Encequidar mesylate (HM30181A mesylate) is a competitive P-glycoprotein inhibitor.

Administration of Encequidar at concentrations of 0.1 or 1 nM resulted in a reduction of cell survival by 20% and 42% upon exposure to 100 nM and 1000 nM of NSC 125973, respectively [2].

When administered simultaneously, Encequidar demonstrates increased plasma concentrations with the microcapsule formulation compared to the powder, showing notable differences from 1 to 2 hours. The microcapsule formulation achieves a 1.7-fold quicker Tmax and a 1.6-fold greater AUC value than the powder (2.5±0.6 vs. 4.3±0.9 hours; 107.7±20.1 vs. 64.3±18.0 h ng/mL), indicating faster and more efficient absorption. This enhanced absorption of Encequidar in microcapsule format is likely attributed to its improved aqueous solubility and dissolution rates, facilitated by the conversion from crystalline to amorphous form and the reduction in particle size [1].