Simultaneous determination of ceftazidime and pyridine in human plasma by LC-UV.

A sensitive, accurate and precise liquid chromatography (LC) method for the simultaneous determination of ceftazidime and pyridine in human plasma has been developed and validated. Acetonitrile (ACN) was employed to precipitate the proteins in the plasma samples. Chromatographic separation was performed with a Kinetex® C18 (150 mm × 3 mm, 2.6 µm) column with gradient elution. Ammonium formate 20 mM and ACN were mixed in a ratio of 98:2 (v/v) for mobile phase A and 85:15 (v/v) for mobile phase B. Both were adjusted to pH 4.5 with formic acid. The flow rate was 0.4 mL/min. UV detection was performed at 254 nm. Calibration curves were linear in the range from 0.3 to 225 µg/mL for ceftazidime and from 0.2 to 10 µg/mL for pyridine with correlation coefficients ≥ 0.999. Within- and between-run precision and accuracy were satisfactory with coefficients of variation (CV) ≤ 8.0% and deviations ≤ 7.0%, respectively. The method fulfilled all validation criteria prescribed by the European Medicines Agency guidelines. Next, it has been used successfully to analyze plasma samples of patients who received ceftazidime under intermittent and continuous administration. With intermittent administration, the concentration of the antibiotics reached a peak and then dropped quickly, which may be below the minimal inhibitory concentration (MIC). With continuous administration, the concentration of the antibiotics remained stable over 24 h, certainly above the MIC. Although the same tendency in ceftazidime concentration changes over time was observed, a difference in concentration amongst the patients was noticeable. The concentration of pyridine in plasma was negligible.

Effects of the Moderate CYP3A4 Inhibitor Erythromycin on the Pharmacokinetics of Palbociclib: A Randomized Crossover Trial in Patients With Breast Cancer.

Palbociclib is an oral inhibitor of cyclin-dependent kinases 4 and 6 used in the treatment of locally advanced and metastatic breast cancer, and is extensively metabolized by cytochrome P450 enzyme 3A4 (CYP3A4). A pharmacokinetic/pharmacodynamic relationship between palbociclib exposure and neutropenia is well known. This study aimed to investigate the effects of the moderate CYP3A4 inhibitor erythromycin on the pharmacokinetics of palbociclib. We performed a randomized crossover trial comparing the pharmacokinetics of palbociclib monotherapy 125 mg once daily (q.d.) with palbociclib 125 mg q.d. plus oral erythromycin 500 mg three times daily for seven days. Pharmacokinetic sampling was performed at steady-state for both dosing schedules. Eleven evaluable patients have been enrolled. For palbociclib monotherapy, geometric mean area under the plasma concentration-time curve from zero to infinity (AUC0-24h ), maximum plasma concentration (Cmax ), and minimum plasma concentration (Cmin ) were 1.46 × 103  ng•h/mL (coefficient of variation (CV) 45.0%), 80.5 ng/mL (CV 48.5%), and 48.4 ng/mL (CV 38.8%), respectively, compared with 2.09 × 103  ng•h/mL (CV 49.3%, P = 0.000977), 115 ng/mL (CV 53.7%, P = 0.00562), and 70.7 ng/mL (CV 47.5%, P = 0.000488) when palbociclib was administered concomitantly with erythromycin. Geometric mean ratios (90% confidence intervals) of AUC0-24h , Cmax , and Cmin for palbociclib plus erythromycin vs. palbociclib monotherapy were 1.43 (1.24-1.66), 1.43 (1.20-1.69), and 1.46 (1.30-1.63). Minor differences in adverse events were observed, and only one grade ≥ 3 toxicity was observed in this short period of time. To conclude, concomitant intake of palbociclib with the moderate CYP3A4 inhibitor erythromycin resulted in an increase in palbociclib AUC0-24h and Cmax of both 43%. Therefore, a dose reduction of palbociclib to 75 mg q.d. is rational, when palbociclib and moderate CYP3A4 inhibitors are used concomitantly.

A new dried blood spot LC-MS/MS method for therapeutic drug monitoring of palbociclib, ribociclib, and letrozole in patients with cancer.

