Validation of an LC-MS/MS method for the determination of sotorasib, a KRASG12C inhibitor, in human plasma.

Background: Sotorasib (AMG 510) is a first-in-class KRASG12C inhibitor that received accelerated US FDA approval in 2021 for the treatment of patients with KRASG12C-mutated locally advanced or metastatic non-small-cell lung cancer. Method: An LC-MS/MS method was developed and validated for the determination of sotorasib in human plasma to support clinical development studies. Samples were prepared using protein precipitation and analyzed by LC-MS/MS using gradient elution with a calibration standard curve range of 10.0-10,000 ng/ml. Stable isotope labeled [13C, D3]-sotorasib was used as an internal standard. Results & conclusion: The method fully met FDA guidelines for all validation parameters, including precision, accuracy, selectivity, matrix effect, recovery and stability and has been extensively used to support multiple clinical studies.

Activity-based exposure comparisons among humans and nonclinical safety testing species in an extensively metabolized drug candidate.

1. Extensive metabolism of a drug candidate can complicate the interpretation of comparative safety and efficacy data from humans and preclinical species. 2. The 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) inhibitor, AMG 221 underwent extensive oxidative metabolism to structurally similar but differentially active primary and secondary metabolites. Relative potency data from synthetic metabolites enabled a stepwise quantitative assessment of AMG 221 in vivo metabolism that compared relative exposure to metabolites in plasma across species and discerned which active metabolites to monitor in preclinical and clinical safety and efficacy studies. 3. Pooled plasma samples from AMG 221-dosed human subjects were profiled using high-resolution liquid chromatography-mass spectrometry (LC-MS) with a mass-defect-filter. The most abundant peak, M1 accounted for 47%-59% of peaks followed by AMG 221 at 27%-40%. Other metabolites were each less than 7%. Activity-normalized data indicated both M1 and AMG 221 should be monitored to assist pharmacokinetic-pharmacodynamic (PK-PD) modeling. 4. Rat and dog area under the plasma concentration time curve (AUC) exposures to M1 at preclinical no observable adverse effect level (NOAEL) doses were 2-42-fold higher than human, indicating M1 was not a disproportionate metabolite, as defined by International Committee on Harmonization (ICH) M3(R2) guidance. 5. Development decisions regarding active metabolite monitoring and potentially disproportionate metabolites in extensively metabolized drug candidates are enabled by metabolite synthesis and liquid chromatography high-resolution mass spectrometry (LC-HRMS)-based assessment of potency-normalized plasma metabolite AUCs.

Simultaneous determination of a p38 MAP kinase inhibitor and its amide hydrolyzed metabolite in Cynomolgus monkey plasma by LC-MS/MS, and its application to a toxicokinetic study.

A LC-MS/MS method was developed for the determination of a p38 MAP kinase inhibitor (Compound I) and its amide hydrolyzed metabolite (M7) in Cynomolgus monkey plasma over the concentration range of 1.00-1000ng/mL. Stable isotope labeled compounds (d(3)-Compound I and d(3)-M7) were used as internal standards (IS). Samples were prepared using protein precipitation in the 96-well format with a 30µL plasma sample volume. Chromatographic separation was performed with reversed-phase liquid chromatography on a Varian Monochrom C(18) (100mm×2.00mm, 5µm) analytical column. The mobile phases were 5mM ammonium formate in acetonitrile/water (95/5, v/v) pH 7.0 and 5mM ammonium formate in acetonitrile/water (5/95, v/v) pH 7.0. Gradient elution, at a flow rate of 550µL/min, was used to separate Compound I and M7. Positive atmospheric pressure chemical ionization was utilized with detection by multiple reaction monitoring (MRM). Total run time was about 3.2min. This method was validated following the current Food and Drug Administration (FDA) guidance for bioanalytical method validation. The intra- and inter-day precision (% CV) and accuracy (% bias) at all concentrations tested were below 15% for both analytes. The mean recoveries for Compound I, M7, d(3)-Compound I, and d(3)-M7 were 106%, 107%, 108% and 105%, respectively. The method was successfully applied to support a GLP toxicokinetic study in Cynomolgus monkeys after oral administration of Compound I. A total of 48 samples (∼12.5% of the total number of samples) were selected for incurred sample reanalysis (ISR). The % difference between the reassay concentrations and the original concentrations were all less than 20% of their mean values and met the acceptance criteria for ISR.

