Characterization of NVX-207, a novel betulinic acid-derived anti-cancer compound

Background Development of betulinic acid derivatives for clinical use has been hampered by adverse pharmacological and physico‐chemical characteristics of this class of compounds. We here present a novel semi‐synthetic betulinic acid‐derived drug candidate well suited for further clinical development. Materials and methods In vitro activity and mode of action of NVX‐207 were determined using normal as well as cancer cell lines. Gene expression profiling was performed with Affymetrix U133 microarrays. NVX‐207 binding partners were identified using a heterobifunctional chemical crosslinker system. Potential binding proteins were identified by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) analysis. Clinical studies were conducted in canine cancer patients suffering from spontaneously arising pre‐treated tumours. Results NVX‐207 showed anti‐tumour activity (mean IC50 = 3·5 μM) against various human and canine cell lines. NVX‐207‐induced apoptosis was associated with activation of the intrinsic apoptotic pathway via cleavage of caspases ‐9, ‐3, ‐7 and of poly (ADP‐ribose) polymerase (PARP). Global gene expression profiling demonstrated regulation of genes associated with lipid metabolism, most notably an upregulation of genes coding for insulin‐induced gene 1 (Insig‐1), low‐density lipoprotein receptor (LDL‐R) and of 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA). NVX‐207 bound to apolipoprotein A‐I, a major regulator of lipid metabolism and cholesterol transport. A phase I/II study in dogs suffering from naturally occurring cancer receiving local treatment of NVX‐207 (10 mg mL−1) showed excellent clinical responses including a complete remission in so far 5/5 treated animals. Conclusions NVX‐207 is well tolerated and has significant anti‐cancer activity in vitro and in vivo in dogs with treatment‐resistant malignancies.