Safety and blood levels of daratumumab after switching from intravenous to subcutaneous administration in patients with multiple myeloma.

The intravenous administration (IV) of daratumumab sometimes causes an infusion reaction and needs a long infusion time. Recently, a subcutaneous formulation (SC) of daratumumab, which has fewer infusion reactions and shorter administration time, was approved. However, because SC has a fixed dose, overdosing is a concern for patients with low body weights. In this study, we investigated the safety and blood levels of daratumumab after switching from IV to SC in patients with multiple myeloma (MM). Patients who switched from IV to SC of daratumumab between June 2021 and May 2022 at Kobe City Medical Center General Hospital were included in the study. Blood daratumumab levels were measured using liquid chromatography-tandem mass spectrometry. Safety after switching from IV to SC was evaluated for six months and graded according to the Common Terminology Criteria for Adverse Events, version 5.0. The median body weight of ten patients included in the analysis was 57.4 kg (range: 45.0-74.4). Blood daratumumab levels were significantly increased after switching to SC (p = 0.002); median through concentration at the last IV dose was 403.6 µg/mL (range: 96.3-776.3) and that at the third SC dose was 557.1 µg/mL (range: 288.3-997.2). Grade 1-2 injection site reactions were observed in six patients (60.0%) after switching to SC. A new grade 3 adverse event was observed in only one patient (neutropenia). The blood levels of daratumumab were significantly increased after switching from IV to SC in patients with MM; however, the dosage was tolerable.

Population Pharmacokinetics of Nivolumab in Japanese Patients with Nonsmall Cell Lung Cancer.

BACKGROUND: Nivolumab is an antiprogrammed death-1 (PD-1) antibody used for immuno-oncological therapy of various cancers, including nonsmall cell lung cancer (NSCLC). This study aimed to characterize the real-world population pharmacokinetics (PK) of nivolumab in patients with NSCLC. METHODS: PK samples were collected by opportunistic sampling of Japanese patients with NSCLC treated with nivolumab monotherapy. Population PK analysis was performed using a two-compartment model in Nonlinear Mixed Effect Model. Patient-specific factors such as body weight, age, sex, serum albumin, estimated glomerular filtration rate, performance status, programmed cell death receptor ligand 1 expression in tumors, and treatment periods were evaluated as potential covariates for clearance. RESULTS: A total of 223 serum samples collected from 34 patients were available for analysis. The median (min-max) age and weight were 69 years (38-83 years) and 62.7 kg (36.8-80.5 kg), respectively. The mean (95% confidence interval) clearance estimate was 0.0064 L/h (0.0058-0.0070 L/h). The inclusion of the ALB level, estimated glomerular filtration rate, and treatment period significantly improved the model fit. CONCLUSIONS: A real-world nivolumab population PK model was developed using an opportunistic sampling strategy in Japanese patients with NSCLC. Further studies are warranted to characterize the exposure-response relationship and determine the optimal dosing regimens for these patients.

Pharmacokinetics of Temozolomide in a Patient With Glioblastoma Undergoing Hemodialysis: A Short Communication.

BACKGROUND: Temozolomide (TMZ) is an alkylating agent used to treat glioblastoma. However, the pharmacokinetics of TMZ to establish a treatment strategy for patients undergoing hemodialysis (HD) remain unclear. In this case report, we evaluated the pharmacokinetics and HD removal rate of TMZ in a patient with glioblastoma undergoing HD to determine optimal dosing of TMZ. METHODS: A 78-year-old man with glioblastoma who underwent HD 3 times a week was treated with TMZ concomitant with radiotherapy. One dose of TMZ was prescribed at 75 mg/m 2 on the day before HD and another dose of 37.5 mg/m 2 on the day before non-HD. Peak and trough concentrations (1 hour and 12 hours after dosing, respectively) were evaluated before HD and on non-HD days. HD removal rate of TMZ was calculated based on the predialyzer and postdialyzer plasma concentrations. Furthermore, the TMZ plasma concentrations were measured using liquid chromatography-tandem mass spectrometry. RESULTS: The mean plasma peak and trough concentrations ± SD after 75 mg/m 2 TMZ were 2917 ± 914 and 108 ± 17.6 ng/mL, respectively. Those after 37.5 mg/m 2 TMZ dosage were 1305 ± 650 and 53.8 ± 11.8 ng/mL, respectively. The mean HD TMZ removal rate was 84.9 ± 1.9%. CONCLUSIONS: TMZ was tolerable in patients undergoing HD. Based on the data from a single individual pharmacokinetic perspective, the pharmacokinetics of TMZ in this patient undergoing HD were comparable with those observed in patients with normal renal function. In addition, it may be reasonable to administer TMZ after HD because of the high HD removal rate.

