New drugs are needed to treat toxoplasmosis. Toxoplasma gondii calcium-dependent protein kinases (TgCDPKs) are attractive targets because they are absent in mammals. We show that TgCDPK1 is inhibited by low nanomolar levels of bumped kinase inhibitors (BKIs), compounds designed to be inactive against mammalian kinases. Cocrystal structures of TgCDPK1 with BKIs confirm that the structural basis for selectivity is due to the unique glycine gatekeeper residue in the ATP-binding site at residue 128. We show that BKIs interfere with an early step in T. gondii infection of human cells in culture. Furthermore, we show that TgCDPK1 is the in vivo target of BKIs because T. gondii cells expressing a glycine to methionine gatekeeper mutant enzyme show significantly decreased sensitivity to this class of selective kinase inhibitors. Thus, design of selective TgCDPK1 inhibitors with low host toxicity may be achievable.The food-borne apicomplexan protozoan Toxoplasma gondii is the causative agent of toxoplasmosis and may be the most common infectious eukaryotic parasite of humans, based Correspondence should be addressed to W.C.V.V. (wesley@u.washington.edu) or E.A.M. (merritt@u.washington.edu). Accession codes. Protein Data Bank: Atomic coordinates and structure factors have been deposited with accession numbers 3I79 (apo), 3I7c (NA-PP2 complex) and 3I7b (NM-PP1 complex).Note: Supplementary information is available on the Nature Structural & Molecular Biology website. AUTHOR CONTRIBUTIONSK.K.O., K.R.K., K.K.I. and W.C.V.V. were involved in the biochemical characterization and testing of inhibitors of TgCDPK1; L.J.C., K.K.O., K.R.K., A.J.N., C.L.M.J.V., F.S.B. and W.C.V.V. selected, cloned and purified the recombinant wild-type and mutant TgCDPK1 protein; E.T.L., J.E.K., T.L.A., L.Z., W.G.J.H. and E.A.M. crystallized and solved the structure of TgCDPK1; R.M. and D.J.M. synthesized the inhibitors; A.E.D. and M.P. performed the cellular T. gondii experiments; K.K.O., E.T.L., A.E.D., D.J.M., M.P., E.A.M. and W.C.V.V. wrote the paper; all authors reviewed and edited the paper. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests.Reprints and permissions information is available online at http://npg.nature.com/reprintsandpermissions/. 10 . These drugs are problematic in that they can cause rash, leucopenia and nephrotoxicity11, and sulfadiazine and pyrimethamine can result in complications during pregnancy. New therapeutics against T. gondii are needed. NIH Public AccessCalcium levels have long been associated with T. gondii's interrelated processes of invasion, gliding motility and secretion 12 . The intracellular Ca 2+ level oscillates during gliding motility and is promptly dampened upon cell invasion, preventing T. gondii from immediately gliding out of cells 13 . Calcium oscillations control many targets in the cell, and the mediation of invasion, micronemal secretion and gliding motility is thought to be largely due to T. gondii calcium-dependent protein kinases (TgCDPKs) 12,14 .Protein ...

The protozoans Cryptosporidium parvum and Toxoplasma gondii are parasites of major health concern to humans. Both parasites contain a group of calcium-dependent protein kinases (CDPKs), which are found in plants and ciliates but not in humans or fungi. Here we describe a series of potent inhibitors that target CDPK1 in C. parvum (CpCDPK1) and T. gondii (TgCDPK1). These inhibitors are highly selective for CpCDPK1 and TgCDPK1 over the mammalian kinases SRC and ABL. Furthermore, they are able to block an early stage of C. parvum invasion of HCT-8 host cells, which is similar to their effects on T. gondii invasion of human fibroblasts.

