LETTER
A recent article by Xu et al. (1) examined the on- and off-target toxicity of remdesivir (RDV) and its parent nucleoside, GS-441524. Notably, primary human hepatocytes (PHHs) and HepG2 cells (liver cancer cell line) were exceptionally sensitive to RDV treatment. Still, the authors conclude, “In clinical settings of COVID-19 [coronavirus disease 2019] treatment in hospitalized patients, the risk associated with possible RDV-related liver enzyme elevations is substantially lower compared to its established benefits in hospitalized COVID-19 patients.” Whereas we commend the authors’ rigorous study, we deplore the omission of citations of key clinical studies demonstrating no clear benefit with RDV (2, 3). The clinical efficacy of RDV is contentious; major clinical trials conducted with RDV yield mixed results (Table 1). The claim of “established benefits in hospitalized COVID-19 patients” rests on favorable results of a single double-blind, randomized controlled trial (RCT) (4) and at the omission of unfavorable interim results from the WHO Solidarity trial (3) and a double-blinded RCT by Wang et al. (2). By undermining these trial results (5, 6), Gilead implicitly acknowledges that the clinical benefits of RDV are modest, requiring the most stringent trial design to extract a favorable, statistically significant result (4). Ironically, Gilead dismisses the interim results from Solidarity on the basis of potential heterogeneity in controls and its open-label nature (6) yet touts their self-sponsored, open-label trials (7, 8) lacking a control group (7). Beyond its questionable clinical efficacy, it is unclear whether the current RDV regimen effectively reduces viral loads in patients’ lungs (2, 9). Wang et al. (2) found no difference in viral reduction in the upper respiratory tracts of RDV-treated versus placebo groups. Given RDV’s limited clinical and antiviral efficacy, we ask, why not dose higher?
Clinical efficacy of RDV, by major clinical trial
In a phase 1 trial with RDV in healthy volunteers, graded transaminase elevations were observed in 25% of participants in the 7-day multiple-ascending-dose (MAD) cohort (150 mg daily, 1,050 mg cumulative dose) and in 75% of participants in the 14-day MAD cohort (150 mg daily, 2,100 mg cumulative dose) (10), which concurs with the unique sensitivity of PHHs to RDV in vitro (1, 11). Comparing the magnitude of hepatotoxicity in healthy participants ties transaminase elevations to total dose exposure (Table 2); hepatotoxicity was not observed in the 225-mg single-dose cohort (10). For reference, the recommended dosage (200-mg loading dose, 100-mg maintenance) results in total doses of 600 mg (5 days) and 1,100 mg (10 days), which fall below the threshold for hepatotoxicity (1,050 to 2,100 mg). If viral suppression is a Cmax (maximum concentration)-driven effect and the degree of hepatotoxicity relates to cumulative exposure, then it may be possible to compress the dosing schedule to enable higher dosing while maintaining the same cumulative dose. For instance, a 300-mg loading dose with 200-mg maintenance for 5 days yields a cumulative dose of 1,100 mg. Although we foresaw these shortcomings with RDV some time ago and have advocated for clinical investigation of GS-441524 in regard to safety (12–16), investigating dose modifications with RDV may benefit patients more readily (17), and we urge Gilead to do so.
Dose-dependent hepatotoxicity of RDV in healthy volunteers
ACKNOWLEDGMENT
We thank Steve Kirsch and the COVID-19 Early Treatment Fund (CETF) for financial support.
FOOTNOTES
- Accepted manuscript posted online 8 February 2021.
Supplemental material is available online only.
For the author reply, see https://doi.org/10.1128/AAC.00085-21.
- Copyright © 2021 American Society for Microbiology.