Use of liquid chromatography-tandem mass spectrometry for foscarnet quantification in human serum and cerebrospinal fluid.

RATIONALE: Foscarnet (FCV) is used to treat cytomegalovirus, human herpesvirus, and human immunodeficiency virus infections. It is a low-molecular-weight compound containing carboxylate and phosphate groups. There are no reports on the use of liquid chromatography-tandem mass spectrometry (LC/MS/MS) to analyze FCV via bioanalysis. In the present study, we developed the ion-pair LC/MS/MS method to analyze FCV in human serum and cerebrospinal fluid (CSF). METHODS: FCV was extracted from human serum and CSF by weak anion exchange (WAX) solid-phase extraction. The LC/MS/MS systems were coated with 0.1% phosphoric acid in methanol to avoid nonspecific absorption. FCV was detected using ion-pair LC/MS/MS with dibutylammonium acetate. Selected reaction monitoring transition of FCV in the negative ion mode was selected at m/z 125.1 → 62.9. RESULTS: FCV was selectively detected in human serum and CSF, and the liner range was 5-1000 µM (R2 = 0.99). The intraday and interday accuracy and precision were within ±15%. FCV was constantly extracted from human serum and CSF by WAX solid-phase extraction (recovery ratio = 76.0-77.9%). No matrix effect was observed. CONCLUSIONS: A robust LC/MS/MS method to analyze FCV was successfully developed. FCV was selectively measured using LC/MS/MS in very low extract volumes (20 µL). The method will be useful in evaluating the FCV level in human serum and CSF.

Effects of ABCB1 and ABCG2 polymorphisms on the pharmacokinetics of abemaciclib.

PURPOSE: Adverse events after the use of the CDK4/6 inhibitor abemaciclib are dose-dependent. However, its pharmacokinetics varies among individuals. Abemaciclib is reportedly transported by P-glycoprotein and breast cancer resistance protein. Therefore, we evaluated whether ABCB1 and ABCG2 polymorphisms are pharmacokinetic predictive factors of abemaciclib. METHODS: A total of 45 patients with breast cancer taking abemaciclib (150 mg twice per day) for 2 weeks were evaluated to determine the associations among abemaciclib concentration; adverse events; and ABCB1 1236 T > C, 2677G > T/A, 3435C > T, and ABCG2 421C > A gene polymorphisms. RESULTS: The trough concentration of abemaciclib was significantly higher in the group with grade 2 or greater neutropenia and thrombocytopenia than in those with grades 0 or 1. For ABCB1 2677G > T/A polymorphisms, the concentration of abemaciclib tended to be higher in the homozygous group (TT + AT) than in the wild-type + heterozygous group (GG + GA + GT) (median [range], 222.8 [80.5-295.8] ng/mL vs. 113.5 [23.6-355.2] ng/mL, P = 0.09), Moreover, the ABCB1 2677G > T/A homozygous group had a higher tendency of abemaciclib withdrawal or dose reduction within 4 weeks than the wild-type + heterozygous group (odds ratio, 4.22; 95% confidence interval, 0.86-20.7; P = 0.08). No significant association was observed among abemaciclib concentration; adverse reactions; and ABCB1 1236 T > C, 3435C > T, and ABCG2 421C > A polymorphisms. CONCLUSION: ABCB1 2677G > T/A polymorphism might be a predictor of the pharmacokinetics and tolerability of abemaciclib.

Serum concentration of the CKD4/6 inhibitor abemaciclib, but not of creatinine, strongly predicts hematological adverse events in patients with breast cancer: a preliminary report.

