Mapping the Extended Pain Pathway: Human Genetic and Multi-Omic Strategies for Next-Generation Analgesics

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study by Ari-Pekka Koivisto is a timely, well-written, and thought-provoking review that addresses a highly relevant question in pain research and drug discovery: why the translation of promising pain targets into effective therapies remains so difficult. The manuscript is ambitious in scope yet remains coherent and focused throughout. It successfully integrates human genetics, transcriptomics, multiomics, electrophysiology, PK/PD considerations, and translational pharmacology into a unified framework for pain target validation. In this regard, the review offers both conceptual clarity and practical value for the field.

A major strength of the manuscript is its strong translational perspective. The discussion of NaV1.8, NaV1.7, and TRPA1 is particularly compelling, as it moves beyond a descriptive literature summary and instead develops a reasoned argument about target engagement, anatomical site of action, and the importance of central versus peripheral access. The manuscript also makes good use of recent literature and presents an original, critical interpretation of why some clinically promising approaches may have failed.

The figures are helpful and support the manuscript well. In particular, the schematic distinction between peripheral and central NaV1.8 blockade and the five-dimensional framework for an ideal chronic pain drug target improve readability and reinforce the main take-home messages of the review.

Overall, I believe this review makes a valuable contribution to the field and is suitable for publication after very minor revision.

Minor suggestions:

-Comment #1: The manuscript would benefit from a light language edit to improve readability in a few places, particularly where long sentences could be streamlined for flow and precision.

-Comment #2: In some sections, especially those discussing VX993 and CNS penetration, it may help to distinguish slightly more clearly between evidence-based conclusions and hypothesis-driven interpretation.

-Comment #3: A final brief paragraph in the conclusions explicitly summarizing the main practical criteria for future pain-target selection could further strengthen the translational impact of the review.

Comments on the Quality of English Language

#1:Original - “Transcriptomics, the study of all RNA molecules in a cell or tissue helps reveal gene expression patterns under different conditions.”
Sugestion - “Transcriptomics, the study of all RNA molecules in a cell or tissue, helps reveal gene expression patterns under different conditions.”

#2: Original - “Recent transcriptomic analyses of human dorsal root ganglion (DRG) neurons and non-neuronal cells have produced a harmonized DRG atlases, now freely available online.”
Sugestion - “Recent transcriptomic analyses of human dorsal root ganglion (DRG) neurons and non-neuronal cells have produced harmonized DRG atlases, which are now freely available online.”

#3: Original: -“An additional complication for drawing conclusions from in vivo studies performed in rat: when human NaV1.8 is expressed in rat NaV1.8 knockout DRG neurons, its peak current is about 2 fold larger, action potential width is about ~3 times longer and show increased firing frequencies compared with rat DRG neurons.”
Sugestion - “An additional complication in drawing conclusions from in vivo studies performed in rats is that, when human NaV1.8 is expressed in rat NaV1.8-knockout DRG neurons, its peak current is about twofold larger, action potential duration is about three times longer, and firing frequency is increased compared with rat DRG neurons.”

Author Response

Thank you for the positive and constructive feedback. In light of the new experimental evidence, I have updated the manuscript regarding the site of suzetrigine action and introduced a revised proposal on the role of P‑glycoprotein (P‑gp) in the DRG. Based on the data, I now suggest that VX‑993 is a P‑gp substrate, which may limit its exposure within the DRG.

I have also added a new paragraph on target prioritization informed by human genetics, as well as a dedicated limitations section where I discuss several challenges encountered across multiple target validation projects. In addition, I corrected several typos and minor errors as suggested throughout the manuscript. Five new references and a list of abbreviations were added to support the manuscript.

I hope these revisions strengthen the clarity and scientific rigor of the work, and I believe the manuscript is now suitable for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

1. The title suggests a broad, general framework for identifying pain therapeutic targets. However, the manuscript is in practice strongly centered on voltage-gated sodium channels, particularly NaV1.7 and NaV1.8, with additional discussion of TRPA1. This creates a mismatch between the promised scope and the actual content. The title should be narrowed or the manuscript broadened to better reflect a balanced overview of molecular targets in pain.

2. The manuscript would benefit from a clearer conceptual structure. At present, the discussion moves quickly into sodium channels without first establishing the broader landscape of molecular pain targets (e.g., receptors, inflammatory mediators, neuroimmune pathways). A more logical flow would be: overview of molecular targets in pain pathways, positioning of ion channels within this framework, detailed discussion of NaV/TRP channels in specific pain states

3. The manuscript would benefit from a dedicated and explicit limitations section. Current discussion acknowledges certain uncertainties but does not systematically address key limitations
4. The review strongly promotes human genetics and human-derived datasets, which is scientifically justified. However, the role of preclinical models risks being somewhat undercontextualized. While the authors do defend animal models later in the manuscript, the narrative could be better balanced earlier to avoid the impression of overcorrection toward human-only approaches.
5. The redundancy argument for NaV channels is compelling but currently somewhat qualitative. If the authors wish to argue strongly for multi-target NaV inhibition strategies, it would help to include quantitative electrophysiological comparisons, modeling data, orclearer links to clinical outcomes. Otherwise the conclusion risks sounding mechanistically reasonable but not fully demonstrated.
6. The multiomics discussion in osteoarthritis is interesting but somewhat loosely connected to the central thesis about ion channel target validation. 
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Author Response

Thank you for the positive and constructive feedback. The manuscript focuses on voltage‑gated sodium channels and TRPA1 because both target classes have strong human genetic support for their relevance, particularly NaVs, and to a somewhat lesser extent TRPA1, which also benefits from pathway‑level evidence. I agree that a broader and more general discussion of molecular targets could provide a more logical flow. However, my intention was to concentrate specifically on targets with robust human genetic validation and supporting clinical trial data.

