A Comparative Clinical Pharmacology Analysis of FDA-Approved Targeted Covalent Inhibitors vs. Reversible Inhibitors in Oncology.

Targeted covalent inhibitors (TCIs) are an emerging class of anticancer therapeutics. TCIs are designed to selectively engage their targeted proteins via covalent warheads. From the drug development standpoint, the covalent inhibition mechanism is anticipated to elicit the following theoretical benefits: (i) an extended duration of therapeutic action that is determined by the target protein turnover rate and not necessarily by drug half-life, (ii) a lower therapeutic dose owing to greater pharmacological potency, (iii) lower risk of off-target binding and associated adverse events, and (iv) reduced drug-drug interaction (DDI) liability due to high selectivity and low dose.

Divarasib plus cetuximab in KRAS G12C-positive colorectal cancer: a phase 1b trial.

KRAS G12C mutation is prevalent in ~4% of colorectal cancer (CRC) and is associated with poor prognosis. Divarasib, a KRAS G12C inhibitor, has shown modest activity as a single agent in KRAS G12C-positive CRC at 400 mg. Epidermal growth factor receptor has been recognized as a major upstream activator of RAS-MAPK signaling, a proposed key mechanism of resistance to KRAS G12C inhibition in CRC.

Single-Agent Divarasib (GDC-6036) in Solid Tumors with a G12C Mutation.

Background: Divarasib (GDC-6036) is a covalent KRAS G12C inhibitor that was designed to have high potency and selectivity.

Methods: In a phase 1 study, we evaluated divarasib administered orally once daily (at doses ranging from 50 to 400 mg) in patients who had advanced or metastatic solid tumors that harbor a G12C mutation. The primary objective was an assessment of safety; pharmacokinetics, investigator-evaluated antitumor activity, and biomarkers of response and resistance were also assessed.

Improving Drug Delivery While Tailoring Prodrug Activation to Modulate and by Optimization of (Carbonyl)oxyalkyl Linker-Based Prodrugs of Atazanavir.

Structure-property relationships associated with a series of (carbonyl)oxyalkyl amino acid ester prodrugs of the marketed HIV-1 protease inhibitor atazanavir (), designed to enhance the systemic drug delivery, were examined. Compared to previously reported prodrugs, optimized candidates delivered significantly enhanced plasma exposure and trough concentration ( at 24 h) of in rats while revealing differentiated PK paradigms based on the kinetics of prodrug activation and drug release. Prodrugs incorporating primary amine-containing amino acid promoieties offered the benefit of rapid bioactivation that translated into low circulating levels of the prodrug while delivering a high value of .

Evolution of preclinical characterization and insights into clinical pharmacology of checkpoint inhibitors approved for cancer immunotherapy.

Cancer immunotherapy has significantly advanced the treatment paradigm in oncology, with approvals of immuno-oncology agents for over 16 indications, many of them first line. Checkpoint inhibitors (CPIs) are recognized as an essential backbone for a successful anticancer therapy regimen. This review focuses on the US Food and Drug Administration (FDA) regulatory approvals of major CPIs and the evolution of translational advances since their first approval close to a decade ago.

BMS-813160: A Potent CCR2 and CCR5 Dual Antagonist Selected as a Clinical Candidate.

BMS-813160 (compound ) was identified as a potent and selective CCR2/5 dual antagonist. Compound displayed good permeability at pH = 7.4 in PAMPA experiments and demonstrated excellent human liver microsome stability.

Discovery of BMS-753426: A Potent Orally Bioavailable Antagonist of CC Chemokine Receptor 2.

To improve the metabolic stability profile of BMS-741672 (), we undertook a structure-activity relationship study in our trisubstituted cyclohexylamine series. This ultimately led to the identification of (BMS-753426) as a potent and orally bioavailable antagonist of CCR2. Compared to previous clinical candidate , the -butyl amine showed significant improvements in pharmacokinetic properties, with lower clearance and higher oral bioavailability.

(Carbonyl)oxyalkyl linker-based amino acid prodrugs of the HIV-1 protease inhibitor atazanavir that enhance oral bioavailability and plasma trough concentration.

We describe the design, synthesis and pharmacokinetic (PK) evaluation of a series of amino acid-based prodrugs of the HIV-1 protease inhibitor atazanavir (1) derivatized on the pharmacophoric secondary alcohol using a (carbonyl)oxyalkyl linker. Prodrugs of 1 incorporating simple (carbonyl)oxyalkyl-based linkers and a primary amine in the promoiety were found to exhibit low chemical stability. However, chemical stability was improved by modifying the primary amine moiety to a tertiary amine, resulting in a 2-fold enhancement of exposure in rats following oral dosing compared to dosing of the parent drug 1.