Purpose The CKD4/6 inhibitor abemaciclib is related to adverse events such as hematological toxicity and increase in serum creatinine levels associated with abemaciclib pharmacokinetics. Increase in serum creatinine levels is considered a result of competition with abemaciclib via organic cation transporter 2 and multidrug and toxic compound extrusion. Therefore, we evaluated the association among serum creatinine levels, serum abemaciclib concentrations, and adverse events and whether increase in serum creatinine levels is a useful indicator for predicting the onset of the adverse events of abemaciclib. Methods In total, the data of 12 patients with breast cancer who were treated with abemaciclib (150 mg twice daily) were evaluated to determine the association between increased serum creatinine levels and abemaciclib concentrations and hematological toxicity. Results Grade 3 neutropenia, thrombocytopenia, and anemia were observed at 4 weeks in four (33%), two (17%), and one (8%) patients, respectively. A significant association was observed between steady-state abemaciclib concentrations and the rate of decrease in neutrophil and platelet counts (r = - 0.80, P = 0.003 and r = - 0.70, P = 0.016, respectively). Compared with baseline levels (0.61 [0.53-0.82] mg/mL), serum creatinine levels significantly increased and reached a steady state in at least 2 weeks (0.84 [0.61-1.02] mg/mL, P = 0.01). However, we did not find a significant association between increase in serum creatinine levels and abemaciclib concentrations and hematological toxicity. Conclusions Abemaciclib concentrations are associated with neutropenia and thrombocytopenia. However, increase in serum creatinine levels may not be a useful predictor for estimating abemaciclib pharmacokinetics and hematological toxicity.

Population pharmacokinetics of tacrolimus in umbilical cord blood transplant patients focusing on the variation in red blood cell counts.

WHAT IS KNOWN AND OBJECTIVE: The distribution of tacrolimus (TAC), an immunosuppressant used during cord blood transplantation (CBT)-one of the haematopoietic stem cell transplantations, to red blood cell (RBC) is approximately 90% in whole blood. In CBT patients, the total RBC count shows dramatic fluctuation due to conditioning before transplantation, including anticancer agents and total body irradiation, as well as RBC transfusions during the treatment period. Therefore, the amount of TAC in whole blood may show wide variation. However, therapeutic drug monitoring (TDM) of TAC has been performed based on the whole blood concentration. In this study, to contribute to TDM of TAC in CBT, we performed the population pharmacokinetic (PPK) analysis of TAC in 56 CBT patients and investigated the factors that affected the concentration of TAC, focusing the variation of RBC count. METHOD: A one-compartment model was applied to the observed whole blood TAC concentrations, and a PPK analysis was conducted with a non-linear mixed effect model. RESULTS AND DISCUSSION: Our final PPK model indicated good robustness and accuracy. In addition, haemoglobin (Hb) level was an influential covariate on Vd, which was expressed as Vd(L) = 91.4 × (Hb/8.2)(-1.07) . WHAT IS NEW AND CONCLUSION: In this study, our results showed the necessity for the Hb level monitoring during TDM of TAC in CBT patients and provided useful information for improving TDM strategy of TAC.

Osimertinib in a patient with non-small cell lung cancer and renal failure undergoing hemodialysis: a case report.

Osimertinib is a key drug for cancer patients with EGFR mutations. However, there is little information about its safety in cancer patients who require hemodialysis (HD) for chronic renal failure, despite notable increases in their numbers. Herein, we examined osimertinib safety in such a patient via pharmacokinetics analysis. A 66-year-old man was diagnosed with relapsed stage IV non-small cell lung cancer with an EGFR mutation in exon 21 (L858R) 2 years after stereotactic body radiotherapy. He was undergoing HD three times a week owing to worsening diabetic nephropathy. We administered osimertinib (80 mg/day) as the first-line therapy. We measured osimertinib concentrations on multiple days, either before, after, or in the absence of HD. Maximum concentrations and areas under the curve were determined. We found that HD did not affect the pharmacokinetics of osimertinib. We conclude that osimertinib can be safely administered to cancer patients undergoing HD.

Pharmacokinetic analysis for model-supported therapeutic drug monitoring of busulfan in Japanese pediatric hematopoietic stem cell transplantation recipients.

