Pyrrolopyrimidine Bumped Kinase Inhibitors for the Treatment of Cryptosporidiosis

Abstract

Bumped kinase inhibitors (BKIs) that target Cryptosporidium parvum calcium-dependent protein kinase 1 have been well established as potential drug candidates against cryptosporidiosis. Recently, BKI-1649, with a 7H-pyrrolo[2,3-d]pyrimidin-4-amine, or "pyrrolopyrimidine", central scaffold, has shown improved efficacy in mouse models of Cryptosporidium at substantially reduced doses compared to previously explored analogs of the pyrazolopyrimidine scaffold. Here, two pyrrolopyrimidines with varied substituent groups, BKI-1812 and BKI-1814, were explored in several in vitro and in vivo models and show improvements in potency over the previously utilized pyrazolopyrimidine bumped kinase inhibitors while maintaining equivalent results in other key properties, such as toxicity and efficacy, with their pyrazolopyrimidine isosteric counterparts.

Keywords: Cryptosporidium; bumped kinase inhibitors; cryptosporidiosis; pyrazolopyrimidines; pyrrolopyrimidines.

Figure 1.

Central scaffolds of bumped kinase inhibitors that target calcium-dependent protein kinase 1 in Cryptosporidium.

Figure 2.

Chemical structures of pyrrolopyrimidines BKIs-1812, –1814, and –1649 and pyrazolopyrimidines BKIs-1369, –1547, and –1677.

Figure 3.

Pharmacokinetics of a single, 25 mg/kg oral dose in uninfected adult female BALB/c mice (n=3) for BKI-1812 and BKI-1814.

Figure 4.

Dose titration of BKI-1812 and BKI-1814 in adult female IFN-γ KO mice (n=3) infected with nanoluciferase-expressing Cryptosporidium parvum. Blood was sampled on Day 9 post infection for LC-MS/MS analysis of plasma concentrations, as indicated in Table 3.