Rachel A. Gibson

Fast-acting antimalarial drugs are needed to address the emergence of artemisinin resistance in the protozoan parasite Plasmodium falciparum, the major cause of severe malaria worldwide. The pyrrolidinamide antimalarial drug MMV367 (GSK3772701) potentially interferes with parasite metabolism mediated by P. falciparum acyl-CoA synthetases 10 and 11. In this volunteer infection study, the antimalarial activity of MMV367 was tested against blood-stage P. falciparum in 12 healthy malaria-naïve adults. The study participants were inoculated with P. falciparum 3D7–infected erythrocytes on day 0 and received a single oral dose of MMV367 at 3 mg ( n = 3), 5 mg ( n = 2), 10 mg ( n = 1), 20 mg ( n = 3), 90 mg ( n = 2), or 1500 mg ( n = 1) on day 8. All participants received artemether-lumefantrine on or before day 24. Maximum MMV367 plasma concentrations occurred 2 to 4 hours postdose, and the elimination half-life was 12.9 to 18 hours. For doses of ≥20 mg, the parasite clearance half-life was 2.2 to 4.3 hours with viable parasites declining more rapidly (elimination half-life of 1.1 to 2.7 hours). A clearance pharmacokinetic/pharmacodynamic model described the relationship between MMV367 concentrations and parasite killing and subsequent clearance of nonviable parasites. Model-derived efficacy parameters included a minimum inhibitory concentration of 6.3 ng/ml (95% CI, 5.2 to 7.8) and a minimum parasiticidal concentration with 90% of maximum effect of 54 ng/ml (95% CI, 43 to 68). No reduction in in vitro susceptibility to MMV367 or genetic determinants of resistance were observed in drug-exposed parasite lines. Most adverse events were attributed to malaria challenge, and none were serious. Higher MMV367 doses were not associated with an increased incidence or severity of adverse events. These findings support further clinical development of MMV367.

Aim: To evaluate the safety, tolerability and pharmacokinetics in healthy participants of orally administered MMV367 (GSK3772701), a novel antimalarial interfering with Plasmodium falciparum acyl coenzyme A synthetase 10/11 function.Methods: This first‐in‐human study enrolled 47 healthy male and female participants. Part 1 was a randomised, double‐blind, placebo‐controlled study in which four sequential fasted cohorts received MMV367 single ascending doses (100, 300, 750 and 1500 mg) or placebo (six active, two placebo per cohort). Part 2 was a randomised, open‐label crossover (fed‐fasted) pilot food‐effect study of MMV367 440 mg (n = 8). In Part 3 MMV367 400 mg was administered once daily for 3 days in a single cohort (six active, two placebo).Results: Treatment‐emergent adverse events (TEAEs) occurred in 36.8% (14/38) of participants receiving MMV367 vs 44.4% (4/9) with placebo. There were two MMV367‐related TEAEs, and no serious or severe TEAEs or clinically relevant changes in electrocardiograms, vital signs or laboratory tests. In Part 1 (fasted), maximum plasma concentrations occurred between 2.0 and 5.0 h post dose, with a geometric mean half‐life of 16.5‐18.4 h. Approximate dose proportionality was demonstrated across the dose range (100‐1500 mg). In Part 2, MMV367 relative bioavailability (fed vs fasted) was 161.4% (90% confidence interval 148.3, 175.6) for maximum observed concentration (C_max), 130.4% (122.2, 139.1) for the area under the curve (AUC) until the last measurable concentration and 132.9% (124.1, 142.3) for AUC extrapolated to infinity. In Part 3, geometric mean day 1:3 exposure ratios (geometric co‐efficient of variability) were 1.9 (4.9%) for C_max and 2.1 (7.7%) for the AUC for the defined interval between doses after once‐daily dosing for 3 days.Conclusions: MMV367 demonstrated acceptable safety, tolerability and pharmacokinetic profiles supporting further development as an antimalarial drug.

Aim: To evaluate the safety, tolerability and pharmacokinetics in healthy participants of orally administered MMV367 (GSK3772701), a novel antimalarial interfering with Plasmodium falciparum acyl coenzyme A synthetase 10/11 function.Methods: This first‐in‐human study enrolled 47 healthy male and female participants. Part 1 was a randomised, double‐blind, placebo‐controlled study in which four sequential fasted cohorts received MMV367 single ascending doses (100, 300, 750 and 1500 mg) or placebo (six active, two placebo per cohort). Part 2 was a randomised, open‐label crossover (fed‐fasted) pilot food‐effect study of MMV367 440 mg (n = 8). In Part 3 MMV367 400 mg was administered once daily for 3 days in a single cohort (six active, two placebo).Results: Treatment‐emergent adverse events (TEAEs) occurred in 36.8% (14/38) of participants receiving MMV367 vs 44.4% (4/9) with placebo. There were two MMV367‐related TEAEs, and no serious or severe TEAEs or clinically relevant changes in electrocardiograms, vital signs or laboratory tests. In Part 1 (fasted), maximum plasma concentrations occurred between 2.0 and 5.0 h post dose, with a geometric mean half‐life of 16.5‐18.4 h. Approximate dose proportionality was demonstrated across the dose range (100‐1500 mg). In Part 2, MMV367 relative bioavailability (fed vs fasted) was 161.4% (90% confidence interval 148.3, 175.6) for maximum observed concentration (C_max), 130.4% (122.2, 139.1) for the area under the curve (AUC) until the last measurable concentration and 132.9% (124.1, 142.3) for AUC extrapolated to infinity. In Part 3, geometric mean day 1:3 exposure ratios (geometric co‐efficient of variability) were 1.9 (4.9%) for C_max and 2.1 (7.7%) for the AUC for the defined interval between doses after once‐daily dosing for 3 days.Conclusions: MMV367 demonstrated acceptable safety, tolerability and pharmacokinetic profiles supporting further development as an antimalarial drug.