Therapeutic drug monitoring (TDM) is strongly suggested to define the proper drug dosage to overcome inter- and intra-patient variability in drug exposure, which is typically observed with oral anticancer agents, such as palbociclib (PALBO), ribociclib (RIBO) and letrozole (LETRO), all approved for the treatment of HR+, HER2- locally advanced or metastatic breast cancer (BC). Optimal TDM implementation requires a blood sampling organization that can be hampered by limited availability of health and laboratory personnel. Dried Blood Spot (DBS) sampling is proposed to overcome such limitations. The aim of this work was the development of a new LC-MS/MS method to analyze DBS samples containing PALBO, RIBO, and LETRO. Analytes extraction from DBS was performed by adding a methanolic solution containing the corresponding internal standards. LC-MS/MS analysis was performed using a LC Nexera (Shimadzu) system coupled with an API 4000 QTrap (SCIEX) mass spectrometer. The chromatographic separation was performed on a Luna Omega Polar C18 column (Phenomenex). The method was applied to 38 clinical samples collected by finger prick. The influence of hematocrit and spot size, sample homogeneity, stability, and correlation between finger prick and venous DBS measurement were assessed. The analytical validation was performed according to EMA and FDA guidelines. The analytical range of the method was 1 to 250 ng/mL for PALBO, 40 to 10000 ng/mL for RIBO, and 2 to 500 ng/mL for LETRO, where linearity was assessed, obtaining mean coefficients of determination (R2) of 0.9979 for PALBO, 0.9980 for RIBO, and 0.9987 for LETRO). The LC-MS/MS method runtime was 6.6 min. Incurred sample reanalysis demonstrated reproducibility, as the percentage difference between the two quantifications was lower than 20% for 100% of PALBO, 81.8% of RIBO, and 90.9% of LETRO paired samples. Intra- and inter-day precision (CV (%)) was lower than 11.4% and intra- and inter-day accuracy was between 90.0 and 106.5%. DBS sample stability at room temperature was confirmed for 2.5 months. A positive correlation was observed between DBS and plasma concentrations for the 3 drugs, Lin's concordance correlation coefficients obtained by DBS normalization applying a selected strategy were 0.958 for PALBO, 0.957 for RIBO, and 0.963 for LETRO. In conclusion, a fast, easy, and reproducible DBS LC-MS/MS method for the simultaneous quantification of palbociclib; ribociclib and letrozole was developed to be used in clinical practice.

ABCB1 and ABCG2, but not CYP3A4 limit oral availability and brain accumulation of the RET inhibitor pralsetinib.

BACKGROUND AND PURPOSE: Pralsetinib is an FDA-approved oral small-molecule inhibitor for treatment of rearranged during transfection (RET) proto-oncogene fusion-positive non-small cell lung cancer. We investigated how the efflux transporters ABCB1 and ABCG2, the SLCO1A/1B uptake transporters and the drug-metabolizing enzyme CYP3A influence pralsetinib pharmacokinetics. EXPERIMENTAL APPROACH: In vitro, transepithelial pralsetinib transport was assessed. In vivo, pralsetinib (10 mg/kg) was administered orally to relevant genetically modified mouse models. Pralsetinib concentrations in cell medium, plasma samples and organ homogenates were measured using liquid chromatography-tandem mass spectrometry. KEY RESULTS: Pralsetinib was efficiently transported by human (h)ABCB1 and mouse (m)Abcg2, but not hACBG2. In vivo, mAbcb1a/1b markedly and mAbcg2 slightly limited pralsetinib brain penetration (6.3-and 1.8-fold, respectively). Testis distribution showed similar results. Abcb1a/1b;Abcg2-/- mice showed 1.5-fold higher plasma exposure, 23-fold increased brain penetration, and 4-fold reduced recovery of pralsetinib in the small intestinal content. mSlco1a/1b deficiency did not affect pralsetinib oral availability or tissue exposure. Oral coadministration of the ABCB1/ABCG2 inhibitor elacridar boosted pralsetinib plasma exposure (1.3-fold) and brain penetration (19.6-fold) in wild-type mice. Additionally, pralsetinib was a modest substrate of mCYP3A, but not of hCYP3A4, which did not noticeably restrict the oral availability or tissue distribution of pralsetinib. CONCLUSIONS AND IMPLICATIONS: SLCO1A/1B and CYP3A4 are unlikely to affect the pharmacokinetics of pralsetinib, but ABCG2 and especially ABCB1 markedly limit its brain and testis penetration, as well as oral availability. These effects are mostly reversed by oral coadministration of the ABCB1/ABCG2 inhibitor elacridar. These insights may be useful in the further clinical development of pralsetinib.

