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. Plasmodium falciparum infection causes febrile illness and severe disease with multiple organ failure and death when treatment is delayed. Antipyretic treatment is standard, and inducing hypothermia has been proposed to protect the brain in cerebral malaria. Here, we investigated the temperature dependence of asexual-stage parasite development and parasite multiplication in vitro. Plasmodium falciparum laboratory strain TM267 was incubated for 2 hours (short exposure) or 48 hours (continuous exposure) at different temperatures (32°C, 34°C, 35°C, 38°C, 39°C, and 40°C). The starting parasite developmental stage (ring, trophozoite, or schizont) varied between experiments. The parasite multiplication rate (PMR) was reduced under both hyper- and hypothermic conditions; after continuous exposure, the mean PMR ± SD was 9.1 ± 1.2 at 37°C compared with 2.4 ± 1.8 at 32°C, 2.3 ± 0.4 at 34°C, and 0.4 ± 0.1 at 40°C ( P < 0.01). Changes in PMR were not significant after 2-hour exposure at temperatures ranging from 32°C to 40°C. Morphological changes in parasite cytoplasm and nucleus could be observed after long exposure to low or high temperature. After 48-hour incubation, rosette formation (≥ 2 uninfected red blood cells bound to infected red blood cells) was decreased at 34°C or 39°C compared with that at 37°C. In conclusion, both hyper- and hypothermia reduce PMR and delay erythrocytic stage development of P. falciparum , subsequently reducing rosette formation.

Background Uncertainty over the therapeutic benefit provided by parenteral remdesivir in COVID-19 has resulted in varying treatment guidelines. Methods In a multicenter open label, controlled, adaptive, pharmacometric platform trial, low-risk adult patients with early symptomatic COVID-19 were randomized to one of eight treatment arms including intravenous remdesivir (200 mg followed by 100 mg daily for five days) or no study drug. The primary outcome was the rate of viral clearance (estimated under a linear model fit to the daily log10 viral densities, days 0-7) in standardized duplicate oropharyngeal swab eluates, in a modified intention-to-treat population (mITT). This ongoing adaptive trial is registered at ClinicalTrials.gov (NCT05041907). Results The two study arms enrolled 131 patients (remdesivir n = 67, no study drug n = 64) and estimated viral clearance rates from a median of 18 swab samples per patient (a total of 2356 qPCRs). Under the linear model, compared with the contemporaneous control arm (no study drug), remdesivir accelerated mean estimated SARS-CoV-2 viral clearance by 42% (95% credible interval [CI] 18 to 73). Interpretation Parenteral remdesivir accelerates viral clearance in early symptomatic COVID-19. Pharmacometric assessment of therapeutics using the described method can rapidly and efficiently determine in vivo clinical efficacy.