A single 300 mg dose of tafenoquine (an 8-aminoquinoline), in combination with a standard 3-day course of chloroquine, is approved in several countries for the radical cure (prevention of relapse) of Plasmodium vivax malaria in patients aged ≥ 16 years. Despite this, questions have arisen on the optimal dose of tafenoquine. Before the availability of tafenoquine, a 3-day course of chloroquine in combination with the 8-aminoquinoline primaquine was the only effective radical cure for vivax malaria. The World Health Organization (WHO)-recommended standard regimen is 14 days of primaquine 0.25 mg/kg/day or 7 days of primaquine 0.5 mg/kg/day in most regions, or 14 days of primaquine 0.5 mg/kg/day in East Asia and Oceania, however the long treatment courses of 7 or 14 days may result in poor adherence and, therefore, low treatment efficacy. A single dose of tafenoquine 300 mg in combination with a 3-day course of chloroquine is an important advancement for the radical cure of vivax malaria in patients without glucose-6-phosphate dehydrogenase (G6PD) deficiency, as the use of a single-dose treatment will improve adherence. Selection of a single 300 mg dose of tafenoquine for the radical cure of P. vivax malaria was based on collective efficacy and safety data from 33 studies involving more than 4000 trial participants who received tafenoquine, including over 800 subjects who received the 300 mg single dose. The safety profile of single-dose tafenoquine 300 mg is similar to that of standard-dosage primaquine 0.25 mg/kg/day for 14 days. Both primaquine and tafenoquine can cause acute haemolytic anaemia in individuals with G6PD deficiency; severe haemolysis can lead to anaemia, kidney damage, and, in some cases, death. Therefore, relapse prevention using an 8-aminoquinoline must be balanced with the need to avoid clinical haemolysis associated with G6PD deficiency. To minimize this risk, the WHO recommends G6PD testing for all individuals before the administration of curative doses of 8-aminoquinolines. In this article, the authors review key efficacy and safety data from the pivotal trials of tafenoquine and argue that the currently approved dose represents a favourable benefit–risk profile.

A single 300 mg dose of tafenoquine, in combination with chloroquine, is currently approved in several countries for the radical cure (prevention of relapse) of Plasmodium vivax malaria in patients aged ≥16 years. Recently, however, Watson et al. suggested that the approved dose of tafenoquine is insufficient for radical cure, and that a higher 450 mg dose could reduce P. vivax recurrences substantially (Watson et al., 2022). In this response, we challenge Watson et al.'s assertion based on empirical evidence from dose-ranging and pivotal studies (published) as well as real-world evidence from post-approval studies (ongoing, therefore currently unpublished). We assert that, collectively, these data confirm that the benefit–risk profile of a single 300 mg dose of tafenoquine, co-administered with chloroquine, for the radical cure of P. vivax malaria in patients who are not G6PD-deficient, continues to be favourable where chloroquine is indicated for P. vivax malaria. If real-world evidence of sub-optimal efficacy in certain regions is observed or dose-optimisation with other blood-stage therapies is required, then well-designed clinical studies assessing safety and efficacy will be required before higher doses are approved for clinical use.

Sustainable access to essential medicines in low-income and middle-income countries requires innovative cross-sectoral collaboration throughout the lifecycle of a medicine. Partnerships are essential to address the systemic challenges of global health and health inequity. Pharmaceutical companies, funders, governments, international non-governmental organisations (I-NGOs) and other key stakeholders can leverage, through effective partnership working, their unique expertise to help drive innovation and share learnings and risks. Here, we reflect on one approach taken in the development and supply of chlorhexidine digluconate 7.1% w/w gel (equivalent to 4% w/w chlorhexidine) for neonatal cord care. We describe and analyse the steps taken by GSK to increase access to chlorhexidine gel, including partnering with the I-NGO Save the Children in Western Kenya. Learning points gained along the journey are shared, together with subsequent steps taken to increase access, with the aim of making recommendations that may be applicable to similar enterprises in the future.

