Preemptive treatment of Cytomegalovirus infection in kidney transplant recipients with letermovir: results of a Phase 2a study

Resource Use and Financial Impact of Oral Step-Down Therapy for Resistant Cytomegalovirus in Solid Organ Transplant Recipients

BACKGROUND

Cytomegalovirus (CMV) infections are common opportunistic infections in solid organ transplants (SOT) with increased health care resource USE and costs. Costs are further increased with ganciclovir-resistance (GR). This study aimed to evaluate the real-world impact of conversion to oral step-down therapy on duration of foscarnet and hospital length of stay (LOS) for treatment of GR-CMV infections in SOT.

METHODS

This study included adult recipients of kidney or lung transplants who received foscarnet for genotypically documented GR-CMV while admitted at the University of Wisconsin Hospital from October 1, 2015, to January 31, 2022. Patients in the oral step-down group were converted from standard of care (SOC; foscarnet) to maribavir or letermovir; patients in the historical control group were treated with SOC.

RESULTS

Twenty-six patients met the inclusion criteria: 5 in the intervention group and 21 in the SOC group. The median viral load at foscarnet initiation was 11,435 IU/mL. Patients who received oral step-down conversion had shorter mean foscarnet duration than those who received SOC (7 ± 4 vs 37 ± 25 days, P = .017). Mean hospital LOS in the oral step-down group (16 ± 3 days) was shorter than the SOC group (33 ± 21 days; P < .001). In the SOC group, 9 patients lost their graft, and 9 patients died; 2 deaths were attributed to CMV. There were 2 deaths in the oral step-down group, neither of which was attributed to CMV.

CONCLUSION AND RELEVANCE

In this real-world case series of patients receiving treatment for GR-CMV infection, oral step-down conversion decreased foscarnet therapy duration and hospital LOS. Future studies are needed to evaluate better the effect of oral step-down in treating GR-CMV infection on treatment duration and cost-savings.

Impact of letermovir prophylaxis in CMV reactivation and disease after allogenic hematopoietic cell transplantation: a real-world, observational study

Letermovir for CMV prevention in CMV-seropositive adults undergoing allo-HCT was implemented at our program in 2021. This study investigates the results from the use of letermovir. The study includes all the 140 CMV-seropositive patients who underwent an allo-HCT during the years 2020, 2021, and 2022 at our institution. Thirty-eight (27.4%) of these patients received letermovir, administered from day + 7 to day + 100 and restarted if patients were on treatment with steroids. The day + 180 and 1-year cumulative incidences of CMV reactivation were 5.3% and 12.1% for patients who received letermovir and 52.9% and 53.9% for those who did not (P < 0.001) (HR 0.19, P < 0.001). Four (10.5%) of these thirty-eight patients had a CMV reactivation, but only 2 (5.3%) cases occurred during the administration of letermovir. During the first year after allo-HCT, 13 (9.2%) patients had CMV disease; the day + 180 and 1-year cumulative incidences were 2.6% and 6.0% for patients who received letermovir and 9.9% and 12.3% for those who did not (P = 0.254) (HR 1.01, P = 0.458). Two (4.2%) of the patients included in the letermovir group had CMV disease, but both of them after letermovir discontinuation. Letermovir induced a protective effect on CMV reactivation risk, but its use was not associated with a significant reduction of CMV disease. The fact that the CMV disease in patients who received letermovir occurred after the discontinuation of the drug, questions whether CMV prophylaxis should be used in patients with high risk for CMV reactivation or disease.

