Eritoran is an investigational drug for the treatment of severe sepsis

Sepsis

Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

, an excessive inflammatory response to an infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

. It is being developed by Eisai Co.

Eisai Co.

is a Japanese pharmaceutical company, ranking among the top 25 in the world by revenue and achieving $8 billion USD in sales for the fiscal 2008 year. Headquartered in Tokyo, Japan, it has some 10,000 employees, among them about 1,500 in research. Eisai is a member of the Topix 100 and Nikkei 225...

 and administered intravenously as eritoran tetrasodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

. , a Phase III clinical trial

Clinical trial

Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...

 is recruiting patients.

Mechanism of action

Toll-like receptor

Toll-like receptor

Toll-like receptors are a class of proteins that play a key role in the innate immune system. They are single, membrane-spanning, non-catalytic receptors that recognize structurally conserved molecules derived from microbes...

s (TLRs) play an important role in the innate immune system

Innate immune system

The innate immune system, also known as non-specific immune system and secondary line of defence, comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner...

. They recognise microbes and activate inflammatory immune responses. Toll-like receptor 4 (TLR4) detects lipopolysaccharide

Lipopolysaccharide

Lipopolysaccharides , also known as lipoglycans, are large molecules consisting of a lipid and a polysaccharide joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria, act as endotoxins and elicit strong immune responses in animals.-Functions:LPS is the major...

s found in most Gram-negative

Gram-negative

Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 bacteria.

Because of its similarity to the lipopolysaccharide lipid A

Lipid A

Lipid A is a lipid component of an endotoxin held responsible for toxicity of Gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane...

, eritoran acts as TLR4 antagonist

Receptor antagonist

A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...

and so blocks the excessive reaction triggered by this receptor.