Population pharmacokinetic/pharmacodynamic model of subcutaneous adipose 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) activity after oral administration of AMG 221, a selective 11ß-HSD1 inhibitor.

Inhibition of 11ß-HSD1 is hypothesized to improve measures of insulin sensitivity and hepatic glucose output in patients with type II diabetes. AMG 221 is a potent, small molecule inhibitor of 11ß-HSD1. The objective of this analysis is to describe the pharmacokinetic/pharmacodynamic (PK/PD) relationship between AMG 221 and 11ß-HSD1 inhibition in ex vivo adipose tissue samples. Healthy, obese subjects were administered a single dose of 3, 30, or 100 mg of oral AMG 221 (n = 44) or placebo (n = 11). Serial blood samples were collected over 24 hours. Subcutaneous adipose tissue samples were collected by open biopsy. Population PK/PD analysis was conducted using NONMEM. The inhibitory effects (mean ± standard error of the estimate) of AMG 221 on 11ß-HSD1 activity were directly related to adipose concentrations with I(max) (the maximal inhibition of 11ß-HSD1 activity) and IC50 (the plasma AMG 221 concentration associated with 50% inhibition of enzyme activity) of 0.975 ± 0.003 and 1.19 ± 0.12 ng/mL, respectively. The estimated baseline 11ß-HSD1 enzyme activity was 755 ± 61 pmol/mg. An equilibration rate constant (k(eo)) of 0.220 ± 0.021 h⁻¹ described the delay between plasma and adipose tissue AMG 221 concentrations. AMG 221 potently blocked 11ß-HSD1 activity, producing sustained inhibition for the 24-hour study duration as measured in ex vivo adipose samples. Early characterization of concentration-response relationships can support rational selection of dose and regimen for future studies.

Characterization and optimization of AMG 517 supersaturatable self-emulsifying drug delivery system (S-SEDDS) for improved oral absorption.

Supersaturatable self-emulsifying drug delivery systems (S-SEDDS) were explored to improve the oral absorption of AMG 517, a poorly water-soluble drug candidate. In vitro characterizations indicate the level of Tween 80 in the formulation dictates the initial degree of supersaturation of AMG 517, and, therefore, its precipitation kinetics. The presence of a small amount of cellulosic polymer (e.g., HPMC) effectively sustained a metastable supersaturated state by retarding precipitation kinetics. Precipitates from the S-SEDDS formulations (with HPMC) from in vitro test media were identified as amorphous AMG 517 while crystalline AMG 517 precipitates were found when either HPMC was absent or PVP was present in the formulation. In vivo pharmacokinetic study in Cynomolgus monkeys reveals that the S-SEDDS formulation showed approximately 30% higher mean C(max) and comparable exposure (AUC) of AMG 517 as compared to an aqueous suspension at a dose of 12.5 mg. The rapid absorption characteristics of AMG 517 from the S-SEDDS formulation as evidenced by high C(max) and short T(max) are attributed to a high free drug concentration in vivo, implying a supersaturated state. This case demonstrates that S-SEDDS technology is an effective approach for improving the rate and extent of absorption of poorly soluble drugs.

Pharmacological blockade of the vanilloid receptor TRPV1 elicits marked hyperthermia in humans.

