Semi-Automated Recording of Facial Sensitivity in Rat Demonstrates Antinociceptive Effects of the Anti-CGRP Antibody Fremanezumab

Round 1

Reviewer 1 Report

Please explain why the method is called "semi-automated"? is not this an objective measure? The device was built for operant orofacial pain assessment.

Please add if this response (reduction of hypersensitivity) has also been recorded in humans using the same drug. In other words, is the finding translatable? Migraine patients have facial allodynia but also in other body regions. Please add that it could have been interesting to check other body regions (e.g., limbs).

How the authors can describe a differentiation in sensitivity to thermal and mechanical stimuli and better response to one of those compared with another? Most migraine patients report sensitivity to mechanical rather than thermal or what? Please elaborate.

Please add the limitation of this study and the clinical use of the findings. How these findings can help in the clinic while patients take medication for headaches?

Please explain the potential role of time and the length of the effect. Does it correlate with headache reduction? In other words, do headache and hypersensitivity correlate, and drug effect can be for both at similar time courses and magnitude?

Author Response

Response to Reviewer 1

 We like to thank the reviewer for his/her careful reading of our manuscript.

Please explain why the method is called "semi-automated"? is not this an objective measure? The device was built for operant orofacial pain assessment.

Response: Yes, the device allows an objective measure of orofacial sensitivity but the animals were placed by hand into the recording cage and kept there for a constant time, and the consumed volume of the sugar solution was also determined non-automatically. The term “semi-automated” was chosen to emphasize the novelty of this procedure. However, we are willing to omit the term “semi-automated” if it causes misinterpretation and the Reviewer insists in removing it.    

Please add if this response (reduction of hypersensitivity) has also been recorded in humans using the same drug. In other words, is the finding translatable? Migraine patients have facial allodynia but also in other body regions. Please add that it could have been interesting to check other body regions (e.g., limbs).

How the authors can describe a differentiation in sensitivity to thermal and mechanical stimuli and better response to one of those compared with another? Most migraine patients report sensitivity to mechanical rather than thermal or what? Please elaborate.

Please add the limitation of this study and the clinical use of the findings. How these findings can help in the clinic while patients take medication for headaches?

Response to the above three points: We appreciate the comments of the Reviewer indicating that it may be useful to address the clinical relevance of our study. Therefore, we have added another paragraph to the Discussion (for additional references, please see revised version of the manuscript):

“4.4. Clinical relevance and limitations

Migraine patients frequently show facial allodynia and are hypersensitive also in other body regions (Burstein et al. 2015, Goadsby 2005). To our knowledge, changes in cutaneous sensitivity have not been systematically monitored in patients treated with fremanezumab. Following repetitive treatment with galcanezumab, another anti-CGRP antibody, cutaneous allodynia during migraine attacks has been found to improve, however, without reaching statistical significance after correction for multiple comparison (Silvestro et al. 2022). Similar late responses including the decrease in allodynia to galcanezumab, fremanezumab and the anti-CGRP receptor antibody erenumab have re-cently been communicated (Barbanti et al. 2023). These data are based on self-reports of patients and did not differentiate between body regions. It would be interesting to test, in addition to facial sensitivity, other regions of rat’s body with the device used in our experiments.

Thermal hypersensitivity is usually not tested in migraine, and patients do usually not report thermal hypersensitivity. Thermal pain thresholds have been shown to be de-creased immediately prior to migraine attacks (Sand et al. 2008). Derived from the present data, we assume that thermal hypersensitivity in the face of migraineurs may be reduced after treatment with anti-CGRP antibodies. Developing a standard test for evaluation of mechanical and thermal sensitivity in migraineurs would possibly be very useful for monitoring the effect of treatments targeting CGRP or its receptors”. 

Please explain the potential role of time and the length of the effect. Does it correlate with headache reduction? In other words, do headache and hypersensitivity correlate, and drug effect can be for both at similar time courses and magnitude?

There is no data answering this question due to the lack of information about changes in facial sensitivity following anti-CGRP antibody treatment. We have chosen a waiting time of at least 10 days after fremanezumab injection, because in our previous experiments the effect on CGRP release was optimal after this time (Dux et al. 2022) .

Reviewer 2 Report

Dear Authors,

I have read your paper with great interest. I believe it adds valuable knowledge in the field of migraine therapy. Therefore, I have only minor comments/suggestions.

1. Are you aware of any experiments with CGRP injections in rodents? Does such injection would lead to headache-like behavior in rats? If so, - in what percentage of rodens would such an injection provoke headache-like behavior? I would add such information (if available) to the introduction

2. Do you know any data about differences in response to CGRP injection in rodents related to animals' sex? I would use such information in discussion over the sex effect that you have observed.

3 . Do you know any data on pharmacodynamics of fremanezumab in rodents? After how many days the observer should expect start of action of the drug? Such data would add more sundness to the interpretation of the results.

Author Response

Response to Reviewer 2

We like to thank the reviewer for his/her careful reading of our manuscript.

Dear Authors,

I have read your paper with great interest. I believe it adds valuable knowledge in the field of migraine therapy. Therefore, I have only minor comments/suggestions.

1. Are you aware of any experiments with CGRP injections in rodents? Does such injection would lead to headache-like behavior in rats? If so, - in what percentage of rodens would such an injection provoke headache-like behavior? I would add such information (if available) to the introduction

Response to points 1 and 2: We thank the Reviewer for these valuable questions regarding the CGRP actions and have added to the Introduction (for additional references please see revised manuscript):

“Intraperitoneal injection of CGRP induced grimace responses indicative of pain (Rea et al 2018) but the sensitivity to CGRP seems to depend on the mouse strain (Mogil et al 2005). Injection of CGRP into facial skin has been found to cause dose-dependent periorbital allodynia, which could be prevented by administration of the CGRP receptor antagonist olcegepant or a monoclonal antibody against CGRP (De Logu et al 2019). In rats, injection of CGRP into the facial skin did not induce signs of facial pain unless rats were sensitized by preadministration of nitroglycerin (Capuano et al 2014). Remarkably, application of CGRP to the rat dura mater has been shown to cause periorbital hypersensitivity selectively in female animals (Avona et al 2019)”.

2. Do you know any data about differences in response to CGRP injection in rodents related to animals' sex? I would use such information in discussion over the sex effect that you have observed.
3. Do you know any data on pharmacodynamics of fremanezumab in rodents? After how many days the observer should expect start of action of the drug? Such data would add more sundness to the interpretation of the results.

Response: In our previous experiments using fremanezumab application in the same mode, we measured significant reduction in CGRP release earliest after 3 days up to 30 days. 10 days after injection yielded a robust effect, which was the reason to choose waiting times of 4-13 days for the present experiments.