In light of new experimental evidence, I have revised the manuscript to clarify the site of suzetrigine action and to present an updated proposal regarding the role of P‑glycoprotein (P‑gp) in the DRG. The new data suggest that VX‑993 is a P‑gp substrate, which may restrict its exposure in the DRG.

I have also added a paragraph on target prioritization derived from human genetics, as well as a dedicated limitations section in which I discuss several challenges encountered across multiple target‑validation projects. This section now includes expanded commentary on the limitations of experimental animal models. In addition, I corrected several typographical and minor errors throughout the text, and added five new references to strengthen the scientific grounding of the manuscript.

I hope these revisions improve the clarity, coherence, and scientific rigor of the work, and I believe the manuscript is now suitable for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

 

The author conducted a narrative review of the progress and approaches that could reshape the discovery of pain medications, encouraged by the approval of a selective NaV1.8 inhibitor, suzetrigine. Throughout the text, he addressed various aspects of the most recent research on the subject.

The manuscript occasionally shifts from a review of the literature to a hypothesis-driven perspective. Statements proposing mechanistic explanations (e.g., the suggested role of limited CNS exposure in VX993 failure) should either be more clearly framed as hypotheses or supported with additional references.

My suggestions are below:

• The manuscript would benefit from a brief description of how the literature was identified and selected. Even in narrative reviews, a short methodological note (databases searched, time frame, inclusion criteria) improves transparency.
• Figure 1 is conceptually interesting, but visually heavy. Simplifying the diagram and reducing the textual elements within the figure would improve readability, or even improving the contrast and font size.
•  
• Some words are spelled differently throughout the text (NaV 1.7 with and without a space, Suzetrigine with the first letter capitalized or lowercase, in addition to a spelling Suzatrigine in the key word).
• A list of abbreviations at the end of the text would be very helpful.

This manuscript provides an interesting and timely overview of emerging strategies for analgesic target validation, integrating human genetics, multiomic approaches, and translational pharmacology. However, the manuscript would benefit from clearer differentiation between literature review and author hypotheses. With these improvements, the article could provide a valuable contribution to the field of pain therapeutics.

Author Response

Thank you for the positive and constructive feedback. My aim was to write a research‑strategy–style review to support the Special Issue, which naturally involves a degree of subjective selection among published studies and manuscripts currently under evaluation. I have reviewed the spelling throughout the manuscript and corrected inconsistencies. In addition, I have added a list of abbreviations as suggested.

In light of new experimental evidence, I have updated the manuscript to clarify the site of suzetrigine action and to introduce a revised proposal regarding the role of P‑glycoprotein (P‑gp) in the DRG. The data now support the view that VX‑993 is a P‑gp substrate, which may limit its exposure within the DRG.

I have also added a new paragraph on target prioritization informed by human genetics, as well as a dedicated limitations section in which I discuss several challenges encountered across multiple target‑validation projects. Additionally, I corrected the typographical and minor errors noted, and incorporated five new references to further support the manuscript.

I hope these revisions enhance the clarity, coherence, and scientific rigor of the work, and I believe the manuscript is now suitable for publication.

Reviewer 4 Report

Comments and Suggestions for Authors

First of all, I'd like to note that I enjoyed reading this review. The author took a very original approach to the problem of using pain medications and explained their positive and negative pharmacological effects quite clearly. I believe this review will be of interest to a wide range of readers. I have a few minor comments.

 

The author's stated goal for the review at the end of the Introduction (Lines 45-46) and the title of the manuscript itself are inconsistent. Judging by the title, the author wants to discuss the correct path for pain research, but in fact, the author's goal is to discuss "Why did VX993 fail" and "Why is developing new pain drugs so challenging." The author, in essence, dedicates the review to different research in the pain therapy. I suggest that the authors define more clearly the purpose of the review.

 

Line 65-66. The author claims that mutations in NaV1.7 (SCN9A) and NaV1.8 (SCN10A) are evidence of the role of these channels in pain. But isn't the expression of genes encoding voltage-gated ion channels in nociceptors evidence of the role of these channels in pain? I can certainly agree that sodium channel inhibition serves as evidence, but not direct.

 

Line 96-98. The author raised a rather interesting point: does the author think that in this regard, it would be beneficial to use broader-spectrum NaV inhibitors, such as tetrodotoxin, saxitoxin, and various families of conotoxins? Perhaps the author could also discuss this in this review.

