One health therapeutics: Target-Based drug development for cryptosporidiosis and other apicomplexa diseases

Abstract

This is a review of the development of bumped-kinase inhibitors (BKIs) for the therapy of One Health parasitic apicomplexan diseases. Many apicomplexan infections are shared between humans and livestock, such as cryptosporidiosis and toxoplasmosis, as well as livestock only diseases such as neosporosis. We have demonstrated proof-of-concept for BKI therapy in livestock models of cryptosporidiosis (newborn calves infected with Cryptosporidium parvum), toxoplasmosis (pregnant sheep infected with Toxoplasma gondii), and neosporosis (pregnant sheep infected with Neospora caninum). We discuss the potential uses of BKIs for the treatment of diseases caused by apicomplexan parasites in animals and humans, and the improvements that need to be made to further develop BKIs.

Keywords: Antiparastics; Apicomplexa; Kinase inhibitors.

Figure 1:. Bumped Kinase Inhibitors (BKIs) exploit the small gatekeeper structural differences to achieve both potency and specificity.

Shown at left is the binding site of T. gondii CDPK1 with a small glycine (Gly) gatekeeper residue, forming a large hydrophobic sub-pocket that allows the BKI to bind at the ATP-binding pocket of CDPK1. On the right is the binding pocket of a typical mammalian kinase with a bulky gatekeeper residue, in this case methionine, demonstrating a clash takes place with the “bump” of BKIs, such that BKIs are excluded from the ATP binding pocket, granting BKIs specificity over almost all mammalian protein kinases.

Figure 2:

Pyrazolo-pyrimidine and aminopyrazole-carboxamide scaffolds, compounds described in this paper

Figure 3:. BKI-1369 is effective at reducing nanoluciferase-tagged C. parvum from gamma-interferon knock out mice:

BKI-1369 was administered orally at the doses shown (mpk = milligrams per kg), on day 6–10 post infection (P.I.) with 10,000 oocysts of Nluc-UGA1 C. parvum. The stool was isolated and relative luminescence units (RLU) are shown on the days P.I. Data from that published in (Hulverson et al., 2017a).

Figure 4:. C. parvum neonatal calf model demonstrates efficacy of BKI-1369 via reduction in total oocyst excretion, diminished fecal output, and favorable weight gain compared with control infected calves.

Two-day old calves were infected orally with 5×10⁷ C. parvum (Iowa strain, Cryptosporidium Production Laboratory, Univ. AZ) and two days later begun on BKI-1369 treatment or vehicle alone. Shown, left to right, are (1) the total number of oocysts excreted over the 5 days of treatment and 3 days after treatment in each group of control (vehicle alone treated on days 3–7 post infection (P.I.)) or treated (BKI-1369 5 mg/kg administered twice a day orally); (2) the total daily fecal volume excreted by the calves in each group; and, (3) weight gain or loss in each group over the 10-day observation period. Data replotted from (Hulverson et al., 2017a).

Figure 5:. Gnotobiotic piglet C. hominis infection shows a significant reduction in oocysts excreted during and after therapy with BKI-1369.

Shown are cumulative oocyst counts from daily rectal swabs taken on days 1–10 post-initiation of BKI-1369 (‘C. hominis +1369’, 10 mg/kg administered orally twice a day for the first 5 days) or vehicle alone (‘C. hominis only’). Data replotted from (Lee et al., 2018).