This prospective observational study analyzed the pharmacokinetics of busulfan in Japanese children and evaluated the predicting accuracy of previous pediatric PPK models of busulfan. This study enrolled five patients (aged 2-12 years, BW 14-48 kg) receiving a busulfan-based conditioning regimen for hematopoietic stem cell transplantation at our hospital between January 2017 and December 2018. All patients received a 2-hour intravenous busulfan infusion four times daily for a total of 16 doses. After the infusions, 51 plasma samples were collected with the plasma busulfan concentration measured by liquid chromatography-tandem mass spectrometry. PPK model fitting was analyzed using the (%MPE) and the (%MAPE). Limited sampling strategies for estimating busulfan AUC were also evaluated. High interpatient variability was observed in the PK parameters. The most suitable PPK model that reflected our data was McCune's two-compartment model (%MPE -8.7, %MAPE 19.3). A combination sampling method using the busulfan concentration at 2 and 6 hours after the start of the first busulfan dose was found to be able to estimate AUC4 day . These results provide useful information on busulfan therapeutic drug monitoring in the Japanese pediatric population.

Assessment of exposure risk of irinotecan and its active metabolite, SN-38, through perspiration during chemotherapy.

BACKGROUND: Irinotecan (CPT-11) is the key drug used in chemotherapy for many malignant tumors. CPT-11 has cholinergic activity and induces perspiration during intravenous administration. In this study, concentrations of CPT-11 and its active metabolite, SN-38, released during perspiration were measured and risk of exposure of these drugs was assessed. METHOD: Beads of sweat were collected using a dropper from four patients undergoing a chemotherapy regimen involving intravenous administration of CPT-11. The concentrations of CPT-11 and SN-38 in sweat were measured using liquid chromatography tandem mass spectrometry. RESULT: Chemotherapy regimens were capecitabine and irinotecan plus bevacizumab (n = 1), CPT-11 monotherapy (n = 1), and oxaliplatin-irinotecan-leucovorin-5-fluorouracil (n = 2). Uridine diphosphate-glucuronosyltransferase 1A1 phenotypes were *6 homo-type (n = 1), *6 hetero-type (n = 1), and wild type (n = 2). CPT-11 dose was 292.3 ± 75.5 mg/body weight (mean ± standard deviation). CPT-11 was detected in sweat secreted by all the four patients, and its mean (±standard deviation) concentration was 252.6 (±111.9) ng/ml. SN-38 was detected in only one of the patients who received oxaliplatin-irinotecan-leucovorin-5-fluorouracil treatment and who had the wild-type uridine diphosphate-glucuronosyltransferase 1A1 phenotype at a concentration of 74.37 ng/ml. CONCLUSION: CPT-11 and SN-38 are detected in sweat released during intravenous CPT-11 administration. Beads of sweat or linen clothes that absorb the sweat might be the source of CPT-11 and SN-38 exposure.

Standard-dose osimertinib for refractory leptomeningeal metastases in T790M-positive EGFR-mutant non-small cell lung cancer.

BACKGROUND: Osimertinib demonstrated promising efficacy for refractory leptomeningeal metastases (LM) in preclinical data and a clinical study at 160 mg, but there is limited data for the standard 80 mg dose. METHODS: T790M-positive patients with suspected LM after classical epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) failure were enroled. RESULTS: We investigated 13 patients (5 definitive and 8 possible LM cases). In two of the five definitive cases with T790M in and outside the central nervous system (CNS), osimertinib was effective for both lesions, with cerebrospinal fluid (CSF) clearance of cancer cells and sensitive/T790M mutations. In three definitive cases with extra-CNS T790M without CSF T790M, cancer cells and sensitive mutations in the CSF persisted after osimertinib initiation. The median progression-free survival of all 13 patients was 7.2 months. Osimertinib was generally well-tolerated despite poor performance status, but interstitial lung disease (grade 2) was confirmed in one patient. Based on 25 samples from 13 patients, the osimertinib CSF penetration rate was 2.5±0.3%. CONCLUSIONS: Osimertinib 80 mg is a useful therapeutic option for refractory LM after classical EGFR-TKI failure. It appears more effective in CSF T790M-positive cases.

