Novel irreversible peptidic inhibitors of transglutaminase 2.

Transglutaminase 2 (TG2), also referred to as tissue transglutaminase, plays crucial roles in both protein crosslinking and cell signalling. It is capable of both catalysing transamidation and acting as a G-protein, these activities being conformation-dependent, mutually exclusive, and tightly regulated. The dysregulation of both activities has been implicated in numerous pathologies. TG2 is expressed ubiquitously in humans and is localized both intracellularly and extracellularly. Targeted TG2 therapies have been developed but have faced numerous hurdles including decreased efficacy in vivo. Our latest efforts in inhibitor optimization involve the modification of a previous lead compound's scaffold by insertion of various amino acid residues into the peptidomimetic backbone, and derivatization of the N-terminus with substituted phenylacetic acids, resulting in 28 novel irreversible inhibitors. These inhibitors were evaluated for their ability to inhibit TG2 in vitro and their pharmacokinetic properties, and the most promising candidate 35 (k inact/K I = 760 × 103 M-1 min-1) was tested in a cancer stem cell model. Although these inhibitors display exceptional potency versus TG2, with k inact/K I ratios nearly ten-fold higher than their parent compound, their pharmacokinetic properties and cellular activity limit their therapeutic potential. However, they do serve as a scaffold for the development of potent research tools.

Selective Copper Complex-Catalyzed Hydrodefluorination of Fluoroalkenes and Allyl Fluorides: A Tale of Two Mechanisms.

The transition to more economically friendly small-chain fluorinated groups is leading to a resurgence in the synthesis and reactivity of fluoroalkenes. One versatile method to obtain a variety of commercially relevant hydrofluoroalkenes involves the catalytic hydrodefluorination (HDF) of fluoroalkenes using silanes. In this work it is shown that copper hydride complexes of tertiary phosphorus ligands (L) can be tuned to achieve selective multiple HDF of fluoroalkenes. In one example, HDF of the hexafluoropropene dimer affords a single isomer of heptafluoro-2-methylpentene in which five fluorines have been selectively replaced with hydrogens. DFT computational studies suggest a distinct HDF mechanisms for L2CuH (bidentate or bulky monodentate phosphines) and L3CuH (small cone angle monodentate phosphines) catalysts, allowing for stereocontrol of the HDF of trifluoroethylene.

A systematic comparison of cockcroft-gault and modification of diet in renal disease equations for classification of kidney dysfunction and dosage adjustment.

BACKGROUND: The dosing of drugs in patients with kidney dysfunction is often based on the estimates of kidney function. OBJECTIVE: To systematically compare the performance of the Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault (CG) equations for dosage adjustment. METHODS: We assessed agreement (concordance, kappa statistics [κ,κ(ω)]) between CG and MDRD using a Food and Drug Administration database to evaluate the effect of renal function on the pharmacokinetics of 36 approved drugs. Across the approved drugs, we compared the correlation between these 2 equations for renal drug clearance (Cl(ren)) and area under the concentration-time curve. For 26 approved drugs that require renal dose adjustment, we also compared dosing regimens and expected exposure using these equations. Sensitivity analyses were performed by adjusting the MDRD estimates for individualized body surface area and/or range of serum creatinine assay calibration errors. RESULTS: In the pharmacokinetic database with 973 subjects (age 18-95 years, weight 35-153 kg, female 33%), we found that the CG and the MDRD classification of renal function generally agreed (64.2%, κ = 0.54, κ(ω) = 0.73). Among the subjects studied for drugs requiring renal dose adjustment, dosages in 12% were changed to a higher or lower dosing category by the MDRD compared to the CG equation. In particular, using MDRD in place of CG for dosage modification yielded higher dosing recommendations for subjects with a combination of age >80 years, weight <55 kg, and serum creatinine >0.7 and ≤1.5 mg/dL; the coefficient of determination was also higher by CG than MDRD in trials that enrolled these or similar patients. CONCLUSIONS: For patients with advanced age, low weight, and modestly elevated serum creatinine, further work is needed before the MDRD equations can replace the CG equation for dose adjustment in the labeling.

The influence of body size descriptors on the estimation of kidney function in normal weight, overweight, obese, and morbidly obese adults.

BACKGROUND: Dosing adjustments for patients with impaired kidney function are often based on estimated creatinine clearance (eCrCl) because measuring kidney function is not always possible for dose adjustment. However, there is no consensus on the body size descriptor that should be used in the estimation equations. OBJECTIVE: To compare the use of alternative body size descriptors (ABSDs) on the performance of kidney function estimation equations compared with measured CrCl (mCrCl). METHODS: We combined 2 DATA SOURCES: a Food and Drug Administration clinical trial database that includes subjects with body mass index (BMI) less than 40 kg/m(2) and published data from those 40 kg/m(2) or more. The 3 parent equations (Cockcroft-Gault [CG], Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease-Epidemiology Collaboration [CKDEPI]), and 14 ABSD-modified equations were compared with mCrCl for accuracy, bias, agreement, goodness of fit (R(2)), and prediction error. These equations were also compared across mCrCl and BMI strata. RESULTS: Subjects (n = 590) were aged 19-80 years; 33.9% were female and BMI ranged from 17.2 to 95.6 kg/m(2). Compared with mCrCl, the use of total weight in the CG equation yielded low accuracy (12.5%) and significant bias (-107 mL/min) in the morbidly obese group. In contrast, the use of lean body weights (BMI ≥40 kg/m(2)) and total ± adjusted weights (BMI <40 kg/m(2)) with the CG equation yielded higher accuracy, greater than or equal to 60.7% across all BMI strata, and was unbiased. Transforming the MDRD or CKDEPI equations with body surface area improved accuracy only at mCrCl of 30-80 mL/min and increased the overall prediction error. CONCLUSIONS: No kidney function equation was consistently accurate and unbiased across weight, mCrCl, and estimate ranges. The accuracy and overestimation bias of the CG equation in obese subjects was improved through the selective use of total, adjusted, and lean body weight by BMI strata.

