Venetoclax pharmacokinetics in participants with end-stage renal disease undergoing haemodialysis.

AIMS: Renal insufficiency is a common comorbidity in patients with haematological malignancies. This study aimed to assess how end-stage renal disease (ESRD) might affect the pharmacokinetics of venetoclax, a Bcl-2 inhibitor, in participants with ESRD undergoing haemodialysis. METHODS: Venetoclax was administered as a single 100-mg dose to 6 female participants with ESRD (estimated glomerular filtration rate <15 mL/min) both prior to haemodialysis and between haemodialysis days and 7 healthy female participants with normal renal function (estimated glomerular filtration rate >90 mL/min). Intensive pharmacokinetic and protein binding samples were collected from all participants. Arterial and venous samples were collected from ESRD participants during haemodialysis to assess the effect of haemodialysis on venetoclax pharmacokinetics. Pharmacokinetic parameters were estimated using noncompartmental methods. RESULTS: There was no difference in plasma venetoclax concentrations between arterial and venous samples, suggesting that haemodialysis did not affect the pharmacokinetics of venetoclax. The fraction unbound (fu ) of venetoclax was ~2-fold higher for participants with ESRD compared to participants with normal renal function. The unbound maximum plasma concentration and area under the plasma concentration-time curve from time 0 to 48 h were comparable between ESRD and normal function groups. The mean half-life ranged from 10.4 to 12.2 h across groups, demonstrating that ESRD did not affect the half-life of venetoclax. No new safety signals were observed during this study. CONCLUSION: ESRD and dialysis do not alter unbound venetoclax plasma concentrations. No pharmacokinetics driven dose adjustment is needed for patients with renal insufficiency.

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.

Translation of In Vitro Transport Inhibition Studies to Clinical Drug-Drug Interactions for Glecaprevir and Pibrentasvir.

Glecaprevir and pibrentasvir are oral direct-acting antiviral agents approved in combination for treatment of chronic hepatitis C viral infection. In vitro studies identified the combination as potentially clinically relevant inhibitors of the efflux transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and the hepatic uptake transporters organic anion transporting polypeptide (OATP) 1B1 and OATP1B3. Glecaprevir inhibited P-gp, BCRP, OATP1B1, and OATP1B3 with IC50 values of 0.33, 2.3, 0.017, and 0.064 µM, respectively. Pibrentasvir inhibited P-gp, BCRP, and OATP1B1 with IC50 values of 0.036, 14, and 1.3 µM, respectively. Neither agent inhibited organic cation transporter (OCT) 1, OCT2, organic anion transporter (OAT) 1, OAT3, multidrug and toxin extrusion (MATE) 1, or MATE2K. Open-label phase 1 clinical drug-drug interaction studies were conducted in healthy subjects to evaluate interaction potential of glecaprevir/pibrentasvir and coadministered selective substrates for P-gp (digoxin, dabigatran etexilate, and sofosbuvir), BCRP (rosuvastatin and sofosbuvir), and OATP1B1/3 (pravastatin and rosuvastatin). The pharmacokinetic maximum plasma concentration (C max) and area under the concentration-time curve (AUC) parameters were evaluated for probe substrates alone and in combination with glecaprevir/pibrentasvir. The C max central values increased by 72%, 105%, 123%, 462%, and 66% for digoxin, dabigatran, pravastatin, rosuvastatin, and sofosbuvir, respectively, and the AUC central values increased by 48%, 138%, 130%, 115%, and 125% for digoxin, dabigatran, pravastatin, rosuvastatin, and sofosbuvir, respectively. Exposure of sofosbuvir metabolite GS-331007 (nucleoside analog) was similar with or without glecaprevir/pibrentasvir. The outcomes of the clinical drug-drug interaction studies confirmed clinically relevant inhibition of P-gp, BCRP, and OATP1B1/3, and were used to provide dosing guidance for the concomitant use of glecaprevir/pibrentasvir with relevant transporter substrates.

