The characterization of lodoxamide, a very active inhibitor of mediator release, in animal and human models of asthma.

A most active biologue of disodium cromoglycate (DSCG) available, lodoxamide tromethamine (LT), has been studied and characterized pharmacologically, in animal and human models of asthma. It has self-tachyphylaxis, but has oral activity (lodoxamide ethyl) in rats, primates, and man. In rats (LT) was 2,500 X more active than DSCG (ID50 = 0.001 mg/kg), in primates the drug was also active by several routes (inhalation 1 microgram/kg, IV 0.001 mg/kg, and oral 10 mg/kg). In isolated rat peritoneal mast cells, the compound displayed a biphasic dose response inhibition to histamine release initiated by (48/80, anti-IgE, and the calcium ionophore A23,187) with IC50 values of 0.1-50 microM. The consistent finding relating to its mode of action was its ability to inhibit 45calcium flux into the mast cell in response to antigen or A23,187. Clinical evaluations of lodoxamide tromethamine showed that at aerosol doses of 1.0 mg or less, it demonstrated significant inhibitory activity against antigen or exercise induced bronchospasm. However, in pilot evaluation studies in clinical asthma settings, the compound could not be shown to spare bronchodilator usage, relative to placebo, or be shown to be more effective than placebo treated patients based on other clinical endpoints. The reason for rat and primate models not being predictive for human long-term clinical asthma in the characterization of anti-release compounds is not known.