Eco-Friendly UPLC-MS/MS Method for Determination of a Fostamatinib Metabolite, Tamatinib, in Plasma: Pharmacokinetic Application in Rats.

Fostamatinib is a prodrug of the active metabolite tamatinib, which is a spleen tyrosine kinase (Syk) inhibitor used in the treatment of primary chronic adult immune thrombocytopenia and rheumatoid arthritis. A highly sensitive, rapid, reliable, and green method was developed and validated using ultra-performance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS) for quantification of tamatinib in rat plasma. Ibrutinib was used as internal standard and liquid-liquid extraction was applied using tert-butyl methyl ether. The analyte was separated on an AcquityTM CSH C18 (2.1 mm × 100 mm, 1.7 µm) column using mobile phase consisting of 10 mM ammonium acetate and acetonitrile (10:90) and the flow rate was 0.25 mL/min. Electrospray ionization (ESI) was carried out in positive mode. Quantitation of tamatinib and the IS was performed using multiple reaction monitoring mode with precursor-to-product transitions of m/z 471.1 > 122.0 and m/z 441.1 > 84.0, respectively. The calibration range was 0.1-1000.0 ng/mL and the linearity of the method was ≥0.997. The developed method greenness was investigated. All principal parameters for the method, including linearity, accuracy, precision, recovery, and stability, were within acceptable ranges. Tamatinib pharmacokinetic study in rats was successfully carried out using the developed method.

Evaluation of the in vitro stability of direct oral anticoagulants in blood samples under different storage conditions.

In this study, we evaluated the in vitro stability of direct oral anticoagulants (DOACs) in blood samples of 57 patients under different storage conditions using functional coagulation assays. We determined the analyte concentrations (1) immediately after blood collection (baseline); (2) after storage of citrated whole blood (agitated) at room temperature and citrated plasma at room temperature and at 4 °C for 4, 8, and 24 h, respectively; and (3) after storage of citrated plasma at -20 °C for 30, 60, and 90 days. According to the concept of acceptable change limits (ACL), analytes were considered stable if the mean relative analyte recovery at a given time was >78%. The mean baseline values (range) of dabigatran, rivaroxaban, apixaban, and edoxaban were 115 ng/mL (62-217), 129 ng/mL (31-215), 156 ng/mL (49-362), and 101 ng/mL (33-283), respectively. After applying the analyte stability limit, all four DOACs were stable for 24 h at room temperature and at 4 °C. The mean recovery after 24 h was 102-111% for dabigatran, 88-97% for rivaroxaban, 95-98% for apixaban, and 90-96% for edoxaban. When plasma samples were stored at -20 °C, the mean percentage deviation after 90 days for all four DOACs was ≤10%, even after three freeze-thaw cycles. Thus, for the correct determination of DOAC plasma concentrations, blood samples do not have to be analyzed immediately and can be stored at room temperature for up to 24 h before analysis. In clinical practice, blood sample transport and storage for DOAC measurements appear to be unproblematic.

Isavuconazole for treatment of refractory coccidioidal meningitis with concomitant cerebrospinal fluid and plasma therapeutic drug monitoring.

Coccidioidal meningitis (CM) is a life-threatening infection with limited treatment options. Small series have reported success with isavuconazole; however, limited data exist on cerebrospinal fluid (CSF) penetration. Paired plasma and CSF isavuconazole concentrations were measured. Eleven CSF levels were tested, (7 ventricular, 4 lumbar) in three CM patients. Ventricular CSF levels were undetectable despite detectable plasma levels. All lumbar CSF levels were detectable (mean 1.00 µg/ml). Three pairs of lumbar CSF/plasma concentrations taken within 1 h of each other yielded a mean CSF/plasma ratio of 0.31. Isavuconazole was detectable in lumbar but not ventricular CSF in three patients treated for refractory CM. LAY SUMMARY: Isavuconazole is a triazole antifungal that has been used as salvage therapy in the treatment of coccidioidal meningitis (CM). Few data exist characterizing its concentration in the cerebrospinal fluid (CSF). We report tandem plasma and CSF concentrations of isavuconazole in three patients with CM.

