Randomized, open-label, phase 2a study to evaluate the contribution of artefenomel to the clinical and parasiticidal activity of artefenomel plus ferroquine in African patients with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: The contribution of artefenomel to the clinical and parasiticidal activity of ferroquine and artefenomel in combination in uncomplicated Plasmodium falciparum malaria was investigated. METHODS: This Phase 2a, randomized, open-label, parallel-group study was conducted from 11th September 2018 to 6th November 2019 across seven centres in Benin, Burkina Faso, Gabon, Kenya, and Uganda. Patients aged ≥ 14-69 years with microscopically confirmed infection (≥ 3000 to ≤ 50,000 parasites/µL blood) were randomized 1:1:1:1 to 400 mg ferroquine, or 400 mg ferroquine plus artefenomel 300, 600, or 1000 mg, administered as a single oral dose. The primary efficacy analysis was a logistic regression evaluating the contribution of artefenomel exposure to Day 28 PCR-adjusted adequate clinical and parasitological response (ACPR). Safety was also evaluated. RESULTS: The randomized population included 140 patients. For the primary analysis in the pharmacokinetic/pharmacodynamic efficacy population (N = 121), the contribution of artefenomel AUC0-∞ to Day 28 PCR-adjusted ACPR was not demonstrated when accounting for ferroquine AUC0-d28, baseline parasitaemia, and other model covariates: odds ratio 1.1 (95% CI 0.98, 1.2; P = 0.245). In the per-protocol population, Day 28 PCR-adjusted ACPR was 80.8% (21/26; 95% CI 60.6, 93.4) with ferroquine alone and 90.3% (28/31; 95% CI 74.2, 98.0), 90.9% (30/33; 95% CI 75.7, 98.1) and 87.1% (27/31; 95% CI 70.2, 96.4) with 300, 600, and 1000 mg artefenomel, respectively. Median time to parasite clearance (Kaplan-Meier) was 56.1 h with ferroquine, more rapid with artefenomel, but similar for all doses (30.0 h). There were no deaths. Adverse events (AEs) of any cause occurred in 51.4% (18/35) of patients with ferroquine 400 mg alone, and 58.3% (21/36), 66.7% (24/36), and 72.7% (24/33) with 300, 600, and 1000 mg artefenomel, respectively. All AEs were of mild-to-moderate severity, and consistent with the known profiles of the compounds. Vomiting was the most reported AE. There were no cases of QTcF prolongation ≥ 500 ms or > 60 ms from baseline. CONCLUSION: The contribution of artefenomel exposure to the clinical and parasitological activity of ferroquine/artefenomel could not be demonstrated in this study. Parasite clearance was faster with ferroquine/artefenomel versus ferroquine alone. All treatments were well tolerated. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03660839 (7 September, 2018).

A randomized, double-blind, phase 2b study to investigate the efficacy, safety, tolerability and pharmacokinetics of a single-dose regimen of ferroquine with artefenomel in adults and children with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: For uncomplicated Plasmodium falciparum malaria, highly efficacious single-dose treatments are expected to increase compliance and improve treatment outcomes, and thereby may slow the development of resistance. The efficacy and safety of a single-dose combination of artefenomel (800 mg) plus ferroquine (400/600/900/1200 mg doses) for the treatment of uncomplicated P. falciparum malaria were evaluated in Africa (focusing on children ≤ 5 years) and Asia. METHODS: The study was a randomized, double-blind, single-dose, multi-arm clinical trial in patients aged > 6 months to < 70 years, from six African countries and Vietnam. Patients were followed up for 63 days to assess treatment efficacy, safety and pharmacokinetics. The primary efficacy endpoint was the polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR) at Day 28 in the Per-Protocol [PP] Set comprising only African patients ≤ 5 years. The exposure-response relationship for PCR-adjusted ACPR at Day 28 and prevalence of kelch-13 mutations were explored. RESULTS: A total of 373 patients were treated: 289 African patients ≤ 5 years (77.5%), 64 African patients > 5 years and 20 Asian patients. None of the treatment arms met the target efficacy criterion for PCR-adjusted ACPR at Day 28 (lower limit of 95% confidence interval [CI] > 90%). PCR-adjusted ACPR at Day 28 [95% CI] in the PP Set ranged from 78.4% [64.7; 88.7%] to 91.7% [81.6; 97.2%] for the 400 mg to 1200 mg ferroquine dose. Efficacy rates were low in Vietnamese patients, ranging from 20 to 40%. A clear relationship was found between drug exposure (artefenomel and ferroquine concentrations at Day 7) and efficacy (primary endpoint), with higher concentrations of both drugs resulting in higher efficacy. Six distinct kelch-13 mutations were detected in parasite isolates from 10/272 African patients (with 2 mutations known to be associated with artemisinin resistance) and 18/20 Asian patients (all C580Y mutation). Vomiting within 6 h of initial artefenomel administration was common (24.6%) and associated with lower drug exposures. CONCLUSION: The efficacy of artefenomel/ferroquine combination was suboptimal in African children aged ≤ 5 years, the population of interest, and vomiting most likely had a negative impact on efficacy. Trial registration ClinicalTrials.gov, NCT02497612. Registered 14 Jul 2015, https://clinicaltrials.gov/ct2/show/NCT02497612?term=NCT02497612&draw=2&rank=1.