Despite the enormous economic importance of Neospora caninum related veterinary diseases, the number of effective therapeutic agents is relatively small. Development of new therapeutic strategies to combat the economic impact of neosporosis remains an important scientific endeavor. This study demonstrates molecular, structural and phenotypic evidence that N. caninum calcium-dependent protein kinase 1 (NcCDPK1) is a promising molecular target for neosporosis drug development. Recombinant NcCDPK1 was expressed, purified and screened against a select group of bumped kinase inhibitors (BKIs) previously shown to have low IC50s against Toxoplasma gondii CDPK1 and T. gondii tachyzoites. NcCDPK1 was inhibited by low concentrations of BKIs. The three-dimensional structure of NcCDPK1 in complex with BKIs was studied crystallographically. The BKI-NcCDPK1 structures demonstrated the structural basis for potency and selectivity. Calcium-dependent conformational changes in solution as characterized by small-angle X-ray scattering are consistent with previous structures in low Calcium-state but different in the Calcium-bound active state than predicted by X-ray crystallography. BKIs effectively inhibited N. caninum tachyzoite proliferation in vitro. Electron microscopic analysis of N. caninum cells revealed ultra-structural changes in the presence of BKI compound 1294. BKI compound 1294 interfered with an early step in Neospora tachyzoite host cell invasion and egress. Prolonged incubation in the presence of 1294 interfered produced observable interference with viability and replication. Oral dosing of BKI compound 1294 at 50 mg/kg for 5 days in established murine neosporosis resulted in a 10-fold reduced cerebral parasite burden compared to untreated control. Further experiments are needed to determine the PK, optimal dosage, and duration for effective treatment in cattle and dogs, but these data demonstrate proof-of-concept for BKIs, and 1294 specifically, for therapy of bovine and canine neosporosis.

BackgroundAdherence and persistence to therapy, or how well a patient follows provider directions on frequency and time to discontinuation of prescribed medications, is associated with positive health outcomes, including decreased healthcare costs and patient mortality. A clear literature gap exists assessing adherence and persistence to antidepressants (ADs) in the major depressive disorder (MDD) population at clinically relevant time points and at the therapeutic class level.ObjectiveThis study assessed adherence and persistence to specific ADs, therapeutic classes, and AD therapy overall at multiple time points among US individuals from commercial, Medicare supplemental, and Medicaid insurance plans.MethodsPatients with MDD without AD or MDD claims in the prior 6 months who initiated therapy in 2003–2014 with a selective serotonin reuptake inhibitor (SSRI), serotonin and norepinephrine reuptake inhibitor (SNRI), tricyclic AD (TCA), monoamine oxidase inhibitor (MAOI), or other AD were identified using MarketScan® databases. These databases contain information on diagnoses, billing codes, and dates of service. Adherence (proportion of days covered) and persistence (days until a 30-day gap in therapy) were calculated to AD medication, AD therapeutic class, and AD therapy overall over the first 3, 6, 9, and 12 months from the index prescription date. Multivariable logistic regression estimated the adjusted odds ratios (ORs) of adherence to initial AD medication comparing AD therapeutic classes.ResultsFor 527,907 patients, adherence to initial AD medication decreased over 3, 6, 9, and 12 months (41, 31, 24, and 21%, respectively). Similar patterns were observed for adherence to initial AD therapeutic class, AD therapy overall, and all three persistence calculations. The odds of adherence to SNRIs versus SSRIs were 20–27% greater at 3, 6, 9, and 12 months (ORs 1.20, 1.23, 1.25, 1.27, respectively; p-values all <0.0001). Similar or significantly lower odds of adherence were demonstrated for other classes versus SSRIs at 3, 6, 9, and 12 months [ORs for other ADs 0.80, 0.77, 0.74, 0.72, respectively (p-values all <0.0001); ORs for TCAs 0.46, 0.45, 0.47, 0.49, respectively (p-values all <0.0001); ORs for MAOIs 1.13, 1.0, 0.77, 0.69, respectively (p-values all >0.05)].ConclusionWe found low adherence and persistence to ADs in the MDD population. Within the limitations of the insurance claims data we analysed, our results suggest that adherence may differ based on therapeutic class, as patients initiating SNRI therapy appeared to have a higher likelihood of adherence versus SSRIs over the year assessed, while the odds of adherence appeared similar or lower for other classes versus SSRIs. Further prospective research is needed to confirm these findings and determine additional drivers of these apparent differences by AD therapeutic class.Electronic supplementary materialThe online version of this article (doi:10.1007/s40263-017-0417-0) contains supplementary material, which is available to authorized users.