Design, Synthesis, and Pharmacokinetic Evaluation of Phosphate and Amino Acid Ester Prodrugs for Improving the Oral Bioavailability of the HIV-1 Protease Inhibitor Atazanavir.

Phosphate and amino acid prodrugs of the HIV-1 protease inhibitor (PI) atazanavir (1) were prepared and evaluated to address solubility and absorption limitations. While the phosphate prodrug failed to release 1 in rats, the introduction of a methylene spacer facilitated prodrug activation, but parent exposure was lower than that following direct administration of 1. Val amino acid and Val-Val dipeptides imparted low plasma exposure of the parent, although the exposure of the prodrugs was high, reflecting good absorption.

Use of a Conformational-Switching Mechanism to Modulate Exposed Polarity: Discovery of CCR2 Antagonist BMS-741672.

We encountered a dilemma in the course of studying a series of antagonists of the G-protein coupled receptor CC chemokine receptor-2 (CCR2): compounds with polar C3 side chains exhibited good ion channel selectivity but poor oral bioavailability, whereas compounds with lipophilic C3 side chains exhibited good oral bioavailability in preclinical species but poor ion channel selectivity. Attempts to solve this through the direct modulation of physicochemical properties failed. However, the installation of a protonation-dependent conformational switching mechanism resolved the problem because it enabled a highly selective and relatively polar molecule to access a small population of a conformer with lower polar surface area and higher membrane permeability.

Coupling of an Acyl Migration Prodrug Strategy with Bio-activation To Improve Oral Delivery of the HIV-1 Protease Inhibitor Atazanavir.

HIV-1 protease inhibitors (PIs), which include atazanavir (ATV, 1), remain important medicines to treat HIV-1 infection. However, they are characterized by poor oral bioavailability and a need for boosting with a pharmacokinetic enhancer, which results in additional drug-drug interactions that are sometimes difficult to manage. We investigated a chemo-activated, acyl migration-based prodrug design approach to improve the pharmacokinetic profile of 1 but failed to obtain improved oral bioavailability over dosing the parent drug in rats.

Spotting of external calibration standards on blank dried blood spots as a resource-sparing protocol.

Aim: Dried blood spots (DBS) offer significant ethical and scientific advantages; however preparation of calibration curves often times, off-sets some of these advantages. We have developed a methodology wherein small volumes of external calibration standards can be spiked on to blank DBS cards.

Results: A total of 2 μl of stock solution spotted on to blank blood spots yielded concentrations that were comparable to those obtained using conventional DBS method.

LC-MS determination of triazolam and its hydroxy metabolites in mouse dried blood spots: application to transgenic mouse pharmacokinetic studies.

Aim: The objective of this study was to develop a LC-MS/MS method for the simultaneous determination of triazolam (TRZ) and its two hydroxy metabolites in transgenic mouse dried blood spots (DBS) using BALB/c mouse blood as a surrogate biomatrix.

Methodology/results: The DBS method involved spotting volume of 10 μl using Ahlstrom 226 sample collection cards. A 'whole spot' analysis (6-mm punch) involved extraction of analytes using water and acetonitrile containing an internal standard.

Comparative Evaluation of Plasma Bile Acids, Dehydroepiandrosterone Sulfate, Hexadecanedioate, and Tetradecanedioate with Coproporphyrins I and III as Markers of OATP Inhibition in Healthy Subjects.

Multiple endogenous compounds have been proposed as candidate biomarkers to monitor organic anion transporting polypeptide (OATP) function in preclinical species or humans. Previously, we demonstrated that coproporphyrins (CPs) I and III are appropriate clinical markers to evaluate OATP inhibition and recapitulate clinical drug-drug interactions (DDIs). In the present study, we investigated bile acids (BAs) dehydroepiandrosterone sulfate (DHEAS), hexadecanedioate (HDA), and tetradecanedioate (TDA) in plasma as endogenous probes for OATP inhibition and compared these candidate probes to CPs.

Unmasking the Role of Uptake Transporters for Digoxin Uptake Across the Barriers of the Central Nervous System in Rat.

The role of uptake transporter (organic anion-transporting polypeptide [Oatp]) in the disposition of a P-glycoprotein (P-gp) substrate (digoxin) at the barriers of central nervous system, namely, the blood-brain barrier (BBB), blood-spinal cord barrier (BSCB), and brain-cerebrospinal fluid barrier (BCSFB), was studied using rat as a preclinical species. In vivo chemical inhibition of P-gp and Oatp was achieved using elacridar and rifampicin, respectively. Our findings show that (1) digoxin had a low brain-to-plasma concentration ratio (B/P) (0.

