double-blind, placebo-controlled, tolerability, and pharmacokinetic (PK) parameter study of 5 ascending (400, 800, 1600, 2400, and 3000 mg), once-daily oral doses of NV-5138 in healthy subjects. NV-5138 plasma PK parameter samples were collected at 15 time points over 24 hours on days 1 and 7, and at pre dose on days 2-6 for all doses. NV-5138 CSF PK parameter and CSF biomarker samples were collected on days 1 and 7 at pre dose and 4, 8, and 12 hours post dose for all doses except 3000 mg. A model-based approach was used to develop and validate a model that describes the relationship between NV-5138 in CSF and biomarker concentrations. FINDINGS: Twenty-four of the 42 enrolled subjects had simultaneous plasma and CSF measurements of NV-5138 and CSF biomarker concentrations and were included in the PK parameter and pharmacodynamic (PD) analyses. A 2-compartment plasma and CSF PK parameter, with indirect PD effects, model was developed and validated. NV-5138 plasma concentrations were positively correlated with those in CSF, although CSF concentrations lagged slightly behind those in plasma, as indicated by a counterclockwise hysteresis effect. Similarly, the relationship between the PD measures of mTORC1 activation and NV-5138 was also characterized by counterclockwise hysteresis, when the increase in CSF biomarker concentrations lagged behind those of NV-5138, consistent with a signaling intermediary/cascade, such as mTORC1. Maximal biomarker activation was achieved at NV-5138 CSF concentrations of approximately 3 µg/mL, which were associated with daily doses of 1600 mg NV-5138. The safety profile analysis (n = 42) found that most of the reported adverse events were mild in severity, with no severe, serious, unusual, or unexpected adverse events or any dissociative effects; 2 subjects (400-mg cohort) discontinued due to adverse events that were judged to be unrelated to study medication. IMPLICATIONS: The model will be used for designing future efficacy and tolerability studies. Consecutive daily doses of NV-5138 were well tolerated in this healthy volunteer study.

Interpreting clinical trial outcomes complicated by placebo response with an assessment of false-negative and true-negative clinical trials in depression using propensity-weighting.

The objective of this study was to evaluate the performances of the propensity score weighted (PSW) methodology in a post-hoc re-analysis of a failed and a negative RCTs in depressive disorders. The conventional study designs, randomizations, and statistical approaches do not account for the baseline distribution of major non-specific prognostic and confounding factors such as the individual propensity to show a placebo effect (PE). Therefore, the conventional analysis approaches implicitly assume that the baseline PE is the same for all subjects in the trial even if this assumption is not supported by our knowledge on the impact of PE on the estimated treatment effect (TE). The consequence of this assumption is an inflation of false negative results (type II error) in presence of a high proportion of subjects with high PE and an inflation of false positive (type I error) in presence of a high proportion of subjects with low PE value. Differently from conventional approaches, the inverse of the PE probability was used as weight in the mixed-effects analysis to assess TE in the PSW analysis. The results of this analysis indicated an enhanced signal of drug response in a failed trial and confirmed the absence of drug effect in a negative trial. This approach can be considered as a reference prospective or post-hoc analysis approach that minimize the risk of inflating either type I or type II error in contrast to what happens in the analyses of RCT studies conducted with the conventional statistical methodology.