Gepants are small molecule calcitonin gene-related peptide (CGRP) receptor antagonists. The preventive CGRP monoclonal antibodies(Aimovig, Emgality, Ajovy) are large molecules, delivered once per month as a SQ injection. Seven gepants have been developed since 2004. (1) Telcagepant was extensively studied, but withdrawn due to hepatotoxicity concerns. CGRP has many effects throughout the body. CGRP triggers a cascade of inflammatory mediators that feed into the trigeminovascular system. By blocking CGRP, the gepants stop the process prior to inflammation.
Regarding migraine, CGRP is an inflammatory compound. They will initially be utilized as migraine abortives, but eventually they will also be used to prevent migraine. The gepants may be helpful for 3 groups of migraineurs. They will be prescribed for a number of patients who found triptans (sumatriptan, rizatriptan, zolmitriptan, etc.) to be ineffective. In addition, gepants will be used for certain patients who cannot tolerate triptans. Finally, for those patients with significant cardiac or cerebrovascular risk factors, the gepants may be relatively safe, since they do not constrict cardiac or cranial arteries. While efficacy is modest, these are well tolerated medications.
The first gepant to come to market will be ubrogepant. Almost 2,700 patients participated in the ubrogepant ACHIEVE studies. (2,3) The doses have ranged from 25mg to 100mg. The t-max is 0.7 to 1.5 hours. Approximately 20% of patients who used the 50mg dose were pain free after 2 hours. While 25mg and 100mg tablets of ubrogepant were evaluated, it is likely that 50mg will be the primary dose. Ubrogepant was well tolerated, with 2% to 5% of patients reporting nausea, somnolence, dry mouth, dizziness, or upper respiratory tract infections. No serious adverse events were reported. The safety and tolerability were also explored in a 52 week extension study. Few adverse events, and no hepatotoxicity was reported. The effect of ubrogepant on the patient’s most bothersome migraine symptom was evaluated 2 hours post-dose. 39% of those treated with ubrogepant reported that their worst migraine symptom was resolved. The therapeutic gain for ubrogegepant (active drug vs. placebo) is relatively low, 6.4%-9.4%. In comparison, the therapeutic gain for sumatriptan is 16%-21%.
Rimegepant is another gepant, in development for abortive and preventive use. The dose is 75mg, with a t-max of 2 hours. In the 2 main trials, 19.4% of patients achieved pain freedom at 2 hours. (4) 37% of patients reported freedom from their most bothersome symptom. As with ubrogepant, no significant liver toxicity was reported. Adverse events were low, with nausea being reported by 1.4% of patients. The therapeutic gain for rimegepant is 5% to 7.6%.
A third gepant, atogepant, is currently being studied.
The gepants will be a useful alternative to triptans. Many patients find triptans to be ineffective. Some migraineurs cannot tolerate the adverse effects of the triptans. For certain patients with cardiovascular risk factors, triptans may not be completely safe. Gepants will be considered in these clinical settings. The initial (2 hour) efficacy rates are fairly low, but it appears that gepants may become more effective over 2 to 8 hours. During the trials, these were fairly well tolerated medications. It will take at least several years before we are able to accurately assess the true adverse effect profile of the gepants.
1. Olesen J, Diener H-C, Husstedt IW et al Calcitonin gene-related peptide receptor antagonist BIBN 4096 BS for the acute treatment of migraine. 2004. N Eng J Med 350:1104-1110.
2. Allergan Announces Positive Top Line Phase 3 Clinical Trial for Ubrogepant- an Oral CGRP Receptor Antagonist for the Acute Treatment of Migraine. Available at http://www.allergan.com/news/news/thomson-reuters/allergan-announces-positive-phase-3-resul.
3. Allergan Announces Second Positive Phase 3 Clinical Trial for Ubrogepant- an Oral CGRP Receptor Antagonist for the Acute Treatment of Migraine. Available at http://www.allergan.com/News/News/Thomson-Reuters/Allergan-Announces-Second-Positive-Phase-3-Clinica.
4. Biohaven Announces Successful Achievement of Both Co-Primary regulatory Endpoints in Two Pivotal Phase 3 Trials of Rimegepant an Oral CGRP Receptor Antagonist for the Acute Treatment of Migraine Available at https://biohavenpharma.com/wp-content/uploads/2018/03/CONFIDENTIAL-BIOHAVEN-PRESS-RELEASE-FINAL-v2.pdf.