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

Executive Summary: Tivozanib (AV-951) is a second-generation quinoline-urea tyrosine kinase inhibitor (TKI) with picomolar potency against VEGFR-2 (IC₅₀ = 160 pM) and strong selectivity for VEGFR-1/2/3 [product page]. Its low off-target activity, including minimal inhibition of c-KIT and nanomolar-level effects on PDGFRβ, reduces adverse effects relative to earlier TKIs. Tivozanib demonstrates robust anti-proliferative and pro-apoptotic effects across in vitro, xenograft, and clinical settings, including a 12.7 month median progression-free survival (PFS) in metastatic RCC at 1.5 mg daily dosing. The compound is water-insoluble, stable at -20°C, and used at 10 μM for 48h in cell-based assays. Tivozanib shows synergism when combined with EGFR inhibitors in ovarian carcinoma models (Schwartz 2022).

Biological Rationale

Angiogenesis, the formation of new blood vessels, is critical for tumor growth and metastasis. Vascular endothelial growth factor receptors (VEGFR-1, VEGFR-2, VEGFR-3) are principal mediators of angiogenic signaling. Many solid tumors, including renal cell carcinoma (RCC), depend on sustained VEGFR signaling for vascularization and proliferation. By blocking VEGFR signaling, angiogenesis and subsequent tumor expansion can be suppressed. Tivozanib (AV-951) is engineered for high specificity towards VEGFRs while minimizing interactions with unrelated kinases, thus reducing off-target toxicity (Schwartz 2022). This design allows for precise dissection of VEGFR-driven mechanisms in cancer biology and therapy.

Mechanism of Action of Tivozanib (AV-951)

Tivozanib acts as a competitive inhibitor at the ATP binding site of VEGFR-1, VEGFR-2, and VEGFR-3. Its binding affinity is highest for VEGFR-2 (IC₅₀: 160 pM), followed by potent inhibition of VEGFR-1 and VEGFR-3 in the nanomolar range. In cell-based assays, Tivozanib also inhibits phosphorylation of PDGFRβ and c-KIT, but at higher, nanomolar concentrations (Schwartz 2022). By blocking VEGFR signaling, Tivozanib suppresses endothelial cell proliferation and migration, leading to reduced microvessel density in tumors. This mechanism translates to tumor growth inhibition in preclinical xenograft models and clinical efficacy in RCC. The compound’s minimal impact on non-target kinases, such as c-KIT, distinguishes it from older TKIs like sunitinib and sorafenib.

Evidence & Benchmarks

• Tivozanib exhibits an IC₅₀ of 160 pM against VEGFR-2 in biochemical assays, outperforming sunitinib and sorafenib in potency (Schwartz 2022, https://doi.org/10.13028/wced-4a32).
• In cell-based systems, Tivozanib inhibits VEGFR auto-phosphorylation and downstream signaling at 10 μM after 48 hours of exposure (Schwartz 2022, https://doi.org/10.13028/wced-4a32).
• Clinically, Tivozanib at 1.5 mg orally once daily for 3 weeks results in a median progression-free survival (PFS) of 12.7 months in metastatic RCC, one of the best PFS outcomes in this indication (Schwartz 2022, https://doi.org/10.13028/wced-4a32).
• Tivozanib demonstrates synergistic inhibition of cell proliferation and induction of apoptosis when combined with EGFR inhibitors in ovarian carcinoma cell lines (Schwartz 2022, https://doi.org/10.13028/wced-4a32).
• The compound is insoluble in water but soluble at ≥22.75 mg/mL in DMSO and ≥2.68 mg/mL in ethanol with gentle warming (ApexBio, https://www.apexbt.com/tivozanib-av-951.html).
• Minimal off-target inhibition of c-KIT and other kinases is observed at concentrations used for VEGFR inhibition, reducing adverse effects (Schwartz 2022, https://doi.org/10.13028/wced-4a32).

Applications, Limits & Misconceptions

Tivozanib is widely used in oncology research for the interrogation of VEGFR-driven angiogenesis and as an anti-angiogenic therapy in RCC and other solid tumors. Its selectivity makes it a preferred tool for dissecting VEGFR signaling without confounding off-target kinase effects. In vitro, it is typically used at 10 μM for 48 hours to assess cell proliferation and apoptosis. For in vivo studies, Tivozanib’s oral bioavailability and stability are advantageous for chronic dosing regimens.

Tivozanib is also used in combination regimens, particularly with EGFR-directed therapies, to enhance anti-proliferative effects and promote apoptosis in cancer cell lines.

Common Pitfalls or Misconceptions

• Water solubility: Tivozanib is insoluble in water; improper solvent selection leads to ineffective dosing and unreliable results. Use DMSO or ethanol as recommended.
• Cytotoxicity at high concentration: Although selective, off-target effects may occur at supra-therapeutic concentrations. Adhere to validated dosing protocols (e.g., 10 μM for 48h in vitro).
• Long-term solution storage: Tivozanib solutions are unstable over time; fresh solutions should be prepared for each experiment to ensure potency.
• Non-VEGFR driven tumors: Tivozanib is ineffective in tumor models that do not rely on VEGFR-mediated angiogenesis.
• Direct cytotoxicity assumption: Tivozanib inhibits proliferation primarily via anti-angiogenesis; direct cytotoxic effects on non-endothelial cells are minimal at standard dosing.

For additional insights into experimental design and troubleshooting, see "Applied Use of Tivozanib: Optimizing VEGFR Inhibition in Translational Oncology", which provides hands-on workflow details not covered here. This article updates previous reviews, such as "Tivozanib (AV-951): Redefining VEGFR Inhibition in Translational Oncology", by focusing on benchmarked data and combination strategies, and extends the mechanistic analysis in "Tivozanib (AV-951): Mechanistic Insight and Strategic Guidance" with up-to-date clinical efficacy outcomes.

Workflow Integration & Parameters

Tivozanib is supplied as a solid compound (molecular weight: 454.86; formula: C₂₂H₁₉ClN₄O₅). For in vitro use, dissolve at ≥22.75 mg/mL in DMSO or ≥2.68 mg/mL in ethanol with gentle warming. The recommended storage temperature is -20°C; avoid long-term storage of prepared solutions. For cell-based assays, a typical protocol involves 10 μM Tivozanib exposure for 48 hours, with assessment of proliferative arrest and apoptosis. In clinical or preclinical animal studies, oral dosing at 1.5 mg once daily for three weeks has been shown to achieve optimal efficacy in RCC models.

Combining Tivozanib with EGFR inhibitors is a validated approach for synergistic growth inhibition in select carcinoma models. When designing experiments, select appropriate endpoints (e.g., fractional viability, proliferation, apoptosis) and measurement timepoints based on drug mechanism and cell line characteristics.

Conclusion & Outlook

Tivozanib (AV-951) is established as a reference VEGFR TKI for anti-angiogenic therapy and research, offering superior potency, selectivity, and safety compared to earlier agents. Its validated use in RCC and translational oncology models, along with robust combinatorial potential, supports its integration into advanced anti-cancer workflows. Future research is likely to expand its use in personalized combination regimens and further refine biomarker-driven application in solid tumors. For ordering and technical specifications, refer to the A2251 kit product page.