Tivozanib (AV-951): Potent and Selective VEGFR Inhibitor for Oncology Research

Executive Summary: Tivozanib (AV-951) is a quinoline-urea derivative and a next-generation oral VEGFR tyrosine kinase inhibitor with picomolar potency and high selectivity for VEGFR-1, -2, and -3 (APExBIO, product page). It demonstrates an IC50 of 160 pM against VEGFR-2, superior to sunitinib, sorafenib, and pazopanib under equivalent assay conditions (Schwartz 2022, DOI). Tivozanib shows robust anti-tumor activity in renal cell carcinoma (RCC) xenograft models and in clinical trials, with a reported PFS of 12.7 months in metastatic RCC. The compound exhibits minimal off-target kinase inhibition, including low c-KIT activity, supporting its use in selective VEGFR pathway inhibition. Tivozanib’s efficacy is further enhanced in combination with EGFR inhibitors, leading to synergistic cell growth inhibition and apoptosis in preclinical studies (related article).

Biological Rationale

The vascular endothelial growth factor receptors (VEGFR-1, VEGFR-2, and VEGFR-3) are central mediators of angiogenesis, which is essential for tumor growth and metastasis in solid tumors (Schwartz 2022). Dysregulation of the VEGFR signaling pathway is a hallmark of many cancers, notably renal cell carcinoma (RCC) and ovarian carcinoma. Inhibition of these receptors with selective tyrosine kinase inhibitors (TKIs) like Tivozanib disrupts angiogenic signaling, reducing tumor vascularization and proliferation. Tivozanib is designed as a second-generation pan-VEGFR inhibitor, with improved selectivity and efficacy profiles over earlier agents such as sunitinib and sorafenib (interlink: extends selectivity discussion). The precision targeting of VEGFRs minimizes off-target toxicity and enhances anti-tumor efficacy in both in vitro and in vivo models.

Mechanism of Action of Tivozanib (AV-951)

Tivozanib is a potent, selective tyrosine kinase inhibitor that targets VEGFR-1, VEGFR-2, and VEGFR-3 with picomolar to low nanomolar affinity (APExBIO). The compound binds to the ATP-binding pocket of these receptors, inhibiting their kinase activity and downstream signaling. The reported IC50 against VEGFR-2 is 160 pM in biochemical assays. In cellular systems, Tivozanib inhibits phosphorylation of PDGFRß and C-KIT at nanomolar concentrations, but with minimal off-target inhibition of other kinases (Schwartz 2022). This results in selective blockade of angiogenic signaling, leading to reduced endothelial cell proliferation, migration, and new vessel formation. The compound also exhibits synergistic activity when combined with EGFR inhibitors, enhancing apoptosis and growth inhibition, particularly in ovarian carcinoma models (interlink: expands on synergy mechanisms).

Evidence & Benchmarks

• Tivozanib (AV-951) inhibits VEGFR-2 kinase activity with an IC50 of 160 pM in biochemical assays at 25°C, pH 7.4 (APExBIO, product page).
• Demonstrates significantly higher potency than sunitinib, sorafenib, and pazopanib in matched enzyme inhibition studies (Schwartz 2022, DOI).
• Exhibits anti-tumor activity in RCC xenograft models, leading to tumor growth inhibition at oral doses (10–30 mg/kg, daily) in mice (Schwartz 2022, Table 5.2).
• Clinical trials report a progression-free survival (PFS) of 12.7 months in patients with metastatic RCC, one of the longest among VEGFR inhibitors (Schwartz 2022).
• Low off-target inhibition, including minimal effect on c-KIT and other kinases, as measured by kinase selectivity panels (related article).
• Synergy with EGFR inhibitors observed in ovarian carcinoma cell lines: combined treatment at 10 μM for 48 hours in vitro led to enhanced cell death and reduced proliferation (related article).

Applications, Limits & Misconceptions

Tivozanib is validated as a research tool for:

• In vitro cell proliferation and apoptosis assays in RCC and other solid tumor cell lines.
• In vivo anti-angiogenic studies using xenograft tumor models.
• Translational research in metastatic renal cell carcinoma and advanced solid tumors.
• Combination therapy studies with EGFR inhibitors in ovarian and other cancers (see synergy evidence).

Common Pitfalls or Misconceptions

• Not effective against VEGFR-independent tumors: Tivozanib will not show efficacy in cancers where angiogenesis is not driven by VEGFR signaling (Schwartz 2022).
• Limited activity in c-KIT driven malignancies: Due to low c-KIT inhibition, it is unsuitable as a primary agent for c-KIT mutant cancers.
• Not water soluble: The compound is insoluble in water; improper solvent use may lead to precipitation or loss of activity (APExBIO).
• Long-term solution storage is not recommended: Stability data indicate solutions should be used promptly and not stored for extended periods.
• Should not be used as a pan-kinase inhibitor: Tivozanib is selective; it will not broadly inhibit unrelated kinases or pathways.

Workflow Integration & Parameters

For in vitro experiments, Tivozanib is typically applied at 10 μM for 48 hours, with solubility in DMSO (≥22.75 mg/mL) or ethanol (≥2.68 mg/mL, warming required). The solid form (molecular weight 454.86, formula C22H19ClN4O5) should be stored at -20°C. Solutions should be freshly prepared. For in vivo mouse studies, oral dosing regimens range from 10–30 mg/kg daily. In cell-based assays, use gentle warming and ultrasonic treatment to ensure full solubilization (product page). For combination therapy workflows, Tivozanib can be co-administered with EGFR inhibitors to evaluate synergistic anti-tumor effects (interlink: adds translational guidance).

Conclusion & Outlook

Tivozanib (AV-951), as supplied by APExBIO, is a highly potent and selective VEGFR tyrosine kinase inhibitor optimized for research use in anti-angiogenic and combination cancer therapy models. Its robust selectivity, low off-target activity, and proven efficacy in preclinical and clinical settings make it a preferred benchmark for VEGFR pathway inhibition in RCC and beyond. Future research will likely expand its application to new combination regimens and resistance mechanisms. This article extends the technical and translational insights available in earlier reviews (mechanistic foundation, selectivity update), offering actionable guidance for research optimization.