Discovery of an orally bioavailable isoxazoline benzoxaborole (AN8030) as a long acting animal ectoparasiticide.

A novel series of isoxazoline benzoxaborole small molecules was designed and synthesized for a structure-activity relationship (SAR) investigation to assess the ectoparasiticide activity against ticks and fleas. The study identified an orally bioavailable molecule, (S)-3,3-dimethyl-5-(5-(3,4,5-trichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)benzo[c][1,2]oxaborol-1(3H)-ol (38, AN8030), which was long lasting in dogs (t1/2=22 days). Compound 38 demonstrated 97.6% therapeutic effectiveness within 24 h of treatment, with residual efficacy of 95.3% against American dog ticks (Dermacentor variabilis) on day 30% and 100% against cat fleas (Ctenocephalides felis) on day 32 after a single oral dose at 50 mg/kg in dogs.