Pharmacokinetic drug evaluation of letermovir prophylaxis for cytomegalovirus in hematopoietic stem cell transplantation

Role of letermovir therapeutic drug monitoring for cytomegalovirus prophylaxis in allogeneic hematopoietic stem cell transplantation recipients: a prospective study

PURPOSE

The role of therapeutic drug monitoring (TDM) in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients receiving letermovir has not yet been clarified. This study is to explore letermovir trough concentration (Cmin) correlation with its clinical efficacy and adverse events, and factors affecting its plasma concentrations.

METHODS

A prospective, non-interventional study was performed in allo-HSCT recipients receiving letermovir prophylaxis. Plasma concentrations were determined using high-performance liquid chromatography-tandem mass spectrometry. Data analysis was performed using logistic regression, linear regression, and classification and regression tree (CART) models.

RESULTS

701 trough concentrations from 71 recipients were included, uncovering pronounced intra- and inter-individual variability in letermovir Cmin. During 24-week follow-up, CMV infection incidence was 16.4%. A significant correlation was identified between letermovir Cmin and its clinical efficacy, and the CART model showed an increased risk of CMV infection when Cmin ≤ 2731 ng/mL. However, no clear correlation was found between Cmin and adverse events. Gastrointestinal graft-versus-host disease, cyclosporine Cmin, gender, and concomitant medications, including mycophenolate mofetil, ondansetron, caspofungin, and methylprednisolone, may impact letermovir Cmin. Additionally, coadministration with cyclosporine injection significantly decreased median letermovir Cmin compared with cyclosporine capsules (2311 vs. 3386 ng/mL). Moreover, with the extension of time post-transplant, trough concentrations of both cyclosporine and letermovir significantly decreased.

CONCLUSION

TDM for letermovir may be beneficial in allo-HSCT recipients considering the variability in letermovir Cmin and its correlation with clinical efficacy. Moreover, drug interactions and the effects of changes in cyclosporine dosage forms or concentrations require careful monitoring for their effect on letermovir Cmin.

Clinical Pharmacokinetics and Pharmacodynamics of Letermovir in Allogenic Hematopoietic Cell Transplantation

Letermovir is a newly developed antiviral agent used for the prophylaxis of human cytomegalovirus infections in patients undergoing allogeneic hematopoietic cell transplantation. This novel anti-cytomegalovirus drug, used for the prophylaxis of cytomegalovirus reactivation until approximately 200 days after transplantation, effectively reduces the risk of clinically significant cytomegalovirus infection. No human counterpart exists for the terminase complex; letermovir is virus specific and lacks some toxicities previously observed with other anti-cytomegalovirus drugs, such as cytopenia and nephrotoxicity. The absolute bioavailability of letermovir in healthy individuals is estimated to be 94% based on a population-pharmacokinetic analysis. In contrast, oral administration of letermovir to patients undergoing hematopoietic cell transplantation results in lower exposure than that in healthy individuals. Renal or hepatic impairment does not influence the intrinsic clearance of letermovir. Co-administration of letermovir may alter the plasma concentrations of other drugs, including itself, as it acts as a substrate and inhibitor/inducer of several drug-metabolizing enzymes and transporters. In particular, attention should be paid to the drug-drug interactions between letermovir and calcineurin inhibitors or azole antifungal agents, which are commonly used in patients undergoing hematopoietic cell transplantation. This article reviews and summarizes the clinical pharmacokinetics and pharmacodynamics of letermovir, focusing on patients undergoing hematopoietic cell transplantation, healthy individuals, and specific patient subsets.

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 (C_trough) were measured on days 3 and 7 postletermovir initiation and weekly thereafter. Letermovir-C_trough 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-C_trough were observed. Patients with letermovir-associated adverse events had higher letermovir-C_trough than patients without (400 versus 266 μg/L, P = 0.02). Letermovir-C_trough 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-C_trough (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-C_trough (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-C_trough. In conclusion, administration of PO letermovir led to measurable and relatively stable letermovir-C_trough, 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.

Pharmacokinetics, Safety, and Tolerability of Letermovir Following Single- and Multiple-Dose Administration in Healthy Japanese Subjects

Letermovir is a human cytomegalovirus terminase inhibitor for the prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant recipients. The pharmacokinetics, safety, and tolerability of letermovir were assessed in healthy Japanese subjects in 2 phase 1 trials: trial 1-single ascending oral doses (240, 480, and 720 mg) and intravenous (IV) doses (240, 480, and 960 mg), and trial 2-multiple oral doses (240 and 480 mg once daily for 7 days). Following administration of oral single and multiple doses, letermovir was absorbed with a median time to maximum plasma concentration of 2 to 4 hours, and concentrations declined in a biphasic manner with a terminal half-life of ≈10 to 13 hours. The post absorption plasma concentration-time profile of letermovir following oral administration was similar to the profile observed with IV dosing. There was minimal accumulation with multiple-dose administration. Letermovir exposure in healthy Japanese subjects was ≈1.5- to 2.5-fold higher than that observed in non-Japanese subjects. Based on the population pharmacokinetic analysis, weight differences primarily accounted for the higher exposures observed in Asians. Letermovir was generally well tolerated following oral and IV administration to healthy Japanese subjects.

