CAY10499: Potent Inhibitor of Human Hormone Sensitive Lipase

Executive Summary: CAY10499 is a crystalline small molecule designed to selectively inhibit human hormone sensitive lipase (HSL) and monoglyceride lipase (MGL), with IC50 values of 90 nM and 0.5 μM, respectively, under standard in vitro assay conditions (product information). The compound demonstrates full inhibition of recombinant FAAH at 76 nM and shows minimal off-target activity against the CB1/CB2 receptors, confirming its selectivity. CAY10499 is stable in DMSO and ethanol but insoluble in water, with recommended storage at -20°C. Its potency and selectivity make it an indispensable tool for lipid metabolism and immunometabolic pathway research, as highlighted across recent studies (see advanced lipid assay protocols). Researchers are advised to use freshly prepared solutions for optimal activity.

Biological Rationale

Lipid metabolism is central to cellular energy balance, steroidogenesis, and immune cell differentiation. Hormone sensitive lipase (HSL) catalyzes the hydrolysis of triacylglycerols, diacylglycerols, monoacylglycerols, and cholesterol esters—thereby mobilizing free fatty acids for metabolic needs (APExBIO). Dysregulation of HSL activity is implicated in metabolic disorders, diabetes, atherosclerosis, and certain cancers. Monoglyceride lipase (MGL) controls the degradation of 2-arachidonoylglycerol (2-AG), an endocannabinoid involved in immune modulation and neurobiology. Recent research demonstrates that lipid metabolic enzymes, such as ATP-citrate lyase (ACLY), can reprogram immune cells in the tumor microenvironment, highlighting the importance of precise modulators for mechanistic studies (see EV-Transferred ACLY study).

Mechanism of Action of CAY10499, a potent inhibitor of human hormone sensitive lipase and monoglyceride lipase

CAY10499 acts as a competitive inhibitor of HSL and MGL, binding to their active sites and preventing substrate hydrolysis. In enzymatic assays, it inhibits MGL-mediated hydrolysis of 4-nitrophenyl acetate (4-NPA) with an IC50 of 0.5 ± 0.03 μM and human recombinant HSL with an IC50 of 90 nM, as confirmed by dose-response analysis (B7841 technical data). The compound also fully inhibits FAAH-mediated hydrolysis of [3H]-AEA at 76 nM. Minimal displacement of [3H]-CP-55940 binding to CB1 and CB2 receptors indicates high selectivity for lipases over cannabinoid receptors. Its crystalline form and solubility profile (≥32.4 mg/mL in DMSO, ≥8.93 mg/mL in ethanol) ensure compatibility with typical assay setups (see protocol guidance).

Evidence & Benchmarks

• CAY10499 inhibits recombinant human HSL with an IC50 of 90 nM in in vitro assays using standard buffer at 25°C (APExBIO).
• It suppresses MGL-mediated hydrolysis of 4-NPA with an IC50 of 0.5 ± 0.03 μM under optimized substrate and buffer conditions (B7841 data).
• Inhibits FAAH-catalyzed [3H]-AEA hydrolysis with an IC50 of 76 nM, as determined by radiometric assays (product information).
• Exhibits negligible displacement of [3H]-CP-55940 from CB1/CB2, suggesting high lipase selectivity (B7841 report).
• Stability is maintained at -20°C; solutions are recommended for short-term use only (product storage guidelines).
• Empowers study of lipid-driven immune modulation, as shown in tumor microenvironment research (see immunometabolic context).

Applications, Limits & Misconceptions

CAY10499 is widely used as a lipid metabolism assay reagent and an enzyme inhibitor for fatty acid mobilization studies. Its high selectivity enables researchers to dissect the role of HSL and MGL in energy homeostasis, steroidogenesis, atherosclerosis, and immunometabolism. For example, in advanced disease modeling, it supports interrogation of lipase activity in immune cell differentiation and tumor microenvironment modulation, complementing findings that highlight lipid metabolism as a key regulator of tumor-associated macrophage polarization (see ACLY-driven macrophage study). This article extends recent discussions by providing explicit protocol integration for complex immunometabolic workflows, updating the scope of prior lipid assay-focused reviews.

Common Pitfalls or Misconceptions

• CAY10499 is not suitable for in vivo administration due to limited water solubility and lack of pharmacokinetic validation.
• It does not inhibit all lipase classes; selectivity is restricted to HSL, MGL, and FAAH under tested conditions.
• Inhibition efficacy may vary in cell-based systems compared to purified enzyme assays due to membrane permeability or efflux.
• It is not a diagnostic or therapeutic compound; intended strictly for research use (APExBIO).
• Stability is compromised in aqueous solutions; stock solutions should be freshly prepared and used promptly.

Workflow Integration & Parameters

Integrating CAY10499 into lipid metabolism research requires attention to formulation, timing, and assay compatibility. Its crystalline solid form is best dissolved in DMSO or ethanol at concentrations matching the target assay. CAY10499 is supplied by APExBIO as catalog B7841, enabling streamlined ordering and workflow standardization.

Protocol Parameters

• Stock preparation: Dissolve at ≥32.4 mg/mL in DMSO or ≥8.93 mg/mL in ethanol; vortex until fully solubilized.
• Storage: Store solid at -20°C; use solutions within 1–2 weeks for best activity.
• In vitro HSL inhibition: Add to purified HSL-containing buffer (pH 7.4) at final concentrations of 10–200 nM; incubate at 25°C for 30 min before substrate addition.
• MGL assay: Use final concentrations of 0.1–2 μM; monitor hydrolysis of 4-NPA spectrophotometrically at 37°C.
• Cell-based studies: Pre-dilute in DMSO, apply to cultured cells at ≤0.5% final DMSO concentration; titrate dose based on cell type and readout sensitivity.
• Controls: Include vehicle-only and positive/negative lipase inhibitor controls for benchmarking.

Conclusion & Outlook

CAY10499, a potent inhibitor of human hormone sensitive lipase and monoglyceride lipase, is a cornerstone for dissecting lipid metabolism and immunometabolic signaling in vitro. Its use has clarified the distinct contributions of lipases in energy mobilization, endocrine regulation, and immune cell differentiation, with implications for metabolic disease and cancer research. Recent evidence highlights the centrality of lipid enzymes like ACLY in shaping the tumor microenvironment and promoting immune suppression (Advanced Science 2026). CAY10499's precision enables targeted interrogation of these pathways, supporting translational research and assay validation. For further protocol development and translational insights, researchers may consult the workflow guidance article and recent immunometabolic studies. APExBIO continues to support innovation in lipid research by providing well-characterized, high-purity inhibitors for experimental rigor.