Regulatory perspectives on designing pharmacokinetic studies and optimizing labeling recommendations for patients with chronic kidney disease.

To optimize drug dosing, it is critical to understand how various intrinsic and extrinsic factors affect systemic exposure of the drug and the response. Chronic kidney disease (or renal impairment) can affect pharmacokinetic characteristics of a therapeutic drug and its metabolites and therefore is one of the most important intrinsic factors that can affect a patient's response to drugs. During drug development, it is critical to understand how renal impairment can affect a drug's pharmacokinetics so that appropriate dosing recommendations can be included in the label. The US Food and Drug Administration (FDA) has published various guidance documents and opinion papers to address scientific and regulatory issues in the study design, data analysis, and labeling recommendations related to dosing in patients with impaired renal function. The 2010 FDA draft guidance on renal impairment provides several updated recommendations that include criteria or principles for evaluating the pharmacokinetics of drugs that are either principally renally cleared or nonrenally cleared in subjects with renal impairment and for categorizing renal function by equations estimating glomerular filtration rate using the Modification of Diet in Renal Disease equations or creatinine clearance using the Cockcroft-Gault equation. The objective of this article is to discuss the FDA's current recommendations and provide examples that illustrate the importance of and challenges in studying effect of renal impairment during drug development.

Renal biomarker qualification submission: a dialog between the FDA-EMEA and Predictive Safety Testing Consortium.

The first formal qualification of safety biomarkers for regulatory decision making marks a milestone in the application of biomarkers to drug development. Following submission of drug toxicity studies and analyses of biomarker performance to the Food and Drug Administration (FDA) and European Medicines Agency (EMEA) by the Predictive Safety Testing Consortium's (PSTC) Nephrotoxicity Working Group, seven renal safety biomarkers have been qualified for limited use in nonclinical and clinical drug development to help guide safety assessments. This was a pilot process, and the experience gained will both facilitate better understanding of how the qualification process will probably evolve and clarify the minimal requirements necessary to evaluate the performance of biomarkers of organ injury within specific contexts.

Renal artery revascularization improves heart failure control in patients with atherosclerotic renal artery stenosis.

BACKGROUND: Renal artery stenosis (RAS) impacts the pathogenesis and control of heart failure (HF) and may further contribute to increased cardiovascular morbidity and mortality in HF patients. However, the long-term effects of renal artery revascularization on cardiovascular outcomes in HF patients are not well studied. METHODS: The prevalence of HF and its effects on all-cause mortality were studied in 163 consecutive patients with systemic hypertension and chronic kidney disease (serum creatinine >2 mg/dL) who underwent percutaneous transluminal renal angioplasty (PTRA) with stenting for atherosclerotic RAS. In addition, in 100 patients with RAS and coexistent HF, we compared the impact of medical treatment (n = 50) versus PTRA (n = 50) on clinical outcomes. RESULTS: HF (predominantly normal ejection fraction) was present in 50/163 (31%) patients with systemic hypertension and chronic kidney disease (serum creatinine >2 mg/ dL) undergoing PTRA for RAS and represented the major predictor of all-cause mortality in these patients. When compared with sex-matched RAS and HF patients treated medically, PTRA with stenting was associated with a significant decrease in the New York Heart Association Functional Class (1.9 +/- 0.8 versus 2.6 +/- 1.0, P < 0.04) and a 5-fold reduction in the number of hospitalizations. However, renal artery revascularization did not impact mortality. CONCLUSION: HF was present in one-third of patients with renal dysfunction and atherosclerotic RAS who were referred for PTRA. The presence of HF was associated with a significantly increased risk of death after PTRA with stenting. Renal artery revascularization resulted in improved HF control and a reduction in HF hospitalizations.

Autosomal dominant polycystic kidney disease coexisting with cystic fibrosis.

Autosomal dominant polycystic kidney disease (ADPKD) is a common, inherited disorder characterized by the progressive enlargement of fluid-filled cysts in the kidneys and liver. Since the cystic fibrosis transmembrane conductance regulator (CFTR) Cl--channel may mediate the secretion of Cl--and fluid into the cysts, it is conceivable that coexisting cystic fibrosis (CF) in patients with ADPKD could attenuate their development. We previously reported that two patients with ADPKD coexisting with cystic fibrosis (CF) had a milder cystic phenotype than that of kindred without CFTR mutations. A subsequent report failed to confirm this protective effect. We now have identified another family with coexisting type 1 ADPKD and CF. The kidney volumes and the number and size of renal and hepatic cysts were markedly less in a member of this family with ADPKD (PKD1 mutation C508R) and CF (homozygous DeltaF508 mutation) than in her sister with ADPKD alone at comparable ages.