Quantitation of ivosidenib in human plasma via LC-MS/MS and its application in clinical trials.

Aim: Ivosidenib is a potent and selective small molecule inhibitor of mutant isocitrate dehydrogenase 1. Accurate measurement of ivosidenib is the key to ivosidenib pharmacokinetics in clinical trials. Materials & methods: Quantitation of ivosidenib was conducted by using a stable isotope labeled compound (ivosidenib-d4) as the internal standard. Results: This assay was validated and successfully applied to support multiple clinical trials. Selected clinical samples were also tested by a chiral LC-MS/MS method against four ivosidenib isomer standards to exclude the possibility of in vivo racemization of ivosidenib. Conclusion: A robust LC-MS/MS method was validated for ivosidenib in human plasma. This is the first time for ivosidenib bioanalytical method in any human matrix to be reported.

Quantification of KRAS inhibitor sotorasib in mouse plasma and tissue homogenates using liquid chromatography-tandem mass spectrometry.

Sotorasib is a KRAS inhibitor with promising anticancer activity in phase I clinical studies. This compound is currently under further clinical evaluation as monotherapy and combination therapy against solid tumors. In this study, a liquid chromatography-tandem mass spectrometric method to quantify sotorasib in mouse plasma and eight tissue-related matrices (brain, liver, spleen, kidney, small intestine, small intestine content, lung, and testis homogenates) was developed and validated. Protein precipitation using acetonitrile was utilized in 96-well format to extract sotorasib and erlotinib (internal standard) from mouse plasma and tissue homogenates. Separation of the analytes was performed on an Acquity UPLC® BEH C18 column by gradient elution of methanol and 0.1% formic acid in water at a flow rate of 0.6 ml/min. Sotorasib was detected by a triple quadrupole mass spectrometer with positive electrospray ionization in selected reaction monitoring mode. A linear calibration range of 2-2,000 ng/ml of sotorasib was achieved during the validation. Accuracy values were in the range of 90.7-111.4%, and precision values (intra- and interday) were between 1.7% and 9.2% for all tested levels in all investigated matrices. The method was successfully applied to investigate the plasma pharmacokinetics and tissue accumulation of sotorasib in female wild-type mice.

A highly sensitive and selective UPLC-MS/MS assay for the determination of enarodustat (JTZ-951) in human plasma.

Enarodustat, a potent, orally bioavailable, selective inhibitor of hypoxia inducible factor-Prolyl hydroxylase (HIF-PH), has been approved recently in Japan for the treatment of anemia in patients with chronic kidney disease (CKD). To evaluate the pharmacokinetics of enarodustat, a bioanalytical assay in human plasma was needed for the quantitation of enarodustat for both healthy subjects and patients with CKD. The UPLC-MS/MS method for the quantitation of enarodustat was initially validated in a bioanalytical laboratory in Japan to support clinical studies conducted in Japan, and then was transferred and validated in a bioanalytical laboratory in United States to support clinical studies conducted here. A cross-validation was successfully performed between the two bioanalytical laboratories using both quality control (QC) samples and incurred study samples. Enarodustat was fortified with its isotopically labeled internal standard in a 25 µL plasma aliquot and extracted with protein precipitation. The chromatographic separation was achieved on an Acquity UPLC BEH C18 (1.7 µm, 2.1 × 50 mm) column with gradient elution. The calibration curve range for the assay was 1.00-500 ng/mL. Assay precision, accuracy, linearity, selectivity, sensitivity and analyte stability covering sample storage and analysis were established. No interferences were observed from medications that may be co-administered along with enarodustat. The validated UPLC-MS-MS method at the US bioanalytical laboratory has been successfully applied to eight clinical studies for the determination of enarodustat concentrations in human plasma for both healthy subjects and patients with CKD.

