Luigi Celio, Francesca Ricchini, Filippo De BraudMedical Oncology Unit 1, Department of Medical Oncology, Fondazione IRCCS Istituto Nazionale Tumori, Milan, ItalyAbstract: Control of chemotherapy-induced nausea and vomiting (CINV) is a crucial factor in ensuring that patients undergoing cancer chemotherapy can get the full benefit of therapy. Current antiemetic guidelines recommend that the neurokinin-1 receptor (NK-1R) antagonist aprepitant should be used as part of a combination regimen with dexamethasone and a serotonin receptor antagonist for the prevention of CINV in patients receiving highly emetogenic chemotherapy (HEC). Fosaprepitant is a water-soluble N-phosphoryl derivative of aprepitant that, when infused, is rapidly metabolized back to an active aprepitant. The existing literature in PubMed about fosaprepitant was screened and selected in order to address the emerging data from two randomized clinical trials evaluating the efficacy and safety of a single-dose fosaprepitant regimen. These phase III trials demonstrated that fosaprepitant given as a single intravenous dose of 150 mg was either noninferior to the conventional 3-day aprepitant or significantly superior to placebo for the prevention of acute and delayed CINV in patients receiving high-dose cisplatin. In both trials, fosaprepitant was well tolerated although more frequent infusion-site adverse events were observed with fosaprepitant. The new dosage regimen of fosaprepitant, therefore, would be an option for CINV control in patients receiving cisplatin-based chemotherapy. The clinical efficacy is consistent with the findings from a time-on-target, positron-emission tomography study evaluating the NK-1R occupancy in the central nervous system (CNS) over 5 days after a single-dose infusion of 150 mg fosaprepitant in healthy participants. The single-dose regimen is capable of blocking more than 90% of the NK-1Rs in the CNS for at least 48 hours after infusion, which is sufficient to control delayed CINV for 2 to 5 days after HEC. The new dosage regimen of fosaprepitant can provide a simplified treatment option that maintains high protection while ensuring adherence to scheduled antiemetic medication throughout most of the 5-day period encompassing the major risk for CINV.Keywords: fosaprepitant, neurokinin-1 receptor antagonist, chemotherapy-induced nausea and vomiting