UCT943, a Next-Generation Plasmodium falciparum PI4K Inhibitor Preclinical Candidate for the Treatment of Malaria.

The 2-aminopyridine MMV048 was the first drug candidate inhibiting Plasmodium phosphatidylinositol 4-kinase (PI4K), a novel drug target for malaria, to enter clinical development. In an effort to identify the next generation of PI4K inhibitors, the series was optimized to improve properties such as solubility and antiplasmodial potency across the parasite life cycle, leading to the 2-aminopyrazine UCT943. The compound displayed higher asexual blood stage, transmission-blocking, and liver stage activities than MMV048 and was more potent against resistant Plasmodium falciparum and Plasmodium vivax clinical isolates. Excellent in vitro antiplasmodial activity translated into high efficacy in Plasmodium berghei and humanized P. falciparum NOD-scid IL-2Rγ null mouse models. The high passive permeability and high aqueous solubility of UCT943, combined with low to moderate in vivo intrinsic clearance, resulted in sustained exposure and high bioavailability in preclinical species. In addition, the predicted human dose for a curative single administration using monkey and dog pharmacokinetics was low, ranging from 50 to 80 mg. As a next-generation Plasmodium PI4K inhibitor, UCT943, based on the combined preclinical data, has the potential to form part of a single-exposure radical cure and prophylaxis (SERCaP) to treat, prevent, and block the transmission of malaria.

Metabolism and Disposition of the Hepatitis C Protease Inhibitor Paritaprevir in Humans.

Paritaprevir (also known as ABT-450), a potent NS3-4A serine protease inhibitor [identified by AbbVie (North Chicago, IL) and Enanta Pharmaceuticals (Watertown, MA)] of the hepatitis C virus (HCV), has been developed in combination with ombitasvir and dasabuvir in a three-direct-acting antiviral agent (DAA) oral regimen for the treatment of patients infected with HCV genotype 1. This article describes the mass balance, metabolism, and disposition of paritaprevir in humans. After the administration of a single 200-mg oral dose of [(14)C]paritaprevir coadministered with 100 mg of ritonavir to four male healthy volunteers, the mean total percentage of the administered radioactive dose recovered was 96.5%, with recovery in individual subjects ranging from 96.0% to 96.9%. Radioactivity derived from [(14)C]paritaprevir was primarily eliminated in feces (87.8% of the dose). Radioactivity recovered in urine accounted for 8.8% of the dose. The biotransformation of paritaprevir in humans involves: 1) P450-mediated oxidation on the olefinic linker, the phenanthridine group, the methylpyrazinyl group, or combinations thereof; and 2) amide hydrolysis at the acyl cyclopropane-sulfonamide moiety and the pyrazine-2-carboxamide moiety. Paritaprevir was the major component in plasma [90.1% of total radioactivity in plasma, AUC from time 0 to 12 hours (AUC0-12hours) pool]. Five minor metabolites were identified in plasma, including the metabolites M2, M29, M3, M13, and M6; none of the metabolites accounted for greater than 10% of the total radioactivity. Paritaprevir was primarily eliminated through the biliary-fecal route followed by microflora-mediated sulfonamide hydrolysis to M29 as a major component in feces (approximately 60% of dose). In summary, the biotransformation and clearance pathways of paritaprevir were characterized, and the structures of metabolites in circulation and excreta were elucidated.

Metabolism and Disposition of Hepatitis C Polymerase Inhibitor Dasabuvir in Humans.