Simulation-Based Interpretation of Therapeutically Monitored Cabozantinib Plasma Concentration in Advanced Adrenocortical Carcinoma with Hemodialysis.

BACKGROUND: Adrenocortical carcinoma is an orphan but aggressive malignancy with limited treatment options. Cabozantinib (CAB), a tyrosine kinase inhibitor, has emerged as a new potential treatment. However, no data are available on whether and how CAB can be administered to patients undergoing hemodialysis. METHODS: An liquid chromatography with tandem mass spectrometry detection method was developed and validated according to the European Medicines Agency and United States Food and Drug Administration guidelines for bioanalytical method validation. The samples were prepared using protein precipitation and online solid-phase extraction. The method was applied to clinical samples of an adrenocortical carcinoma patient receiving CAB treatment (80 mg daily). During the 10 days of observation, the patient received periodic hemodialysis on 7 days. Pharmacokinetic (PK) simulations were performed using Bayesian forecasting according to an existing population PK model for CAB. RESULTS: Based on the PK simulation, a mean plasma trough concentration of 1375 ng/mL [90% prediction interval (PI), 601-2602 ng/mL] in the steady state at a daily dose of 80 mg was expected for CAB. However, an individual simulation involving the measured plasma levels of the patient resulted in a mean trough concentration of 348 ng/mL (90% PI, 278-430 ng/mL). The model based on individual PK parameters estimated accessible plasma levels of 521, 625, and 834 ng/mL by dose adjustment to 100, 120, and 160 mg, respectively. CONCLUSIONS: After establishing an liquid chromatography with tandem mass spectrometry detection method for therapeutic drug monitoring of CAB, our analyses involving a single patient undergoing hemodialysis indicated that higher than expected doses of CAB were required to achieve reasonable plasma concentrations. Our study demonstrates the usefulness of therapeutic drug monitoring for the evaluation of "new" drugs in patients with renal impairment.

Randomized, Double-Blind Comparison of Half-Dose Versus Full-Dose Edoxaban in 14,014 Patients With Atrial Fibrillation.

BACKGROUND: In the ENGAGE AF-TIMI 48 (Effective Anticoagulation with Factor Xa Next Generation in Atrial Fibrillation-Thrombolysis In Myocardial Infarction 48) trial, the lower dose edoxaban regimen (LDER) and the higher dose edoxaban regimen (HDER) were noninferior to well-managed warfarin for stroke prevention in atrial fibrillation. OBJECTIVES: The objective of the present analysis of the ENGAGE AF TIMI-48 trial was to comprehensively compare the net clinical outcome (NCO) of LDER (30 mg once daily, dose reduced to 15 mg in selective patients) versus HDER (60 mg once daily, dose reduced to 30 mg in selective patients). METHODS: This study performed a pre-specified analysis of the ENGAGE AF-TIMI 48 trial, comparing patients on LDER versus HDER. RESULTS: The pre-defined primary NCO (stroke/systemic embolism [SEE], major bleeding, death) was less frequent with LDER (7.26% vs. 8.01%; hazard ratio: 0.90; 95% confidence interval: 0.84 to 0.98; p = 0.014). The secondary (disabling stroke, life-threatening bleeding, or all-cause mortality) and tertiary pre-defined NCOs (stroke, SEE, life-threatening bleeding, or all-cause mortality) were similar between the 2 dosing regimens. Patients randomized to LDER versus HDER had a significantly higher risk of stroke/SEE (2.04% vs. 1.56%; hazard ratio: 1.31; 95% confidence interval: 1.12 to 1.52; p < 0.001). Conversely, major bleeding, intracranial hemorrhage, major gastrointestinal bleeding, and life-threatening bleeding occurred significantly less frequently with LDER compared with those of HDER. These findings were supported by multiple pharmacokinetic findings. CONCLUSIONS: In the ENGAGE AF-TIMI 48 trial, the primary NCO was reduced with LDER versus HDER, whereas the secondary and tertiary NCOs were similar between the 2 dosing regimens. These results may aid physicians in evidence-based individualization of edoxaban dosing. However, the approved HDER remains the standard therapy among the available edoxaban dosing regimens for stroke prevention in atrial fibrillation. (Effective Anticoagulation with Factor Xa Next Generation in Atrial Fibrillation-Thrombolysis In Myocardial Infarction 48 [ENGAGE AF-TIMI 48]; NCT00781391).

