Pharmacokinetics of pertuzumab administered concurrently with trastuzumab in Chinese patients with HER2-positive early breast cancer

In the APHINITY study (NCT01358877, BIG 4-11/ BO25126/TOC4939G), pertuzumab added to trastuzumab and chemotherapy significantly improved invasive diseasefree survival as adjuvant treatment for patients with HER2- positive early breast cancer. The objective of this analysis was to assess the pharmacokinetics of pertuzumab in combination with trastuzumab in Chinese patients with early breast cancer. Samples for pertuzumab and trastuzumab pharmacokinetic analysis were taken from Chinese patients during cycle 1 of treatment and at steadystate in cycle 10. Noncompartmental analysis was used to estimate minimum and maximum serum concentrations (Cmax and Cmin), area under the concentration-time curve, clearance, and other pharmacokinetic parameters. In 15 patients, mean steady-state Cmax and Cmin pertuzumab serum concentrations (368 ± 177 μg/mL, and 122 ± 47 μg/mL, respectively) were numerically higher than observed previously in a pharmacokinetic analysis of the global population in APHINITY and in patients treated in the metastatic setting. The geometric mean ratio and corresponding 90% confidence interval for trastuzumab Cmax and Cmin in the presence (n = 15) or absence (n = 17) of pertuzumab were 104.6 (91.09-120) and 98.23 (84.58-114), respectively, indicating no apparent impact of pertuzumab on the pharmacokinetics of trastuzumab. Increases in pertuzumab Cmax and Cmin were not associated with an increase in adverse events. The APHINITY Chinese pharmacokinetic substudy analysis supports the dosing regimen for pertuzumab (840 mg loading dose followed by 420 mg maintenance doses every 3 weeks administered by intravenous infusion) in a Chinese HER2-positive early breast cancer patient population.