Table 5.

Mass spectral data of radioactive [¹⁴C]pyrotinib peptide adducts obtained by HCl hydrolysis of human plasma incubated with [¹⁴C]pyrotinib for 24 h

[14C]Pyrotinib adducts	[M+H]+, m/z	Characteristic fragment ions, m/z a
Lys*	731.3240	585.2160 (I), 242.1836 (II), 138.0908 (III)
Gly-Lys*	788.3448	585.2174 (I), 299.2056 (II), 138.0905 (III)
Lys*-Ala	802.3630	585.2218 (I), 313.2217 (II), 138.0904 (III)
Gly-Lys*-Ala	859.3845	585.2240 (I), 370.2442 (II), 138.0902 (III)
Lys*-Ala-Ser	889.3903	585.2160 (I), 400.2536 (II), 138.0886 (III)

* the AA residue to which pyrotnib is bound

^aI, II and III in the brackets indicate the fragmentation pathway of product ion formation (see Figure 5b)