As of April 2020[update], remdesivir was viewed as the most promising treatment for COVID-19 by Johns Hopkins University. Data from one randomized controlled trial was released early in error and before peer review; it did not show improvement. Gilead Sciences stated that due to low enrollment the study was halted while a non-associated researcher states it does mean if there is any benefit, then that benefit will be small. Further clinical trials are underway or planned.
On 18 March 2020, the World Health Organization (WHO) announced the launch of a trial that would include one group treated with remdesivir. While a cohort study published in April 2020 saw possible improvement, determining whether or not the medication is effective will require a randomized controlled trial.
In January 2020, Gilead began laboratory testing of remdesivir against SARS-CoV-2, stating that remdesivir had been shown to be active against SARS and MERS in animal models. In March 2020, a small trial of remdesivir in rhesus macaque monkeys with COVID-19 infections found that it prevents disease progression. On 21 January 2020, the Wuhan Institute of Virology applied for a Chinese "use patent", for treating COVID-19.
Remdesivir was rapidly pushed through clinical trials due to the West African Ebola virus epidemic of 2013–2016, eventually being used in people with the disease. Preliminary results were promising; it was used in the emergency setting during the Kivu Ebola epidemic that started in 2018, along with further clinical trials, until August 2019, when Congolese health officials announced that it was significantly less effective than monoclonal antibody treatments such as mAb114 and REGN-EB3. The trials, however, established its safety profile.
On 17 March 2020, the drug was provisionally approved for use for COVID-19 patients in a serious condition as a result of the outbreak in the Czech Republic. On 20 March 2020, United States President Donald Trump announced that remdesivir was available for "compassionate use" by people with COVID-19; FDA Commissioner Stephen Hahn confirmed the statement at the same press conference. On 23 March 2020, Gilead voluntarily suspended access for compassionate use (excepting cases of critically ill children and pregnant women), for reasons related to supply, citing the need to continue to provide the agent for testing in clinical trials.
As of 11 April 2020, access in Canada was only to those who will be involved in a clinical trial.
Mechanism of action and resistance
Remdesivir is a prodrug that metabolizes into its active form GS-441524. An adenosine nucleotide analog, GS-441524 interferes with the action of viral RNA-dependent RNA polymerase and evades proofreading by viral exoribonuclease (ExoN), causing a decrease in viral RNA production. Though in some viruses, such as the respiratory syncytial virus but not Ebola virus, it causes the RNA-dependent RNA polymerases to pause, its predominant effect is to induce an irreversible chain termination. Unlike with many other chain terminators, this was not mediated by preventing addition of the immediately subsequent nucleotide, but is instead delayed, occurring after five additional bases have been added to growing RNA chain.
Mutations in the mouse hepatitis virusRNA replicase that cause partial resistance to remdesivir were identified in 2018. These mutations make the viruses less effective in nature, and the researchers believe they will likely not persist where the drug is not being used.
Remdesivir can be synthesized in multiple steps from ribose derivatives. The figure to the right is one of the synthesis routes of remdesivir invented by Chun and coauthors from Gilead Sciences. In this method, intermediate a is firstly prepared from L-alanine and phenyl phosphorodichloridate in presence of triethylamine and dichloromethane; triple benzyl-protected ribose is oxidized by dimethyl sulfoxide with acetic anhydride and give the lactone intermediate b; pyrrolo[2,1-f] [1,2,4]triazin-4-amine is brominated, and the amine group is protected by excess trimethylsilyl chloride. n-Butyllithium undergoes a halogen-lithium exchange reaction with the bromide at −78 °C (−108 °F) to yield the intermediate c. The intermediate b is then added to a solution containing intermediate c dropwise. After quenching the reaction in a weakly acidic aqueous solution, a mixture of 1: 1 anomers was obtained. It was then reacted with an excess of trimethylsilyl cyanide in dichloromethane at −78 °C (−108 °F) for 10 minutes. Trimethylsilyl triflate was added and reacts for one additional hour, and the mixture was quenched in an aqueous sodium hydrogen carbonate. A nitrile intermediate was obtained. The protective group, benzyl, was then removed with boron trichloride in dichloromethane at −20 °C (−4 °F). The excess of boron trichloride was quenched in a mixture of potassium carbonate and methanol. A benzyl-free intermediate was obtained. The isomers were then separated via reversed-phase HPLC. The optically pure compound and intermediate a are reacted with trimethyl phosphate and methylimidazole to obtain a diastereomer mixture of remdesivir. In the end, optically pure remdesivir can be obtained through chiral resolution methods.
^Lo MK, Jordan R, Arvey A, Sudhamsu J, Shrivastava-Ranjan P, Hotard AL, et al. (March 2017). "GS-5734 and its parent nucleoside analog inhibit Filo-, Pneumo-, and Paramyxoviruses". Scientific Reports. 7: 43395. doi:10.1038/srep43395. PMID28262699.
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^Munster V, Feldmann F, Williamson B, Van Doremalen N, Perez-Perez L, Schultz J, et al. (March 2020). "Respiratory disease and virus shedding in rhesus macaques inoculated with SARS-CoV-2". bioRxiv10.1101/2020.03.21.001628.
^Williamson B, Feldmann F, Schwarz B, Meade-White K, Porter D, Schulz J, et al. (April 2020). "Clinical benefit of remdesivir in rhesus macaques infected with SARS-CoV-2". bioRxiv10.1101/2020.04.15.043166.
^Warren T, Jordan R, Lo M, Soloveva V, Ray A, Bannister R, et al. (Fall 2015). "Nucleotide Prodrug GS-5734 Is a Broad-Spectrum Filovirus Inhibitor That Provides Complete Therapeutic Protection Against the Development of Ebola Virus Disease (EVD) in Infected Non-human Primates". Open Forum Infectious Diseases. 2 (suppl 1): LB–2. doi:10.1093/ofid/ofv130.02.
^Public Health Agency of Canada (11 April 2020). "Coronavirus disease (COVID-19): For health professionals". aem. Retrieved 12 April 2020. Gilead is transitioning the provision of emergency access to remdesivir from individual compassionate use via Health Canada's Special Access Program requests to access through clinical trials.
^US 9724360, Chun BK, Clarke MO, Doerffler E, Hui HC, Jordan R, Mackman RL, Parrish JP, Ray AS, Siegel D, "Methods for treating Filoviridae virus infections", issued 19 July 2017, assigned to Gilead Sciences Inc.
^World Health Organization (2017). "International nonproprietary names for pharmaceutical substances (INN): recommended INN: list 78". WHO Drug Information. 31 (3): 549. hdl:10665/330961.
^"Pipeline". Gilead. 27 February 2020. Retrieved 17 April 2020.