Letermovir Rescue Therapy in Kidney Transplant Recipients with Refractory/Resistant CMV Disease

(1) Background: CMV infections remain a problem after kidney transplantation, particularly if patients are refractory or resistant (r/r) to treatment with valganciclovir (VGCV) or ganciclovir (GCV). (2) Methods: In a single-center retrospective study, kidney transplant recipients (KTR) receiving letermovir (LTV) as rescue therapy for VGCV-/GCV-r/r CMV disease were analyzed regarding CMV history, immunosuppression, and outcomes. (3) Results: Of 201 KTR treated for CMV between 2017 and 2022, 8 patients received LTV following treatment failure with VGCV/GCV. All patients received CMV prophylaxis with VGCV according to the center's protocol, and 7/8 patients had a high-risk (D+/R-) CMV constellation. In seven of eight cases, rising CMV levels occurred during prophylaxis. In seven of eight patients, a mutation in UL97 associated with a decreased response to VGCV/GCV was detected. In four of eight patients, LTV resulted in CMV clearance after 24 ± 10 weeks (16-39 weeks), two of eight patients stabilized at viral loads <2000 cop/mL (6-20 weeks), and two of eight patients developed LTV resistance (range 8-10 weeks). (4) Conclusion: LTV, which is currently evaluated for CMV prophylaxis in kidney transplantation, also shows promising results for the treatment of patients with VGCV/GCV resistance despite the risk of developing LTV resistance. Additional studies are needed to further define its role in the treatment of patients with CMV resistance.

Anti-CMV therapy, what next? A systematic review

Human cytomegalovirus (HCMV) is one of the main causes of serious complications in immunocompromised patients and after congenital infection. There are currently drugs available to treat HCMV infection, targeting viral polymerase, whose use is complicated by toxicity and the emergence of resistance. Maribavir and letermovir are the latest antivirals to have been developed with other targets. The approval of letermovir represents an important innovation for CMV prevention in hematopoietic stem cell transplant recipients, whereas maribavir allowed improving the management of refractory or resistant infections in transplant recipients. However, in case of multidrug resistance or for the prevention and treatment of congenital CMV infection, finding new antivirals or molecules able to inhibit CMV replication with the lowest toxicity remains a critical need. This review presents a range of molecules known to be effective against HCMV. Molecules with a direct action against HCMV include brincidofovir, cyclopropavir and anti-terminase benzimidazole analogs. Artemisinin derivatives, quercetin and baicalein, and anti-cyclooxygenase-2 are derived from natural molecules and are generally used for different indications. Although they have demonstrated indirect anti-CMV activity, few clinical studies were performed with these compounds. Immunomodulating molecules such as leflunomide and everolimus have also demonstrated indirect antiviral activity against HCMV and could be an interesting complement to antiviral therapy. The efficacy of anti-CMV immunoglobulins are discussed in CMV congenital infection and in association with direct antiviral therapy in heart transplanted patients. All molecules are described, with their mode of action against HCMV, preclinical tests, clinical studies and possible resistance. All these molecules have shown anti-HCMV potential as monotherapy or in combination with others. These new approaches could be interesting to validate in clinical trials.

Letermovir for pre-emptive cytomegalovirus therapy after allogeneic hematopoietic cell transplantation

BACKGROUND

Cytomegalovirus (CMV) is a common cause of morbidity after allogeneic haematopoietic cell transplantation (alloHCT). Pre-emptive therapy (PET) with valganciclovir (VGC) is associated with haematological toxicity.

METHODS

We included alloHCT patients from 2018 to 2021 where letermovir (LTV) was used for CMV PET because of cytopenias.

RESULTS

Ten patients were included. Six received VGC prior to LTV. VGC was commenced at median d42, given for median 40 days. LTV was commenced at median d90, given for median 54 days. At commencement of antiviral, CMV viral load was higher for VGC at 3.7 log10 IU/mL, compared to LTV at 2.9 log10 IU/mL. Viral load reduction occurred at 0.18 log10 IU/mL per week for VGC, compared to 0.17 log10 IU/mL per week for LTV. There was no clinically significant CMV viremia after stopping LTV. Cytopenias improved on LTV.

CONCLUSION

LTV was effective in controlling CMV viremia when it was given at a lower starting CMV viral load and later post alloHCT than VGC. Further study is required of LTV as upfront PET following alloHCT.