 

Line 99. In the title of this chapter, the author refers to "common diseases." However, in the chapter itself, the author only talks about osteoarthritis.

 

I suggest to merge Chapters 9 and 10, as these chapters are devoted to animal models.

Author Response

Thank you for the positive and constructive feedback. The manuscript focuses on voltage‑gated sodium channels and TRPA1 because both target classes have strong human genetic support for their relevance, particularly NaVs, and to a somewhat lesser extent TRPA1, which also benefits from pathway‑level evidence. However, my intention was to concentrate specifically on targets with robust human genetic validation and supporting clinical trial data. In other words, the purpose of the review to write a research‑strategy–style review to support the Special Issue, which naturally involves a degree of subjective selection among published studies and manuscripts currently under evaluation.

In light of new experimental evidence, I have revised the manuscript to clarify the site of suzetrigine action and to present an updated proposal regarding the role of P‑glycoprotein (P‑gp) in the DRG. The new data suggest that VX‑993 is a P‑gp substrate, which may restrict its exposure in the DRG.

I have also added a paragraph on target prioritization derived from human genetics, as well as a dedicated limitations section in which I discuss several challenges encountered across multiple target‑validation projects. This section now includes expanded commentary on the limitations of experimental animal models. In addition, I corrected several typographical and minor errors throughout the text, and added five new references to strengthen the scientific grounding of the manuscript.

The discussion of lidocaine’s broad‑spectrum NaV blockade was included to highlight its superior analgesic efficacy, and an appropriate reference has now been added.

The revised title aims to convey the content of the chapter more clearly and effectively: Multiomic insight from common diseases: Osteoarthritis Pain as a Case Study

Chapters 9 and 10 were merged.

I hope these revisions improve the clarity, coherence, and scientific rigor of the work, and I believe the manuscript is now suitable for publication.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciate the author’s efforts to revise the manuscript and respond to the previous comments. The topic is important and timely, and the focus on human genetics and translational aspects of pain therapeutics is valuable. However, several of the major concerns raised in the first review have not been sufficiently addressed and still require substantial revision. 

The central issue regarding the mismatch between the title and the actual scope of the manuscript remains unresolved. The title suggests a broad and general framework for identifying pain therapeutic targets. In contrast, the manuscript continues to be heavily focused on voltage-gated sodium channels (particularly NaV1.7 and NaV1.8) and, to a lesser extent, TRPA1. While the author justifies this focus based on strong human genetic evidence, this does not fully address the concern.

The manuscript still lacks a clear overarching conceptual framework. The discussion moves rapidly into sodium channels without first establishing a broader context of pain mechanisms and target classes (e.g., receptors, inflammatory mediators, neuroimmune pathways).

The discussion of NaV channel redundancy and the rationale for multi-target inhibition strategies remains largely qualitative. While the mechanistic argument is plausible, it would benefit from stronger quantitative support. The addition of a dedicated limitations section is appreciated. However, it would be strengthened by a more structured and explicit discussion of the key conceptual and methodological limitations directly related to the main arguments of the manuscript (e.g., limitations of genetic validation, interpretation of redundancy, translational gaps).

Author Response

Dear Reviewer,

Thank you very much for your constructive and thoughtful feedback on my invited review.

As requested, I have revised the title to more accurately reflect the scope and content of the manuscript. The new title is:

“Mapping the Extended Pain Pathway: Human Genetic and Multi‑Omic Strategies for Next‑Generation Analgesics.”

To strengthen the overarching conceptual framework, I have added two new chapters. The first, “The Pain Pathway and Modern Drug Targets for Pain Relief,” provides a concise background overview of the pain pathway. A new reference was added to support the text. The second, “Evolution of Pain‑Relief Drug Discovery,” clarifies the broader message of the review. Its purpose is not merely to summarize NaV channels and their challenges. The chapter also emphasizes the importance of exploring novel genetically inspired targets, given that many legacy targets have not delivered on expectations.

The abstract has also been fully rewritten to reflect the revised structure of the manuscript and to incorporate the insights introduced in the two new chapters.

I have substantially revised the section on NaV channel redundancy and retitled it:

“From Transcriptomics to Function: How Multichannel Sodium Signaling Shapes Sensory Neuron Excitability.”

This revision includes an additional reference discussing the cardiac NaV1.5 (SCN5A) channel. NaV1.5 exhibits several cardiac and pain‑related phenotypes in the UK Biobank, fully supporting the findings cited in the manuscript. These data reinforce the conclusion that the broad multichannel blockade produced by local anesthetics cannot be replicated by selectively inhibiting a single or few NaV channels.

As requested, I also restructured the Limitations section. Two new paragraphs address the challenges posed by human genetic redundancy, supported by an additional reference. I have also expanded the discussion of current limitations in identifying causal genes from GWAS signals, to better reflect the state of the field.

I sincerely hope that these revisions meet the expectations of the reviewer and that the manuscript is now suitable for publication.

With kind regards,

Ari-Pekka Koivisto

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

The Author has now provided expected improvement, Therefore i suggest to publish the manuscript in the present form