Sunitinib is a versatile tyrosine kinase inhibitor, sold under the brand name Sutent® by Pfizer as its malate salt form. 1 It is currently used to treat renal cell carcinoma and gastrointestinal stromal tumors through its antitumor and antiangiogenic activities, while more of its activities and applications are being explored. Further research endeavors regarding its broader range of application against leukemia and solid tumors (e.g., non-small-cell lung cancer, pancreatic neuroendocrine tumors, and metastatic breast cancer) are currently ongoing. 2 Besides oncological utilization, treatment of age-related macular degeneration is one of its other notable applications which led us to constitute aqueously dispersed sunitinib malate in an eyedrop formulation recently. As of January 2022, 27 clinical trials in 40 countries for sunitinib alone or in combination with other drug(s), are under way for novel applications towards paraganglioma, thymoma, prostate cancer, stomach neoplasm, and more; 4 allowing the medicinal research community to expect greater therapeutic potential. ChemRxiv 2022 2 Given the expanding application of sunitinib base or its malate salt form, adequate pharmaceutical formulation research as well as pharmacochemical study should follow accordingly. For instance, though there have been various attempts to constitute sunitinib malate into novel pharmaceutical formulations, solubility issue that the ionic compound being poorly soluble in water 5 has been a major bottleneck. Recent reports describe different types of nanoparticle, 6 suspension, 7 and micelle 8 formulations, where spectroscopical method such as NMR is particularly important to determine intermolecular interaction between pharmaceutical ingredients. However, on its 1 H and 13 C NMR spectra, each spectral peak signal has not been clearly assigned to each hydrogen and carbon atom in its chemical structure. There have only been a few reports of incomplete assignments in CDCl 3 and DMSO-d6 to date. The assignment of labile H-N hydrogens is of particular interest in aqueous formulations, in order to identify which H-N bond is responsible for intermolecular interaction (e.g., hydrogen bonding) with solvated salt, additive, and solvent. Herein, we report the 1 H and 13 C NMR assignment of sunitinib malate in aqueous media, including the assignment of major labile H-N hydrogens. As a result, spectral peaks of labile H-N hydrogens H-N 1 , H-N 12 , and H-N 19 were well observed with the peak integration of 0.43H, 0.85H, and 0.88H, respectively (Figure ). On the other hand, H-O 29 , H-O 30 , and H-N 22 were not observed where the first two underwent rapid deuterium-hydrogen ChemRxiv 2022 3 exchange.