Development of a novel conjugatable sunitinib analogue validated through in vitro and in vivo preclinical settings

Sunitinib is an oral FDA/EMEA approved multi-targeted tyrosine kinase inhibitor. It possesses anti-angiogenic and antitumor activity against a variety of advanced solid tumors. However, its chemical core does not allow a potential linkage to tumor-homing elements that could eventually enhance its potency. Therefore, a novel linkable sunitinib derivative, designated SB1, was rationally designed and synthesized. The pharmaceutical profile of SB1 was explored both in vitro and in vivo. Mass spectrometry and NMR spectroscopy were utilized for characterization, while MTT assays and LC-MS/MS validated protocols were used to explore its antiproliferative effect and stability, respectively. Cytotoxicity evaluation in three glioma cells showed that SB1 preserved the antiproliferative effect of sunitinib. SB1 was stable in vitro after 24 h incubation in mouse plasma, while both agents exhibited bioequivalent pharmacokinetic characteristics after i.v. administration in Balb/c mice. To evaluate the levels of SB1 in mouse plasma, a novel analytical method was developed and validated in accordance to the US FDA and the EU EMA guidelines. We formulated a novel linkable sunitinib analog exhibiting similar antiproliferative and apoptotic properties with native sunitinib in glioma cell lines. Both SB1 and native sunitinib showed identical in vitro stability in mouse plasma and pharmacokinetics after i.v. administration in Balb/c mice.