Vascular endothelial growth factor receptor 2 (VEGFR2), a key regulator of tumor angiogenesis, is highly expressed across numerous tumor types and has been an attractive target for anti-cancer therapy. However, clinical application of available VEGFR2 inhibitors has been challenged by limited efficacy and a wide range of side effects, potentially due to inadequate selectivity for VEGFR2. Thus, development of potent VEGFR2 inhibitors with improved selectivity is needed. Rivoceranib is an orally administered tyrosine kinase inhibitor that potently and selectively targets VEGFR2. A comparative understanding of the potency and selectivity of rivoceranib and approved inhibitors of VEGFR2 is valuable to inform rationale for therapy selection in the clinic. Here, we performed biochemical analyses of the kinase activity of VEGFR2 and of a panel of 270 kinases to compare rivoceranib to 10 FDA-approved kinase inhibitors (“reference inhibitors”) with known activity against VEGFR2. Rivoceranib demonstrated potency within the range of the reference inhibitors, with a VEGFR2 kinase inhibition IC50 value of 16 nM. However, analysis of residual kinase activity of the panel of 270 kinases showed that rivoceranib displayed greater selectivity for VEGFR2 compared with the reference inhibitors. Differences in selectivity among compounds within the observed range of potency of VEGFR2 kinase inhibition are clinically relevant, as toxicities associated with available VEGFR2 inhibitors are thought to be partly due to their effects against kinases other than VEGFR2. Together, this comparative biochemical analysis highlights the potential for rivoceranib to address clinical limitations associated with off-target effects of currently available VEGFR2 inhibitors.

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 >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 >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.

e15122 Background: Rivoceranib is a novel oral tyrosine kinase inhibitor that potently and selectively inhibits VEGFR2. Rivoceranib is being investigated for indications targeted towards solid malignancies as either monotherapy or in combination with other anticancer therapies. Herein, we assessed the bioequivalence of a single dose of rivoceranib administered as 4 different formulations in healthy subjects. Methods: This single-center, open-label, randomized, single-dose, 4-way crossover study evaluated the bioequivalence of 4 different formulations of rivoceranib oral tablets in healthy adults. Each subject participated in 4 treatment periods, where they were randomized to 1 of 4 sequences: ABCD, BDAC, CADB, and DBAC (Formulation A = rivoceranib 250 mg tablet/clinical formulation used in the pivotal phase 3 study, Formulation B = rivoceranib 200 mg tablet/clinical formulation used in early clinical studies, Formulation C = rivoceranib 250 mg tablet/formulation to be developed for future use, Formulation D = rivoceranib 250 mg tablet/to-be-marketed formulation). Results: Of the 60 subjects enrolled, 66.7% were male, 88.3% were white, and median age was 43 years. The median plasma rivoceranib Tmax was similar following all treatments (2 hours post-dose). The 90% CIs around the geometric mean ratios (GMRs) of plasma rivoceranib AUC0-t, AUC0-inf, and Cmax for Formulation B vs. Formulation A and Formulation D vs. Formulation A were within the 80-125% reference interval, demonstrating bioequivalence between Formulation B and Formulation A as well as Formulation D and Formulation A. The 90% CIs around the GMRs of plasma rivoceranib AUC0-t, AUC0-inf, and Cmax for Formulation C vs. Formulation A were slightly outside of the 80%-125% reference interval. Conclusions: Formulations B (clinical formulation used in early clinical studies) and D (to-be-marketed formulation) were bioequivalent to Formulation A (clinical formulation used in the pivotal phase 3 study). Formulation C (formulation to be developed for future use) and Formulation A were similar, but the difference was slightly outside of the bioequivalence criteria. It remains to be evaluated whether the difference in bioavailability between Formulation C and Formulation A is clinically meaningful. Clinical trial information: NCT05287360 . [Table: see text]