Dasabuvir [also known as ABT-333 or N-(6-(3-(tert-butyl)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-2-methoxyphenyl)naphthalen-2-yl)methanesulfonamide] is a potent non-nucleoside NS protein 5B polymerase inhibitor of the hepatitis C virus (HCV) and is being developed in combination with paritaprevir/ritonavir and ombitasvir in an oral regimen with three direct-acting antivirals for the treatment of patients infected with HCV genotype 1. This article describes the mass balance, metabolism, and disposition of dasabuvir in humans. After administration of a single oral dose of 400-mg [(14)C]dasabuvir (without coadministration of paritaprevir/ritonavir and ombitasvir) to four healthy male volunteers, the mean total percentage of the administered radioactive dose recovered was 96.6%. The recovery from the individual subjects ranged from 90.8% to 103%. Dasabuvir and corresponding metabolites were predominantly eliminated in feces (94.4% of the dose) and minimally through renal excretion (2.2% of the dose). The biotransformation of dasabuvir primarily involves hydroxylation of the tert-butyl group to form active metabolite M1 [N-(6-(5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-3-(1-hydroxy-2-methylpropan-2-yl)-2-methoxyphenyl)naphthalen-2-yl)methanesulfonamide], followed by glucuronidation and sulfation of M1 and subsequent secondary oxidation. Dasabuvir was the major circulating component (58% of total radioactivity) in plasma, followed by metabolite M1 (21%). Other minor metabolites represented < 10% each of total circulating radioactivity. Dasabuvir was cleared mainly through cytochrome P450-mediated oxidation metabolism to M1. M1 and its glucuronide and sulfate conjugates were primarily eliminated in feces. Subsequent oxidation of M1 to the tert-butyl acid, followed by formation of the corresponding glucuronide conjugate, plays a secondary role in elimination. Cytochrome P450 profiling indicated that dasabuvir was mainly metabolized by CYP2C8, followed by CYP3A4. In summary, the biotransformation pathway and clearance routes of dasabuvir were characterized, and the structures of metabolites in circulation and excreta were elucidated.

Metabolite profiling of foslevodopa/foscarbidopa in plasma of healthy human participants by LC-HRMS indicates no major differences compared to administration of levodopa/carbidopa intestinal gel.

Analysis was conducted to compare levodopa/carbidopa pharmacokinetics and drug-related material in plasma of healthy participants after receiving a continuous infusion of Levodopa/Carbidopa Intestinal Gel (LCIG) to a continuous subcutaneous infusion of foslevodopa/foscarbidopa. Study samples were from a randomized, open-label, 2-period crossover study in 20 healthy participants. Participants received either 24-h foslevodopa/foscarbidopa SC infusion to the abdomen or LCIG delivered for 24 h to the jejunum through a nasogastric tube with jejunal extension. Serial blood samples were collected for PK. Comparability of the LD PK parameters between the two treatment regimens was determined. Selected plasma samples were pooled per treatment group and per time point for metabolite profiling. LC-MSn was performed using high-resolution mass spectrometry to identify drug-related material across the dosing regimens and time points. The LD PK parameter central values and 90% confidence intervals following the foslevodopa/foscarbidopa subcutaneous infusion were between 0.8 and 1.25 relative to the LCIG infusion. With LCIG administration, LD, CD, 3-OMD, DHPA, DOPAC, and vanillacetic acid were identified in plasma at early and late time points (0.75 and 24 h); the metabolic profile after administration of foslevodopa/foscarbidopa demonstrated the same drug-related compounds with the exception of the administered foslevodopa. 3-OMD and vanillacetic acid levels increased over time in both treatment regimens. Relative quantification of LC-MS peak areas showed no major differences in the metabolite profiles. These results indicate that neither the addition of monophosphate prodrug moieties nor SC administration affects the circulating metabolite profile of foslevodopa/foscarbidopa compared to LCIG.

Discovery of pyrido[2,3-d]pyrimidine-based inhibitors of HCV NS5A.

