We tested the anti-inflammatory agent methyl-2-acetamidoacrylate (M2AA), an ethyl pyruvate analogue, in a cecal ligation and puncture (CLP) model of sepsis in CD-1 mice. M2AA administration at the time of CLP improved survival, renal function, kidney histology, liver injury, splenocyte apoptosis and lowered cytokine levels (TNF-, IL-6, IFN- and IL-10). When M2AA treatment was delayed 6 h (but not 12 h), M2AA still significantly reduced kidney dysfunction, liver injury, splenocyte apoptosis and cytokine levels. NFB, a M2AA target, was transiently activated in spleen, peaking at 6 h; kidney and liver NFB increased steadily with a plateau at 12-24 h. M2AA reduced NF-B activation in spleen at 6 h, kidney and liver at 24 h. Splenectomy diminished the ability of M2AA to reduce cytokines, especially IL-6, but M2AA still decreased kidney and liver dysfunction, suggesting that splenic NFB is not central to M2AA action. In contrast, beneficial effects of chloroquine on cytokines and organ damage were neutralized by splenectomy, demonstrating a spleen-specific chloroquine target. Because M2AA and chloroquine act differently, we tested this combination. Survival at 96 h was highest with combination therapy (57%) vs. chloroquine (38%), M2AA (47.6%) or vehicle (5%). The benefit of combination therapy over chloroquine or M2AA alone did not reach statistical significance, suggesting some mechanistic overlap. We conclude that the transient target(s) for M2AA responsible for the narrow 6 h therapeutic window is not splenic NFB. Identifying this new target and downstream signaling pathways could lengthen the therapeutic window and improve combination therapy with chloroquine.