Selective I Inhibitors for the Potential Treatment of Atrial Fibrillation: Optimization of the Phenyl Quinazoline Series Leading to Clinical Candidate 5-[5-Phenyl-4-(pyridin-2-ylmethylamino)quinazolin-2-yl]pyridine-3-sulfonamide.

We have recently disclosed 5-phenyl-N-(pyridin-2-ylmethyl)-2-(pyrimidin-5-yl)quinazolin-4-amine 1 as a potent I current blocker with selectivity versus hERG, Na and Ca channels, and an acceptable preclinical PK profile. Upon further characterization in vivo, compound 1 demonstrated an unacceptable level of brain penetration. In an effort to reduce the level of brain penetration while maintaining the overall profile, SAR was developed at the C2' position for a series of close analogues by employing hydrogen bond donors.

Coproporphyrin-I: A Fluorescent, Endogenous Optimal Probe Substrate for ABCC2 (MRP2) Suitable for Vesicle-Based MRP2 Inhibition Assay.

Inside-out-oriented membrane vesicles are useful tools to investigate whether a compound can be an inhibitor of efflux transporters such as multidrug resistance-associated protein 2 (MRP2). However, because of technical limitations of substrate diffusion and low dynamic uptake windows for interacting drugs used in the clinic, estradiol-17-glucuronide (E17G) remains the probe substrate that is frequently used in MRP2 inhibition assays. Here we recapitulated the sigmoidal kinetics of MRP2-mediated transport of E17G, with apparent Michaelis-Menten constant () and values of 170 ±17 M and 1447 ± 137 pmol/mg protein/min, respectively.

Metabolite Identification, Reaction Phenotyping, and Retrospective Drug-Drug Interaction Predictions of 17-Deacetylnorgestimate, the Active Component of the Oral Contraceptive Norgestimate.

Ortho Tri-Cyclen, a two-drug cocktail comprised of ethinylestradiol and norgestimate (13-ethyl-17-acetoxy-18, 19-dinor-17-pregn-4-en-20yn-3 oxime), is commonly prescribed to avert unwanted pregnancies in women of reproductive age. In vivo, norgestimate undergoes extensive and rapid deacetylation to produce 17-deacetylnorgestimate (NGMN), an active circulating metabolite that likely contributes significantly to norgestimate efficacy. Despite being of primary significance, the metabolism and reaction phenotyping of NGMN have not been previously reported.

Single jugular vein cannulated rats may not be suitable for intravenous pharmacokinetic screening of high logP compounds.

Rat is commonly used for pharmacokinetic screening during pharmaceutical lead optimization. To handle the large number of compounds, rats with a single jugular vein cannulation are commonly utilized for intravenous pharmacokinetic studies, where the same cannula is used both for dose administration and blood sampling. We demonstrate that the single cannula method is not suitable for all compounds, especially for high logP compounds.

A Novel Liquid Chromatography Tandem Mass Spectrometry Method for the Estimation of Bilirubin Glucuronides and its Application to In Vitro Enzyme Assays.

Background: Bilirubin is a toxic waste product of metabolism, eliminated mainly through UGT1A1 mediated conjugation to mono- and di-glucuronides. Due to the potentially low Km value of bilirubin glucuronidation, the quantitative sensitivity obtained with most UV/visible light detection methods are not sufficient to accurately calculate UGT1A1 enzyme kinetics at low bilirubin concentrations. In addition, bilirubin, as well as its metabolites, are unstable during sample preparation and bioanalysis.

Discovery of 5-Phenyl-N-(pyridin-2-ylmethyl)-2-(pyrimidin-5-yl)quinazolin-4-amine as a Potent I Kur Inhibitor.

A new series of phenylquinazoline inhibitors of Kv 1.5 is disclosed. The series was optimized for Kv 1.

Inhibition of AAK1 Kinase as a Novel Therapeutic Approach to Treat Neuropathic Pain.

To identify novel targets for neuropathic pain, 3097 mouse knockout lines were tested in acute and persistent pain behavior assays. One of the lines from this screen, which contained a null allele of the adapter protein-2 associated kinase 1 (AAK1) gene, had a normal response in acute pain assays (hot plate, phase I formalin), but a markedly reduced response to persistent pain in phase II formalin. AAK1 knockout mice also failed to develop tactile allodynia following the Chung procedure of spinal nerve ligation (SNL).