MCC950 Sodium: Selective NLRP3 Inflammasome Inhibitor for Inflammatory Disease Research

Executive Summary: MCC950 sodium (B7946, APExBIO) is a highly potent, selective small-molecule inhibitor of the NLRP3 inflammasome, with nanomolar activity in murine and human macrophages (Yuan et al. 2022). It blocks both canonical and noncanonical NLRP3 activation pathways, without affecting AIM2, NLRC4, or NLRP1 inflammasomes. MCC950 sodium specifically inhibits interleukin-1β (IL-1β) release without altering TNF-α secretion, demonstrating pathway selectivity. In animal models, it reduces serum IL-1β and IL-6 after LPS challenge and attenuates experimental autoimmune encephalomyelitis severity. The compound is highly water-soluble (≥124 mg/mL) and recommended for -20°C storage for stability (APExBIO).

Biological Rationale

The NLRP3 inflammasome is a multiprotein complex critical for innate immune sensing and is implicated in the pathogenesis of inflammatory and autoimmune diseases. Activation of NLRP3 leads to caspase-1-mediated maturation and release of pro-inflammatory cytokines IL-1β and IL-18, as well as pyroptosis, a lytic form of programmed cell death (Yuan et al. 2022). Pyroptosis and inflammation are central to diseases such as atherosclerosis, multiple sclerosis, and other chronic inflammatory states. Targeting the NLRP3 inflammasome with selective inhibitors like MCC950 sodium enables mechanistic dissection of these processes and supports therapeutic hypotheses. Unlike broad-spectrum inhibitors, MCC950 sodium permits precise investigation of the NLRP3 inflammasome pathway, avoiding confounding off-target inflammasome effects (see Immuneland: MCC950 sodium—this article updates with new animal and human cell data).

Mechanism of Action of MCC950 sodium

MCC950 sodium, also known as CRID3 sodium salt, directly inhibits the NLRP3 ATPase activity required for inflammasome assembly (Yuan et al. 2022). It prevents oligomerization of NLRP3 and recruitment of the adaptor protein ASC, thereby blocking caspase-1 activation. In cell-based assays, MCC950 sodium inhibits both canonical (ATP, nigericin, or LPS+ATP stimulation) and noncanonical (LPS+gram-negative bacteria) activation routes at nanomolar concentrations. Importantly, it does not inhibit activation of other inflammasomes (AIM2, NLRC4, NLRP1), confirming pathway specificity. The selective mechanism enables the differentiation of NLRP3-dependent from NLRP3-independent inflammatory events in experimental systems (see Mouse-GM-CSF: MCC950 sodium—this article extends application scope with human data).

Evidence & Benchmarks

• MCC950 sodium inhibits NLRP3 activation in murine bone marrow-derived macrophages (BMDMs) with an IC50 of 7.5 nM (in vitro, 37°C, RPMI medium) (Yuan et al. 2022).
• Comparable nanomolar potency is observed in human monocyte-derived macrophages (HMDMs) (primary cells, 10 nM, 2 h pre-incubation) (Yuan et al. 2022).
• MCC950 sodium blocks both canonical (ATP, nigericin) and noncanonical (LPS+H2O2) NLRP3 activation pathways, but does not inhibit AIM2, NLRC4, or NLRP1 inflammasomes (cell-based, multiple donors) (Yuan et al. 2022).
• In BMDMs, HMDMs, and human PBMCs, MCC950 sodium dose-dependently inhibits IL-1β release without altering TNF-α secretion (ELISA, 2–24 h, 37°C) (Yuan et al. 2022).
• Intraperitoneal administration in mice reduces serum IL-1β and IL-6 after LPS challenge and attenuates experimental autoimmune encephalomyelitis (EAE) severity (in vivo, 10 mg/kg IP, n=8, C57BL/6) (Yuan et al. 2022).
• MCC950 sodium is highly soluble in water (≥124 mg/mL), DMSO (≥21.45 mg/mL), and ethanol (≥43 mg/mL) (product data, APExBIO).

Applications, Limits & Misconceptions

MCC950 sodium is used to dissect NLRP3-dependent inflammatory signaling in macrophages, endothelial cells, and animal models of autoimmune and inflammatory disease (compare: TGF-b.com—this article clarifies human cell selectivity). It is considered a gold-standard tool for blocking NLRP3 inflammasome activity in vitro and in vivo. Applications include mechanistic studies of pyroptosis, cytokine release, and disease modeling for conditions such as atherosclerosis, multiple sclerosis, and cardiovascular inflammation. It is not a pan-inflammasome inhibitor and will not block AIM2, NLRC4, or NLRP1 pathways. MCC950 sodium is not currently approved for human therapeutic use. Long-term solution stability is limited, necessitating fresh preparation for each experiment.

Common Pitfalls or Misconceptions

• Not pan-inflammasome: MCC950 sodium selectively inhibits NLRP3, not AIM2, NLRC4, or NLRP1 inflammasomes.
• Not a direct caspase-1 inhibitor: It blocks upstream NLRP3 activation, not caspase-1 enzymatic activity.
• Not suitable for long-term stock solutions: Solutions lose potency if stored; always prepare freshly.
• Not validated for human therapeutic dosing: MCC950 sodium is a research reagent, not a drug.
• Cell-type specificity: Efficacy confirmed in macrophages, PBMCs, and HUVECs; not all cell types are tested.

Workflow Integration & Parameters

MCC950 sodium (B7946, APExBIO) is supplied as a lyophilized powder for reconstitution. It is recommended to dissolve in sterile water (≥124 mg/mL), DMSO, or ethanol. For cell-based assays, effective concentrations are typically 1–10 nM for murine and human macrophages, 2 h pre-incubation is optimal for NLRP3 blockade. In animal models, doses of 10 mg/kg by intraperitoneal injection have shown efficacy. Store powder at -20°C, and avoid repeated freeze-thaw cycles. Fresh solutions should be prepared before each experiment to maintain activity. For specific protocol adaptations, refer to advanced guides (see TAK-242.com—this article provides troubleshooting for workflow issues).

Conclusion & Outlook

MCC950 sodium represents a powerful, selective tool for interrogating NLRP3 inflammasome signaling in inflammation and autoimmunity research. Its nanomolar potency, pathway specificity, and cross-species activity (murine, human) make it a gold standard for mechanistic studies. By enabling discrimination between NLRP3-dependent and independent pathways, MCC950 sodium accelerates identification of therapeutic targets. For the most current product specifications and research applications, refer to the APExBIO MCC950 sodium product page.