BMS-345541: Selective IKK-1/IKK-2 Inhibitor for Precision NF-κB Pathway Modulation

Executive Summary: BMS-345541 (free base) is a small molecule inhibitor exhibiting high selectivity for IκB kinases IKK-1 and IKK-2, with IC₅₀ values of 4 μM and 0.3 μM, respectively, under in vitro assay conditions (product page). It allosterically blocks NF-κB-dependent transcription, thereby reducing pro-inflammatory cytokine production in THP-1 cells and in vivo models (Lv et al., 2020, DOI). BMS-345541 demonstrates dose-dependent inhibition of LPS-induced TNF in mice at 100 mg/kg. It is insoluble in water but readily dissolves in DMSO (≥70 mg/mL) and ethanol (≥2.49 mg/mL) with gentle warming. The compound is a validated tool for dissecting cytokine-induced NF-κB activation and has proven efficacy in both inflammation and cancer research (related article).

Biological Rationale

The NF-κB signaling pathway regulates immune response, inflammation, and apoptosis. Aberrant activation of this pathway contributes to inflammatory diseases and cancers. IκB kinases, IKK-1 (IKKα) and IKK-2 (IKKβ), are essential for cytokine-induced activation of NF-κB. Selective inhibition of IKKs is a strategy to modulate excessive inflammation and control pathological cell survival (Lv et al., 2020). BMS-345541 targets both IKK-1 and IKK-2, directly interfering with the central regulatory node of canonical NF-κB signaling. This enables researchers to study the consequences of precise pathway inhibition in vitro and in vivo.

Mechanism of Action of BMS-345541 (free base)

BMS-345541 (CAS 445430-58-0) is a small molecule that binds to an allosteric site on IKK-1 and IKK-2, inhibiting their kinase activity. The compound demonstrates an IC₅₀ of approximately 4 μM for IKK-1 and 0.3 μM for IKK-2 in enzyme assays (BMS-345541 product page). By blocking IKK activity, BMS-345541 prevents phosphorylation and subsequent degradation of IκB, the inhibitory protein that sequesters NF-κB in the cytoplasm. This blockade results in reduced nuclear translocation of NF-κB, dampening transcription of pro-inflammatory genes including TNF-α, IL-1β, IL-6, and IL-8 (Lv et al., 2020). Cellular studies using THP-1 monocytes confirm that pretreatment with BMS-345541 suppresses cytokine-induced IKK phosphorylation and downstream cytokine production. In cancer cell lines, BMS-345541 reduces proliferation and induces apoptosis, likely due to inhibition of NF-κB-dependent survival pathways (application article).

Evidence & Benchmarks

• BMS-345541 inhibits IKK-2 with an IC₅₀ of 0.3 μM and IKK-1 with an IC₅₀ of 4 μM in biochemical assays (ApexBio).
• In THP-1 monocytes, BMS-345541 pretreatment suppresses LPS-induced phosphorylation of IKK and NF-κB p65, reducing TNF-α, IL-1β, IL-6, and IL-8 production (Lv et al., 2020).
• BMS-345541 demonstrates dose-dependent inhibition of LPS-induced serum TNF in BALB/c mice, with near-complete inhibition at 100 mg/kg administered intraperitoneally (Lv et al., 2020).
• In glioma and melanoma cell models, BMS-345541 reduces cell proliferation and induces apoptosis as measured by standard viability and caspase assays (Application article).
• In a critical limb ischemia (CLI) mouse model, BMS-345541 reverses the pro-angiogenic and NF-κB activating effects of thymosin-β 4, confirming pathway-specific inhibition (Lv et al., 2020).

This article extends the mechanistic context provided in Unraveling the Therapeutic Potential of IKK-NF-κB Pathway by emphasizing practical benchmarks and in vivo efficacy.

Applications, Limits & Misconceptions

BMS-345541 is widely used in models of inflammation, autoimmunity, and cancer. It is also valuable in dissecting angiogenesis mechanisms in vascular disease models. The selective inhibition of IKK-1/IKK-2 enables specific dissection of canonical NF-κB signaling without broadly suppressing unrelated kinases (application guide). However, certain limitations apply.

Common Pitfalls or Misconceptions

• Non-specific effects at high concentrations: Concentrations above 100 μM may affect kinases outside the IKK family (ApexBio).
• Insolubility in aqueous buffers: BMS-345541 is insoluble in water; improper solubilization leads to variable dosing or precipitation.
• Limited effect on non-canonical NF-κB: BMS-345541 primarily inhibits the canonical pathway and has minimal effects on non-canonical NF-κB activation.
• Short-term inhibition: Effects are often transient; long-term pathway suppression may require repeated dosing or genetic methods.
• Storage stability: Stock solutions in DMSO or ethanol degrade over days at room temperature; long-term storage at -20°C is required (ApexBio).

This article clarifies the practical utility and boundaries of BMS-345541, updating previous overviews such as Unveiling IKK-NF-κB Signaling in Inflammatory Models by providing explicit solubility and specificity data.

Workflow Integration & Parameters

BMS-345541 (free base) is supplied as a solid, recommended to be reconstituted in DMSO (≥70 mg/mL) or ethanol (≥2.49 mg/mL) with gentle warming and ultrasound. It is insoluble in water and should not be stored in aqueous buffers. Stocks are aliquoted and stored at -20°C. Working concentrations for cell-based assays range from 1–100 μM, with typical pretreatment times of 30–60 minutes. In animal models, dosing regimens of 25–100 mg/kg intraperitoneally are reported for acute pathway inhibition. Solutions should be freshly prepared to ensure potency (ApexBio). For detailed guidance, see the Strategic IKK-NF-κB Pathway Inhibitor Roadmap, which this article supplements by providing updated experimental parameters and recent in vivo data.

Conclusion & Outlook

BMS-345541 (free base) is a validated, selective inhibitor of IKK-1/IKK-2 and an indispensable pharmacological tool for investigating the IKK-NF-κB signaling pathway in inflammation, apoptosis, and angiogenesis. Its defined selectivity, robust in vitro and in vivo benchmarks, and straightforward handling parameters make it the gold standard for pathway modulation studies. Ongoing research continues to expand its applications in disease modeling and translational research. For ordering or further specifications, refer to the BMS-345541 (free base) product page.