Biodistribution of atogepant and rimegepant in mouse peripheral and central structures of relevance to migraine pathogenesis

Background: Second and third generation gepants have been recently approved for migraine therapy. They represent the first drugs that are able to work as both preventatives and symptomatics of the migraine attack. Their ability to counteract calcitonin gene-related peptide signaling has been convincingly shown, but where they act to exert the therapeutic effects remains unsolved. Although the low brain/plasma ratio suggests peripheral antimigraine activity of gepants, recent preclinical and clinical lines of evidence hint that these compounds may also act centrally. Methods: By means of mass spectrometry analysis, we have measured the biodistribution of atogepant and rimegepant in plasma, dura mater, trigeminal ganglion (TG), parietal brain cortex and hypothalamus of mice. The biodistribution of oxazepam has been also determined as that of a prototypical brain permeant drug. Animals received interspecies (human-to-mouse) converted doses. Drugs were administered orally, as single or repeated (seven days) dosing. Atogepant was also administered as a single oral or intranasal dose matching (mg/kg) that adopted in migraine patients. Results: Upon administration of interspecies converted oral doses, we found that atogepant reached similar Cmax in plasma and TG after three hours, that then rapidly decreased at six and 12 hours. Of note, atogepant contents in the parietal brain cortex linearly increased up to six hours (reaching a brain/plasma concentration ratio of 5.6) and substantially decreased at 12 hours. Tissue contents of rimegepant were lower than those of atogepant, although the drug reached in the brain Cmax analogues to those found in the TG. Three hours after dosing, we also found the highest accumulation of atogepant and rimegepant in the dura, with substantial accumulation even in the hypothalamus where drug contents equaled those present in the TG. Of note, when atogepant was administered orally or intranasally at a dose corresponding to that adopted in patients, it also reached brain contents comparable to those found in the TG. However, a preferred delivery of atogepant to the TG was obtained with the intranasal route. At variance with oxazepam, the two gepants did not accumulate in the TG or parietal brain cortex upon a seven day oral treatment. Conclusions: The data obtained in the present study indicate substantial and transient permeation of the mouse brain by gepants.