Population pharmacokinetic and covariate analyses of intravenous trastuzumab (Herceptin®), a HER2-targeted monoclonal antibody, in patients with a variety of solid tumors.

PURPOSE: The aim of the study was to characterize the population pharmacokinetics (PK) of the intravenous formulation of trastuzumab, assess the impact of patient and pathological covariates on trastuzumab PK, and perform simulations to support dosing recommendations in special situations. METHODS: Serum trastuzumab concentrations were obtained from 1582 patients with metastatic breast cancer (MBC), early breast cancer (EBC), advanced gastric cancer (AGC), or other tumor types/healthy volunteers in 18 phase I, II, and III trials and analyzed by nonlinear mixed-effects modeling. RESULTS: A two-compartment model with parallel linear and nonlinear elimination best described the data. During treatment, linear clearance (CL) dominated, resulting in a total CL of 0.173-0.337 L/day, which is similar to other IgG1 monoclonal antibodies. Covariates influencing CL were baseline body weight, aspartate aminotransferase, albumin, gastric cancer, and the presence of liver metastases. MBC and EBC had similar PK parameters, while CL was higher in AGC. Simulations indicated that at least 95% of patients with BC reach concentrations < 1 µg/mL (~ 97% washout) by 7 months. A dose delay in BC or AGC patients of > 1 week would take approximately 6 weeks to get back within steady-state exposure range. CONCLUSIONS: Trastuzumab PK for the intravenous formulation was well-described across cancer types, disease status, and regimens. No dose adjustment is required for any of the identified patient covariates. A 7-month serum washout period for trastuzumab is recommended. A reloading dose is required if a maintenance dose is missed by > 1 week.

Model-Informed Precision Dosing at the Bedside: Scientific Challenges and Opportunities.

The development of model-informed precision dosing (MIPD) tools, especially in the form of native or web-based applications to be used at the bedside, has garnered marked attention in recent years. Their potential clinical benefit can be large, but it should be ensured that such tools make optimal use of available clinical data and have adequate predictive ability. Unique scientific challenges specific to MIPD remain, which may require adaptation of commonly used diagnostics in pharmacometrics.

Comparative pharmacokinetics of subcutaneous trastuzumab administered via handheld syringe or proprietary single-use injection device in healthy males.

PURPOSE: To demonstrate pharmacokinetic (PK) comparability for a single dose of 600 mg subcutaneous (SC) trastuzumab, administered via a novel single-use injection device (SID) or handheld syringe in 119 randomized healthy male subjects. METHODS: The co-primary PK endpoints area under the time-concentration curve from the start of dosing to day 22 (AUC(0-21 days)) and maximum observed trastuzumab serum concentration (C(max)) were dose-normalized and body-weight-adjusted, and compared using geometric mean ratios (GMRs). SID performance, injection site pain, adverse events, and antidrug antibodies (ADAs) were assessed. RESULTS: GMRs and 90 % confidence intervals (CIs) were 1.01 (0.96-1.07) for AUC(0-21 days) and 1.02 (0.96-1.10) for C(max), which fell within the prespecified bioequivalence range (0.80-1.25). No SID quality issues or failures occurred. Adverse events were mostly mild, with no deaths, adverse event-related withdrawals, or life-threatening, cardiac, or serious events reported. The ADA rate was low, and no neutralizing antibodies were detected. CONCLUSIONS: Trastuzumab SC via SID demonstrated comparable PK and safety to handheld syringe administration. SID performance was very satisfactory.

Population pharmacokinetics of rituximab in patients with chronic lymphocytic leukemia.

This retrospective analysis characterizes rituximab population pharmacokinetics in combination with fludarabine and cyclophosphamide and its effect on fludarabine and cyclophosphamide disposition in chronic lymphocytic leukemia (CLL) patients. Rituximab concentration data were well described by a 2-compartment model comprising a time-varying clearance component related to the target-mediated clearance pathway and a constant clearance component reflecting catabolic elimination pathway. Marked differences were observed compared to pharmacokinetic parameters for non-Hodgkin lymphoma (NHL) obtained previously: in CLL, time-varying clearance at time zero (CL(2)) was faster, volumes of distribution (V(1) and V(2)) were larger, and rate of change (K(des)) from the targetmediated clearance pathway to catabolic elimination was lower than NHL. Fludarabine and cyclophosphamide disposition showed no apparent change when co-administered with rituximab. A positive correlation between pharmacokinetic parameters and clinical response was observed, supporting the use of the higher rituximab dose of 500 mg/m(2) in CLL patients (vs 375 mg/m(2) in NHL) to achieve an effective clinical response.