Pharmacokinetics and pharmacodynamics of voxelotor (GBT440) in healthy adults and patients with sickle cell disease.

Aims: Voxelotor (previously GBT440) is a haemoglobin (Hb) modulator that increases Hb-oxygen affinity, thereby reducing Hb polymerization and sickling of red blood cells (RBCs), being developed as a once-daily oral drug to treat sickle cell disease (SCD). This first-in-human study evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of voxelotor in healthy volunteers and SCD patients.

Methods: A total of 40 healthy volunteers (100, 400, 1000, 2000 or 2800 mg) and 8 SCD patients (1000 mg) were randomly assigned to a single dose of voxelotor once daily (n = 6 per group) or placebo (n = 2 per group).

A phase 1/2 ascending dose study and open-label extension study of voxelotor in patients with sickle cell disease.

New treatments directly targeting polymerization of sickle hemoglobin (HbS), the proximate event in the pathophysiology of sickle cell disease (SCD), are needed to address the severe morbidity and early mortality associated with the disease. Voxelotor (GBT440) is a first-in-class oral therapy specifically developed to treat SCD by modulating the affinity of hemoglobin (Hb) for oxygen, thus inhibiting HbS polymerization and downstream adverse effects of hemolytic anemia and vaso-occlusion. GBT440-001 was a phase 1/2 randomized, double-blind, placebo-controlled, single and multiple ascending dose study of voxelotor in adult healthy volunteers and patients with SCD, followed by a single-arm, open-label extension study.

Safety, pharmacokinetics, and reversal of apixaban anticoagulation with andexanet alfa.

Direct factor Xa (FXa) inhibitors lack a specific reversal agent for emergencies such as major bleeding or urgent surgery. Andexanet alfa, a modified, catalytically inactive, recombinant human FXa derivative, reverses anticoagulant effect by binding and sequestering FXa inhibitors. This original report of safety and dose-finding, phase 1 and 2 randomized, double-blind, placebo-controlled studies, investigated various doses of andexanet in healthy volunteers.

Preclinical safety and efficacy of andexanet alfa in animal models.

Essentials There is currently no approved reversal agent for factor Xa (FXa) inhibitors Andexanet alfa has been developed to reverse the anticoagulant effects of FXa inhibitors Andexanet reduced blood loss and anticoagulation markers in rivaroxaban-anticoagulated rabbits Andexanet was well tolerated in monkeys and rats, with no evidence of prothrombotic activity SUMMARY: Background Andexanet alfa is a recombinant modified form of factor Xa (FXa), designed to bind to and reverse the anticoagulant activity of FXa inhibitors. Objectives To evaluate the ability of andexanet to reverse the anticoagulant activity of rivaroxaban, and assess its pharmacokinetics (PK) and toxicity in animal models. Methods The effects of andexanet on blood loss, anti-FXa activity, rivaroxaban unbound plasma concentrations and other coagulation parameters were assessed in a rabbit liver laceration 'treatment' model.

Discovery of GBT440, an Orally Bioavailable R-State Stabilizer of Sickle Cell Hemoglobin.

We report the discovery of a new potent allosteric effector of sickle cell hemoglobin, GBT440 (), that increases the affinity of hemoglobin for oxygen and consequently inhibits its polymerization when subjected to hypoxic conditions. Unlike earlier allosteric activators that bind covalently to hemoglobin in a 2:1 stoichiometry, binds with a 1:1 stoichiometry. Compound is orally bioavailable and partitions highly and favorably into the red blood cell with a RBC/plasma ratio of ∼150.

Increased hemoglobin-oxygen affinity ameliorates bleomycin-induced hypoxemia and pulmonary fibrosis.

Although exertional dyspnea and worsening hypoxia are hallmark clinical features of idiopathic pulmonary fibrosis (IPF), no drug currently available could treat them. GBT1118 is a novel orally bioavailable small molecule that binds to hemoglobin and produces a concentration-dependent left shift of the oxygen-hemoglobin dissociation curve with subsequent increase in hemoglobin-oxygen affinity and arterial oxygen loading. To assess whether pharmacological modification of hemoglobin-oxygen affinity could ameliorate hypoxemia associated with lung fibrosis, we evaluated GBT1118 in a bleomycin-induced mouse model of hypoxemia and fibrosis.

GBT440 increases haemoglobin oxygen affinity, reduces sickling and prolongs RBC half-life in a murine model of sickle cell disease.

A major driver of the pathophysiology of sickle cell disease (SCD) is polymerization of deoxygenated haemoglobin S (HbS), which leads to sickling and destruction of red blood cells (RBCs) and end-organ damage. Pharmacologically increasing the proportion of oxygenated HbS in RBCs may inhibit polymerization, prevent sickling and provide long term disease modification. We report that GBT440, a small molecule which binds to the N-terminal α chain of Hb, increases HbS affinity for oxygen, delays in vitro HbS polymerization and prevents sickling of RBCs.