New Treatment Options for Refractory/Resistant CMV Infection

Despite advances in monitoring and treatment, cytomegalovirus (CMV) infections remain one of the most common complications after solid organ transplantation (SOT). CMV infection may fail to respond to standard first- and second-line antiviral therapies with or without the presence of antiviral resistance to these therapies. This failure to respond after 14 days of appropriate treatment is referred to as "resistant/refractory CMV." Limited data on refractory CMV without antiviral resistance are available. Reported rates of resistant CMV are up to 18% in SOT recipients treated for CMV. Therapeutic options for treating these infections are limited due to the toxicity of the agent used or transplant-related complications. This is often the challenge with conventional agents such as ganciclovir, foscarnet and cidofovir. Recent introduction of new CMV agents including maribavir and letermovir as well as the use of adoptive T cell therapy may improve the outcome of these difficult-to-treat infections in SOT recipients. In this expert review, we focus on new treatment options for resistant/refractory CMV infection and disease in SOT recipients, with an emphasis on maribavir, letermovir, and adoptive T cell therapy.

Structural and Synthetic Aspects of Small Ring Oxa- and Aza-Heterocyclic Ring Systems as Antiviral Activities

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the structure-activity relationship (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists. The synergistic conclusions are extremely important for the introduction of a newer tool for the future drug discovery program.

Letermovir for Prophylaxis and Pre-emptive Therapy of Cytomegalovirus Infection in Paediatric Allogeneic Haematopoietic Cell Transplant Patients

BACKGROUND

Cytomegalovirus (CMV) infection is a frequent event in patients undergoing allogeneic haematopoietic cell transplantation (HCT) and is associated with increased morbidity and mortality due to eventual progress to end-organ disease. Letermovir prophylaxis for CMV infections has become a standard of care in adult HCT recipients due to its efficacy and high tolerability. However, it is not yet approved for paediatric patients.

OBJECTIVE

In a retrospective single-centre observational study we evaluated the use of letermovir for prophylaxis or pre-emptive treatment of cytomegalovirus (CMV) infection in seropositive paediatric HCT recipients receiving the compound outside of clinical trials. The primary endpoint was CMV reactivation requiring a change of medication.

METHODS

A total of 17 patients (seven female/ten male; median age 12.2 [range 3.5-19] years, median body weight 39.5 [range 15-63] kg; median follow-up time 463.7 [range 41-1022] days) were identified who were started on oral (14) or intravenous (3) followed by oral (2) letermovir shortly after neutrophil engraftment at doses determined on the basis of age, weight, and concomitant cyclosporine use.

RESULTS

Five patients had no evidence of viral replication (prophylactic use), while 12 patients had varying extents of viral replication (pre-emptive therapy). A change of therapy was required in one patient due to a sustained increase in CMV viral load, and in two patients, letermovir was stopped without later reactivation after initiation of palliative care for recurrent leukaemia. Of the 14 patients who completed treatment, 3 had evidence of transient viral replication after end of treatment that required no further antiviral treatment. No patients (of 17) discontinued letermovir due to an adverse event.

CONCLUSION

Letermovir was effective in controlling CMV infection in seropositive paediatric allogeneic HCT recipients and was overall well tolerated. Pending completion of the still ongoing paediatric investigation plans, letermovir will be an important adjunct to our options for control of infectious complications in this special population.

A Case Report of Successful Use of Twice-Daily Letermovir in the Treatment of Resistant Cytomegalovirus in a Small Bowel Transplant Recipient

Cytomegalovirus (CMV) is considered one of the most notable pathogens that affect patients after solid organ transplantation (SOT), especially small bowel transplant patients with a risk of high mortality rate. Its management relies historically on the use of CMV DNA polymerase inhibitors (namely, ganciclovir and valganciclovir). Second-line options include foscarnet and cidofovir, which are highly nephrotoxic and thus less preferred and only used in ganciclovir intolerance or resistance cases. Letermovir is a novel antiviral agent approved for CMV prophylaxis in hematopoietic stem cell transplant, but not for SOT (neither for prophylaxis nor for treatment). We report the first case on the successful use of letermovir in treating CMV disease in a small bowel transplant patient who failed to achieve viral clearance due to ganciclovir resistance and severe intolerance to foscarnet.

