Anlotinib Hydrochloride: Multi-Target Tyrosine Kinase Inhibitor for Tumor Angiogenesis Research

Executive Summary: Anlotinib hydrochloride (CAS 1058157-76-8) is a small-molecule, multi-target tyrosine kinase inhibitor (TKI) designed to inhibit VEGFR2, PDGFRβ, and FGFR1 with nanomolar potency, suppressing angiogenesis in tumor models (Lin et al., 2018). Its IC₅₀ values for these kinases are 5.6 ± 1.2 nM (VEGFR2), 8.7 ± 3.4 nM (PDGFRβ), and 11.7 ± 4.1 nM (FGFR1), establishing a benchmark for pharmacological selectivity. Compared to sunitinib, sorafenib, and nintedanib, anlotinib demonstrates superior inhibition of endothelial cell migration and tube formation (DOI). The compound exhibits rapid oral absorption, high bioavailability (28–77% in preclinical models), and robust tissue penetration, including tumor and lung. Safety assessments report a high median lethal dose (LD₅₀ ~1735.9 mg/kg, oral, 14 days) with mild toxicity and minimal organ or genetic adverse effects (APExBIO technical dossier). For research, anlotinib is recommended for anti-angiogenic, migration, and ERK pathway assays, with storage at -20°C (APExBIO).

Biological Rationale

Angiogenesis is a vital process in tumor development, enabling cancer cells to establish new vasculature for oxygen and nutrient supply (Lin et al., 2018). Key pro-angiogenic factors—VEGF, PDGF-BB, and FGF-2—activate their respective receptor tyrosine kinases (RTKs): VEGFR2, PDGFRβ, and FGFR1. These RTKs initiate downstream signaling (notably via the ERK pathway) to drive endothelial cell proliferation, migration, and capillary tube formation. Tumor progression is tightly linked to the upregulation of these pathways (DOI). Inhibiting RTK-mediated signaling is thus a validated strategy for limiting tumor angiogenesis, as evidenced by the clinical efficacy of existing TKIs (e.g., sunitinib, sorafenib), but the need for increased potency and selectivity remains. Anlotinib hydrochloride addresses these requirements by targeting multiple relevant RTKs simultaneously.

Mechanism of Action of Anlotinib (hydrochloride)

Anlotinib hydrochloride acts as a reversible, ATP-competitive inhibitor of VEGFR2, PDGFRβ, and FGFR1, blocking kinase autophosphorylation and subsequent downstream signaling. The compound demonstrates nanomolar IC₅₀ values: VEGFR2 (5.6 ± 1.2 nM), PDGFRβ (8.7 ± 3.4 nM), and FGFR1 (11.7 ± 4.1 nM), determined using recombinant kinase assays at 25°C in buffer pH 7.5 (Lin et al., 2018). Upon ligand (VEGF, PDGF-BB, or FGF-2) stimulation of endothelial cells, anlotinib inhibits receptor phosphorylation, suppressing ERK1/2 activation. This inhibition leads to reduced cell migration (wound healing and chamber assays), impaired capillary-like tube formation (Matrigel assays), and decreased neovascular density in vivo (CAM and rat aortic ring models). The specificity for VEGFR2, PDGFRβ, and FGFR1 underlies its robust anti-angiogenic profile. Minimal off-target kinase inhibition is observed at 10-fold higher concentrations (DOI).

Evidence & Benchmarks

• Anlotinib inhibits VEGF/PDGF-BB/FGF-2-induced endothelial cell migration with greater efficacy than sunitinib, sorafenib, or nintedanib (wound healing and chamber assays, DOI).
• IC₅₀ values for kinase inhibition: VEGFR2 (5.6 ± 1.2 nM), PDGFRβ (8.7 ± 3.4 nM), FGFR1 (11.7 ± 4.1 nM), determined in vitro at 25°C, pH 7.5 (DOI).
• In vivo, anlotinib reduces microvessel density in both rat aortic ring and chicken CAM assays, outperforming control TKIs under matched dosing (Lin et al., Figure 3, DOI).
• Pharmacokinetic data: oral bioavailability is 28–58% in rats and 41–77% in dogs (APExBIO technical dossier; APExBIO).
• Anlotinib exhibits high plasma protein binding (93% in humans), large tissue distribution, and crosses the blood-brain barrier (APExBIO technical dossier).
• Safety: LD₅₀ (oral, 14 days) is 1735.9 mg/kg in rats, with no significant organ or genetic toxicity (APExBIO technical dossier; APExBIO).