Associations among plasma concentrations of regorafenib and its metabolites, adverse events, and ABCG2 polymorphisms in patients with metastatic colorectal cancers.

PURPOSE: The association between the pharmacokinetics and pharmacodynamics of regorafenib, a multiple tyrosine kinase inhibitor, remains unclear. This study assessed the trough plasma concentrations (Ctrough) of regorafenib and its N-oxide (M2) and N-oxide/desmethyl (M5) metabolites, and evaluated the associations among these levels, adverse events, and pharmacokinetic-related genetic polymorphisms in patients with metastatic colorectal cancer. METHODS: The Ctrough levels of regorafenib and its metabolites were assessed in a single-center, prospective, observational study, 7 days after the initial treatment. The correlation between those values and adverse events was then examined. In addition, the genetic polymorphisms of ABCG2, SLCO1B1, and UGT1A9 were determined and evaluated for associations with the levels of regorafenib, M2, and M5. RESULTS: We analyzed 43 patients who received regorafenib 40-120 mg/day; among them, 35 patients started at 120 mg/day. With regard to bilirubin increase, the Ctrough values of regorafenib were significantly higher in the group with grade ≥ 2 than in groups with grades 0 and 1 (p = 0.010). The M5 Ctrough levels were significantly associated with the severity of hypertension or rash (p < 0.05). In a multivariate analysis, the M5 Ctrough values and age were significant predictors of severe rash. Lastly, significant differences were noted in the M5 concentration-to-dose ratio values between the patients with ABCG2 421A/A and ABCG2 421C/A or C/C polymorphisms (p = 0.035). CONCLUSION: This study showed that the Ctrough of regorafenib was associated with bilirubin increase, and also clarified for the first time that the Ctrough of M5 was significantly correlated with hypertension and severe rash.

Understanding Exposure-Receptor Occupancy Relationships for Metabotropic Glutamate Receptor 5 Negative Allosteric Modulators across a Range of Preclinical and Clinical Studies.

The metabotropic glutamate receptor 5 (mGlu5) is a recognized central nervous system therapeutic target for which several negative allosteric modulator (NAM) drug candidates have or are continuing to be investigated for various disease indications in clinical development. Direct measurement of target receptor occupancy (RO) is extremely useful to help design and interpret efficacy and safety in nonclinical and clinical studies. In the mGlu5 field, this has been successfully achieved by monitoring displacement of radiolabeled ligands, specifically binding to the mGlu5 receptor, in the presence of an mGlu5 NAM using in vivo and ex vivo binding in rodents and positron emission tomography imaging in cynomolgus monkeys and humans. The aim of this study was to measure the RO of the mGlu5 NAM HTL0014242 in rodents and cynomolgus monkeys and to compare its plasma and brain exposure-RO relationships with those of clinically tested mGlu5 NAMs dipraglurant, mavoglurant, and basimglurant. Potential sources of variability that may contribute to these relationships were explored. Distinct plasma exposure-response relationships were found for each mGlu5 NAM, with >100-fold difference in plasma exposure for a given level of RO. However, a unified exposure-response relationship was observed when both unbound brain concentration and mGlu5 affinity were considered. This relationship showed <10-fold overall difference, was fitted with a Hill slope that was not significantly different from 1, and appeared consistent with a simple Emax model. This is the first time this type of comparison has been conducted, demonstrating a unified brain exposure-RO relationship across several species and mGlu5 NAMs with diverse properties. SIGNIFICANCE STATEMENT: Despite the long history of mGlu5 as a therapeutic target and progression of multiple compounds to the clinic, no formal comparison of exposure-receptor occupancy relationships has been conducted. The data from this study indicate for the first time that a consistent, unified relationship can be observed between exposure and mGlu5 receptor occupancy when unbound brain concentration and receptor affinity are taken into account across a range of species for a diverse set of mGlu5 negative allosteric modulators, including a new drug candidate, HTL0014242.

