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High-throughput chemical and gene analyses help identify promising pairs of antimalarial compounds that could prevent resistance. In the world of developing anti-infective drugs, resistance comes with the territory. It is literally in the DNA (or RNA) of the viruses and pathogens targeted for treatment. Because resistance has far-reaching consequences for human health, researchers have studied the resistance of infectious agents such as human immunodeficiency virus (HIV) type 1 with unprecedented intensity and documented in excruciating detail the genetic determinants of resistance to FDA-approved drugs ( 1 ). However, understanding drug resistance in a complex eukaryotic parasite, such as the Plasmodium parasite that causes malaria, is a very different challenge. On page 724 of this issue, Yuan et al. ( 2 ) confront the issue head-on. Using high-throughput chemical and gene analysis methods, they not only identify potential new antimalarial drugs that could be used in combination to suppress the development of drug resistance but also characterize a common set of genetic loci and genes affected by these molecules.

HIV protease inhibitor (PI) therapy results in the rapid selection of drug resistant viral variants harbouring one or two substitutions in the viral protease. To combat PI resistance development, two approaches have been developed. The first is to increase the level of PI in the plasma of the patient, and the second is to develop novel PI with high potency against the known PI-resistant HIV protease variants. Both approaches share the requirement for a considerable increase in the number of protease mutations to lead to clinical resistance, thereby increasing the genetic barrier. We investigated whether HIV could yet again find a way to become less susceptible to these novel inhibitors. We have performed in vitro selection experiments using a novel PI with an increased genetic barrier (RO033-4649) and demonstrated selection of three viruses 4- to 8-fold resistant to all PI compared to wild type. These PI-resistant viruses did not have a single substitution in the viral protease. Full genomic sequencing revealed the presence of NC/p1 cleavage site substitutions in the viral Gag polyprotein (K436E and/or I437T/V) in all three resistant viruses. These changes, when introduced in a reference strain, conferred PI resistance. The mechanism leading to PI resistance is enhancement of the processing efficiency of the altered substrate by wild-type protease. Analysis of genotypic and phenotypic resistance profiles of 28,000 clinical isolates demonstrated the presence of these NC/p1 cleavage site mutations in some clinical samples (codon 431 substitutions in 13%, codon 436 substitutions in 8%, and codon 437 substitutions in 10%). Moreover, these cleavage site substitutions were highly significantly associated with reduced susceptibility to PI in clinical isolates lacking primary protease mutations. Furthermore, we used data from a clinical trial (NARVAL, ANRS 088) to demonstrate that these NC/p1 cleavage site changes are associated with virological failure during PI therapy. HIV can use an alternative mechanism to become resistant to PI by changing the substrate instead of the protease. Further studies are required to determine to what extent cleavage site mutations may explain virological failure during PI therapy.

It is critical to ensure that COVID-19 studies provide clear and timely answers to the scientific questions that will guide us to scalable solutions for all global regions. Significant challenges in operationalizing trials include public policies for managing the pandemic, public health and clinical capacity, travel and migration, and availability of tests and infrastructure. These factors lead to spikes and troughs in patient count by location, disrupting the ability to predict when or if a trial will reach recruitment goals. The focus must also be on understanding how to provide equitable access to these interventions ensuring that interventions reach those who need them the most, be it patients in low resource settings or vulnerable groups.  We introduce a website to be used by The Bill & Melinda Gates Foundation, Wellcome Trust, and other funders of the COVID Therapeutics Accelerator that accept proposals for future clinical research. The portal enables evaluations of clinical study applications that focus on study qualities most likely to lead to informative outcomes and completed studies.

Introduction. RG7128 (prodrug of PSI-6130) shows potent antiviral efficacy in patients infected with hepatitis C virus (HCV) genotypes 1, 2, or 3, with mean viral load decreases of 2.7 and 5 log10 IU/mL, respectively, associated with 1500-mg doses twice daily after monotherapy for 2 weeks and with 1000-mg and 1500-mg doses twice daily after treatment in combination with the standard of care (SOC) for 4 weeks. Results. From 32 patients treated with RG7128 monotherapy for 2 weeks, marginal viral load rebound was observed in 3 HCV genotype 1-infected patients, whereas partial response was observed in 2 genotype 1-infected patients. From 85 patients receiving RG7128 in combination with SOC, 1 HCV genotype 1-infected patient experienced a viral rebound, and 2 genotype 3-infected patients experienced a transient rebound. Five genotype 1-infected patients had an HCV load of >1000 IU/mL at the end of 4-week treatment. No viral resistance was observed, per NS5B sequencing and phenotypic studies. PSI-6130 resistance substitution S282T needs to be present at levels of ⩾90% within a patient's quasispecies to confer low-level resistance. No evidence of S282T was found by population or clonal sequence analyses. Conclusions. The requirement for a predominant S282T mutant quasispecies, its low replication capacity, and the low-level resistance it confers probably contribute to the lack of RG7128 resistance observed in HCV-infected patients.

