It has been hypothesized that inflammatory activators have a pro-apoptotic effect on erythroid progenitor cells and compete with the anti-apoptotic effect of erythropoietin, the end result being erythropoietin resistance.[21] Pentoxyfylline, a nonspecific anti-TNF-α antagonist, has shown encouraging results in erythropoietin unresponsive CKD patients.[22]. This evidence concerns the gene TNF and chronic kidney disease.