Xeljanz (tofacitinib citrate) is an oral small molecule distributed by Pfizer and used to treat moderate to severe active rheumatoid arthritis (RA) patients who have not responded adequately to methotrexate or cannot tolerate it.
The U.S. Food and Drug Administration and the European Commission have both approved Xeljanz to treat adults with RA. Xeljanz is also being investigated as a potential treatment for juvenile arthritis (JA), a group of conditions causing joint swelling in children under age 16.
Although the exact causes of RA and JA are unknown, they are considered to be autoimmune diseases in which the immune system attacks healthy tissues in the body.
How Xeljanz works
Normally, the immune system defends the body from threats or invaders using chemical signals that spread from cell to cell. In this process, the chemical molecules are recognized by receptors that exist on the surface of cells and activate a group of proteins inside the cells, called JAKs. This activation culminates in the formation of new chemical molecules, which spread the message to other cells, maintaining inflammation for as long as it is necessary to clear out the threat.
In RA and JA patients, cells are constantly producing new chemical molecules leading to a higher-than-normal amount of circulating molecules, spreading a message that inflammation should be maintained.
Xeljanz works by inhibiting JAK proteins inside the cell, and in this way, blocking the generation of new molecules and the spreading of the signal needed to maintain inflammation.
Xeljanz in clinical trials
The safety and efficacy of the Xeljanz were investigated by Pfizer in seven Phase 3 clinical trials, which included more than eight years of safety data, representing more than 21,100 patient-years of drug exposure to date. The results, conducted in a diverse RA patient population and published in several peer-reviewed journals, demonstrated the safety and effectiveness of Xeljanz, both with and without methotrexate for the treatment of moderate to severe RA.
Pfizer also tested Xeljanz for the treatment of active JA. A Phase 1 clinical trial (NCT01513902) assessing the pharmacokinetics, safety, and tolerability of Xeljanz in children with JA ages, 2 to 18 has been completed. The preliminary results established dosing regimens to be used in further safety and efficacy studies and have shown that the drug was well tolerated among the children.
Two Phase 3 clinical trials are currently recruiting participants. One of the trials (NCT01500551) aims to evaluate the long-term safety and tolerability of the drug in patients with JA who have previously participated in Xeljanz studies. The second (NCT02592434) is comparing the efficacy of Xeljanz to a placebo for the treatment of JA
Xeljanz side effects include an increased risk of serious infections, tuberculosis, cancers and lymphoma, as well as high cholesterol, respiratory tract infections, headache, and diarrhea in some patients.
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