Cytomegalovirus and other herpesviruses after hematopoietic cell and solid organ transplantation: From antiviral drugs to virus-specific T cells

Herpesviruses can either cause primary infection or may get reactivated after both hematopoietic cell and solid organ transplantations. In general, viral infections increase post-transplant morbidity and mortality. Prophylactic, preemptive, or therapeutically administered antiviral drugs may be associated with serious side effects and may induce viral resistance. Virus-specific T cells represent a valuable addition to antiviral treatment, with high rates of response and minimal side effects. Even low numbers of virus-specific T cells manufactured by direct selection methods can reconstitute virus-specific immunity after transplantation and control viral replication. Virus-specific T cells belong to the advanced therapy medicinal products, and their production is regulated by appropriate legislation; also, strict safety regulations are required to minimize their side effects.

Evaluation of treatment patterns, healthcare resource utilization, and costs among patients receiving treatment for cytomegalovirus following allogeneic hematopoietic cell or solid organ transplantation

AIM

Management of cytomegalovirus (CMV) infection/disease in transplant recipients may be complicated by toxicities and resistance to conventional antivirals, adding to the overall healthcare burden. We characterized treatment patterns, healthcare resource utilization (HCRU), and costs to elucidate the healthcare burden associated with CMV therapies post-transplant.

MATERIALS AND METHODS

A retrospective, longitudinal cohort study of transplant recipients using data from a US commercial insurance claims database (2013-2017) was conducted. Patients with a claim for post-transplant CMV diagnosis and anti-CMV treatment (ganciclovir, valganciclovir, foscarnet, or cidofovir) were identified (Treated CMV cohort) and compared with patients with neither a claim for CMV diagnosis nor anti-CMV treatment (No CMV cohort) for outcomes including HCRU and associated costs. Allogeneic hematopoietic cell transplantation (HCT) or solid organ transplantation (SOT) recipients were analyzed separately. Anti-CMV treatment patterns were assessed in the Treated CMV cohort. Costs were evaluated among subgroups with myelosuppression or nephrotoxicity.

RESULTS

Overall, 412 allogeneic HCT and 899 SOT patients were included in the Treated CMV cohorts, of which 41.7% and 52.5%, respectively, received multiple antiviral courses. Treated CMV cohorts compared with No CMV cohorts had higher mean monthly healthcare visits per patient (allogeneic HCT: 8.83 vs 6.61, SOT: 5.61 vs 4.45) and had an incremental adjusted mean monthly cost per patient differences of $8,157 (allogeneic HCT, p < .004) and $2,182 (SOT, p < .004). Among Treated CMV cohorts, HCRU and costs increased with additional CMV antiviral treatment courses. Mean monthly costs were higher for patients with than without myelosuppression or nephrotoxicity.

LIMITATIONS

Results may not be generalizable to patients covered by government insurance or outside the USA.

CONCLUSIONS

CMV post-transplant managed with conventional treatment is associated with substantial HCRU and costs. The burden remains particularly high for patients requiring multiple treatment courses for post-transplant CMV or for transplant recipients who develop myelosuppression or nephrotoxicity.