Relationship between Paronychia and Drug Concentrations of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors.

PURPOSE: The purpose of the study was to evaluate the site of paronychia in patients with non-small cell lung cancer harboring an epidermal growth factor receptor (EGFR) gene activating mutation who were treated with EGFR tyrosine kinase inhibitors (EGFR TKIs). PATIENTS AND METHODS: The study included 55 patients with non-small-cell lung cancer who were treated with an EGFR TKIs. Resulting all toxicities were graded using the Common Terminology Criteria for Adverse Events version 4.0 system. Drug concentrations were determined with use of a quantum triple-quadrupole mass spectrometer and dried blood spots testing. RESULTS: Paronychia most commonly occurred in the thumb and the big toe. There was no correlation between the severity of paronychia and the drug concentration of each EGFR TKI at the site of paronychia. The mean penetration rates of the drug from plasma to the tip of the finger and toe were 74.1% (erlotinib), 82.2% (gefitinib), and 99.9% (afatinib). CONCLUSIONS: High concentrations of an EGFR TKI at the affected site did not play a role in the onset mechanism of paronychia. Therefore, educating patients about ways to avoid compression may be a better approach to managing this adverse event than reducing the dose of the EGFR-TKI or stopping treatment.

An LC-MS/MS Method for Absolute Quantification of Nivolumab in Human Plasma: Application to Clinical Therapeutic Drug Monitoring.

BACKGROUND: Nivolumab is a fully humanized IgG4 monoclonal antibody that targets the programmed death-1 (PD-1) receptor, disrupting PD-1-mediated signaling and restoring antitumor immunity. The objective of this study was to develop a nivolumab quantification method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and to evaluate its application in clinical therapeutic drug monitoring. METHODS: Nivolumab was purified from human plasma using rProtein A resin and then digested with trypsin. The ASGITFSNSGMHWVR peptide (multiple reaction monitoring transition: m/z 550.6→661.4) was detected as a surrogate peptide of nivolumab by triple quadrupole mass spectrometry. Plasma samples (126) were collected from 14 patients with non-small cell lung cancer who were undergoing clinical dosing regimen with nivolumab. The pharmacokinetic data were analyzed using Phoenix NLME software (Version 7.0, Certara, St. Louis, MO) based on a previously reported population pharmacokinetics (PPK) model of nivolumab. RESULTS: Nivolumab was selectively detected in human plasma and the linear range was 5-200 mcg/mL (R = 0.99). The accuracy and intraday and interday imprecision were within ±15% of the quality control values of 5 (lower limit of quantification), 10 (low), 80 (medium), and 160 (high) mcg/mL. The nivolumab concentrations measured using LC-MS/MS were consistent with those of previously reported PPK models, and the pharmacokinetic parameters could be adequately predicted from a single trough concentration using a Bayesian approach. CONCLUSIONS: An absolute quantification method for nivolumab using LC-MS/MS was successfully developed and validated. Combined with PPK analysis, this method should be useful for the therapeutic drug monitoring of nivolumab in clinical practice.

Successful intracranial response of lorlatinib after resistance with alectinib and brigatinib in patients with ALK-positive lung adenocarcinoma: Implications of CNS penetration rate of brigatinib.

We present the case of a 34-year-old Japanese man with anaplastic lymphoma kinase (ALK)-positive non-small cell lung cancer and brain metastases. After central nervous system (CNS) disease progression with alecintib and brigatinib, treatment with lorlatinib resulted in a good intracranial response. In this case, we investigated brain penetration ratio of brigatinib using cerebrospinal fluid and paired serum samples, and the ratio was 0.012. Further, we investigated resistance mechanisms via next-generation sequencing (NGS) using lung biopsy at lung cancer diagnosis and brain biopsy sample at progressive disease of brigatinib. No apparent resistance mechanism of known ALK resistance, such as ALK mutations, amplifications, epithelial-mesenchymal transition (EMT) and bypass pathway activation were detected. Taken together, we speculate that the low CNS penetration rate of brigatinib confers CNS progression. Further studies are warranted to reveal the resistance mechanism and propose a treatment strategy for CNS progression in ALK-positive patients.

