Quantitative systems pharmacology model of thrombopoiesis and platelet life-cycle, and its application to thrombocytopenia based on chronic liver disease.

Platelets are produced by hematopoietic stem cells via megakaryocytes in the bone marrow and play a critical role in hemostasis. The aim of this study was to develop a new platelet model based on the thrombopoiesis and platelet life-cycle by a quantitative systems pharmacology modeling approach, which could describe changes in platelet count profiles in platelet-related diseases and drug intervention. The proposed platelet model consists of 44 components. The model was applied to thrombopoiesis of a thrombopoietin receptor agonist, lusutrombopag. It could well describe the observed platelet count profiles after administration of lusutrombopag for both healthy subjects and patients with chronic liver disease and thrombocytopenia. This model should be useful for understanding the disease progression of platelet-related conditions, such as thrombocytopenia and for predicting platelet count profiles in various disease situations related to platelets and drug administration in drug development.

Evaluation of drug-drug interaction of lusutrombopag, a thrombopoietin receptor agonist, via metabolic enzymes and transporters.

PURPOSE: Drug-drug interaction (DDI) potentials of lusutrombopag, a thrombopoietin receptor agonist, on the activity of cytochrome P450 (CYP) 3A and of cyclosporine, which inhibits P-glycoprotein and breast cancer resistance protein, on lusutrombopag pharmacokinetics were assessed via clinical studies and physiologically based pharmacokinetic (PBPK) modeling. METHODS: The effect of lusutrombopag on midazolam (a CYP3A probe substrate) pharmacokinetics was assessed in 15 healthy subjects receiving a single midazolam 5-mg dose with or without coadministration of lusutrombopag 0.75 mg for 6 days (first dose: 1.5-mg dose). The effect of cyclosporine on lusutrombopag pharmacokinetics was assessed in 16 healthy subjects receiving a single lusutrombopag 3-mg dose with or without a single cyclosporine 400- to 600-mg dose. PBPK modeling was employed to extrapolate the effect of lusutrombopag at the clinical dose (3 mg once daily) on midazolam pharmacokinetics. RESULTS: In the clinical study, mean ratios (90% confidence intervals [CIs]) of with/without lusutrombopag for maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) of midazolam were 1.01 (0.908-1.13) and 1.04 (0.967-1.11), respectively, indicating no effect of lusutrombopag on midazolam pharmacokinetics. PBPK modeling suggested no effect of lusutrombopag at the clinical dose on midazolam pharmacokinetics. Mean ratios (90% CIs) of with/without cyclosporine for lusutrombopag Cmax and AUC were 1.18 (1.11-1.24) and 1.19 (1.13-1.25), respectively, indicating a slight increase in lusutrombopag exposure. CONCLUSIONS: In consideration with in vitro data, the in vivo and in silico results suggested no clinically significant DDI potential of lusutrombopag with other medical products via metabolic enzymes and transporters.

A randomized controlled trial of lusutrombopag in Japanese patients with chronic liver disease undergoing radiofrequency ablation.

BACKGROUND: Thrombocytopenia represents an obstacle for invasive procedures in chronic liver disease (CLD) patients. We aimed to estimate the appropriate dose and evaluate the efficacy and safety of lusutrombopag for the treatment of thrombocytopenia before percutaneous liver radiofrequency ablation (RFA) for primary hepatic cancer in patients with CLD. METHODS: In this multicenter, randomized, double-blind, placebo-controlled study conducted in Japan, 61 CLD patients with platelet count < 50 × 103/µL at screening were randomized to placebo or lusutrombopag 2, 3, or 4 mg once daily for 7 days, followed by a 28-day post-treatment assessment period. The primary efficacy endpoint was the proportion of patients who did not require platelet transfusion before RFA. The pre-specified key secondary efficacy endpoint was the proportion of responders. Adverse events (AEs) and thrombosis-related AEs were evaluated. RESULTS: The proportion of patients who did not require platelet transfusion before RFA and that of responders were significantly higher (p < 0.01) in the 2-mg (80.0, 66.7%), 3-mg (81.3, 68.8%), and 4-mg groups (93.3, 80.0%) compared with the placebo group (20.0, 6.7%) and showed a dose-dependent effect. The incidence of AEs was 97.8 and 100% in the lusutrombopag (all groups) and placebo groups, respectively; no dose-related increase was observed. Four patients experienced thrombosis-related events (one each in the placebo and 2-mg groups, and two in the 4-mg group). A total of 16 (18%) adverse drug reactions occurred in the safety analysis set. CONCLUSIONS: Lusutrombopag 3 mg once daily for 7 days was effective without raising concerns about excessive increases in platelet count. CLINICAL TRIAL REGISTRATION: The study is registered at JapicCTI-121944.