African isolates show a high proportion of multiple copies of the Plasmodium falciparum plasmepsin-2 gene, a piperaquine resistance marker.

BACKGROUND: Today, the development of new and well-tolerated anti-malarial drugs is strongly justified by the emergence of Plasmodium falciparum resistance. In 2014-2015, a phase 2b clinical study was conducted to evaluate the efficacy of a single oral dose of Artefenomel (OZ439)-piperaquine (PPQ) in Asian and African patients presenting with uncomplicated falciparum malaria. METHODS: Blood samples collected before treatment offered the opportunity to investigate the proportion of multidrug resistant parasite genotypes, including P. falciparum kelch13 mutations and copy number variation of both P. falciparum plasmepsin 2 (Pfpm2) and P. falciparum multidrug resistance 1 (Pfmdr1) genes. RESULTS: Validated kelch13 resistance mutations including C580Y, I543T, P553L and V568G were only detected in parasites from Vietnamese patients. In Africa, isolates with multiple copies of the Pfmdr1 gene were shown to be more frequent than previously reported (21.1%, range from 12.4% in Burkina Faso to 27.4% in Uganda). More strikingly, high proportions of isolates with multiple copies of the Pfpm2 gene, associated with piperaquine (PPQ) resistance, were frequently observed in the African sites, especially in Burkina Faso and Uganda (> 30%). CONCLUSIONS: These findings were considered to sharply contrast with the recent description of increased sensitivity to PPQ of Ugandan parasite isolates. This emphasizes the necessity to investigate in vitro susceptibility profiles to PPQ of African isolates with multiple copies of the Pfpm2 gene and estimate the risk of development of PPQ resistance in Africa. Trial registration Clinicaltrials.gov reference: NCT02083380. Study title: Phase II efficacy study of artefenomel and piperaquine in adults and children with P. falciparum malaria. https://clinicaltrials.gov/ct2/results?cond=&term=NCT02083380&cntry=&state=&city=&dist= . FSFV: 23-Jul-2014; LSLV: 09-Oct-2015.

A randomised, double-blind clinical phase II trial of the efficacy, safety, tolerability and pharmacokinetics of a single dose combination treatment with artefenomel and piperaquine in adults and children with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: The clinical development of a single encounter treatment for uncomplicated malaria has the potential to significantly improve the effectiveness of antimalarials. Exploratory data suggested that the combination of artefenomel and piperaquine phosphate (PQP) has the potential to achieve satisfactory cure rates as a single dose therapy. The primary objective of the study was to determine whether a single dose of artefenomel (800 mg) plus PQP in ascending doses is an efficacious treatment for uncomplicated Plasmodium falciparum malaria in the 'target' population of children ≤ 5 years of age in Africa as well as Asian patients of all ages. METHODS: Patients in six African countries and in Vietnam were randomised to treatment with follow-up for 42-63 days. Efficacy, tolerability, safety and pharmacokinetics were assessed. Additional key objectives were to characterise the exposure-response relationship for polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response at day 28 post-dose (ACPR28) and to further investigate Kelch13 mutations. Patients in Africa (n = 355) and Vietnam (n = 82) were included, with 85% of the total population being children < 5 years of age. RESULTS: ACPR28 in the per protocol population (95% confidence interval) was 70.8% (61.13-79.19), 68.4% (59.13-76.66) and 78.6% (70.09-85.67) for doses of 800 mg artefenomel with 640 mg, 960 mg and 1440 mg of PQP respectively. ACPR28 was lower in Vietnamese than in African patients (66.2%; 54.55-76.62 and 74.5%; 68.81-79.68) respectively. Within the African population, efficacy was lowest in the youngest age group of ≥ 0.5 to ≤ 2 years, 52.7% (38.80-66.35). Initial parasite clearance was twice as long in Vietnam than in Africa. Within Vietnam, the frequency of the Kelch13 mutation was 70.1% and was clearly associated with parasite clearance half-life (PCt1/2). The most significant tolerability finding was vomiting (28.8%). CONCLUSIONS: In this first clinical trial evaluating a single encounter antimalarial therapy, none of the treatment arms reached the target efficacy of > 95% PCR-adjusted ACPR at day 28. Achieving very high efficacy following single dose treatment is challenging, since > 95% of the population must have sufficient concentrations to achieve cure across a range of parasite sensitivities and baseline parasitaemia levels. While challenging, the development of tools suitable for deployment as single encounter curative treatments for adults and children in Africa and to support elimination strategies remains a key development goal. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02083380 . Registered on 7 March 2014.

