5-Aminopyrazole-4-Carboxamide-Based Compounds Prevent the Growth of Cryptosporidium parvum

Abstract

Cryptosporidium parvum calcium-dependent protein kinase 1 (CpCDPK1) is a promising target for drug development against cryptosporidiosis. We report a series of low-nanomolar CpCDPK1 5-aminopyrazole-4-carboxamide (AC) scaffold inhibitors that also potently inhibit C. parvum growth in vitro Correlation between anti-CpCDPK1 and C. parvum growth inhibition, as previously reported for pyrazolopyrimidines, was not apparent. Nonetheless, lead AC compounds exhibited a substantial reduction of parasite burden in the neonatal mouse cryptosporidiosis model when dosed at 25 mg/kg.

Keywords: 5-aminopyrazole-4-carboxamide; Cryptosporidium parvum; bumped kinase inhibitors.

FIG 1

Structures of BKIs 1, 2, and 3 and structures of select CpCDPK1 inhibitors (AC-BKIs).

FIG 2

Cell inhibition EC₅₀ versus CpCDPK1 IC₅₀ plot to determine correlation. Plot and analysis showing the poor correlation between CpCDPK1 IC₅₀ and C. parvum in vitro growth and proliferation EC₅₀s. Pearson's correlation coefficient (r) was determined and added to the graph: r ranges were between 1 and −1, with 0 indicating no correlation at all, 0.1 to −0.1 also indicating no correlation, <0.5 indicating weak correlation, and 0.5 to 1 indicating strong correlation. Closer to 1 is stronger correlation and closer to 0 is weaker correlation, so r = 0.07 indicates extremely weak to no correlation.