Quantification of cerebrospinal fluid tumor DNA in lung cancer patients with suspected leptomeningeal carcinomatosis.

Cerebrospinal fluid tumor-derived DNA (CSF-tDNA) analysis is a promising approach for monitoring the neoplastic processes of the central nervous system. We applied a lung cancer-specific sequencing panel (CAPP-Seq) to 81 CSF, blood, and tissue samples from 24 lung cancer patients who underwent lumbar puncture (LP) for suspected leptomeningeal disease (LMD). A subset of the cohort (N = 12) participated in a prospective trial of osimertinib for refractory LMD in which serial LPs were performed before and during treatment. CSF-tDNA variant allele fractions (VAFs) were significantly higher than plasma circulating tumor DNA (ctDNA) VAFs (median CSF-tDNA, 32.7%; median plasma ctDNA, 1.8%; P < 0.0001). Concentrations of tumor DNA in CSF and plasma were positively correlated (Spearman's ρ, 0.45; P = 0.03). For LMD diagnosis, cytology was 81.8% sensitive and CSF-tDNA was 91.7% sensitive. CSF-tDNA was also strongly prognostic for overall survival (HR = 7.1; P = 0.02). Among patients with progression on targeted therapy, resistance mutations, such as EGFR T790M and MET amplification, were common in peripheral blood but were rare in time-matched CSF, indicating differences in resistance mechanisms based on the anatomic compartment. In the osimertinib cohort, patients with CNS progression had increased CSF-tDNA VAFs at follow-up LP. Post-osimertinib CSF-tDNA VAF was strongly prognostic for CNS progression (HR = 6.2, P = 0.009). Detection of CSF-tDNA in lung cancer patients with suspected LMD is feasible and may have clinical utility. CSF-tDNA improves the sensitivity of LMD diagnosis, enables improved prognostication, and drives therapeutic strategies that account for spatial heterogeneity in resistance mechanisms.

[Pharmacokinetic Study of Antiviral Drugs in Patients with COVID-19].

The Faculty of Pharmaceutical Sciences, Kobe Gakuin University has collaborated in clinical research with Kobe City Medical Center General Hospital. In this university-medical institution collaboration, university faculty members discuss clinical problems with on-site pharmacists and doctors, and carry out clinical research to resolve these problems. During the coronavirus disease 2019 (COVID-19) pandemic, many patients with COVID-19 were treated at Kobe City Medical Center General Hospital. In February 2020, during the first increase in the number of patients with COVID-19 in Japan, treatment for COVID-19 was not established, and some existing anti-viral drugs, such as favipiravir, were experimentally used for COVID-19 treatment. However, since these drugs were not developed specifically for treating COVID-19, their pharmacokinetics have not been sufficiently studied. In particular, the pharmacokinetics of favipiravir in critically ill patients with COVID-19 was of concern, because critically ill patients have an urgent need for life-saving anti-viral drug treatment. Therefore, we conducted a collaborative clinical study to evaluate the pharmacokinetics of favipiravir in patients with COVID-19. The blood concentration of favipiravir in patients with COVID-19 at Kobe City Medical Center General Hospital was measured by lipid chromatography-tandem mass spectrometry at Kobe Gakuin University. Population pharmacokinetics analysis was then performed. In this symposium review, we introduce our pharmacokinetic study of antiviral drugs in patients with COVID-19, focusing on the university-medical institution collaboration. We believe collaborative clinical research will be useful for solving clinical issues and ensuring the effectiveness and safety of pharmacotherapies.

Effects of ABCB1 and ABCG2 Polymorphisms on the Pharmacokinetics of Abemaciclib Metabolites (M2, M20, M18).

