Queen's School of Business Presentation
Issue link: http://invivo.uberflip.com/i/1501332
Dialogues in Cytomegalovirus 5 CMV Management in the Post-DNA Polymerase Inhibitor Era rates of leukopenia or neutropenia. These data suggest that letermovir would be a compelling alternative to valganciclovir for CMV prophylaxis following SOT. In brief, letermovir is a novel antiviral agent that has shown promising results for the prophylaxis of CMV in allo-HCT recipients and SOT. It has also been studied for the treatment of CMV viremia or disease, yet further research would be required to confirm its clinical use for this indication, particularly as it has a relatively low genetic barrier to resistance. 22 Maribavir Maribavir is a novel antiviral agent approved by Health Canada in 2022 for the treatment of adults with post-transplant CMV infection/disease who are refractory (with or without genotypic resistance) to one or more prior antiviral therapies. 23 Unlike other CMV antivirals, it functions by attaching to the UL97 enzyme and inhibiting the enzyme's activity in processes such as DNA replication, encapsidation, and the nuclear egress of newly formed CMV virions. 23,24 Similar to letermovir, maribavir is not active against HSV or VZV. Maribavir has shown to be a safe and generally well-tolerated treatment across several Phase I, II and III studies. It was initially evaluated for CMV prophylaxis following allo-HCT and demonstrated promising results in a randomized, double-blind, placebo-controlled, dose-ranging trial. 25 In this study, 111 patients were randomized to receive maribavir (at doses of 100 mg twice daily, 400 mg once daily, or 400 mg twice daily) or placebo for up to 12 weeks. The results demonstrated a significantly lower incidence of CMV viremia (as measured by pp65 antigen levels) in each of the maribavir subgroups vs placebo throughout the first 100 days post-transplantation. 25 With these data, study investigators chose to proceed with a dose of 100 mg PO BID in its placebo-controlled, double- blind, randomized Phase III study, which enrolled 681 participants and randomized 454 to maribavir and 227 to placebo. 26 The study demonstrated a similar incidence of CMV disease in the maribavir and placebo groups within 6 months of transplant. Similarly, the incidence of CMV viremia (as measured by plasma CMV DNA PCR) was similar between groups. 26 While several factors may have contributed to the negative findings in this Phase III trial, the lower dose of maribavir was certainly chief among them. 27 With emerging data of maribavir successfully being used for the treatment of CMV, 28 clinicians were eager to evaluate the drug for cases of refractory and resistant CMV viremia or disease. In a randomized, dose-ranging, parallel-group Phase II study, SOT and allo-HCT recipients with refractory or resistant CMV viremia or disease were randomized to receive maribavir 400, 800 or 1200 mg PO BID for up to 24 weeks. 29 The results suggested an overall response rate of approximately 66.7% and encouraged a larger, confirmatory study. 29 In a follow-up multicentre, randomized, open-label Phase 3 trial, SOT and allo-HCT recipients ≥12 years of age with refractory or resistant CMV viremia or disease were randomized 2:1 Definitions of Refractory and Resistant CMV viremia and CMV disease 15 Refractory CMV viremia: CMV viremia that increases† following at least 2 weeks of appropriately dosed antiviral therapy. Refractory CMV disease: Worsening in signs and symptoms or progression into end-organ disease following at least 2 weeks of appropriately dosed antiviral therapy. Antiviral drug resistance: Viral genetic alteration that decreases susceptibility to one or more antiviral drugs.‡ † More than 1 log₁₀ increase in CMV DNA levels in blood or serum and determined by log₁₀ change from the peak viral load within the first week to the peak viral load at ≥2 weeks as measured in the same laboratory with the same assay. ‡ Known examples involve genes involved in antiviral drug anabolism, the antiviral drug target, or compensation for antiviral inhibition of biological function.