It is critical to ensure that COVID-19 studies provide clear and timely answers to the scientific questions that will guide us to scalable solutions for all global regions. Significant challenges in operationalizing trials include public policies for managing the pandemic, public health and clinical capacity, travel and migration, and availability of tests and infrastructure. These factors lead to spikes and troughs in patient count by location, disrupting the ability to predict when or if a trial will reach recruitment goals. The focus must also be on understanding how to provide equitable access to these interventions ensuring that interventions reach those who need them the most, be it patients in low resource settings or vulnerable groups. We introduce a website to be used by The Bill & Melinda Gates Foundation, Wellcome Trust, and other funders of the COVID Therapeutics Accelerator that accept proposals for future clinical research. The portal enables evaluations of clinical study applications that focus on study qualities most likely to lead to informative outcomes and completed studies.

Snakebite clinical trials have often used heterogeneous outcome measures and there is an urgent need for standardisation. A globally representative group of key stakeholders came together to reach consensus on a globally relevant set of core outcome measurements. Outcome domains and outcome measurement instruments were identified through searching the literature and a systematic review of snakebite clinical trials. Outcome domains were shortlisted by use of a questionnaire and consensus was reached among stakeholders and the patient group through facilitated discussions and voting. Five universal core outcome measures should be included in all future snakebite clinical trials: mortality, WHO disability assessment scale, patient-specific functional scale, acute allergic reaction by Brown criteria, and serum sickness by formal criteria. Additional syndrome-specific core outcome measures should be used depending on the biting species. This core outcome measurement set provides global standardisation, supports the priorities of patients and clinicians, enables meta-analysis, and is appropriate for use in low-income and middle-income settings.

The end of the twentieth century saw dramatic improvements in the prognosis of HIV infection brought about by the introduction of new agents (the protease inhibitors and the non‐nucleoside reverse transcriptase inhibitors) and their use in highly active combinations. However, the durability of these combination treatments is limited by a number of factors including adverse effects and extensive intra‐class cross‐resistance so that new antiretrovirals acting on alternative targets and having improved systemic tolerability profiles are required. The HIV binding and entry process offers several potential targets for antiviral interaction. These include gp120 binding to CD4 and to chemokine co‐receptor molecules as well as the fusion process itself, which involves interactions between two leucine zipper‐like 4‐3 repeat regions within gp41 known as heptad repeat (HR)1 and HR2. Peptides such as enfuvirtide (formerly DP178 or T‐20), that mimic the HR2 region of gp41, inhibit HIV‐1 by a mechanism that is thought to involve competitive binding to HR1. This review summarises the clinical development of enfuvirtide, providing an overview of the pharmacokinetic, efficacy and safety data in various patient populations, and also considers the evidence for the key role of genotypic changes in the HR1 region (amino acids 36–45) in determining viral susceptibility to inhibition by enfuvirtide. Copyright © 2004 John Wiley & Sons, Ltd.

Introduction. RG7128 (prodrug of PSI-6130) shows potent antiviral efficacy in patients infected with hepatitis C virus (HCV) genotypes 1, 2, or 3, with mean viral load decreases of 2.7 and 5 log sub(10) IU/mL, respectively, associated with 1500-mg doses twice daily after monotherapy for 2 weeks and with 1000-mg and 1500-mg doses twice daily after treatment in combination with the standard of care (SOC) for 4 weeks. Results. From 32 patients treated with RG7128 monotherapy for 2 weeks, marginal viral load rebound was observed in 3 HCV genotype 1-infected patients, whereas partial response was observed in 2 genotype 1-infected patients. From 85 patients receiving RG7128 in combination with SOC, 1 HCV genotype 1-infected patient experienced a viral rebound, and 2 genotype 3-infected patients experienced a transient rebound. Five genotype 1-infected patients had an HCV load of >1000 IU/mL at the end of 4-week treatment. No viral resistance was observed, per NS5B sequencing and phenotypic studies. PSI-6130 resistance substitution S282T needs to be present at levels of 90% within a patient's quasispecies to confer low-level resistance. No evidence of S282T was found by population or clonal sequence analyses. Conclusions. The requirement for a predominant S282T mutant quasispecies, its low replication capacity, and the low-level resistance it confers probably contribute to the lack of RG7128 resistance observed in HCV-infected patients.