Targeting myeloid differentiation 2 for treatment of sepsis.

Sepsis continues to be a leading cause of intensive care unit (ICU) death. Gram-negative bacteria are among the most important pathogens of sepsis and their LPS content is regarded to be an important stimulator that elicits the systemic inflammatory reaction. MD-2 is a small secreted glycoprotein that can bind to both the hydrophobic portion of LPS and to the extracellular domain of TLR4. The interaction between MD-2 and LPS bridges the two TLR4 molecules and induces the dimerization of LPS-MD-2-TLR4, which forms the structural basis for biological functions of TLR4/MD-2 complex. Due to its essential role in mediating the interaction between LPS and TLR4, MD-2 has been extensively explored as a therapeutic target for treatment of inflammatory disorders such as sepsis. Eritoran is a synthetic tetraacylated lipid A that binds directly to MD-2 and antagonizes LPS binding to the same site. Although eritoran showed positive results in phase I and phase II clinical trials of severe sepsis, a phase III clinical study for severe sepsis has failed. More effective therapeutic strategies are in need to treat this devastating clinical disorder.