Evaluation of the QT effect of a combination of piperaquine and a novel anti-malarial drug candidate OZ439, for the treatment of uncomplicated malaria.

AIMS: The aim was to investigate the QT effect of a single dose combination regimen of piperaquine phosphate (PQP) and a novel aromatic trioxolane, OZ439, for malaria treatment. METHODS: Exposure-response (ER) analysis was performed on data from a placebo-controlled, single dose, study with OZ439 and PQP. Fifty-nine healthy subjects aged 18 to 55 years received OZ439 alone or placebo in a first period, followed by OZ439 plus PQP or matching placebos in period 2. OZ439 and PQP doses ranged from 100-800 mg and 160-1440 mg, respectively. Twelve-lead ECG tracings and PK samples were collected serially pre- and post-dosing. RESULTS: A significant relation between plasma concentrations and placebo-corrected change from baseline QTc F (ΔΔQTc F) was demonstrated for piperaquine, but not for OZ439, with a mean slope of 0.047 ms per ng ml(-1) (90% CI 0.038, 0.057). Using an ER model that accounts for plasma concentrations of both piperaquine and OZ439, a largest mean QTc F effect of 14 ms (90% CI 10, 18 ms) and 18 ms (90% CI 14, 22 ms) was predicted at expected plasma concentrations of a single dose 800 mg OZ439 combined with PQP 960 mg (188 ng ml(-1) ) and 1440 mg (281 ng ml(-1) ), respectively, administered in the fasted state. CONCLUSIONS: Piperaquine prolongs the QTc interval in a concentration-dependent way. A single dose regimen combining 800 mg OZ439 with 960 mg or 1440 mg PQP is expected to result in lower peak piperaquine plasma concentrations compared with available 3 day PQP-artemisinin combinations and can therefore be predicted to cause less QTc prolongation.

Animal models of Alzheimer's disease and drug development.

Animal disease models are considered important in the development of drugs for Alzheimer's disease. This brief review will discuss possible reasons why their success in identifying efficacious treatments has been limited, and will provide some thoughts on the role of animal experimentation in drug development. Specifically, none of the current models of Alzheimer's disease have either construct or predictive validity, and no model probably ever will. Clearly, specific animal experiments contribute to our understanding of the disease and generate hypotheses. Ultimately, however, the hypothesis can only be tested in human patients and only with the proper tools. These tools are a pharmacologically active intervention (in humans) and a clinical trial suited to evaluate the mechanism of action. Integration of knowledge in quantitative (sub) models is considered important if not essential in this process.

A randomized, double-blind, placebo-controlled trial to assess the efficacy and safety of gabapentin enacarbil in subjects with neuropathic pain associated with postherpetic neuralgia (PXN110748).