Combined Therapy with Intravenous Immunoglobulins, Letermovir and (Val-)Ganciclovir in Complicated Courses of CMV-Infection in Transplant Recipients

The treatment options for cytomegalovirus (CMV) infections in immunosuppressed patients are limited, mainly consisting of (val-)ganciclovir (VGC/GCV) as the first-line treatment. We report on three transplant recipients, one stem cell transplant (allo-HSCT) patient and two kidney transplant (KTx) recipients, with prolonged CMV viremia treated with a combined therapy based on letermovir (LMV), CMV-specific intravenous immunoglobulins (IVIg), and VGC/GCV, which led to the sustained control of CMV viremia in all patients.

Clinical and Pharmacological Considerations for Concomitant Administration of Posaconazole and Isavuconazole with Letermovir

We sought in this case-control retrospective study to compare posaconazole and isavuconazole (PCZ and IVC, respectively) plasma trough concentration (C _trough) levels in high-risk allogeneic hematopoietic cell transplant (HCT) recipients who received letermovir (LET) or not. PCZ/IVC C _trough levels were not found to be significantly different between cases and controls, as they were 1.31 mg/liter (median) (interquartile range [IQR], 0.90) versus 1.36 mg/liter (IQR, 1.16) (P = 0.31) and 3.20 mg/liter (IQR, 2.40) versus 2.35 mg/liter (IQR, 1.50) (P = 0.17), respectively. In conclusion, we observed PCZ/IVC C _trough levels within the expected range and no significant effect of LET coadministration.

Letermovir for Cytomegalovirus Prophylaxis in Lung Transplant Patients with Valganciclovir-Induced Leukopenia

Cytomegalovirus (CMV) prophylaxis with valganciclovir is the standard of practice in most transplant centers, but treatment-related leukopenia can limit valganciclovir’s use. Therefore, we evaluated letermovir, a novel antiviral agent recently approved for use in hematopoietic cell transplant patients as CMV prophylaxis, in lung transplant recipients unable to tolerate valganciclovir due to severe leukopenia. We performed a retrospective analysis of all lung transplant patients at our center who received letermovir for CMV prophylaxis between 1 December 2018 and 1 January 2020. A repeated measures mixed model was used to analyze white blood cell (WBC) trends, and descriptive statistics were used to analyze secondary endpoints, including CMV DNAemia, renal function, immunosuppression dosing, and allograft function. Seventeen patients were administered letermovir during the study period due to valganciclovir-induced leukopenia (median WBC nadir 1.1 K/uL, range <0.30–2.19 K/uL). Median WBC improvement was noted in 15 (88.2%) patients after starting letermovir. Breakthrough CMV DNAemia necessitating treatment occurred in two patients, with one of the two cases being due to patient noncompliance. CMV resistance to letermovir was detected in two patients, necessitating a change to an alternative agent in one of these patients. No major side effects were reported in any patient. Letermovir is a generally safe and effective alternative for CMV prophylaxis in lung transplant recipients unable to tolerate valganciclovir due to leukopenia.

Extended letermovir administration, beyond day 100, is effective for CMV prophylaxis in patients with graft versus host disease

BACKGROUND

Cytomegalovirus (CMV) reactivation is associated with significant morbidity and mortality after an allogeneic hematopoietic cell transplant (AHCT), and graft versus host disease (GVHD) increases the risk of CMV reactivation. Letermovir is approved for CMV prophylaxis in CMV-seropositive patients, but has only been studied through day 100 post-transplantation in the registration trial. Its efficacy in preventing CMV in patients with GVHD requiring treatment beyond the day 100 milestone has not been studied.

METHODS

We retrospectively analyzed all patients who underwent an AHCT at a single center over a period of 24 months, and identified a cohort of 20 patients who received extended duration of letermovir (beyond 100 days) after the diagnosis of GVHD. The primary end point was the incidence of clinically significant CMV infection, defined as onset of CMV disease or initiation of preemptive therapy with alternative antiviral agents.

RESULTS

In this high-risk cohort, only one patient (5%) developed a clinically significant CMV infection, requiring preemptive therapy. No patients developed CMV organ disease. Three additional patients developed CMV viremia of ≥150 IU/mL while on letermovir and after the onset of GVHD, and none required additional treatment. Receipt of post-transplant cyclophosphamide (PTCy) and low CD4 count after the development of GVHD were associated with breakthrough CMV viremia while on extended duration letermovir.

CONCLUSIONS

Extended duration letermovir was efficacious in preventing clinically significant CMV infections in patients with GVHD.