Comparative physiology, pharmacology and toxicology of beta-blockers: mammals versus fish.

On the premise that human medicines may potentially induce similar pharmacological and toxicological profiles in fish and other lower vertebrates, we have applied this comparative approach to beta-adrenergic receptor antagonists ('beta-blockers') which are widely detected in surface waters. While reported concentrations of beta-blockers are typically in the low ng/L range, data are needed to define whether this contamination poses any long-term threat to fish or other aquatic organisms. We argue that gathering experimental data in fish for these compounds may be done more efficiently by considering mammalian toxicology data. Extensive mammalian pharmacological and toxicological studies are central to development of medicines and these can provide valuable information to guide ecotoxicological studies. For beta-blockers, we can increasingly exploit the knowledge from molecular approaches to understand phenotypes and functions of adrenergic receptors in mammals versus fish. Some beta-adrenergic receptors have been characterised in fish using both traditional molecular cloning methods, or via mining of genomic sequences from various organisms. These approaches demonstrate that fish have beta-adrenergic receptors very similar to those present in mammals. Since we believe that any effects of beta-blockers in fish are most likely to be mediated via beta-adrenergic receptors, it is the physiological processes regulated by these receptors that are most likely to be affected. Thus, cardiovascular dysfunction is one possible consequence of exposure of fish to these compounds, leading to impaired fitness (e.g. reduced growth and fecundity). More broadly, conceptual mathematical models suggest it might be possible to predict plasma concentrations of beta-blockers in fish from mammals, although these models cannot be regarded as reliable until thoroughly validated. Experimental data are therefore urgently needed to define plasma levels and metabolism of beta-blockers compared in fish with mammals. Finally, accurate citation of CAS numbers is essential for pharmaceuticals in order to compare nominal concentration data in terms of either the drug free base or the drug salt complex.

Complement blockade with a C1 esterase inhibitor in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, clonal, hematopoietic stem cell disorder that manifests with a complement-mediated hemolytic anemia, bone marrow failure, and a propensity for thrombosis. These patients experience both intra- and extravascular hemolysis in the context of underlying complement activation. Currently eculizumab effectively blocks the intravascular hemolysis PNH. There remains an unmet clinical need for a complement inhibitor with activity early in the complement cascade to block complement at the classical and alternative pathways. C1 esterase inhibitor (C1INH) is an endogenous human plasma protein that has broad inhibitory activity in the complement pathway through inhibition of the classical pathway by binding C1r and C1s and inhibits the mannose-binding lectin-associated serine proteases in the lectin pathway. In this study, we show that commercially available plasma derived C1INH prevents lysis induced by the alternative complement pathway of PNH erythrocytes in human serum. Importantly, C1INH was able to block the accumulation of C3 degradation products on CD55 deficient erythrocytes from PNH patient on eculizumab therapy. This could suggest a role for inhibition of earlier phases of the complement cascade than that currently inhibited by eculizumab for incomplete or nonresponders to that therapy.

An acute rat in vivo screening model to predict compounds that alter blood glucose and/or insulin regulation.

INTRODUCTION: Drug-induced glucose dysregulation and insulin resistance have been associated with weight gain and potential induction and/or exacerbation of diabetes mellitus in the clinic suggesting they may be safety biomarkers when developing antipsychotics. Glucose and insulin have also been suggested as potential efficacy biomarkers for some oncology compounds. The objective of this study was to qualify a medium throughput rat in vivo acute Intravenous Glucose Tolerance Test (IVGTT) for predicting compounds that will induce altered blood glucose and/or insulin levels. METHODS: Acute and sub-chronic studies were performed to qualify an acute IVGTT model. Double cannulated male rats (Han-Wistar and Sprague-Dawley) were administered vehicle, olanzapine, aripiprazole or other compounds at t=-44min for acute studies and at time=-44min on the last day of dosing for sub-chronic studies, treated with dextrose (time=0min; i.v.) and blood collected using an automated Culex® system for glucose and insulin analysis (time=-45, -1, 2, 10, 15, 30, 45, 60, 75, 90, 120, 150 and 180min). RESULTS: Olanzapine significantly increased glucose and insulin area under the curve (AUC) values while aripiprazole AUC values were similar to control, in both acute and sub-chronic studies. All atypical antipsychotics evaluated were consistent with literature references of clinical weight gain. As efficacy biomarkers, insulin AUC but not glucose AUC values were increased with a compound known to have insulin growth factor-1 (IGF-1) activity, compared to control treatment. DISCUSSION: These studies qualified the medium throughput acute IVGTT model to more quickly screen compounds for 1) safety - the potential to elicit glucose dysregulation and/or insulin resistance and 2) efficacy - as a surrogate for compounds affecting the glucose and/or insulin regulatory pathways. These data demonstrate that the same in vivo rat model and assays can be used to predict both clinical safety and efficacy of compounds.

