VIROMARKERS GA n.101194735 - CMV and TTV Biomarkers Study Protocol

The study is one of the researches carried out in the VIROMARKERS Project.

The project VIROMARKERS is supported by the Innovative Health Initiative Joint Undertaking (IHI JU) under grant agreement No 101194735. The JU receives support from the European Union's Horizon Europe research and innovation programme and COCIR, EFPIA, Europa Bio, MedTech Europe, Vaccines Europe, and Roboscreen.

To date, the virological surveillance for CMV replication relies basically on the quantification of CMV-DNA in blood or plasma by using Real-Time PCR assays, and CMV-DNAemia is known to correlate with both CMV-related disease and non-relapse mortality [Ljungman, 2025]. However, the detection of CMV-DNAemia is not always associated with an active CMV replication, particularly in patients exposed to letermovir. Therefore, the identification of new virological markers to accurately monitor CMV activity in the early and late post-HSCT phases, remains a crucial issue especially in individuals receiving letermovir as prophylaxis to ensure a proper diagnosis of CMV infection/disease and to guide prophylactic and pre-emptive antiviral treatment.

In this setting, the quantification of CMV-RNA represents a potential candidate marker capable of better reflecting the presence of complete, infectious CMV virions than CMV-DNAemia. Despite several data support a correlation of CMV UL21.5-mRNA with viral activity [Nicastro, 2025], studies investigating the kinetics of this viral mRNA among immune-suppressed patients at risk of CMV re-uptake are largely missing, especially in the setting of patients receiving antiviral prophylaxis with letermovir after HSCT.

TTV-DNA load was mostly investigated in solid organ transplant patients (SOT), where it showed a good correlation of high viral load and degree of immunosuppression. In HSCT patients the interaction of the immune system, which is under reconstitution, and clinically relevant CMV infection is more complex. First data have been reported by our group [Gilles et al., 2017] showing high TTV load as a prognostic marker for risk of complications after HSCT. Little information is available for HSCT patients under letermovir prophylaxis.

Specific primary objectives related to CMV monitoring in the HSCT setting are the following:

Primary In participants who received HSCT, to estimate the rate of initiation of anti-CMV therapy during letermovir-based prophylaxis and the rate of CMV re-activation (based on symptoms, signs of organ dysfunction and CMV-DNAemia) after suspension of letermovir.

To evaluate the kinetics of CMV-RNAemia, CMV-DNAemia and TTV-DNAemia and their correlation during prophylaxis with letermovir.

To establish whether early quantitative CMV-RNA level or the early kinetics of CMV-RNAemia and TTV-DNAemia during prophylaxis can predict initiation of anti-CMV therapy.

In participants not initiating anti-CMV therapy during prophylaxis, to establish whether quantitative CMV-RNA level at time of letermovir suspension or the kinetics of CMV-RNAemia and TTV-DNAemia during prophylaxis can predict CMV re-activation (based on symptoms signs of organ dysfunction and CMV-DNAemia) after suspension of letermovir.

Secondary objectives include to establish a cut-off for CMV-RNAemia and TTV DNAemia to maximize the accuracy of prediction of CMV re-activation after suspension of prophylaxis; to explore the kinetics of CMV-RNAemia and TTV-DNAemia in participants treated with anti CMV drugs.

The information used from this study on participants in the HSCT setting will be rapidly analyzed and shared broadly to guide policymakers for the use and monitoring of CMV-DNAemia, CMV-RNAemia and TTV-DNAemia in CMV disease and to design future studies. For exact plans regarding the expected date of study completion and plans for dissemination please refer to separate documents produced within the WP5 of VIROMARKERS.