Relationship of Edoxaban Plasma Concentration and Blood Coagulation in Healthy Volunteers Using Standard Laboratory Tests and Viscoelastic Analysis.

The capability of viscoelastic measurement parameters to screen anticoagulation activity of edoxaban in relation to its plasma concentrations was evaluated in 15 healthy male volunteers. Blood samples were drawn before the oral administration of edoxaban 60 mg and 2, 4, 6, 8, and 24 hours after administration. At each time, standard coagulation tests were performed, blood viscoelastic properties were measured with a thromboelastometry device ROTEM delta analyzer (Instrumentation Laboratory, Werfen, Barcelona, Spain), and edoxaban plasma concentrations were measured. Our primary interest was the possible correlation between edoxaban plasma concentrations and values for ROTEM ExTEM, and FibTEM. We also studied the correlation of edoxaban plasma concentrations with the results of standard coagulation tests. We saw the effect of a single dose of edoxaban most clearly in clotting time (CT) of ROTEM ExTEM and FibTEM. Changes in these parameters correlated significantly with edoxaban plasma concentrations up to 6 hours from the ingestion of the drug. Activated partial thromboplastin time, prothrombin time, and anti-factor Xa were also affected. Peak changes were observed 2 and 4 hours after administration of edoxaban. The changes were mostly reversed after 8 hours. In conclusion, ROTEM CT correlates significantly with edoxaban plasma concentrations and can be used to estimate the effect of edoxaban. ROTEM should be considered as part of the assessment of coagulation, with the big advantage of being readily available on site.

Effect of Mild and Moderate Hepatic Impairment on the Pharmacokinetics, Safety, and Tolerability of a Single Dose of Oral Ivosidenib in Otherwise Healthy Participants.

Ivosidenib, a small-molecule inhibitor of mutant isocitrate dehydrogenase 1, is primarily cleared by hepatic metabolism. This open-label study investigated the impact of hepatic impairment on ivosidenib pharmacokinetics (ClinicalTrials.gov: NCT03282513). Otherwise healthy participants with mild (n = 9) or moderate (n = 8) hepatic impairment (Child-Pugh score) and matched participants with normal hepatic function (n = 16) received 1 oral dose of 500-mg ivosidenib. Mild hepatic impairment had a negligible effect on total ivosidenib plasma exposure, with geometric mean ratios (90% confidence interval [CI]) of 0.933 (0.715-1.22) for maximum concentration (Cmax ) and 0.847 (0.624-1.15) for area under the plasma concentration-time curve (AUC) in participants with mild hepatic impairment versus matched controls. Moderate hepatic impairment reduced total ivosidenib exposure by 28% to 44%, with geometric mean ratios (90%CI) of 0.565 (0.419-0.763) for Cmax and 0.716 (0.479-1.07) for AUC, although the 90%CI for AUC included 1.00. The ivosidenib unbound fraction was concentration dependent and higher in participants with mild/moderate hepatic impairment compared with matched controls. There was no apparent trend to increasing unbound Cmax with increased hepatic impairment severity. A single 500-mg ivosidenib dose was well tolerated, with no serious or severe adverse events and no adverse events leading to discontinuation. We conclude that mild/moderate hepatic impairment did not lead to clinically relevant changes in ivosidenib exposure following a single 500-mg dose.

Characterization of Isavuconazole serum concentrations after enteral feeding tube administration in a hospitalized cohort: A case series.

WHAT IS KNOWN AND OBJECTIVE: Invasive fungal infections often occur in patients with comorbidities that complicate oral administration. Serum concentrations of isavuconazole were characterized after enteral tube administration. CASE DESCRIPTION: Thirteen of 14 isavuconazole concentrations were >1 mg/dl (median 1.6 mg/dl) among those receiving enteral tube administration, which was comparable to intravenous (median 1.9 mg/dl). Higher concentrations were observed during oral administration (median 3 mg/dl). WHAT IS NEW AND CONCLUSION: Administration of isavuconazole via tube resulted in concentrations comparable to FDA-approved routes of administration. This route may be feasible and appropriate for select patients.

