Why Certain Repurposed Drugs Are Unlikely to Be Effective Antivirals to Treat SARS-CoV-2 Infections

Round 1

Reviewer 1 Report

Evaluation of repurposed drugs for treating COVID-19 using Ratios of reported unbound peak plasma concentrations (Cmax)/EC50 appears to be a good idea. It can save the resources by ruling out those unpromising candidates. I only have few comments for this manuscript below. 

1. Since there are many variants of SARS-CoV-2, it should be mention what type of the virus in this research. Limitations of the current platform should be discussed.

2. Three cell models represents different targeted tissues for SARS-CoV-2 virus. Can author discuss which tissue target is more vulnerable for infection? Whether the results from three cell models should have weighted score?  Please add your comments in discussion.

(Line 19) The 20 drugs with the highest ratios were retested in human human Calu-

(Line258) In table 2. Drug name is not fit well in the table. Font size should be adjusted.

Author Response

Thank you for your reviewing, please find our responses in the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This work presents an approach to evaluate drugs suggested to be repurposed for the treatment of COVID-19 by using ratios of reported unbound peak plasma concentrations over median effective concentrations (C_max/EC₅₀). In addition, by testing drugs in a panel of SARS-CoV-2 permissive cells, they suggested that EC₅₀ of nucleoside analogs are cell-type dependent, which correlated with variations in intracellular metabolism of the test drugs in various cell types. The authors concluded that this approach may be useful to prioritize repurposed drugs for evaluation in prospective clinical trials.

Some minor points need attention:

There appears to have a missing statement in Line 225.

Line 642: the reference number 71 is missing.

Starting from Line 933: the reference numbers from 89 to the last one are repeated.

Author Response

Thank you for your reviewing, please find our responses in the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript entitled „Why Certain Repurposed Drugs are Unlikely to Be Effective Antivirals to Treat SARS-CoV-2 Infections” by Hurwitz et al. describes the results of testing repurposed drugs from clinical trials for their potency to inhibit virus replication in Vero, Calu-3 and Caco-2 cells. Moreover, the authors analysed the in vitro cytotoxicity of these compounds and compared the results with PK data from the literature.

The manuscript is well written and the relevant literature is cited.

There are several remarks concerning the presentation of the data and the text:

1) Material and Methods: Line 183: how much supernatant was added to RLT buffer?

2) The text of paragraph 1 of the Results section is confusing. It looks, as if lines 218-225 or at least 222 – 225 should be a footnote below Table 1.

The same applies to text of lines 237 – 242, and lines 247 – 249, 255-256 which should be a footnote below Table 2.

3) Table 2 is overloaded. The toxicity data could be shown separately or as supplementary information. The same Vero data are shown in Table 1 and 2.

4) Discussion: the underlying mechanism of the differential response of infected Vero and Calu-3/Caco-2 to chloroquine should be described.

5) Line 384: should read “In the same clinical trials,…”

6) Paragraph 1 of 4.4 (lines 466-489) is repeated as a whole in section 4.6 (lines 522-545)

7) Doubled numbers of references from ref. 89 onwards

General points:

Although the analysis of the compounds is very extensively evaluated and compared with the literature data, a take-home message is missing. What should be done to avoid unnecessary clinical testing in future, what are their recommendations.

Author Response

Thank you for your reviewing, please find our responses in the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors have made the corrections as suggested. However, the manuscript still contains several writing errors some of which appeared after correction. It is therefore highly recommended that the whole manuscript is revised again carefully by the authors.

Further remarks:

1) The authors response says: “In line 83 of revised manuscript I Changed to 100 μL in the revised manuscript” – however, it was asked how much supernatant was used and mixed with RLT buffer

2) Table 1: * should refer to VV116, ** should be used for molnupiravir, *** etc.

3) Table 2

Third line of Table 2 says only (NHC) but not the drug name

Footnote Table 2, line 266 “Therapeutic classes” needs to be removed

4) Table 3

Ciclesonide: GLC should be corrected to GC as in the footnote (GC)

Table 3 footnote refers to compounds which are shown in Table 1 and needs to be removed:

“* Oral molnupiravir, delivers -D-N4-281 hydroxycytidine (NHC) into the plasma, so t1/2 and cellular pharmacology is reported in terms of NHC. Fun of apilimod was 282 computed in silico, and that of lotilaner was approximated as 0.01, as it was described as highly bound. Within each therapeutic 283 category, compounds are listed in descending order of adjusted Cmax/EC50 in Vero CCL-81 cells. qd = once daily, bid = twice daily, 284 tid = three times daily. NE, not estimated. * Orally administered VV116, obeldesivir, and GS-441524, deliver GS-441524 into the 285 plasma, so their CC50 and EC50, EC90 and CC50 values were assumed equal to those of GS-441524 (depicted as ---)”

5) Iine 302 : sentence is not finished

6) Title 4.1. Relevance of cell lines and SARS-CoV-2 variant. Should be variants (plural) since there were more than one

7) Line 372: I assume “male” is correct

8) Graphical Abstract was removed in the revision but not further commented

Author Response

Thank you for your review. Please see the responses in the attachment.

Author Response File: Author Response.pdf