For the past 3 decades, erythropoiesis-stimulating agents (ESA) in conjunction with iron supplementation has been the mainstay of treatment for anemia in chronic kidney disease (CKD). Although ESAs are well-established and highly efficacious treatment, clinical trials demonstrated that the use of ESAs with a high hemoglobin (Hb) target was associated with increased risk of cardiovascular events. This safety concern raised considerable interest in developing an alternative therapeutic strategy. Hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) are such novel agents to treat anemia in CKD. They stimulate endogenous erythropoietin production via HIF activation and thereby induce erythropoiesis. At least 6 small-molecule HIF-PHIs have been developed to date. The phase 3 clinical trials demonstrated that their effects were noninferior to ESAs. HIF-PHIs may have several advantages over the conventional treatment, such as oral route of administration and their ability to raise Hb levels in patients with chronic inflammation. Although many of the phase 3 clinical trials demonstrated that HIF-PHIs were noninferior to placebo or ESAs with respect to cardiovascular safety, one of the compounds failed to meet the prespecified noninferiority criterion in non-dialysis-dependent CKD patients, and some studies of another HIF-PHI indicated potential risks for thromboembolic events. While the regulatory agencies of some countries including Japan and the European Union concluded that roxadustat, one of the HIF-PHIs, had a favorable benefit-risk profile, the U.S. Food and Drug Administration decided not to approve the drug because of safety reasons. In order to establish the optimal anemia management in CKD, further studies are needed to evaluate important aspects of HIF-PHIs, such as long-term safety, appropriate Hb target, and the types of patients who would gain benefits from these new drugs.

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of oral medicines being developed for the treatment of anemia in chronic kidney disease (CKD) patients. This study aimed to compare the efficacy and safety of HIF-PHI vs epoetin and darbepoetin in CKD patients with anemia not undergoing dialysis. The PubMed, Embase, Cochrane Library, Web of Science, and clinicaltrials.gov databases were searched from inception to October 2019 for randomized controlled trials investigating different agents (six HIF-PHIs, epoetin, darbepoetin, and placebo) for treating CKD patients with anemia that did not undergo dialysis. The outcomes included a change in hemoglobin (Hb) levels and all-cause mortality. A total of 19 studies were included. Compared with the placebo, except for vadadustat (mean differences: 1.12, 95 % confidence interval [CI]: ‒0.11-2.35), the other drugs significantly increased Hb levels, with mean differences of 2.46 (95 % CI: 0.93-3.99) for desidustat, 1.81 (0.87-2.75) for enarodustat, 1.68 (0.64-2.72) for molidustat, 1.66 (0.89-2.44) for epoetin, 1.63 (0.69-2.56) for darbepoetin, 1.61 (0.99-2.22) for roxadustat, and 1.55 (0.74-2.36) for daprodustat. No differences were found in the Hb level elevations among these eight drugs. Compared with the placebo, there also was no significant association between the drugs and all-cause mortality (molidustat of RR, 0.39 [95 % CI, 0.06-2.59]; roxadustat, 0.40 (0.06-2.84); enarodustat, 0.33 (0.01-16.25); desidustat, 0.34 (0.01-17.00); epoetin, 0.50 (0.18-1.42); daprodustat, 0.54 (0.09-3.31); darbepoetin, 1.03 (0.65-1.65); and vadadustat, 1.43 (0.15-13.27)). No differences were observed in the all-cause mortality among the drugs. In conclusion, these HIF-PHIs are effective and relatively tolerant for treating anemia patients with CKD not undergoing dialysis. Further research should consider the limitations of our study to evaluate the value of these HIF-PHIs in clinical settings.