Comparison of Toxicities among Different Bumped Kinase Inhibitor Analogs for Treatment of Cryptosporidiosis

Recent advances on the development of bumped kinase inhibitors for treatment of cryptosporidiosis have focused on the 5-aminopyrazole-4-carboxamide scaffold, due to analogs that have less hERG inhibition, superior efficacy, and strong in vitro safety profiles. Three compounds, BKI-1770, -1841, and -1708, showed strong efficacy in C. parvum infected mice. Both BKI-1770 and BKI-1841 had efficacy in the C. parvum newborn calf model, reducing diarrhea and oocyst excretion. However, both compounds caused hyperflexion of the limbs seen as dropped pasterns. Toxicity experiments in rats and calves dosed with BKI-1770 showed enlargement of the epiphyseal growth plate at doses only slightly higher than the efficacious dose. Mice were used as a screen to check for bone toxicity, by changes to the tibia epiphyseal growth plate, or neurological causes, by use of a locomotor activity box. These results showed neurological effects from both BKI-1770 and BKI-1841 and bone toxicity in mice from BKI-1770, indicating one or both effects may be contributing to toxicity. However, BKI-1708 remains a viable treatment candidate for further evaluation as it showed no signs of bone toxicity or neurological effects in mice.

Disconnect between COX-2 selective inhibition and cardiovascular risk in preclinical models

INTRODUCTION

Secondary pharmacology profiling is routinely applied in pharmaceutical drug discovery to investigate the pharmaceutical effects of a drug at molecular targets distinct from (off-target) the intended therapeutic molecular target (on-target). Data from a randomized, placebo-controlled clinical trial, the APPROVe (Adenomatous Polyp Prevention on VIOXX, rofecoxib) trial, raised significant concerns about COX-2 inhibition as a primary or secondary target, shaping the screening and decision-making processes of some pharmaceutical companies. COX-2 is often included in off-target screens due to cardiovascular (CV) safety concerns about secondary interactions with this target. Several potential mechanisms of COX-2-mediated myocardial infarctions have been considered including, effects on platelet stickiness/aggregation, vasal tone and blood pressure, and endothelial cell activation. In the present study, we focused on each of these mechanisms as potential effects of COX-2 inhibitors, to find evidence of mechanism using various in vitro and in vivo preclinical models.

METHODS

Compounds tested in the study, with a range of COX-2 selectivity, included rofecoxib, celecoxib, etodolac, and meloxicam. Compounds were screened for inhibition of COX-2 vs COX-1 enzymatic activity, ex vivo platelet aggregation (using whole blood from multiple species), ex vivo canine femoral vascular ring model, in vitro human endothelial cell activation (with and without COX-2 induction), and in vivo cardiovascular assessment (anesthetized dog).

RESULTS

The COX-2 binding assessment generally confirmed the COX-2 selectivity previously reported. COX-2 inhibitors did not have effects on platelet function (spontaneous aggregation or inhibition of aggregation), cardiovascular parameters (mean arterial pressure, heart rate, and left ventricular contractility), or endothelial cell activation. However, rofecoxib uniquely produced an endothelial mediated constriction response in canine femoral arteries.

CONCLUSION

Our data suggest that rofecoxib-related cardiovascular events in humans are not predicted by COX-2 potency or selectivity. In addition, the vascular ring model suggested possible adverse cardiovascular effects by COX-2 inhibitors, although these effects were not seen in vivo studies. These results may also suggest that COX-2 inhibition alone is not responsible for rofecoxib-mediated adverse cardiovascular outcomes.

Tumor necrosis factor receptor superfamily members 1a and 1b contribute to exacerbation of atherosclerosis by Chlamydia pneumoniae in mice

The host immune responses that mediate Chlamydia-induced chronic disease sequelae are incompletely understood. The role of TNF-α, TNF receptor 1 (TNFR1), and TNF receptor 2 (TNFR2), in Chlamydia pneumoniae (CPN)-induced atherosclerosis was studied using the high-fat diet-fed male C57BL/6J mouse model. Following intranasal CPN infection, TNF-α knockout (KO), TNFR1 KO, TNFR2 KO, and TNFR 1/2 double-knockout, displayed comparable serum anti-chlamydial antibody response, splenic antigen-specific cytokine response, and serum cholesterol profiles compared to wild type (WT) animals. However, atherosclerotic pathology in each CPN-infected KO mouse group was reduced significantly compared to WT mice, suggesting that both TNFR1 and TNFR2 promote CPN-induced atherosclerosis.