UNLABELLED: Gabapentin enacarbil (GEn) is an actively transported prodrug of gabapentin that provides sustained, dose-proportional exposure to gabapentin. This randomized, double-blind, parallel-group, placebo-controlled study evaluated the safety and efficacy of 3 different maintenance doses of oral GEn in subjects with postherpetic neuralgia. Adults with a 24-hour average pain intensity score of ≥4.0 received GEn 1,200 mg, 2,400 mg, 3,600 mg, or placebo for 14 weeks (including a 1-week up-titration, 12-week maintenance, and 1-week taper). The primary endpoint was change from baseline to end of maintenance treatment in mean 24-hour average pain intensity score. The intent-to-treat population consisted of 371 subjects (GEn 1,200 mg = 107, 2,400 mg = 82, 3,600 mg = 87, placebo = 95). With regard to the primary endpoint, all 3 GEn treatment groups demonstrated a statistically significant difference relative to placebo. The adjusted mean change from baseline for the treatment groups ranged from -2.36 to -2.72 versus -1.66 for the placebo group. Exposure-response modeling suggested an ED50 around 1,200 mg/day, which was consistent with historical findings reported for gabapentin. The most commonly reported adverse events were dizziness and somnolence. All studied doses of GEn significantly improved pain associated with postherpetic neuralgia as compared to placebo and were well tolerated. PERSPECTIVE: GEn provides clinically important pain relief with doses from 1,200 mg to 3,600 mg and is generally well tolerated and efficacious. As an actively transported prodrug of gabapentin, it provides dose-proportional and extended exposure to gabapentin.

Pharmacokinetic and pharmacodynamic profiling of a P2X7 receptor allosteric modulator GSK1482160 in healthy human subjects.

AIMS: This paper describes findings from the first-in-human study for GSK1482160, an orally available allosteric P2X7 receptor modulator. The study aimed to assess the pharmacokinetics (PK), pharmacodynamics (PD), safety and tolerability of the compound in healthy subjects. METHODS: Escalating single doses of up to 1 g were administered to healthy subjects in a single-blind and placebo-controlled fashion. Safety, tolerability, blood drug concentrations and ex vivo Il-1ß production in blood were evaluated. RESULTS: Drug concentration peaked within 3.5 h of dosing under fasting conditions and declined thereafter with a relatively short half-life of less than 4.5 h. Exposure was proportional to dose with between subject variability of less than 60%. A PK/PD model quantified Il-1ß as a function of drug exposure. The model allowed simulation of in vivo pharmacology for various untested dose levels and regimens. Furthermore, the mechanistic model supported the hypothesis that the compound reduces the efficacy of ATP at the P2X7 receptor without affecting its affinity. No major safety or tolerability concerns were identified in this small study (n = 29), except for one case of asymptomatic accelerated idioventricular rhythm at the top dose. CONCLUSION: The model-based approach maximized analysis power by integrating all biomarker data and revealed mechanistic insight into the pharmacology of P2X7 modulation by GSK1482160. Simulations by this model ultimately led to the discontinuation of the development of this compound. The therapeutic relevance of the P2X7 receptor remains to be tested in patients. The mechanistic-model-based approach can be applied widely to drug development.

Lack of efficacy of the selective iNOS inhibitor GW274150 in prophylaxis of migraine headache.

INTRODUCTION: This study investigated the efficacy and tolerability of the highly selective iNOS inhibitor GW274150 in prophylaxis of migraine headache. SUBJECTS AND METHODS: The study was conducted in two parts, each comprising a 4-week baseline period, a 12-week, double-blind, parallel-group treatment period, and a 4-week follow-up period. The study had an adaptive design in that findings of Part 1 of the study were used to inform the conduct of Part 2. Following an interim analysis at the end of Part 1, the trial could be stopped for futility or continued in Part 2 to study the full-dose response or to increase sample size in case initial assumptions had been violated. The primary end-point in both parts of the study was the probability of the occurrence of a migraine headache day during the baseline period and the treatment period. RESULTS: In Part 1, adult male and female patients with migraine received GW274150 60 mg (n = 37), 120 mg (n = 37), or placebo (n = 38) once daily for 12 weeks. In Part 2, female patients with migraine received GW274150 60 mg (n= 160) or placebo (n = 154) once daily for 12 weeks. GW274150 was no more effective than placebo for the primary efficacy end-point or any secondary efficacy end-point in Part 1 or Part 2. GW274150 was generally well tolerated. CONCLUSIONS: GW274150 at doses predicted to inhibit iNOS >80% did not differ from placebo in the prophylaxis of migraine. The results do not support a role of iNOS inhibition in migraine prevention.

Prolonged pharmacodynamic effects of S-0139, an intravenously administered endothelin A (ET) antagonist, in the human forearm blood flow model.

