PONE-D-21-16930A Dose-Finding Safety and Feasibility Study of Oral Activated Charcoal and its Effects on the Gut Microbiota in Healthy Volunteers not Receiving AntibioticsPLOS ONE

Dear Dr. Rashidi,

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PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: A dose-finding safety and feasibility clinical trial was conducted in which 12 healthy volunteers drank 4 different preparations (2 OAC doses and 2 solutions). Pre- and post-OAC stool samples were gene sequenced. The preferred preparation was 12 gram of OAC in apple juice which demonstrated safety and tolerability.

Minor revisions:

1- Indicate the date range subjects were enrolled in the study.

2- Page 6: In addition to stating the frequencies of AEs, provide the corresponding percentages.

3- Indicate if AEs were collected according to standard methods, i.e. CTCAE.

Reviewer #2: This study nicely shows that OAC can be made palatable and does not appear to adversely affect the microbiome when dosed intermittently at low levels.

I agree that the low dose OAC with apple juice was liked by the most patients, but medicine doesn’t always have to be taste nice and an equally important question to be answered later is what is the correct dose for preventing antibiotic microbiome effects? It could be 12g, it could be 25g it could be more. What they actually showed is that lower dose OAC is more palatable and mixed with apple juice is more palatable. They This should be described in the results and acknowledged in the discussion. They also subsequently say the most likely scenario for this treatments use would be in surgical patients on IV antibiotics, where presumably the OAC therapy would only be needed 1-3 times at most. Maybe not so big a deal how nice it tastes.

The microbiome data is nice and very clearly shows that within an individual the OAC made no great difference. But this was in 12 people minus the dropout. Not really enough to say conclusively that OAC does not exert its anti-bloating effects by altering the microbiome.

Reviewer #3: PONE_21_16930 A Dose-Finding Safety and Feasibility Study of Oral Activated Charcoal and its Effects on the Gut Microbiota in Healthy Volunteers not Receiving Antibiotics

This is an interesting manuscript describing the dose and feasibility of OAC on the gut microbiota. It is not really an RCT given that only one arm is present and only before and after samples are used and compared within individuals. It is however, important information before the start of RCTs with antibiotics and OAC. I only have a few comments.

1. Consort diagram: would it be possible to add to the consort diagram the breakdown of people receiving the different amounts and the loss to follow-up for each of these?

2. It would be good to have a table with some of the characteristics for the participants e.g. gender, age, BMI. This could also be added as text.

3. The methods seem to suggest that the gut microbiota samples after were obtained prior to dose 4, the results suggest that the results were obtained after the two weeks (6 doses). Please check and make consistent.

4. Was the increased palatability of the OAC in apple juice due to masking of the taste? Would it therefore be possible to dissolve the OAC in other types of juices or other flavoured drinks as well?

5. How many doses do the authors think people should take when they receive IV prophylactic antibiotics in conjunction with procedures in order to protect the gut microbiota?

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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A Dose-Finding Safety and Feasibility Study of Oral Activated Charcoal and its Effects on the Gut Microbiota in Healthy Volunteers not Receiving Antibiotics

PONE-D-21-16930R1

Dear Dr. Rashidi,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

James Mockridge

Staff Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #3: (No Response)

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #3: (No Response)

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #3: (No Response)

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #3: (No Response)

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: The authors have listened to the reviewer comments and have answered them all to my satisfaction noting the limitations of the study.

Reviewer #3: (No Response)

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No