Cytokines are a broad and loose category of small proteins (~5–20 kDa) that are important in cell signaling, modulate the balance between humoral and cell-based immune responses, and are heavily involved in autoimmune and inflammatory diseases. Blocking cytokine signaling pathways by biologics has shown clinical effectiveness in these diseases.

Cytokines act through receptors and activate related signaling to modulate gene expression and cell functions. Cytokine receptors activate many signaling pathways: JAK-STAT, NF-kB, MAPK, PI3K, etc. A number of small molecular weight inhibitors targeting cytokine signaling have been identified as research progresses and some are approved to be marketed. Cytokines Inhibitors Library from TargetMol, containing 604 compounds targeting cytokine signaling, can be used for high throughput and high content screening for drug discovery.