AIMS: To estimate the pharmacologically active dose range of a new investigational compound S-0139, a selective endothelin A (ET(A)) receptor antagonist, in man, and to examine the duration of its pharmacodynamic effect. METHODS: Venous occlusion plethysmography was performed to assess changes in forearm blood flow following intra-brachial administration of endothelin-1 (ET-1). ET(A) antagonists have been shown to block ET-1-induced vasoconstriction in this model. The study was conducted in three parts: (1) a pilot study to explore dose-response (dose range 0.08-13.33 microg kg(-1) min(-1)), (2) a randomized study to confirm dose-response (placebo, 2.5, 6.67 and 15 microg kg(-1) min(-1)), and (3) a delayed administration study (15.7 microg kg(-1) min(-1)) to explore the duration of the pharmacodynamic effect. In all studies a 3-h infusion of S-0139 was given and during the last 90 min of the infusion, ET-1 was infused concurrently for 90 min. In study (3) a second ET-1 infusion was given starting 3 h after completion of the first. RESULTS: Intravenously administered S-0139 resulted in significant inhibition of ET-1-induced vasoconstriction in the forearm (plasma concentration 800-2000 ng ml(-1)). In the delayed administration study, the same extent of inhibition was still present when ET-1 was administered 3 h after the end of infusion of S-0139, even though the S-0139 plasma concentrations (mean 17 ng ml(-1)) were well below pharmacologically active concentrations as determined in studies 1 and 2. CONCLUSIONS: S-0139 dose-dependently blocks ET-1-mediated vasoconstriction in the forearm and has a prolonged duration of effect beyond that expected from its pharmacokinetic profile.

In vitro, pharmacokinetic, and pharmacodynamic interactions of ketoconazole and midazolam in the rat.

Interactions of midazolam and ketoconazole were studied in vivo and in vitro in rats. Ketoconazole (total dose of 15 mg/kg intraperitoneally) reduced clearance of intravenous midazolam (5 mg/kg) from 79 to 55 ml/min/kg (p < 0.05) and clearance of intragastric midazolam (15 mg/kg) from 1051 to 237 ml/min/kg (p < 0.05), increasing absolute bioavailability from 0.11 to 0.36 (p < 0.05). Presystemic extraction occurred mainly across the liver as opposed to the gastrointestinal tract mucosa. Midazolam increased electroencephalographic (EEG) amplitude in the beta-frequency range. Ketoconazole shifted the concentration-EEG effect relationship rightward (increase in EC(50)), probably because ketoconazole is a neutral benzodiazepine receptor ligand. Ketoconazole competitively inhibited midazolam hydroxylation by rat liver and intestinal microsomes in vitro, with nanomolar K(i) values. At a total serum ketoconazole of 2 microg/ml (3.76 microM) in vivo, the predicted reduction in clearance of intragastric midazolam by ketoconazole (to 6% of control) was slightly greater than the observed reduction in vivo (to 15% of control). However, unbound serum ketoconazole greatly underpredicted the observed clearance reduction. Although the in vitro and in vivo characteristics of midazolam in rats incompletely parallel those in humans, the experimental model can be used to assess aspects of drug interactions having potential clinical importance.

Effect of 7-day exposure to midazolam on electroencephalogram pharmacodynamics in rats: a model to study multiple pharmacokinetic-pharmacodynamic relationships in individual animals.

The objective of this study was to determine the concentration-electroencephalogram (EEG) relationships for midazolam, a full-agonist benzodiazepine ligand, on multiple occasions in individual rats, and to examine the effect of chronic midazolam exposure on that relationship. Rats were chronically instrumented with venous and arterial cannulas, and cortical EEG electrodes. The rats received either: 7 days of midazolam 10 mg kg(-1) intravenously once a day (midazolam group); or midazolam on days 1 and 7 and vehicle on days 2-6 (vehicle group). Concentration-effect relationships were determined on days 1, 4 and 7 from multiple blood and EEG samples before and after the administration of the midazolam dose. The concentration-EEG effect relationships were consistent with a sigmoidal Emax (maximal effect) model. No differences in pharmacokinetic or pharmacodynamic parameters were found between day 1 and day 7 in either group. However, in the midazolam group, both the fraction unbound of midazolam in serum and the EC50 (concentration at half-maximal effect) for free midazolam increased from days 1-7 by 35 +/- 3% and 54 +/- 25%, respectively (means +/- s.d., P< 0.05). This may be related to decreased serum albumin levels in the midazolam group (-19+5%, P < 0.05) which, in turn, could be explained by the sedation associated with daily midazolam treatment. We concluded that concentration-EEG effect relationships can be studied on multiple occasions in individual animals, reducing animal use and variability. A modest degree of tolerance to midazolam was found with this paradigm, the effect only being evident after correction for the fraction unbound of midazolam.