A specific antidote for reversal of anticoagulation by direct and indirect inhibitors of coagulation factor Xa.

Inhibitors of coagulation factor Xa (fXa) have emerged as a new class of antithrombotics but lack effective antidotes for patients experiencing serious bleeding. We designed and expressed a modified form of fXa as an antidote for fXa inhibitors. This recombinant protein (r-Antidote, PRT064445) is catalytically inactive and lacks the membrane-binding γ-carboxyglutamic acid domain of native fXa but retains the ability of native fXa to bind direct fXa inhibitors as well as low molecular weight heparin-activated antithrombin III (ATIII).

Anthranilamide-based N,N-dialkylbenzamidines as potent and orally bioavailable factor Xa inhibitors: P4 SAR.

Anthranilamide-based benzamidine compound 4 and its N-substituted analogs were designed and examined as factor Xa inhibitors using substituted benzamidines as unconventional S4 binding element. A group of N,N-dialkylbenzamidines (11, 17 and 24) have been discovered as potent factor Xa inhibitors with strong anticoagulant activity and promising oral PK profiles.

Discovery of betrixaban (PRT054021), N-(5-chloropyridin-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxybenzamide, a highly potent, selective, and orally efficacious factor Xa inhibitor.

Systematic SAR studies of in vitro factor Xa inhibitory activity around compound 1 were performed by modifying each of the three phenyl rings. A class of highly potent, selective, efficacious and orally bioavailable direct factor Xa inhibitors was discovered. These compounds were screened in hERG binding assays to examine the effects of substitution groups on the hERG channel affinity.

Identification of 4-piperazin-1-yl-quinazoline template based aryl and benzyl thioureas as potent, selective, and orally bioavailable inhibitors of platelet-derived growth factor (PDGF) receptor.

4-[4-(N-Substituted-thio-carbamoyl)-1-piperazinyl]-6-methoxy-7-alkoxyamino-quinazoline derivatives such as 14 (CT53986) have been identified to be potent and selective inhibitors of the phosphorylation of PDGFR. SAR-investigations are described in the arylamine segment, C-7 appendage, and the thiourea moiety. Bioisosteres of thiourea (cyanoguanidine), and of quinazoline (quinoline-3-carbonitrile) were synthesized and are compared for their in vitro inhibitory activity.

Parallel synthesis and structure-activity relationships of a series of highly potent, selective, and neutral factor Xa inhibitors.

Parallel synthesis and iterative optimization led to the discovery of a series of potent and specific factor Xa inhibitors demonstrating excellent in vitro activity with promising pharmacokinetics.

N,N-Dialkylated 4-(4-arylsulfonylpiperazine-1-carbonyl)-benzamidines and 4-((4-arylsulfonyl)-2-oxo-piperazin-1-ylmethyl)-benzamidines as potent factor Xa inhibitors.

A class of N,N-dialkylated 4-(4-arylsulfonylpiperazine-1-carbonyl)-benzamidines and 4-((4-arylsulfonyl)-2-oxo-piperazin-1-ylmethyl)-benzamidines has been discovered as potent factor Xa inhibitors with desirable in vitro and in vivo anticoagulant activity, but with low oral bioavailability. The 5-chloroindole and 6-chlorobenzo[b]thiophene groups are optimal as the factor Xa S1 binding elements. The strategy of incorporating a side chain on the piperazine nucleus to enhance binding affinity has been examined.

Design, synthesis, and SAR of anthranilamide-based factor Xa inhibitors with improved functional activity.

Compound 2 containing an aminomethylbenzoyl moiety as the S4 binding motif was synthesized in order to modulate hydrophlicity of anthranilamide-based factor Xa inhibitors with substituted biphenyl P4 groups. Structure-activity relationship studies around 2 have led to a series of potent factor Xa inhibitors which are highly active in the human plasma-based thrombin generation assay with 2XTG values less than 1 microM. Compound 55 shows strong antithrombotic activity in our rabbit deep vein thrombosis model, and also exhibits good oral bioavailability and a long half life in rats.

Design, synthesis, and SAR of anthranilamide-based factor Xa inhibitors incorporating substituted biphenyl P4 motifs.

Anthranilamides 4 and 5 were designed and synthesized as selective and orally bioavailable factor Xa inhibitors. Structural modifications aimed at lowering their lipophilicity were performed at the central phenyl ring and at the S4 binding biphenyl region by incorporating water solublizing substituents. The resulting compounds (e.

1-(2-Naphthyl)-1H-pyrazole-5-carboxylamides as potent factor Xa inhibitors. Part 3: Design, synthesis and SAR of orally bioavailable benzamidine-P4 inhibitors.

