Neurophysiological and Biomolecular Effects of Atogepant in Episodic Migraine

BACKGROUND:

Migraine is a highly prevalent neurological disease associated to a severe burden for patients and society. Despite recent advances, the knowledge of the molecular and biochemical pathways that turn on and off a migraine attack and lead to an increased frequency of attacks is still limited. In addition, the lack of predictors of the therapeutic response is a barrier to access to care and to a personalized approach. In recent years, several migraine-specific drugs have become available for the preventive treatment of the disease, which is aimed at reducing the frequency and the intensity of the attacks. Among the drugs currently available for migraine treatment, there are molecules that directly interfere with the calcitonin gene-related peptide (CGRP) pathway. Gepants, oral drugs that are CGRP receptor antagonists, represent a recently available pharmacological class for the acute and preventive treatment of migraines due to their specific mechanism of action.

The potential mechanism underlying the therapeutic benefit derived from drugs that block CGRP, as well as their impact on various biochemical and functional parameters associated with migraine pathophysiology, remains a topic of debate.

The objective of the ATOM project is to characterize the neurophysiological and biomolecular mechanisms underlying the therapeutic action of Atogepant (ATO), a drug belonging to the new pharmacological class of gepants. ATO has been shown to be effective in the preventive treatment of both chronic and episodic migraine. However, preventive treatment with gepants is still ineffective (reducing the number of monthly migraine days by less than 50%) in 30% of patients. This finding suggests that other biological pathways independent of CGRP may play a role in migraine pathophysiology. Among these, the endocannabinoid system has gained increasing importance over the years.

From a neurofunctional perspective, central sensitization is a significant aspect of migraine pathophysiology. Our group has demonstrated the utility of the nociceptive withdrawal reflex at the lower limb (RIII) in studying central sensitization. A subsequent study showed improvement in RIII reflex parameters in 30% of chronic migraine patients who responded to Erenumab after three months of treatment, suggesting a potential correlation between improved central sensitization and clinical benefit from anti-CGRP antibody treatment.

Additionally, migraine patients exhibit altered responses following repeated cranial stimulation, specifically a deficit in habituation to such stimuli. It has been described that the habituation pattern follows a characteristic course throughout the migraine cycle. The habituation deficit has been demonstrated through various neurophysiological methods, such as the nociceptive blink reflex (nBR) and visual evoked potentials (VEPs). These assessments provide information about the modulation of relevant stations in the trigemino-vascular system, specifically the trigemino-cervical complex and the occipital cortex.

Our study includes an evaluation of brain functional connectivity using High-Density Electroencephalography (HD-EEG). Recently, we analyzed potential variations in functional connectivity within the Resting State Network (RSN) in migraine patients undergoing six months of treatment with monoclonal antibodies targeting the CGRP pathway through serial HD-EEG evaluations (unpublished data). Our findings demonstrate that migraine patients, when compared to healthy controls, exhibit widespread hyperconnectivity in the theta and delta frequency bands, potentially attributable to dysfunction of the generators of these frequency bands, highlighting the importance of the thalamo-cortical dysrhythmia concept in migraine pathophysiology. Conversely, longitudinal comparisons revealed a trend towards normalization of connectivity in patients with a good clinical response to anti-CGRP monoclonal antibodies.

From a biochemical standpoint, our group has demonstrated that the gene expression of endocannabinoid catabolizing enzymes - fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) - is altered in peripheral cells of patients with episodic and chronic migraine and is correlated with migraine severity. Similarly, various literature evidence supports the role of microRNAs in the mechanisms underlying migraines. Elevated expression levels of miR-382-5p and miR-34a-5p, combined with lower levels of miR-30a-5p expression, have been found in migraine patients compared to healthy controls, confirming an epigenetic alteration. In a previous study, we reported that peripheral levels of miR-382-5p and miR-34a-5p in migraine patients were correlated with disease severity, as they were increased in patients with chronic migraine and medication-overuse headache (CM-MOH) compared to episodic migraine (EM) patients, suggesting involvement in chronicization, while not excluding an influence of pharmacological migraine treatments . Elevated levels of miR-155, a microRNA known to modulate inflammation, have been found in peripheral cells of both EM and CM-MOH patients compared to healthy controls, with higher levels in chronic patients.

