Therapeutic Drug Monitoring of Orally Administered Letermovir Prophylaxis in Allogeneic Hematopoietic Stem Cell Transplant Recipients.

With balanced safety-efficacy profile, letermovir anti-cytomegalovirus (CMV) prophylaxis is used in hematopoietic stem cell transplant recipients (HSCTR). We assessed feasibility and usefulness of letermovir therapeutic drug monitoring (TDM) in HSCTR. We performed a prospective observational study on letermovir-TDM including 40 consecutive adult CMV-seropositive allogeneic-HSCTR who received orally (PO) administered letermovir. Minimal blood concentrations of letermovir (Ctrough) were measured on days 3 and 7 postletermovir initiation and weekly thereafter. Letermovir-Ctrough remained stable during the first 70 days post-HSCT at a median of 286 µg/L (interquartile range, 131 to 591 µg/L), with large interpatient/intrapatient variability. No associations between breakthrough clinically significant CMV infection or detectable CMV DNAemia and letermovir-Ctrough were observed. Patients with letermovir-associated adverse events had higher letermovir-Ctrough than patients without (400 versus 266 µg/L, P = 0.02). Letermovir-Ctrough was similar in patients with or without gastrointestinal symptoms (280 versus 300 µg/L, P = 0.49). Acute grade ≥2 GvHD was associated with higher letermovir-Ctrough (479 versus 248 µg/L, P = 0.001), including gastrointestinal GvHD (499 versus 263 µg/L, P = 0.004). Concomitantly administered posaconazole and cyclosporine were associated with higher letermovir-Ctrough (707 versus 259 µg/L, P < 0.001 and 437 versus 248 µg/L, P = 0.01, respectively). In multivariable analysis, both posaconazole (odds ratio [OR], 4.9; 95% confidence interval [CI], 2.4 to 9.7; P < 0.0001) and cyclosporine-adjusted letermovir dose at 240 mg daily (OR, 3.5; 95% CI, 1.4 to 9.0; P = 0.01) were independently associated with higher letermovir-Ctrough. In conclusion, administration of PO letermovir led to measurable and relatively stable letermovir-Ctrough, without noticeable associations with clinical efficacy. Letermovir exposure was not affected by gastrointestinal symptoms, but with posaconazole and cyclosporine administration. Associations between letermovir and concomitantly administered agents and adverse events warrant additional clinical studies.

Predictors of breakthrough clinically significant cytomegalovirus infection during letermovir prophylaxis in high-risk hematopoietic cell transplant recipients.

Letermovir prophylaxis in allogeneic hematopoietic cell transplant recipients significantly reduces the incidence of clinically significant cytomegalovirus infection. However, breakthrough infections still occur despite adequate prophylaxis. In the present retrospective cohort study, we identified clinically relevant predictive factors for clinically significant CMV breakthrough infection during letermovir prophylaxis. Low-grade CMV replication (21-149 IU/ml), both at the time of letermovir initiation or during prophylaxis, was a significant risk factor for breakthrough clinically significant CMV infection. In addition, development of acute gastrointestinal graft-versus-host disease was significantly associated with breakthrough infection. Altogether these findings could call clinicians' attention to closer CMV monitoring and allow for prompt preemptive treatment initiation.

Letermovir Primary Prophylaxis in High-Risk Hematopoietic Cell Transplant Recipients: A Matched Cohort Study.

BACKGROUND: Real-life data on the administration of letermovir as cytomegalovirus (CMV) primary prophylaxis after allogeneic hematopoietic cell transplantation (HCT) remain limited. METHODS: We conducted a retrospective single-center matched cohort study, comparing consecutive high-risk allogeneic HCT recipients (cases) receiving primary prophylaxis with letermovir and untreated matched historical controls, during a study period of 180 days. The primary outcome was the incidence of clinically significant (cs) CMV infection. Secondary outcomes included duration and costs of CMV-antiviral treatments, hospital resource utilization, hematology and laboratory parameters. RESULTS: Letermovir prophylaxis decreased csCMV infection incidence from 82.7% (controls) to 34.5% (cases; p-value < 0.0001). Controls were more likely to have >1 episode of csCMV infection (59.6%) compared to cases (11.5%; p-value < 0.0001). Letermovir was associated with: shorter overall CMV-associated treatment duration (49 days vs. 77.8 days; p-value: 0.02) and a trend for lower costs of CMV-associated treatments ($4096 vs. $9736; p-value: 0.07) and reduced length of stay (44.8 days vs. 59.8 days; p-value: 0.16). Letermovir administration was associated with significantly shorter duration (27.3 days vs. 57.1 days; p-value: 0.008) and lower costs ($1089 vs. $2281; p-value: 0.008) of valganciclovir treatment. Compared to controls, higher platelet counts were observed in cases (138 G/L vs. 92 G/L; p-value: 0.03) and renal function was improved (94 mL/min/1.73 m2 vs. 74 mL/min/1.73 m2; p-value: 0.006). CONCLUSIONS: Primary anti-CMV letermovir prophylaxis decreased the incidence of csCMV infection and the administration of CMV-associated treatments and costs, particularly those associated with valganciclovir. An effect of letermovir on platelet reconstitution and renal function of csCMV post-HCT was observed and needs further investigation.