Tonabersat (Synonyms: SB-220453)

Migraine is a common, recurrent and primary headache disorder. Optimisation of novel cis- and trans-4-(substituted-anfido)benzopyran-3-ol derivatives has led to the identification of Tonabersat (SB-220453) with potential antimigraine activity.

In vitro: Topiramate targets multiple cortical and subcortical loci, altering voltage-gated ion channels and chemical transmission to decrease abnormal brain excitability. Preclinical studies have identified four properties that may account for the drug’s efficacy in epilepsy and migraine prophylaxis: (i) blockage of voltage-dependent sodium channels; (ii) augmentation of the activity of the neurotransmitter g-aminobutyric acid (GABA) at some subtypes of the GABA-A receptor; (iii) antagonism of the AMPA/kainate subtype of the glutamate receptor; and (iv) inhibition of the carbonic anhydrase enzymes, particularly isozymes II and IV [1].

In vivo: Tonabersat binds selectively to a unique site in the brain. Moreover, tonabersat could markedly reduce cortical spreading depression (CSD) and CSD-associated events and inhibite gap-junction communication between neurons and satellite glial cells in the trigeminal ganglion. Together, these findings indicate that tonabersat should have clinical application in preventing migraine attacks [2].

Clinical trial: Tonabersat showed a preventive eff ect on attacks of migraine aura but no efficacy on non-aura attacks, in keeping with its known inhibitory eff ect on CSD. The results support the theory that auras are caused by CSD and that this phenomenon is not involved in attacks without aura [3].

References:
[1] Silberstein SD.  Tonabersat, a novel gap-junction modulator for the prevention of migraine. Cephalalgia. 2009;29 Suppl 2:28-35.
[2] Durham PL, Garrett FG.  Neurological mechanisms of migraine: potential of the gap-junction modulator tonabersat in prevention of migraine. Cephalalgia. 2009;29 Suppl 2:1-6.
[3] Hauge AW, Asghar MS, Schytz HW, Christensen K, Olesen J.  Effects of tonabersat on migraine with aura: a randomised, double-blind, placebo-controlled crossover study. Lancet Neurol. 2009;8(8):718-23.