Background: Delayed gastric emptying may impair l‐dopa absorption, contributing to motor fluctuations. We evaluated the effect of camicinal (GSK962040), a gastroprokinetic, on the absorption of l‐dopa and symptoms of PD.Methods: Phase II, double‐blind, placebo‐controlled trial. Participants were randomized to receive camicinal 50 mg once‐daily (n = 38) or placebo (n = 20) for 7 to 9 days.Results: l‐dopa exposure was similar with coadministration of camicinal compared to placebo. Median time to maximum l‐dopa concentration was reduced, indicating more rapid absorption of l‐dopa. Camicinal resulted in significant reduction in OFF time (–2.31 hours; 95% confidence interval: –3.71, –0.90), significant increase in ON time (+1.88 hours; 95% confidence interval: 0.28, 3.48) per day, and significant decrease in mean total MDS‐UPDRS score (–12.5; 95% confidence interval: –19.67, ‐5.29). Camicinal treatment was generally well tolerated.Conclusions: PD symptom improvement with camicinal occurred in parallel with more rapid absorption of l‐dopa. This study provides evidence of an improvement of the motor response to l‐dopa in people with PD treated with camicinal 50 mg once‐daily compared with placebo, which will require further evaluation. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Transient receptor potential vanilloid type 1 (TRPV1) is a non-selective cation channel widely expressed in skin tissues, and peripheral sensory nerve fibres. Activation of TRPV1 releases neuropeptides; the resulting neurogenic inflammation is believed to contribute to the development of pruritus. A TRPV1 antagonist has the potential to perform as an anti-pruritic agent. SB705498 is a TRPV1 antagonist that has demonstrated in vitro activity against cloned TRPV1 human receptors and when orally administered has demonstrated pharmacodynamic activity in animal models and clinical studies. To select a topical dose of SB705498 using the TRPV1 agonist capsaicin; to confirm engagement of the TRPV1 antagonistic action of SB705498 and assess whether the dose selected has an effect on itch induced by two challenge agents. A clinical study was conducted in 16 healthy volunteers to assess the effects of 3 doses of SB705498 on skin flare induced by capsaicin. Subjects with a robust capsaicin response were chosen to determine if the selected topical formulation of SB705498 had an effect on challenge agent induced itch. Following capsaicin challenge the greatest average reduction in area of flare was seen for the 3% formulation. This dose was selected for further investigation. Itch intensity induced by two challenge agents (cowhage and histamine) was assessed on the Computerised Visual Analogue Scale. The difference in average itch intensity (Weighted Mean Over 15 Mins) between the 3% dose of SB705498 and placebo for the cowhage challenge was −0.64, whilst the histamine challenge showed on average a −4.65 point change. The 3% topical formulation of SB705498 cream was clinically well tolerated and had target specific pharmacodynamic activity. However there were no clinically significant differences on pruritus induced by either challenge agent in comparison to placebo. SB705498 is unlikely to be of symptomatic benefit for histaminergic or non-histaminergic induced itch. ClinicalTrials.gov NCT01673529

A Saskatchewan multi-incident family was clinically characterized with Parkinson disease (PD) and Lewy body pathology. PD segregates as an autosomal-dominant trait, which could not be ascribed to any known mutation. DNA from three affected members was subjected to exome sequencing. Genome alignment, variant annotation and comparative analyses were used to identify shared coding mutations. Sanger sequencing was performed within the extended family and ethnically matched controls. Subsequent genotyping was performed in a multi-ethnic case–control series consisting of 2928 patients and 2676 control subjects from Canada, Norway, Taiwan, Tunisia, and the USA. A novel mutation in receptor-mediated endocytosis 8/RME-8 (DNAJC13 p.Asn855Ser) was found to segregate with disease. Screening of cases and controls identified four additional patients with the mutation, of which two had familial parkinsonism. All carriers shared an ancestral DNAJC13 p.Asn855Ser haplotype and claimed Dutch–German–Russian Mennonite heritage. DNAJC13 regulates the dynamics of clathrin coats on early endosomes. Cellular analysis shows that the mutation confers a toxic gain-of-function and impairs endosomal transport. DNAJC13 immunoreactivity was also noted within Lewy body inclusions. In late-onset disease which is most reminiscent of idiopathic PD subtle deficits in endosomal receptor-sorting/recycling are highlighted by the discovery of pathogenic mutations VPS35, LRRK2 and now DNAJC13. With this latest discovery, and from a neuronal perspective, a temporal and functional ecology is emerging that connects synaptic exo- and endocytosis, vesicular trafficking, endosomal recycling and the endo-lysosomal degradative pathway. Molecular deficits in these processes are genetically linked to the phenotypic spectrum of parkinsonism associated with Lewy body pathology.

Background: Variants within the leucine‐rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson's disease. Leucine‐rich repeat kinase 2 variation related to disease susceptibility displays many features that reflect the nature of complex, late‐onset sporadic disorders like Parkinson's disease.Methods: The Genetic Epidemiology of Parkinson's Disease Consortium recently performed the largest genetic association study for variants in the leucine‐rich repeat kinase 2 gene across 23 different sites in 15 countries.Results: Herein, we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K‐R1398H‐K1423K) nominated in the original publication. Simple population allele frequencies not only can provide insight into the clinical relevance of specific variants but also can help genetically define patient groups.Conclusions: Establishing individual patient‐based genomic susceptibility profiles that incorporate both risk factors and protective factors will determine future diagnostic and treatment strategies. © 2013 International Parkinson and Movement Disorder Society