Remdesivir: A Review of Its Discovery and Development Leading to Emergency Use Authorization for Treatment of COVID-19
Authors: Anton Simeonov
Matthew D Hall
Jacob S Roth
Richard T Eastman
Samarjit Patnaik
Min Shen
Kyle R Brimacombe
Journal: ACS Central Science (2020)
Discipline: CHEMISTRY
Keywords: SARS-CoV-2; COVID-19; antiviral interventions; remdesivir; nucleotide analogue prodrug
Affiliations: National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States, Albert Einstein College of Medicine, New York, New York 10461, United States

Abstract:  The global pandemic of SARS-CoV-2, the causative viral pathogen of COVID-19, has driven the biomedical community to action-to uncover and develop antiviral interventions. One potential therapeutic approach currently being evaluated in numerous clinical trials is the agent remdesivir, which has endured a long and winding developmental path. Remdesivir is a nucleotide analogue prodrug that perturbs viral replication, originally evaluated in clinical trials to thwart the Ebola outbreak in 2014. Subsequent evaluation by numerous virology laboratories demonstrated the ability of remdesivir to inhibit coronavirus replication, including SARS-CoV-2. Here, we provide an overview of remdesivir's discovery, mechanism of action, and the current studies exploring its clinical effectiveness. 

Retracted: No

PubPeer comments:
 https: medium.com @victoriacyanide fact-checking-the-acs-central-science-review-on-remdesivir-44a9e1240731 A recently published article by Eastman et al. in ACS Central Science has emerged as the go-to authority on matters related to remdesivir bioactivation. But it has a number of concerning errors. SECTION 1: DEVELOPMENT OF REMDESIVIR Paragraph 2: Nucleosides are poorly cell-permeable (and therefore can have a low hit rate in cell-based screens such as antiviral screens), so modified nucleosides such as monophosphate, ester, and phosphoramidate prodrugs com- posed a significant portion of the library. Such prodrugs are typically more permeable and metabolized to liberate the nucleoside or phosphorylated nucleoside within cells (40u201342). Issue: Confuses nucleosides with nucleotides. Nucleosides consist of a nucleobase and a ribose sugar. Nucleotides consist of a nucleobase, a ribose sugar, and phosphate(s). Phosphates are negatively charged at physiological pH. Nucleotides are thus poorly cell-permeable. In contrast, nucleosides are uncharged at physiological pH, making them cell permeable either via passive diffusion or nucleoside transporters (Figure 1). The authors seem to confuse nucleosides with nucleotides. Their first sentence suggests that u201cnucleoside analoguesu201d would be able to u201ctarget RNA virusesu201d when in fact, this is accomplished by nucleotide analogues. The authors then state that u201cNucleosides are poorly cell permeable.u201d However, there are a number of nucleoside transporters in the cell membrane that facilitate uptake of natural and non-natural nucleosides, as extensively studied in many chemotherapies (see Fludarabine). Nucleotide analogues (mono-, di-, or triphosphate) are poorly permeable due to their anionic phosphate(s). The authors then suggest that u201cnucleosides such as monophosphateu201d would somehow be more permeable than the u201cnucleosidesu201d that are u201cpoorly cell permeable,u201d which is incorrect. One of the papers they cite (ref 41) in the next sentence is explicitly titled, u201cAryloxy phosphor- amidate triesters: a technology for delivering monophosphorylated nucleosides and sugars into cells.u201d Monophosphorylated nucleosides = nucleotide monophosphate. The u201cAryloxy phosphor- amidate triestersu201d technology the cited paper refers to is actually the phosphate prodrug on remdesivir. Why do we need it? Because phosphates are negatively charged and cannot easily permeate the cell membrane without prodrug protection. Paragraph 3: The study by Madelain et al. found that GS-5734 [remdesivir] reduced EBOV replication in HeLa cells with an IC50 u2248 100 nM, and it retained potency in in vivo nonhuman primate EBOV infection models, while GS-441524 was inactive (46,47). In addition to demonstrating activity against EBOV, Warren et al. showed that remdesivir also had antiviral activity against several other viruses, including the coronavirus MERS, with an IC50 of 340 nM in vitro. Issue: GS-441524 DOES actually have activity in EBOV-infected human cells. According to in vitro studies by Warren et al. (Nature, 2016) in EBOV-infected human cells, both remdesivir and GS-441524 can exert antiviral activity (Figure 2). Indeed, these data show that remdesivir is more potent than GS-441524. However, the data clearly show that GS-441524 has activity in HMVEC-TERT cells and Huh-7 cells infected with EBOV. Paragraph 5: In nonhuman primates, daily administration of 10 mg kg of remdesivir yielded a short plasma half-life of the prodrug (t1 2= 0.39 h), but sustained intracellular levels of the triphosphate form (45). Issue: Omits the key detail that the remdesivir metabolite, GS-441524 persists in serum. As the authors note, multiple studies have documented the low stability of the intact remdesivir prodrug. However, this naturally raises the question: what metabolite persists in the plasma? This critical detail has been extensively documented in citations notably absent (Warren et al. Nature 2016, Sheahan et al. Sci. Transl. Med. 2017, Williamson et al. bioRxiv 2020; Figure 3) u2014 all of which repeat the same finding ad nauseum: short plasma half-life of remdesivir results in transient conversion to the L-Alanine intermediate metabolite, followed by persistence of the nucleoside, GS-441524. SECTION 2: REMDESIVIR MODE OF ACTION Paragraph 2: While the nucleoside analogue core of remdesivir, GS-441524, can diffuse into cells, the initial phosphorylation step for nucleosides is rate-limiting (slow), which is believed to account for the reduced antiviral activity of GS-441524 compared to remdesivir (49, 71). Issue 1: Mechanism of action figure does not match this discussion. The authors correctly note that the nucleoside, GS-441524, can diffuse into cells (Figure 4). However, their depiction u2014 which shows poor permeability of GS-441524 u2014 is incorrect. Their depiction also omits the premature serum hydrolysis of remdesivir, which has been extensively documented, as noted above (Warren et al. Nature 2016, Sheahan et al. Sci. Transl. Med. 2017, Williamson et al. bioRxiv 2020; Figure 3b). Issue 2 (personal editorial): Omission of the direct comparison between remdesivir and GS-441524 in Agostini et al. mBio (2018), which shows no statistically significant different EC50 between remdesivir and GS-441524. The point that I will make here is minor in the context of the authorsu2019 task (which is to write a general review), but nevertheless significant with regards to critically reviewing the literature. A key experiment conducted by Agostini et al. mBio (2018) compared the in vitro potencies between remdesivir (GS-5734) and GS-441524 in primary human airway epithelial cells (HAE). While the mean EC50 of remdesivir was lower than that of GS-441524, the standard deviations are so large, making these differences not statistically significant (Figure 5). Thus, while remdesivir has outperformed GS-441524 in certain cell-based models, this particular experiment is perhaps the most relevant in vitro experiment in the context of SARS-CoV-2. ,