Efforts to improve the genotype 1a potency and pharmacokinetics of earlier naphthyridine-based HCV NS5A inhibitors resulted in the discovery of a novel series of pyrido[2,3-d]pyrimidine compounds, which displayed potent inhibition of HCV genotypes 1a and 1b in the replicon assay. SAR in this system revealed that the introduction of amides bearing an additional 'E' ring provided compounds with improved potency and pharmacokinetics. Introduction of a chiral center on the amide portion resulted in the observation of a stereochemical dependence for replicon potency and provided a site for the attachment of functional groups useful for improving the solubility of the series. Compound 21 was selected for administration in an HCV-infected chimpanzee. Observation of a robust viral load decline provided positive proof of concept for inhibition of HCV replication in vivo for the compound series.

High potency improvements to weak aryl uracil HCV polymerase inhibitor leads.

Described herein is the development of a potent non-nucleoside, small molecule inhibitor of genotype 1 HCV NS5B Polymerase. A 23 µM inhibitor that was active against HCV polymerase was further elaborated into a potent single-digit nanomolar inhibitor of HCV NS5B polymerase by additional manipulation of the R and R1 substituents. Subsequent modifications to improve physical properties were made in an attempt to achieve an acceptable pharmacokinetic profile.

Synthesis and SAR of 4-aminocyclopentapyrrolidines as orally active N-type calcium channel inhibitors for inflammatory and neuropathic pain.

A novel series of N-type calcium channel inhibitors have been discovered. Optimization of potency and HT-ADME properties provides 4-aminocyclopentapyrrolidines with analgesic efficacy after oral dosing.

Species-dependent metabolism of a novel selective α7 neuronal acetylcholine receptor agonist ABT-107.

Metabolism of ABT-107 was investigated in in vitro hepatic systems, in rat and monkey receiving [¹4C]ABT-107, and in vivo plasma in rat, dog, monkey and human. In in vitro hepatic systems, ABT-107 was primarily cleared via oxidative metabolism, and proceeded via two parallel pathways. Pathway 1, ABT-107 was oxidized at the nitrogen of quinuclidine moiety to form M1. Pathway 2, oxidation occurred at indole-containing moiety to form M2. Metabolism via N-oxidation was predominant in dog and rat, while in monkey and human, metabolism proceeded primarily via oxidation of indole-containing moiety. ABT-107 was extensively metabolized in vivo in rat and monkey. M1 was primarily found in rat urine and bile; whereas, M2 was the major metabolite in monkey urine and feces. M1 was the predominant circulating metabolite in dog and rat. M2 was the primary circulating metabolite in monkey and human. Enzymatic studies suggested M1 formation was primarily mediated by renal FMO1. CYP3A4, 1A2, 2J2 and 2D6 were primary enzymes catalyzing M2 formation. Biotransformation of ABT-107 in human and monkey is markedly different from that in dog and rat, suggesting that monkey is an appropriate model for predicting human biotransformation and toxicology of ABT-107.

A Phase-I pharmacokinetic, safety and food-effect study on flubentylosin, a novel analog of Tylosin-A having potent anti-Wolbachia and antifilarial activity.

BACKGROUND: The parasitic filariae responsible for onchocerciasis and lymphatic filariasis are host to an endosymbiotic bacterium, Wolbachia, which is essential to the fertility and development of the parasites. We performed a Phase-I pharmacokinetic, safety and food-effect study on single and multiple ascending doses of flubentylosin (ABBV-4083), a macrolide antibacterial with activity against Wolbachia, intended to sterilize and eliminate the parasites. METHODS: Seventy-eight healthy adults were exposed to flubentylosin; 36 were exposed to single ascending 40, 100, 200, 400 or 1000 mg doses; 12 received 1000 mg in the food-effect part; and 30 received multiple ascending daily doses of 100 mg for 7 days, 200 mg for 7 or 14 days, or 400 mg for 7 or 14 days. Twenty-two subjects received placebo. RESULTS: Maximum concentrations (Cmax) of flubentylosin were reached after 1-2 hours, with a half-life < 4 hours at doses ≤ 400 mg. Cmax and AUC increased in a more than dose-proportional manner, with similar exposure after multiple dose administration. The most frequently reported adverse events were nausea (8/78, 10%) and headache (6/78, 8%). Two subjects given a single dose of flubentylosin 1000 mg in the food-effect part experienced reversible asymptomatic ALT and AST elevations at Grade 2 or Grade 4, with no elevation in bilirubin, deemed related to study drug. The effect of food on exposure parameters was minimal. No treatment-related serious adverse events were reported. DISCUSSION: Flubentylosin 400 mg for 14 days was the maximum tolerated dose in this first-in-human, Phase-I study in healthy adults. Based on preclinical pharmacokinetic/pharmacodynamic modeling, flubentylosin 400 mg once daily for 7 or 14 days is expected to be an effective dose. A Phase-II, proof-of-concept study with flubentylosin using these regimens is currently ongoing in patients with onchocerciasis in Africa.