The overarching aim of this project is the identification of specific neurophysiological and biomolecular signatures that differentiate subjects with migraine who benefit or do not benefit from atogepant treatment. This aim will be achieved via a thorough neurophysiological and biochemical profiling of subjects with high frequency episodic migraine treated with atogepant 60 mg for a period of 3 months.

STUDY DESIGN:

Patients will be enrolled from those attending the outpatient clinic of IRCCS Mondino Institute (Pavia). The investigators will enroll 30 patients with high-frequency episodic migraine (8-14 monthly migraine days) with clinical indications to start atogepant (ATO - 60 mg daily) according to the Italian regulations.

The investigators will collect clinical data and perform biochemical and neurofunctional profiling of migraine patients at baseline (T0) and after three months of atogepant treatment (T1).

METHODS: All patients will undergo at T0 and T1:

1. Biochemical profiling that will include analysis of:

   • eCBome system: FAAH, MAGL mRNA in PBMCs;
   • plasma levels of CGRP, PACAP, and VIP;
   • miR-382-5p, miR-34a and miR-155 in PBMCs. The investigators will collect biochemical sampling between 9 and 11 a.m. to avoid circadian rhythm influence. All evaluation will be performed in the interictal phase.

   The following collection methods will be adopted: • mRNA and microRNA analysis in PBMCs. Blood samples will be collected within ethylenediamine tetra-acetic acid tubes, the investigators will first isolate PBMCs and total RNA. Ubiquitin C and U6 will act as housekeeping genes for genes coding for the eCBome enzymes and miRNAs. • CGRP alpha, PACAP-38 and VIP levels will be measured using a commercial enzyme linked immunosorbent assay.

2. Neurofunctional profiling that will include:

   • recording of the Nociceptive Withdrawal Reflex (RIII);
   • recording of the nociceptive Blink Reflex (nBR);
   • recording of High-Density EEG (HD-EEG);
   • recording of Visual Evoked Potentials (VEP). The following methods will be adopted: - Nociceptive Withdrawal Reflex (RIII reflex): The sural nerve will be stimulated via surface electrodes behind the right lateral malleolus. Reflex threshold (≥20 μV, >10 msec) will be determined using the ladder method. Temporal summation threshold (TST) will be assessed by increasing stimulus intensity (5 stimuli at 2 Hz) until facilitation of the reflex response appears. (De Icco et al., 2020).- Nociceptive Blink Reflex (nBR): nBR R2 response will be recorded using a concentric electrode above the supraorbital nerve and surface electrodes at the orbicularis oculi muscle. Habituation will be evaluated with 25 stimuli at varying frequencies, with area under the curve (AUC) calculated for 5 averaged blocks. Habituation index (HI) will reflect percentage change in AUC from the last to the first block. (Perrotta et al., 2017). - Visual Evoked Potentials (VEP) recording: VEP will be recorded during monocular stimulation using black-and-white checkered patterns. Components (N70, P100, N145) will be analyzed, and habituation will be defined as the percentage change in P100 amplitude between the last and first block. (Ambrosini et al., 2017). High Density Electroencephalography recording (HD-EEG): Recordings (128 channels, high-pass: 0.5 Hz, low-pass: 100 Hz) will include four 6-minute resting-state sessions (2 with eyes open, 2 with eyes closed). Frequency bands (delta to gamma) will be analyzed using a validated custom pipeline to reconstruct cortical/subcortical neural sources.

STATISTICAL ANALYSIS: Sample size calculation was performed for the primary outcome of ATOM project (namely compare the TST threshold of the RIII reflex between T0 and T1. From previous papers, preliminary data and experience of our research group, an expected difference between the means at T0 and T1 of 2 mA is inferred, with a standard deviation of 4 mA for both measurements. The comparison will be made by t test for paired data or corresponding nonparametric test (Wilcoxon Signed Rank Test), after performing a preliminary test on the normality of the data (Shapiro test). The investigators will consider a test power of β=0.8 and a 95% confidence. The suggested sample size is n=30. Regarding the co-primary outcome (Aim 2 - gene expression of MAGLs in PBMCs) a power analysis was performed, considering a significant difference between T0 and T1 of 5 RQ (standard deviation 4 and 10 respectively). Assuming a sample size of 30, the expected power is more than 80%.