Determination of selpercatinib, a RET kinase inhibitor, in rat plasma and its application to a pharmacokinetic study.

Selpercatinib (LOXO-292) is a selective and potent RET inhibitor. A highly sensitive, rapid and specific high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for quantification of selpercatinib in rat plasma is reported. The method was validated in terms of selectivity, linearity, accuracy and precision, extraction recovery and matrix effect, stability and carryover as per the US Food and Drug Administration guidelines for bioanalytical method validation. Selpercatinib was detected by an electrospray ionization interface under selective reaction monitoring conditions in the positive ion mode. The calibration curve was linear over the concentration range from 1 to 2000 ng/ml with r2 = 0.9951. The intra- and inter-batch accuracy values ranged from 97.45 to 100.97% and from 98.70 to 100.74% with coefficients of variation of 2.45-6.99% and 5.89-7.99%, respectively. The extraction recovery and IS-normalized matrix factor were acceptable for the bioanalysis of selpercatinib. Additionally, selpercatinib was found to be stable under the detected conditions. It showed linear pharmacokinetic characteristics following oral administration to rats at 2.0-18.0 mg/kg. The results showed that the novel method for detecting selpercatinib in rat plasma could be successfully applied for quantification of selpercatinib in biosamples from nonclinical studies.

Validated HPLC-MS/MS method for quantitation of AMG 510, a KRAS G12C inhibitor, in mouse plasma and its application to a pharmacokinetic study in mice.

AMG 510 is the first-in-class KRASG12C inhibitor, currently in phase 2 clinical trials as an orphan drug to treat non-small cell lung cancer patients. We developed and validated a sensitive, selective, and high-throughput HPLC-MS/MS method for the quantitation of AMG 510 in mouse plasma per the regulatory guideline of the US Food and Drug and Administration. AMG 510 and the IS (MRTX-1257) were extracted from mouse plasma using tert-butyl methyl ether and chromatographed using an isocratic mobile phase (0.2% formic acid:acetonitrile; 25:75, v/v) at a flow rate of 0.65 mL/min on an Atlantis dC18 column. AMG 510 and the IS eluted at ~0.95 and 0.73 min, respectively. AMG 510 and the IS were detected by positive electrospray ionization in multiple reaction monitoring using transition pair (Q1 → Q3) m/z 561.1 → 134.1 and m/z 566.5 → 98.2, respectively. Excellent linearity was achieved in the concentration range of 1.08-5040 ng/mL (r > 0.0996). No matrix effect and carryover were observed. Intra- and inter-day accuracies and precisions were within the acceptance range. AMG 510 was demonstrated to be stable under the tested storage conditions. This novel method has been applied to a pharmacokinetic study in mice.

Absence of ethnic difference on single-dose pharmacokinetics of rivoceranib between healthy male Caucasian, Japanese, and Chinese subjects.

Rivoceranib (known in China as apatinib) is a selective vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase inhibitor which inhibits angiogenesis in solid tumors. The aim of study was to evaluate potential pharmacokinetic (PK) differences between the Caucasian, Japanese, and Chinese populations. An open-label, single-dose, parallel-design PK study of rivoceranib was conducted in Caucasian, Japanese, and Chinese subjects. A total of 18 healthy males were recruited to each group (54 total), and 201 mg rivoceranib tablets (as 250 mg rivoceranib mesylate) were administered orally to subjects. Plasma samples were collected, and rivoceranib plasma concentration was determined using LC-MS/MS. For PK analysis, non-compartmental and compartmental analyses were performed. Intrinsic factors (CYP2C19 and CYP3A4 genotype) were also examined. Non-compartmental analysis showed no significant difference in AUC0-t , AUC0-∞ , Cmax , tmax , and t1/2 . Apparent clearance and volume of distribution were different across the three populations; however, the extent of this difference does not require dose modification. For compartmental modeling, a two-compartment model was used to fit the plasma concentrations. No significant difference was observed in absorption, elimination, and intercompartmental transfer rate constants among the three groups. The present study shows no major ethnic PK differences between Caucasian, Japanese, and Chinese populations.