Abstract 4014: Comparative biochemical kinase activity analysis identifies rivoceranib as the most selective VEGFR-2 inhibitor compared with other TKIs with known activity against VEGFR-2
Authors: Jang Seong , Strickland Bill , Finis Lynda , Koojiman Jeffrey J. , Melis Janneke J. , Zaman Guido J. , Tornout Jan V. 
Published: April 2023

Introduction: Vascular endothelial growth factor receptor 2 (VEGFR-2) is a key regulator of tumor angiogenesis that is highly expressed in several tumor types and is a known target for anti-cancer therapy. Yet the clinical use of VEGFR-2 inhibitors has been challenged by limited efficacy and various side effects, potentially due to the low selectivity of these TKIs for VEGFR-2. Thus, potent VEGFR-2 inhibitors with improved selectivity are needed. Rivoceranib is an oral tyrosine kinase inhibitor (TKI) that potently and selectively inhibits VEGFR-2. A comparison of the potency and selectivity of VEGFR-2 inhibitors can provide a rationale for selecting a specific TKI for anticancer therapy in the clinic.

Methods: Binding of rivoceranib to VEGFR-2 was determined on a Biacore T200. The affinity constant (KD) was derived from the association and dissociation rate constants. Inhibitory potency of rivoceranib and 10 FDA-approved reference inhibitors on kinase enzyme activity was determined using mobility shift assays (MSA) or immobilized metal ion affinity particle (IMAP) assays. The half-maximum inhibitory activity (IC50) of the 11 inhibitors on VEGFR-2 was determined in 10-point dose-response curves. The selectivity of the inhibitors was determined on 270 wild-type kinases at a fixed concentration of each inhibitor. Rivoceranib was tested at 10- and 100-times IC50 (160 nmol/L and 1.6 µmol/L). Reference inhibitors were tested at 1 µmol/L (35 to 1056-times IC50).

Results: Rivoceranib had a KD of 3 nmol/L on VEGFR-2. In enzyme activity assays, rivoceranib had intermediate potency compared with the 10 reference inhibitors, with a VEGFR-2 kinase inhibition IC50 value of 16 nmol/L. Analysis of the residual activity of the panel of 270 kinases in the presence of rivoceranib or the reference inhibitors showed wide variation in selectivity for VEGFR-2, with rivoceranib identified as the most selective inhibitor (activity of 16 additional kinases inhibited by &gt;50% at 1.6 µmol/L). Tivozanib, the most potent VEGFR-2 inhibitor, displayed greater than 50% inhibitory activity against more than 70 additional kinases. Sunitinib was identified as the least selective inhibitor included in this study, inhibiting 125 additional kinases by &gt;50%.

Conclusion: Variations in selectivity among TKIs with similar anti-VEGFR-2 potency can help explain differences in their clinical toxicity profiles, which may be partially due to variant inhibitory effects against TKIs other than VEGFR-2. This comparative biochemical analysis highlights the potential for rivoceranib to address clinical limitations associated with the poor selectivity of currently available VEGFR-2 inhibitors. Rivoceranib is under ongoing investigation as monotherapy and in combination with chemotherapy in various tumor types.

Citation Format: Seong Jang, Bill Strickland, Lynda Finis, Jeffrey J. Koojiman, Janneke J. Melis, Guido J. Zaman, Jan V. Tornout. Comparative biochemical kinase activity analysis identifies rivoceranib as the most selective VEGFR-2 inhibitor compared with other TKIs with known activity against VEGFR-2. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4014.