Pharmacological properties and procognitive effects of ABT-288, a potent and selective histamine H3 receptor antagonist.

Blockade of the histamine H(3) receptor (H(3)R) enhances central neurotransmitter release, making it an attractive target for the treatment of cognitive disorders. Here, we present in vitro and in vivo pharmacological profiles for the H(3)R antagonist 2-[4'-((3aR,6aR)-5-methyl-hexahydro-pyrrolo[3,4-b]pyrrol-1-yl)-biphenyl-4-yl]-2H-pyridazin-3-one (ABT-288). ABT-288 is a competitive antagonist with high affinity and selectivity for human and rat H(3)Rs (K(i) = 1.9 and 8.2 nM, respectively) that enhances the release of acetylcholine and dopamine in rat prefrontal cortex. In rat behavioral tests, ABT-288 improved acquisition of a five-trial inhibitory avoidance test in rat pups (0.001-0.03 mg/kg), social recognition memory in adult rats (0.03-0.1 mg/kg), and spatial learning and reference memory in a rat water maze test (0.1-1.0 mg/kg). ABT-288 attenuated methamphetamine-induced hyperactivity in mice. In vivo rat brain H(3)R occupancy of ABT-288 was assessed in relation to rodent doses and exposure levels in behavioral tests. ABT-288 demonstrated a number of other favorable attributes, including good pharmacokinetics and oral bioavailability of 37 to 66%, with a wide central nervous system and cardiovascular safety margin. Thus, ABT-288 is a selective H(3)R antagonist with broad procognitive efficacy in rodents and excellent drug-like properties that support its advancement to the clinical area.

Discovery of diphenyl lactam derivatives as N-type calcium channel blockers.

A novel series of diphenyl lactam containing calcium channel blockers is described. Extensive SAR studies resulted in compounds with low molar activity and good plasma exposure after oral dosing. Compounds 2, 6 and 7 demonstrated significant efficacy in the capsaicin model of secondary hyperalgesia following oral administration.

Synthesis and SAR of 4-aminocyclopentapyrrolidines as N-type Ca²âº channel blockers with analgesic activity.

A novel 4-aminocyclopentapyrrolidine series of N-type Ca(2+) channel blockers have been discovered. Enantioselective synthesis of the 4-aminocyclopentapyrrolidines was enabled using N-tert-butyl sulfinamide chemistry. SAR studies demonstrate selectivity over L-type Ca(2+) channels. N-type Ca(2+) channel blockade was confirmed using electrophysiological recording techniques. Compound 25 is an N-type Ca(2+) channel blocker that produces antinociception in inflammatory and nociceptive pain models without exhibiting cardiovascular or motor liabilities.

Identification and characterization of a small molecule AMPK activator that treats key components of type 2 diabetes and the metabolic syndrome.