The vanilloid receptor TRPV1 has been identified as a molecular target for the treatment of pain associated with inflammatory diseases and cancer. Hence, TRPV1 antagonists have been considered for therapeutic evaluation in such diseases. During Phase I clinical trials with AMG 517, a highly selective TRPV1 antagonist, we found that TRPV1 blockade elicited marked, but reversible, and generally plasma concentration-dependent hyperthermia. Similar to what was observed in rats, dogs, and monkeys, hyperthermia was attenuated after repeated dosing of AMG 517 (at the highest dose tested) in humans during a second Phase I trial. However, AMG 517 administered after molar extraction (a surgical cause of acute pain) elicited long-lasting hyperthermia with maximal body temperature surpassing 40 degrees C, suggesting that TRPV1 blockade elicits undesirable hyperthermia in susceptible individuals. Mechanisms of AMG 517-induced hyperthermia were then studied in rats. AMG 517 caused hyperthermia by inducing tail skin vasoconstriction and increasing thermogenesis, which suggests that TRPV1 regulates vasomotor tone and metabolic heat production. In conclusion, these results demonstrate that: (a) TRPV1-selective antagonists like AMG 517 cannot be developed for systemic use as stand alone agents for treatment of pain and other diseases, (b) individual susceptibility influences magnitude of hyperthermia observed after TRPV1 blockade, and (c) TRPV1 plays a pivotal role as a molecular regulator for body temperature in humans.

The co-crystal approach to improve the exposure of a water-insoluble compound: AMG 517 sorbic acid co-crystal characterization and pharmacokinetics.

Co-crystals are relatively novel in the pharmaceutical field and are not reported extensively. AMG 517 is an insoluble small molecule VR1 (vanilloid receptor 1) antagonist. In animal studies, good exposure of AMG 517 is seen from a 10% (w/v) Pluronic F108 in OraPlus suspension. Investigation of the suspension formulation revealed that AMG 517 forms a co-crystal with sorbic acid, a preservative in OraPlus. This co-crystal of AMG 517 was isolated by coslurrying AMG 517 and sorbic acid; studied by DSC and XRD; and identified by solution NMR, TGA, and HPLC to be a 1:1 association of AMG 517 and sorbic acid. Single crystal structure analysis revealed a 1:1 co-crystal of AMG 517 and sorbic acid, held together by two hydrogen bonds and other noncovalent, nonionic forces. The co-crystal has better aqueous solubility initially as compared to AMG 517 free base but does revert back to a form of the free base hydrate during prolonged slurry in FaSIF (fasted simulated intestinal fluid). Pharmacokinetic evaluation of the co-crystal in rats using 10% (w/v) Pluronic F108 in OraPlus suspensions revealed that a 30 mg/kg dose in suspension had comparable exposure to a 500 mg/kg dose of the free base.

Enhanced bioavailability of a poorly soluble VR1 antagonist using an amorphous solid dispersion approach: a case study.

Amorphous solid dispersions (ASD) of a poorly soluble water-soluble VR1 antagonist (AMG 517) were explored for improving physical stability and in vivo exposure. AMG 517 was incorporated at 15 or 50 wt % into polymeric microparticles of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and hydroxypropyl methylcellulose (HPMC) by spray-drying. Solid particles having a collapsed, corrugated structure were observed by SEM. Median particle size ranged from 29 to 40 microm by laser light scattering, and residual solvent levels were below 2% by thermal gravimetric analysis. ASD powders exhibited single glass transition temperatures (Tg) in the range of 98-117 degrees C by modulated DSC and were amorphous by XRPD. Amorphous stability, characterized at 40 degrees C/75% RH (open dish) by XRPD, was at least six months for ASD formulations. Drug dissolution and supersaturation testing in a USP-2 apparatus indicated superior performance of ASD formulations over micronized AMG 517. PK of an ASD formulation in capsule (15 wt % AMG 517 in HPMCAS blended with 5 wt % SDS) in cynomolgus monkeys (n = 6, crossover) increased AUC 163% and Cmax 145% in comparison to an OraPlus suspension control. The study demonstrates the ASD approach provides improved amorphous physical stability and oral bioavailability for a poorly soluble development-stage molecule.