Baricitinib (Olumiant) is a new European Commission-approved rheumatoid arthritis (RA) treatment. Eli Lilly and Company and Incyte Corporation developed baricitinib, the first JAK inhibitor the European Union has authorized. It is for adults with moderate-to-severe active rheumatoid arthritis.

Scientists have yet to determine the cause of RA, a chronic inflammatory disease. Whatever is behind it triggers an autoimmune reaction that leads to the thickening of synovial membranes, connective tissues lining joint cavities. This results in joint inflammation and pain.

The immune system is a complex network that the body regulates at different stages to ensure a correct response to an external attack. When the system detects a threat, it sets in motion an inflammatory response that protects cells from the invader.

In order for inflammation to start, the immune system has to read genes that have the capacity to originate inflammation. When our body detects a threat, it spreads a chemical signal throughout our cells. Receptors in the cells recognize the signal and activate proteins known as JAKs that are inside the cells. This activation is crucial to the chain of events that leads to the immune system reading the genes that cause inflammation.

How baricitinib (Olumiant) works

Baricitinib works by inhibiting JAK proteins at the beginning of the chain of events that cause inflammation. The chemical signal is still spread from cell to cell, but because JAKs do not become activated, the signal does not generate a response.

Baricitinib helps patients with RA by decreasing inflammation and, therefore, pain.

Baricitinib studies in rheumatoid arthritis

Eli Lilly has conducted several Phase 3 clinical trials of baricitinib (Olumiant) in patients with moderate-to-severe active RA.

The studies assessed baricitinib’s ability to help patients who failed to respond to other treatments. They included patients who took conventional disease-modifying antirheumatic drugs (cDMARDs) (NCT01721057), patients who took a tumor necrosis factor inhibitor (NCT01721044), and patients who took a methatrexate-based therapy (NCT02265705). Two of the trials compared baricitinib’s effectiveness with the methatrexate treatments metrotexate (NCT01711359) and adalimumab (NCT01710358).

Patients who completed a Phase 3 trial can now enroll in a five-year extension study (NCT01885078) that will assess the long-term effects of the drug.

Side effects of Baricitinib

The United States has yet to approve the drug because of safety concerns. The Food and Drug Administration has warned that JAK inhibitors may increase the risk of serious infections, tuberculosis, cancers, and lymphoma. It also said the drug may lead to higher cholesterol, respiratory tract infections, headache, and diarrhea in some patients.