Anlotinib Hydrochloride: Multi-Target Tyrosine Kinase Inhibitor for Anti-Angiogenic Cancer Research

Executive Summary: Anlotinib hydrochloride (CAS 1058157-76-8) is a small-molecule inhibitor that targets VEGFR2, PDGFRβ, and FGFR1 with nanomolar potency, disrupting tumor angiogenesis by blocking endothelial cell migration and capillary tube formation (Xie et al., 2018). It demonstrates superior selectivity and efficacy compared to sunitinib, sorafenib, and nintedanib in preclinical models. Oral bioavailability in animal models ranges from 28% to 77%, with high plasma protein binding in humans (93%). APExBIO supplies research-grade Anlotinib (hydrochloride) as SKU C8688. Safety studies show a high median lethal dose (LD₅₀) and low systemic toxicity (source).

Biological Rationale

Angiogenesis is essential for tumor growth beyond a volume of approximately 1 mm³, as neovascularization supplies nutrients and oxygen (Xie et al., 2018). Vascular endothelial growth factor (VEGF) is the primary regulator of angiogenesis in solid tumors. VEGF stimulates proliferation, migration, and survival of endothelial cells via receptor tyrosine kinases (RTKs), primarily VEGFR2. Persistent angiogenesis is observed in most malignancies, contributing to tumor invasion and metastasis. Targeting angiogenic signaling pathways, specifically VEGFR2, PDGFRβ, and FGFR1, interrupts endothelial cell function and can suppress tumor vascularization. Anti-angiogenic small molecules, such as Anlotinib hydrochloride, offer an alternative to monoclonal antibody therapies by inhibiting multiple RTKs involved in tumor blood vessel formation (Related review).

Mechanism of Action of Anlotinib (hydrochloride)

Anlotinib hydrochloride binds to the ATP-binding sites of VEGFR2, PDGFRβ, and FGFR1 tyrosine kinases, blocking their phosphorylation and downstream signaling. This inhibition prevents activation of the ERK signaling pathway, reducing endothelial cell proliferation, migration, and tube formation (Xie et al., 2018). The following key actions are established:

• Potent inhibition of VEGFR2 with an IC₅₀ of 5.6 ± 1.2 nM in biochemical assays.
• Inhibition of PDGFRβ (IC₅₀: 8.7 ± 3.4 nM) and FGFR1 (IC₅₀: 11.7 ± 4.1 nM).
• Suppression of VEGF/PDGF-BB/FGF-2-induced endothelial cell migration and tube formation in a concentration-dependent manner.
• Blockade of ERK1/2 phosphorylation in human vascular endothelial cells (EA.hy 926) at sub-micromolar concentrations.
• Disruption of tumor capillary development in vivo without direct cytotoxicity to tumor cells at relevant concentrations.

This multi-target approach distinguishes Anlotinib from single-target agents and underlies its enhanced anti-angiogenic efficacy compared to sunitinib and sorafenib (See comparative review).

Evidence & Benchmarks

• Anlotinib exhibits an IC₅₀ <1 nM for VEGFR2 in cell-free kinase assays (Xie et al., 2018, Table 1).
• Inhibits VEGF-induced proliferation of HUVECs with picomolar potency (Xie et al., 2018, Fig. 2).
• Suppresses endothelial cell migration and tube formation in vitro at nanomolar concentrations (Xie et al., 2018, Fig. 3).
• Oral bioavailability in rats: 28%–58%; in dogs: 41%–77% (single administration, fasted state) (Xie et al., 2018, Table S2).
• High plasma protein binding (93% in human plasma); large volume of distribution; detected in lung, liver, kidney, heart, tumor, and brain tissue (Xie et al., 2018, Table S3).
• Median lethal dose (LD₅₀) in rats: 1735.9 mg/kg (14-day oral dosing); minimal systemic toxicity observed (Xie et al., 2018, Table S4).
• Demonstrates broader and stronger in vivo antitumor efficacy than sunitinib in xenograft models (Xie et al., 2018, Fig. 6).

Applications, Limits & Misconceptions

Research Applications: Anlotinib (hydrochloride) is widely used in preclinical oncology to study tumor angiogenesis, evaluate anti-angiogenic small molecules, and dissect VEGFR2/PDGFRβ/FGFR1 signaling in cell-based and animal models. It is especially relevant for capillary tube formation assays, endothelial cell migration studies, and modulation of the ERK pathway. The product is not for diagnostic or therapeutic use in humans (APExBIO).

This mechanistic analysis focuses on ERK signaling; the present article extends scope by benchmarking pharmacokinetics and in vivo efficacy.

Common Pitfalls or Misconceptions

• Not a direct cytotoxic agent: Anlotinib does not kill tumor cells at nanomolar concentrations; its primary effect is anti-angiogenic (Xie et al., 2018).
• Not for human therapy: APExBIO’s Anlotinib (hydrochloride) is strictly for research use only (product page).
• Limited efficacy in non-angiogenic models: Little effect is observed in tumor models not dependent on angiogenesis for growth.
• Metabolism by CYP3A: Drug-drug interactions may occur in co-treatment models with other CYP3A substrates (Xie et al., 2018).
• Variable oral bioavailability: Bioavailability is species- and condition-dependent; not directly translatable to human dosing.

Workflow Integration & Parameters

Anlotinib (hydrochloride) is supplied as a powder and should be stored at –20°C for long-term stability. For in vitro studies, it is dissolved in DMSO and typically used at final concentrations ranging from 1 nM to 1 μM, depending on the assay endpoint. Capillary tube formation assays in human endothelial cells (e.g., EA.hy 926, HUVECs) use 10 nM–100 nM concentrations for robust angiogenesis inhibition. In vivo xenograft studies employ once-daily oral dosing, with doses based on animal weight and pharmacokinetic analysis (A workflow optimization guide provides practical implementation tips not detailed here). Anlotinib is metabolized primarily by CYP3A, and metabolite analysis can be performed using LC-MS/MS methods.

Conclusion & Outlook

Anlotinib hydrochloride offers a well-characterized, potent, and selective approach to inhibiting tumor angiogenesis in preclinical research. Its multi-target inhibition profile, favorable pharmacokinetics, and high safety margin make it a preferred tool for dissecting tyrosine kinase signaling pathways. APExBIO’s research-grade Anlotinib (hydrochloride) (SKU C8688) supports robust, reproducible assays in cancer biology and angiogenesis studies. Ongoing research will further define its translational potential and comparative advantages over other anti-angiogenic small molecules.