Targeting the kidney and glucose excretion with dapagliflozin: preclinical and clinical evidence for SGLT2 inhibition as a new option for treatment of type 2 diabetes mellitus.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are a novel class of glucuretic, antihyperglycemic drugs that target the process of renal glucose reabsorption and induce glucuresis independently of insulin secretion or action. In patients with type 2 diabetes mellitus, SGLT2 inhibitors have been found to consistently reduce measures of hyperglycemia, including hemoglobin A1c, fasting plasma glucose, and postprandial glucose, throughout the continuum of disease. By inducing the renal excretion of glucose and its associated calories, SGLT2 inhibitors reduce weight and have the potential to be disease modifying by addressing the caloric excess that is believed to be one of the root causes of type 2 diabetes mellitus. Additional benefits, including the possibility for combination with insulin-dependent antihyperglycemic drugs, a low potential for hypoglycemia, and the ability to reduce blood pressure, were anticipated from the novel mechanism of action and have been demonstrated in clinical studies. Mechanism-related risks include an increased incidence of urinary tract and genital infections and the possibility of over-diuresis in volume-sensitive patients. Taken together, the results of Phase III clinical studies generally point to a positive benefit-risk ratio across the continuum of diabetes patients. To date, data on dapagliflozin, a selective SGLT2 inhibitor in development, demonstrate that the kidney is an efficacious and safe target for therapy, and that SGLT2 inhibition may have benefits for patients with type 2 diabetes mellitus beyond glycemic control.

Targeting renal glucose reabsorption for the treatment of type 2 diabetes mellitus using the SGLT2 inhibitor dapagliflozin.

Sodium-glucose co-transporter 2 (SGLT2) plays a key role in glucose homeostasis as the key transporter responsible for most renal glucose reabsorption in the proximal tubules of the kidney. Dapagliflozin is a potent, selective, and reversible inhibitor of SGLT2 that lowers blood glucose levels in an insulin-independent fashion. This novel agent has been studied extensively in patients with type 2 diabetes mellitus (T2DM). In these clinical trials, dapagliflozin significantly decreased glycated hemoglobin and fasting plasma glucose levels when administered alone or as add-on treatment in patients who were already receiving metformin, a sulfonylurea (glimepiride), pioglitazone, or insulin. Moreover, dapagliflozin decreased body weight when taken as monotherapy or in combination with metformin, a sulfonylurea, or insulin, and mitigated weight gain in patients receiving pioglitazone. Consistent with preclinical toxicology studies, dapagliflozin has a manageable adverse event profile that is largely predictable from its mechanism of action. While there are no clinically significant negative effects on renal function or electrolytes, dapagliflozin treatment is associated with increased frequencies of urinary tract infections and vulvovaginitis/balanitis. With a mechanism of action that is distinct from and complementary to that of existing antihyperglycemic therapies, dapagliflozin is an effective antihyperglycemic agent that is well tolerated and may enhance weight loss. As such, dapagliflozin promises to become an important adjunctive therapy for comprehensive treatment of T2DM.

Synthesis and structure-activity relationships of 8-(pyrid-3-yl)pyrazolo[1,5-a]-1,3,5-triazines: potent, orally bioavailable corticotropin releasing factor receptor-1 (CRF1) antagonists.

This report describes the syntheses and structure-activity relationships of 8-(substituted pyridyl)pyrazolo[1,5-a]-1,3,5-triazine corticotropin releasing factor receptor-1 (CRF(1)) receptor antagonists. These CRF(1) receptor antagonists may be potential anxiolytic or antidepressant drugs. This research resulted in the discovery of compound 13-15, which is a potent, selective CRF(1) antagonist (hCRF(1) IC(50) = 6.1 +/- 0.6 nM) with weak affinity for the CRF-binding protein and biogenic amine receptors. This compound also has a good pharmacokinetic profile in dogs. Analogue 13-15 is orally effective in two rat models of anxiety: the defensive withdrawal (situational anxiety) model and the elevated plus maze test. Analogue 13-15 has been advanced to clinical trials.