This article builds upon the practical insights from "Applied Cancer Research with Anlotinib Hydrochloride" by providing a quantitative, target-specific analysis and comparative benchmarks for kinase inhibition. For reproducibility-focused guidance on angiogenesis assays, "Optimizing Tumor Angiogenesis Assays with Anlotinib (hydrochloride)" addresses workflow challenges, while the current article extends this by detailing mechanistic selectivity and off-target considerations.

Applications, Limits & Misconceptions

Anlotinib hydrochloride is designed for in vitro and in vivo research on tumor angiogenesis, endothelial migration, and tyrosine kinase signaling. It is widely used in:

• Capillary tube formation assays (e.g., Matrigel, EA.hy 926 cells)
• Endothelial cell migration and wound healing models
• Signaling pathway mapping (ERK, downstream of VEGFR2/PDGFRβ/FGFR1)
• Tumor xenograft and neovascularization studies

APExBIO supplies anlotinib (hydrochloride) under SKU C8688 for research use only; not for diagnostic or therapeutic purposes (APExBIO).

Common Pitfalls or Misconceptions

• Not a direct anti-tumor cytotoxic agent: Anlotinib does not induce significant apoptosis in tumor cells at concentrations used for angiogenesis inhibition; its primary effect is anti-angiogenic (DOI).
• Limited efficacy in non-angiogenic tumor models: Tumors that grow independently of angiogenesis may not respond to anlotinib in preclinical tests.
• Not suitable for clinical or diagnostic use: The compound is strictly intended for research applications (APExBIO technical dossier).
• Concentration-dependent effects: Off-target kinase inhibition may emerge at concentrations >10x IC₅₀; dose titration is required for selectivity.
• Potential for interspecies PK differences: Rodent and canine pharmacokinetics may not translate directly to human models; confirm parameters in the intended system.

Workflow Integration & Parameters

Anlotinib hydrochloride integrates into standard angiogenesis and migration assay workflows. For endothelial cell assays (e.g., EA.hy 926), pre-treat cells with anlotinib at 1–100 nM for 1–24 hours, followed by ligand (VEGF/PDGF-BB/FGF-2) stimulation. Migration is assessed via wound healing or transwell chamber assays. Capillary-like tube formation is measured on Matrigel matrices after 6–24 hours of incubation. For signaling studies, western blotting confirms ERK phosphorylation status post-treatment. The compound is soluble in DMSO and can be diluted in serum-free media. Storage at -20°C preserves stability; avoid repeated freeze-thaw cycles (APExBIO).

For further assay optimization and troubleshooting, consult the detailed procedural guidance in "Optimizing Tumor Angiogenesis Assays with Anlotinib (hydrochloride)", which this article updates with new selectivity data and performance metrics.

Conclusion & Outlook

Anlotinib hydrochloride is a validated, multi-target TKI with superior potency against VEGFR2, PDGFRβ, and FGFR1. Its anti-angiogenic activity is robust, reproducible, and well-characterized in both cellular and animal models. Compared to legacy TKIs, anlotinib offers improved selectivity, tissue distribution, and safety margins, making it a preferred choice for mechanistic and translational cancer research (Lin et al., 2018). Ongoing studies may further expand its applications in signaling pathway dissection and preclinical anti-angiogenic drug evaluation. For reagent sourcing and technical support, visit the Anlotinib (hydrochloride) product page at APExBIO.