TNF Receptor 2 on CD8+ T cells and TNF receptor 1 on non-CD8+ T cells Contribute Significantly to Chlamydia pneumoniae-Induced Atherosclerosis

Chlamydia pneumoniae is an important cause of community-acquired pneumonia and has been associated with exacerbation of atherosclerosis. A role of TNF-α in Chlamydia pneumoniae (Cpn) induced atherosclerosis has been reported previously; however, the relative contribution of the two cognate receptors of TNF-α, TNF receptor 1 (TNFR1) and TNFR2 had not been studied. In the current study, C57BL/6J (WT) mice, TNFR1, TNFR2 and TNFR1/2 DKO mice were infected intranasally on days 0, 14 and 28 with 1 × 107 IFU of Cpn (AR39) and were fed a high fat (HF) diet throughout the experiment. One group of WT mice were mock infected with PBS as a control. All Cpn-infected KO mice displayed serum anti-Cpn antibody response, splenic cellular Cpn-specific IFN-γ and TNF-α response, and serum total cholesterol levels comparable to infected WT animals. On day 100 following infection, Cpn infected TNFR1, TNFR2 and TNFR1/2 DKO mice displayed significantly reduced atherosclerotic pathology compared to infected WT mice, and at levels comparable to mock-infected WT animals., suggesting that TNFR1 and TNFR2 play a significant role in Cpn-induced atherosclerosis. We demonstrated recently that CD8+ T cells induce Cpn-mediated atherosclerosis; therefore, we further investigated the role of TNFR1 and TNFR2 on CD8+ T cells in pathogenesis. TNFR2 KO mice, not TNFR1 KO mice, replete with WT CD8+ T cells displayed enhancement of atherosclerotic pathology to levels observed in Cpn-infected WT animals. Collectively, these results demonstrate that TNFR2 on CD8+ T cells and TNFR1 on non-CD8+ T cells contribute significantly to Chlamydia pneumoniae induced atherosclerosis.

CD8+ T cells mediate Chlamydia pneumoniae-induced atherosclerosis in mice

Chlamydia pneumoniae is a community-acquired bacterial pathogen that has been strongly associated with exacerbation of atherosclerosis. We evaluated the role of CD8(+) T cells in the C57BL/6J mouse model of C. pneumoniae-induced atherosclerosis. Groups of 4- to 6-week-old male wild-type C57BL/6J (WT) mice and mice with a gene deficiency in CD8α (CD8 KO mice) were infected with C. pneumoniae and fed a high fat (HF) diet. Serum antibody response and serum cholesterol were comparable between infected CD8 KO and WT mice. However, infected CD8 KO mice displayed significantly reduced atherosclerotic plaque lesions on day 100 compared to infected WT mice, at a level comparable to both uninfected WT and CD8 KO mice fed the HF diet. Moreover, repletion of CD8 KO mice with WT CD8(+) T cells (1 × 10(7) cells/mouse intravenously) at the time of infection reverted atherosclerotic plaque lesions to WT levels. These results demonstrate that CD8(+) T cells play an important role in mediating C. pneumoniae-induced exacerbation of atherosclerotic pathology.

Intranasal vaccination with Chlamydia pneumoniae induces cross-species immunity against genital Chlamydia muridarum challenge in mice

Chlamydia trachomatis is the most common bacterial sexually transmitted disease in the world and specifically in the United States, with the highest incidence in age-groups 14-19 years. In a subset of females, the C. trachomatis genital infection leads to serious pathological sequelae including pelvic inflammatory disease, ectopic pregnancy, and infertility. Chlamydia pneumoniae, another member of the same genus, is a common cause of community acquired respiratory infection with significant number of children aged 5-14 yr displaying sero-conversion. Since these bacteriae share several antigenic determinants, we evaluated whether intranasal immunization with live C. pneumoniae (1×10(6) inclusion forming units; IFU) in 5 week old female C57BL/6 mice would induce cross-species protection against subsequent intravaginal challenge with Chlamydia muridarum (5×10(4) IFU), which causes a similar genital infection and pathology in mice as C. trachomatis in humans. Mice vaccinated intranasally with live C. pneumoniae, but not mock (PBS) immunized animals, displayed high levels of splenic cellular antigen-specific IFN-γ production and serum antibody response against C. muridarum and C. trachomatis. Mice vaccinated with C. pneumoniae displayed a significant reduction in the vaginal C. muridarum shedding as early as day 12 after secondary i.vag. challenge compared to PBS (mock) immunized mice. At day 19 after C. muridarum challenge, 100% of C. pneumoniae vaccinated mice had cleared the infection compared to none (0%) of the mock immunized mice, which cleared the infection by day 27. At day 80 after C. muridarum challenge, C. pneumoniae vaccinated mice displayed a significant reduction in the incidence (50%) and degree of hydrosalpinx compared to mock immunized animals (100%). These results suggest that respiratory C. pneumoniae infection induces accelerated chlamydial clearance and reduction of oviduct pathology following genital C. muridarum challenge, and may have important implications to the C. trachomatis-induced reproductive disease in humans.