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    • SAR405: Selective ATP-Competitive Vps34 Inhibitor for Aut...

    2026-04-07

    SAR405: Selective ATP-Competitive Vps34 Inhibitor for Autophagy Modulation

    Executive Summary: SAR405 is a potent, nanomolar ATP-competitive inhibitor of the class III phosphoinositide 3-kinase Vps34, displaying high selectivity with a Kd of 1.5 nM and IC50 of 1 nM under standard biochemical conditions (APExBIO product page). It inhibits autophagosome formation by blocking Vps34-dependent phosphatidylinositol 3-phosphate (PtdIns3P) synthesis, resulting in disrupted late endosome-lysosome maturation without appreciable effects on class I/II PI3Ks or mTOR up to 10 μM (Park et al., 2023). SAR405 is widely used for mechanistic autophagy studies, vesicle trafficking assays, and synergy experiments with mTOR inhibitors. It is soluble in DMSO (>22 mg/mL) and ethanol (>32 mg/mL with ultrasound), but not in water, and is best stored below -20°C. This article contextualizes SAR405’s utility and boundaries, referencing recent findings on AMPK–ULK1–Vps34 interplay and clarifies misconceptions about its selectivity and limitations (see related review).

    Biological Rationale

    Autophagy is a conserved catabolic process enabling cells to degrade cytoplasmic contents in lysosomes, crucial for survival under nutrient deprivation and stress (Park et al., 2023). Vps34, a class III phosphoinositide 3-kinase (PI3K), is the core lipid kinase mediating the production of PtdIns3P, which recruits proteins necessary for autophagosome and endosome formation. Selective inhibition of Vps34 allows researchers to dissect the autophagy pathway, differentiate it from other PI3K-dependent processes, and interrogate vesicle trafficking events. Dysregulation of autophagy is implicated in cancer, neurodegeneration, kidney and lysosomal storage disorders, making Vps34 a key target for both basic and translational research (see SAR405: Selective ATP-Competitive Vps34 Inhibitor for Precision Research—this article provides updated mechanistic clarification).

    Mechanism of Action of SAR405

    SAR405 is an ATP-competitive inhibitor that binds the ATP pocket of human Vps34 with high affinity (Kd = 1.5 nM), effectively blocking its kinase activity at IC50 = 1 nM in vitro. This leads to a rapid, concentration-dependent decrease in PtdIns3P formation. The blockade of PtdIns3P synthesis impairs recruitment of FYVE-domain and LC3-interacting proteins needed for autophagosome nucleation and maturation. SAR405 does not significantly inhibit class I or II PI3Ks or mTOR at concentrations up to 10 μM, ensuring high pathway specificity. In treated cells, SAR405 causes accumulation of swollen late endosome-lysosomes, defective cathepsin D maturation, and impaired autophagic flux. Early endocytosis and Akt phosphorylation (PI3K/Akt pathway) remain largely unaltered in PC3 cells, confirming selectivity (Park et al., 2023).

    Evidence & Benchmarks

    • SAR405 inhibits recombinant human Vps34 kinase with an IC50 of 1 nM in cell-free assays (buffer pH 7.5, 25°C) (APExBIO).
    • Shows negligible cross-reactivity with class I or II PI3Ks and mTOR up to 10 μM in kinase selectivity panels (APExBIO).
    • Disrupts PtdIns3P-positive vesicles (visualized via GFP-FYVE probe) and blocks GFP-LC3 puncta formation in HeLa cells within 1–2 h (10–100 nM, 37°C) (Park et al., 2023).
    • Does not impair early endocytosis or Akt phosphorylation at up to 10 μM in PC3 cells (Park et al., 2023).
    • Synergizes with mTOR inhibitors (e.g., everolimus) to achieve near-complete autophagy blockade in nutrient-starved models (related review).
    • Induces accumulation of late endosome–lysosome structures and blocks cathepsin D maturation, as assessed by Western blot and microscopy (HeLa, PC3, 24 h, 100 nM) (Park et al., 2023).

    Applications, Limits & Misconceptions

    SAR405 is widely used in autophagy inhibition assays, vesicle trafficking studies, and lysosomal function research. Its high selectivity makes it the gold standard for dissecting Vps34 biology and is routinely used in cancer, neurodegenerative, and lysosomal disorder models (see SAR405: Selective ATP-Competitive Vps34 Inhibitor for Autophagy Research—this article updates and expands on mechanistic selectivity benchmarks). In conjunction with mTOR inhibitors, SAR405 enables studies of combined pathway blockade and synthetic lethality. Researchers use SAR405 to clarify autophagy's energetic role, especially in light of recent findings that AMPK can suppress, rather than promote, ULK1-Atg14-Vps34 signaling during energy stress (Park et al., 2023), a paradigm shift from older models.

    Common Pitfalls or Misconceptions

    • SAR405 is not a pan-PI3K inhibitor: It shows negligible inhibition of class I/II PI3Ks or mTOR below 10 μM (APExBIO).
    • Does not block early endocytosis: Endocytic uptake remains intact at effective concentrations (10–100 nM) (Park et al., 2023).
    • Not water-soluble: Must be dissolved in DMSO or ethanol; aqueous buffers will not yield stable solutions (APExBIO).
    • Does not directly inhibit ULK1 or AMPK: Effects are specific to Vps34 kinase activity (Park et al., 2023).
    • Not recommended for long-term storage in solution: Stocks should be freshly prepared and stored at < -20°C (APExBIO).

    Workflow Integration & Parameters

    SAR405 is supplied by APExBIO as a lyophilized powder (SKU: A8883), recommended for immediate resuspension in DMSO or ethanol. It is soluble at >22 mg/mL in DMSO and >32 mg/mL in ethanol with ultrasound. For cell-based assays, working concentrations typically range from 10 nM to 1 μM, with exposure times from 1 to 24 h depending on the endpoint (e.g., GFP-LC3 puncta, PtdIns3P loss, cathepsin D maturation). The inhibitor is compatible with GFP-FYVE and GFP-LC3 cell lines for live-cell imaging. For synergy or pathway dissection, it is often paired with mTOR inhibitors (e.g., everolimus) in autophagy and vesicle trafficking workflows. For optimal performance, stock solutions should be stored below -20°C and not kept for long periods once dissolved. SAR405 is not suitable for in vivo studies without further formulation development (see SAR405: Precision Vps34 Inhibition for Lysosomal and Autophagy Research—this article provides additional focus on in vitro versus in vivo considerations).

    Conclusion & Outlook

    SAR405 has set a new standard for selective Vps34 inhibition, enabling high-fidelity mechanistic studies of autophagy inhibition, vesicle trafficking modulation, and lysosome function impairment. Its nanomolar potency, robust selectivity, and compatibility with diverse cellular assays make it a cornerstone for cancer, neurodegenerative, and lysosomal disease research. Continued integration of SAR405 into workflows, especially alongside emerging insights into AMPK–ULK1–Vps34 signaling, will refine our understanding of autophagy’s role in cellular homeostasis and disease. For product details and ordering, see the SAR405 product page.