Drug-drug interaction of cefiderocol, a siderophore cephalosporin, via human drug transporters.

PURPOSE: Cefiderocol, a siderophore cephalosporin, will be used concomitantly with other medications for treatment of bacterial infections. In vitro studies demonstrated inhibition potential of cefiderocol on organic anion transporter (OAT) 1, OAT3, organic cation transporter (OCT) 1, OCT2, multidrug and toxin extrusion (MATE) 2-K, and organic anion transporting polypeptide (OATP) 1B3. The aim of this study was to assess in vivo drug-drug interaction (DDI) potential of cefiderocol using probe substrates for these transporters. METHODS: DDI potentials of cefiderocol as inhibitors were assessed in a clinical study consisting of 3 cohorts. Twelve or 13 healthy adult subjects per cohort orally received a single dose of furosemide 20 mg (for OAT1/3), metformin 1000 mg (for OCT1/2 and MATE2-K), or rosuvastatin 10 mg (for OATP1B3) with or without co-administration with cefiderocol 2 g every 8 h with 3-h infusion (a total of 3, 6, and 9 doses of cefiderocol with furosemide, metformin, and rosuvastatin, respectively). DDI potentials were assessed based on the pharmacokinetics of the substrates. RESULTS: Ratios (90% confidence intervals) of maximum plasma concentration and area under the plasma concentration-time curve were 1.00 (0.71-1.42) and 0.92 (0.73-1.16) for furosemide, 1.09 (0.92-1.28) and 1.03 (0.93-1.15) for metformin, and 1.28 (1.12-1.46) and 1.21 (1.08-1.35) for rosuvastatin, respectively. Exposures to furosemide or metformin did not change when co-administered with cefiderocol. Slight increase in rosuvastatin exposure was observed with co-administered with cefiderocol, which was not considered to be clinically significant. Each treatment was well tolerated. CONCLUSIONS: Cefiderocol has no clinically significant DDI potential via drug transporters.

Targeted prevention of renal accumulation and toxicity of gentamicin by aminoglycoside binding receptor antagonists.

Receptor-mediated endocytosis plays an important role in accumulation of aminoglycosides in renal proximal tubule. To prevent aminoglycoside-induced nephrotoxicity following concentrated accumulation of gentamicin in the kidney, effect of cationic proteins and their peptide fragments, which could inhibit gentamicin binding to its binding receptor(s), was investigated. Among several substrates for megalin, an endocytic receptor responsible for renal accumulation of aminoglycosides, cytochrome c potently inhibited gentamicin accumulation in renal cortex. Concentration-dependent inhibition by cytochrome c on gentamicin uptake was also observed in OK kidney epithelial cells expressing megalin. In addition, gentamicin-induced increase in urinary excretion of N-acetyl-beta-d-glucosaminidase (NAG), a marker of renal tubular damage, was significantly reduced by cytochrome c. We next attempted to find a peptide fragment with lower molecular size showing inhibitory effect on gentamicin uptake. Cyto79-88 inhibited gentamicin uptake in OK cells, but had little effect on renal accumulation of gentamicin in mice in vivo. On one hand, a peptide fragment of neural Wiskott-Aldrich syndrome protein (N-WASP), which interacts with acidic phospholipids like aminoglycosides, inhibited gentamicin accumulation not only in OK cells but also in mouse kidney. These results show that substrates and/or their peptide fragments for aminoglycoside binding receptor such as megalin might be useful for preventing aminoglycoside-induced nephrotoxicity.