The objective of this study was to compare the safety and antitumor activity of F14512 and etoposide phosphate in dogs with spontaneous NHL and to investigate the potential benefit of F14512 in P-glycoprotein overexpressing lymphomas, with the primary aim of showing that effectively designed comparative oncology studies would offer bidirectional benefit to both pet animals and humans with cancer. Here, ABCB1 is linked to non-Hodgkin lymphoma.