Using N,N-dialkylated benzamidines as the novel P4 motifs, we have designed and synthesized a class of 1-(2-naphthyl)-1H-pyrazole-5-carboxylamides as highly potent and selective fXa inhibitors with significantly improved hydrophilicity and in vitro anticoagulant activity. These benzamidine-P4 fXa inhibitors have displayed excellent oral bioavailability and long half-life.

1-(2-Naphthyl)-1H-pyrazole-5-carboxylamides as potent factor Xa inhibitors. Part 2: A survey of P4 motifs.

A variety of P4 motifs have been examined to increase the binding affinity and in vitro anticoagulant potency of our biphenyl 1-(2-naphthyl)-1H-pyrazole-5-carboxylamide-based fXa inhibitors. Highly potent 2-naphthyl-P1 fXa inhibitors (K(i)< or =2 nM) with improved in vitro anticoagulant activity (2xTG< or =1 microM) and respectable pharmacokinetic properties have been discovered.

Identification of orally active, potent, and selective 4-piperazinylquinazolines as antagonists of the platelet-derived growth factor receptor tyrosine kinase family.

We have previously found that the 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazolines can function as potent and selective inhibitors of platelet-derived growth factor receptor (PDGFR) phosphorylation. A series of highly potent, specific, orally active, small molecule kinase inhibitors directed against members of PDGFR receptor have been developed through modifications of the novel quinazoline template I. Systematic modifications in the A-bicyclic ring and D-rings of protype I were carried out to afford potent analogues, which display IC(50) values of <250 nM in cellular betaPDGFR phosphorylation assays.

Allometric pharmacokinetic scaling: towards the prediction of human oral pharmacokinetics.

Purpose: To evaluate (1) allometric scaling of systemic clearance (CL) using unbound drug concentration, (2) the potential usage of brain weight (BRW) correction in allometric scaling of both CL and oral clearance (CL/F).

Methods: Human clearance was predicted allometrically (CLu = a x W(biv)) using unbound plasma concentration for eight Parke-Davis compounds and 29 drugs from literature sources. When the exponent b(iv) was higher than 0.

Enantiomeric determination of amphetamine and methamphetamine in urine by precolumn derivatization with Marfey's reagent and HPLC.

An analytical method was developed for enantiomeric determination of amphetamine and methamphetamine in human urine. The enantiomers were isolated from urine by solid-phase extraction, and diastereomers were formed by derivatization with the chiral Marfey's reagent (1-fluoro-2,4-dinitrophenyl-5-l-aniline amide). The diastereomers were separated by reversed-phase high-performance liquid chromatography in a water/methanol mobile phase and detected by absorbance spectrophotometry at 340 nm.

p-Hydroxymethamphetamine enantiomer pharmacokinetics and metabolism in rats: absence of N-demethylation.

p-hydroxymethamphetamine (OHMAP) is one of the major metabolites of the widely abused drug methamphetamine (MAP). The demethylation of OHMAP to p-hydroxyamphetamine (OHAP) has been shown in vitro but has never been reported in vivo. The disposition kinetics as well as the metabolism of OHMAP was investigated employing a sensitive HPLC method which can separate the enantiomers of OHMAP and OHAP.

Simple apparatus for serial blood sampling in rodents permitting simultaneous measurement of locomotor activity as illustrated with cocaine.

A simple device has been developed for serial venous blood sampling which permits the simultaneous measurement of locomotor activity in the freely moving rat. The device can be easily constructed from routine laboratory material and it does not interfere with the light beams used to measure locomotor activity. The device, in conjunction with an activity cage, has been applied to the combined pharmacokinetic and pharmacodynamic modeling of cocaine.

Comparative pharmacokinetics and interspecies scaling of amphotericin B in several mammalian species.

This study employed several interspecies scaling methods, to evaluate the applicability of extrapolating to man, pharmacokinetic information obtained from animals for amphotericin B, an anti-fungal drug. Pharmacokinetic parameters from four animal species (mouse, rat, monkey and dog) and man were obtained from the literature or from analysis of data reported in the literature. The allometric relationships (obtained from four animal species) as a function of species body weight (W; kg) for systemic clearance per maximum life span potential (CLS/MLP), steady-state volume of distribution (VSS), apparent volume of distribution (V beta) and volume of the central compartment (VC) were: 5691W1.

Influence of activated charcoal on the disposition kinetics of methamphetamine enantiomers in the rat following intravenous dosing.

Methamphetamine (MAP) is a central nervous system stimulant that is widely abused by populations of several countries. There is no specific antidote for the treatment of an overdose. Activated charcoal administered orally has been used to enhance the systemic elimination of certain toxic substances via "gastrointestinal dialysis".