Eoxin C<sub>4</sub> (EXC<sub>4</sub>), also known as 14,15-leukotriene C<sub>4</sub>, is an eoxin. Cells make eoxins by metabolizing arachidonic acid with a 15-lipoxygenase enzyme to form (i.e. 15(S)-HpETE). This product is then converted serially to EXA<sub>4</sub>, EXC<sub>4</sub>, EXD<sub>4</sub>, and EXE<sub>4</sub> by LTC<sub>4</sub> synthase, an unidentified gamma-glutamyltransferase, and an unidentified dipeptidase, respectively, in a pathway which appears similar if not identical to the pathway which forms leukotrienes, i.e. LTA<sub>4</sub>, LTC<sub>4</sub>, LTD<sub>4</sub>, and LTE<sub>4</sub>. This pathway is schematically shown as follows:
EXA<sub>4</sub> is viewed as an intracellular-bound, short-lived intermediate which is rapidly metabolized to the downstream eoxins. The eoxins downstream of EXA<sub>4</sub> are secreted from their parent cells and, it is proposed but not yet proven, serve to regulate allergic responses and the development of certain cancers (see eoxins).