BACKGROUND/AIM: Abemaciclib, an oral anticancer drug used in the treatment of breast cancer, is metabolised to its active forms - M2, M20 and M18; these forms have a potency similar to that of the parent drug. Abemaciclib and its active metabolites are reportedly transported by P-glycoprotein and breast cancer resistance protein (BCRP). We previously reported that the ABCB1 2677G>T/A homozygous type is associated with a higher abemaciclib concentration leading to treatment withdrawal and/or dose reduction. However, the pharmacokinetics of its metabolites have not been investigated. The purpose of the present study was to evaluate the effects of ABCB1 and ABCG2 polymorphisms on the pharmacokinetics of the abemaciclib metabolites M2, M20 and M18. PATIENTS AND METHODS: We evaluated 40 patients with breast cancer who received 150 mg abemaciclib twice per day for 2 weeks at the Aichi Cancer Center Hospital, Japan. Peak areas (arbitrary unit) of abemaciclib metabolites were measured using liquid chromatography tandem with mass spectrometry and compared between ABCB1 1236T>C, 2677G>T/A, 3435C>T and ABCG2 421C>A gene polymorphisms. RESULTS: For ABCB1 2677G>T/A polymorphisms, exposure doses for the abemaciclib metabolites M2 and M20 were higher in the homozygous (TT + AT) group than in the wild-type and heterozygous (GG + GA + GT) groups (p=0.09 and p=0.06, respectively). No significant association was observed between abemaciclib metabolites and ABCB1 1236T>C, ABCB1 3435C>T and ABCG2 421C>A polymorphisms. CONCLUSION: The ABCB1 2677G>T/A polymorphism may influence tolerance to abemaciclib in breast cancer patients by affecting the pharmacokinetics of the agent and its active metabolites.

Population pharmacokinetics and exposure-clinical outcome relationship of remdesivir major metabolite GS-441524 in patients with moderate and severe COVID-19.

Although remdesivir, a prodrug of nucleoside analog (GS-441524), has demonstrated clinical benefits in coronavirus disease 2019 (COVID-19) treatment, its pharmacokinetics (PKs) in patients with COVID-19 remain poorly understood. Therefore, in this study, the PKs of remdesivir and its major metabolite, GS-441524, were evaluated using a population PK (PopPK) approach to understand the PK aspect and exposure-clinical outcome relationship. The serum concentrations of remdesivir and GS-441524 (102 points in 39 patients) were measured using liquid chromatography-tandem mass spectrometry. All patients received 200 mg remdesivir on the first day, followed by 100 mg on 2-5 days, except for one patient who discontinued remdesivir on day 4. The median (range) age, body surface area, and estimated glomerular filtration rate (eGFR) were 70 (42-85), 1.74 m2 (1.36-2.03), and 68 mL/min/1.73 m2 (33-113), respectively. A compartment model with first-order elimination combined with remdesivir and GS-441524 was used for nonlinear mixed-effects model analysis. Remdesivir was rapidly eliminated after infusion, whereas GS-441524 was eliminated relatively slowly (half-time = 17.1 h). The estimated apparent clearance (CL) and distribution volume of GS-441524 were 11.0 L/h (intersubject variability [ISV]% = 43.0%) and 271 L (ISV% = 58.1%), respectively. The CL of GS-441524 was significantly related to the eGFR (CL × [eGFR/68]0.745 ). The post hoc area under the curve of GS-441524 was unrelated to the recovery rate or aspartate aminotransferase/alanine aminotransferase elevation. Overall, PopPK analysis showed the rapid elimination of remdesivir in the blood, and GS-441524 accumulation depended on eGFR in patients with COVID-19. However, no relevance of exposure-clinical outcome was not suggestive of the dose adjustment of remdesivir.

Ceftriaxone-associated encephalopathy in a patient with high levels of ceftriaxone in blood and cerebrospinal fluid.

Neurotoxicity is a rare and intolerable adverse effect of ceftriaxone therapy. In most cases, it has been diagnosed on the basis of medical history rather than quantitative blood and cerebrospinal fluid testing. We report the case of a woman aged 78 years with ceftriaxone-associated encephalopathy. She regularly underwent hemodialysis. The patient received intravenous ceftriaxone at a dose of 1 g/day for 10 days for a urinary tract infection, and her consciousness level began to deteriorate during the therapy. Five days after ceftriaxone discontinuation, her symptoms rapidly improved. Thus, ceftriaxone-associated encephalopathy was suspected. Ceftriaxone levels in the blood and cerebrospinal fluid were high while the patient had disturbed consciousness. This case showed that ceftriaxone levels were related to ceftriaxone-associated encephalopathy. Therefore, the estimation of ceftriaxone levels may facilitate an accurate diagnosis.