AMP-activated protein kinase (AMPK) is a key sensor and regulator of intracellular and whole-body energy metabolism. We have identified a thienopyridone family of AMPK activators. A-769662 directly stimulated partially purified rat liver AMPK (EC50 = 0.8 microM) and inhibited fatty acid synthesis in primary rat hepatocytes (IC50 = 3.2 microM). Short-term treatment of normal Sprague Dawley rats with A-769662 decreased liver malonyl CoA levels and the respiratory exchange ratio, VCO2/VO2, indicating an increased rate of whole-body fatty acid oxidation. Treatment of ob/ob mice with 30 mg/kg b.i.d. A-769662 decreased hepatic expression of PEPCK, G6Pase, and FAS, lowered plasma glucose by 40%, reduced body weight gain and significantly decreased both plasma and liver triglyceride levels. These results demonstrate that small molecule-mediated activation of AMPK in vivo is feasible and represents a promising approach for the treatment of type 2 diabetes and the metabolic syndrome.

Pharmacokinetic modeling and [¹²³]5-IA-85380 single photon emission computed tomography imaging in baboons: optimization of dosing regimen for ABT-089.

Neuronal acetylcholine nicotinic receptors (nAChRs) are targets for the development of novel treatments of brain diseases. However, adverse effects (for example, emesis or nausea) associated with high drug maximal exposures or C(max) at nAChRs often hinder the advancement of experimental compounds in clinical trials. Therefore, it is essential to explore the feasibility of maintaining exposures below a predetermined C(max) while sustaining targeted CNS effects. By use of a [¹²³I]5-IA [5-[¹²³I]iodo-3-[2(S)-azetidinylmethoxy]pyridine] displacement SPECT imaging paradigm in nonhuman primates, we compared brain nAChR binding activity elicited by either a bolus injection or by slow infusion of an identical dose of a novel neuronal nicotinic agonist, ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride], where the slow infusion scheme was derived from a two-compartment pharmacokinetic modeling designed to limit the C(max). We determined [¹²³I]5-IA displacement using doses of ABT-089 (0.04, 0.4, and 1.0 mg/kg i.v.) that encompassed efficacious drug exposures in nonhuman primates and examined the relationship between ABT-089 displacement ratios and plasma exposures. Our results indicated that calculated displacement ratios were quite similar between the two different dosing regimens despite substantial differences in C(max). In addition, displacement ratios correlated well with drug exposures calculated as the area-under-curve (AUC) of plasma concentration and varied in a dose-dependent manner, suggesting that displacement ratios are driven by the AUC of drug plasma exposure but not C(max). Our data demonstrate the feasibility of predicting plasma exposures using a two-compartment pharmacokinetic model and its potential for optimizing dosing regimens.

Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.

Novel chroman and tetrahydroquinoline ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that aryl substituents on the 7- or 8-position of both bicyclic scaffolds imparted the best in vitro potency at TRPV1. The most potent chroman ureas were assessed in chronic and acute pain models, and compounds with the ability to cross the blood-brain barrier were shown to be highly efficacious. The tetrahydroquinoline ureas were found to be potent CYP3A4 inhibitors, but replacement of bulky substituents at the nitrogen atom of the tetrahydroisoquinoline moiety with small groups such as methyl can minimize the inhibition.

Pyrrolopyrimidine Bumped Kinase Inhibitors for the Treatment of Cryptosporidiosis.

Bumped kinase inhibitors (BKIs) that target Cryptosporidium parvum calcium-dependent protein kinase 1 have been well established as potential drug candidates against cryptosporidiosis. Recently, BKI-1649, with a 7H-pyrrolo[2,3-d]pyrimidin-4-amine, or "pyrrolopyrimidine", central scaffold, has shown improved efficacy in mouse models of Cryptosporidium at substantially reduced doses compared to previously explored analogs of the pyrazolopyrimidine scaffold. Here, two pyrrolopyrimidines with varied substituent groups, BKI-1812 and BKI-1814, were explored in several in vitro and in vivo models and show improvements in potency over the previously utilized pyrazolopyrimidine bumped kinase inhibitors while maintaining equivalent results in other key properties, such as toxicity and efficacy, with their pyrazolopyrimidine isosteric counterparts.