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Abstract
Recent antimalarial drug discovery has been a race to produce new medicines that overcome
emerging drug resistance, whilst considering safety and improving dosing convenience.
Discovery efforts have yielded a variety of new molecules, many with novel modes of
action, and the most advanced are in late-stage clinical development. These discoveries
have led to a deeper understanding of how antimalarial drugs act, the identification
of a new generation of drug targets, and multiple structure-based chemistry initiatives.
The limited pool of funding means it is vital to prioritize new drug candidates. They
should exhibit high potency, a low propensity for resistance, a pharmacokinetic profile
that favours infrequent dosing, low cost, preclinical results that demonstrate safety
and tolerability in women and infants, and preferably the ability to block
Plasmodium transmission to
Anopheles mosquito vectors. In this Review, we describe the approaches that have been successful,
progress in preclinical and clinical development, and existing challenges. We illustrate
how antimalarial drug discovery can serve as a model for drug discovery in diseases
of poverty.
Plasmodium falciparum resistance to artemisinin derivatives in southeast Asia threatens malaria control and elimination activities worldwide. To monitor the spread of artemisinin resistance, a molecular marker is urgently needed. Here, using whole-genome sequencing of an artemisinin-resistant parasite line from Africa and clinical parasite isolates from Cambodia, we associate mutations in the PF3D7_1343700 kelch propeller domain ('K13-propeller') with artemisinin resistance in vitro and in vivo. Mutant K13-propeller alleles cluster in Cambodian provinces where resistance is prevalent, and the increasing frequency of a dominant mutant K13-propeller allele correlates with the recent spread of resistance in western Cambodia. Strong correlations between the presence of a mutant allele, in vitro parasite survival rates and in vivo parasite clearance rates indicate that K13-propeller mutations are important determinants of artemisinin resistance. K13-propeller polymorphism constitutes a useful molecular marker for large-scale surveillance efforts to contain artemisinin resistance in the Greater Mekong Subregion and prevent its global spread.
Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand-Cambodia border. Slowly clearing infections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the "propeller" region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.).
How much do drug companies spend on research and development to bring a new medicine to market? In this study, which included 63 of 355 new therapeutic drugs and biologic agents approved by the US Food and Drug Administration between 2009 and 2018, the estimated median capitalized research and development cost per product was $985 million, counting expenditures on failed trials. Data were mainly accessible for smaller firms, products in certain therapeutic areas, orphan drugs, first-in-class drugs, therapeutic agents that received accelerated approval, and products approved between 2014 and 2018. This study provides an estimate of research and development costs for new therapeutic agents based on publicly available data; differences from previous studies may reflect the spectrum of products analyzed and the restricted availability of data in the public domain. The mean cost of developing a new drug has been the subject of debate, with recent estimates ranging from $314 million to $2.8 billion. To estimate the research and development investment required to bring a new therapeutic agent to market, using publicly available data. Data were analyzed on new therapeutic agents approved by the US Food and Drug Administration (FDA) between 2009 and 2018 to estimate the research and development expenditure required to bring a new medicine to market. Data were accessed from the US Securities and Exchange Commission, Drugs@FDA database, and ClinicalTrials.gov, alongside published data on clinical trial success rates. Conduct of preclinical and clinical studies of new therapeutic agents. Median and mean research and development spending on new therapeutic agents approved by the FDA, capitalized at a real cost of capital rate (the required rate of return for an investor) of 10.5% per year, with bootstrapped CIs. All amounts were reported in 2018 US dollars. The FDA approved 355 new drugs and biologics over the study period. Research and development expenditures were available for 63 (18%) products, developed by 47 different companies. After accounting for the costs of failed trials, the median capitalized research and development investment to bring a new drug to market was estimated at $985.3 million (95% CI, $683.6 million-$1228.9 million), and the mean investment was estimated at $1335.9 million (95% CI, $1042.5 million-$1637.5 million) in the base case analysis. Median estimates by therapeutic area (for areas with ≥5 drugs) ranged from $765.9 million (95% CI, $323.0 million-$1473.5 million) for nervous system agents to $2771.6 million (95% CI, $2051.8 million-$5366.2 million) for antineoplastic and immunomodulating agents. Data were mainly accessible for smaller firms, orphan drugs, products in certain therapeutic areas, first-in-class drugs, therapeutic agents that received accelerated approval, and products approved between 2014 and 2018. Results varied in sensitivity analyses using different estimates of clinical trial success rates, preclinical expenditures, and cost of capital. This study provides an estimate of research and development costs for new therapeutic agents based on publicly available data. Differences from previous studies may reflect the spectrum of products analyzed, the restricted availability of data in the public domain, and differences in underlying assumptions in the cost calculations. This study uses publicly available data to analyze research and development spending to win FDA approval and bring new drugs to market between 2009 and 2018.
Publication date Nihms-submitted: 21
September
2023
Publication date
(Print):
October
2023
Publication date
(Electronic):
31
August
2023
Publication date PMC-release: 02
October
2023
Volume: 22
Issue: 10
Pages: 807-826
Affiliations
[1
]University of California, San Diego, La Jolla, CA, USA.
[2
]Holistic Drug Discovery and Development (H3D) Centre, University of Cape Town, Rondebosch,
South Africa.
[3
]South African Medical Research Council Drug Discovery and Development Research Unit,
Department of Chemistry and Institute of Infectious Disease and Molecular Medicine,
University of Cape Town, Rondebosch, South Africa.
[4
]Medicines for Malaria Venture, Geneva, Switzerland.
[5
]Department of Microbiology and Immunology and Center for Malaria Therapeutics and
Antimicrobial Resistance, Division of Infectious Diseases, Department of Medicine,
Columbia University Irving Medical Center, New York, NY, USA.
Author notes
Author contributions
The authors contributed equally to all aspects of the article.
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