The main PK parameters were estimated by a standard noncompartmental method using Phoenix WinNonLin (Pharsight, version 6.3, Pharsight Corp.), including elimination half‐life (In pyrotinib monotherapy part, blood samples were obtained on D1 and D21 of the first cycle at predose; 1, 2, 3, 4, 5, 6, 8, 12, and 24 h after the first dose; and on C1D8 and C1D15 at predose. In pyrotinib in combination with docetaxel part, the samples were obtained on D1 of the first cycle at predose; 5 min, 30 min, 1, 1.25, 1.5, 2, 3, 4, 5, 6, 8, 12, and 24 h after the first dose; and on C1D8 and C1D15 at predose. Samples were also collected on Day 21 of the first cycle at predose and 1, 2, 3, 4, 5, 6, 8, 12, and 24 h after the first dose. The whole blood was centrifuged (3500 rpm at 4°C for 10 min) and obtained plasma samples were stored at −80°C until analysis.