The Effect of Oral Letermovir Administration on the Pharmacokinetics of a Single Oral Dose of P-Glycoprotein Substrate Digoxin in Healthy Volunteers

Letermovir is a human cytomegalovirus (CMV) terminase inhibitor approved in the United States, Canada, Japan, and the European Union for prophylaxis of CMV infection and disease in CMV-seropositive, allogeneic, hematopoietic stem-cell transplant recipients. In vitro, letermovir is a substrate and potential modulator of P-glycoprotein. The potential of letermovir to alter the pharmacokinetics of digoxin (a P-glycoprotein substrate) upon coadministration in healthy subjects was therefore investigated in a phase 1 trial (EudraCT: 2011-004516-39). Oral letermovir 240 mg was administered twice daily for 12 days with a single oral digoxin 0.5-mg dose on day 7; after a washout period, oral digoxin 0.5 mg was administered on day 35 (sequence 1). The period order was reversed after a 28-day washout for sequence 2. Pharmacokinetics and safety were evaluated. The presence of steady-state letermovir reduced digoxin area under the plasma concentration-time curve from administration until last quantifiable measurement by 12% and maximum plasma concentration by 22% compared with digoxin alone; digoxin half-life and elimination rate remained similar in both conditions. The between-subject variability of digoxin maximum plasma concentration was higher with letermovir than without (42% vs 31%) and similar for digoxin area under the plasma concentration-time curve in both periods. No specific safety or tolerability concerns were identified. Overall, letermovir had no clinically relevant effect on concomitant administration with digoxin.

Letermovir conversion after valganciclovir treatment in cytomegalovirus high-risk abdominal solid organ transplant recipients may promote development of cytomegalovirus-specific cell mediated immunity

PURPOSE

To evaluate the association of conversion from valganciclovir to letermovir on cytomegalovirus-specific cellular immunity.

METHODS

Adult patients were included if they received a kidney or liver transplant between 8/1/2018-12/31/20, developed symptomatic, high-level CMV viremia and were converted to letermovir 480 mg daily as monotherapy after treatment with ganciclovir-derivatives for a minimum of 4 weeks and had subsequent CMV cell-mediated immunity (CMI) testing via ICS assay by flow cytometry (Viracor Eurofins T Cell Immunity Panel).

RESULTS

Seven patients met inclusion criteria; 87.5% were male and recipients of a kidney transplant. All patients were CMV high risk (D+/R-). Mean time from transplant to CMV disease was 200 ± 91 days. Peak viral load (VL) during CMV treatment was 540,341 ± 391,211 IU/mL. Patients received a mean of 30 ± 24 weeks (range: 4-78 weeks) of therapy with ganciclovir-derivatives at induction doses prior to letermovir introduction. The median absolute lymphocyte count (ALC) at letermovir initiation was 400/μL (IQR 575) and the median VL was 51.6 (range: ND-490) IU/mL. Most patients (n = 5/7, 71.4%) experienced an increase in VL 1 and/or 2 weeks after conversion to letermovir. All patients had positive CMI per ICS assay after conversion. Patients received a mean of 10.3 ± 6.9 weeks of letermovir prior to having a positive result. Median ALC at positivity was 900/μL. Immunosuppression was not further reduced from initiation of letermovir to demonstration of CMV CMI. No patient had progressive replication or breakthrough disease while maintained on letermovir and three patients (42.9%) underwent antiviral withdrawal without recurrence at the last follow-up.

CONCLUSION

In this case series of abdominal transplant recipients with severe or persistent CMV infection, patients developed CMV-specific CMI after conversion to letermovir monotherapy. These data suggest that using letermovir in place of valganciclovir for secondary prophylaxis may address the lack of efficacy previously seen with this approach, as well as the issues that plague antiviral withdrawal with systematic monitoring. Future prospective studies are needed to evaluate this effect in a more controlled research environment with serial CMI testing to elucidate the optimal duration of letermovir when used in this way.

Letermovir treatment for CMV infection in kidney and pancreas transplantation: A valuable option for complicated cases

Cytomegalovirus (CMV) infection remains a major challenge in solid organ transplantation. Ganciclovir has changed the prognosis, but with the expense of possible viral resistance. New antiviral drugs, such as letermovir, have not been studied sufficiently in kidney and pancreas transplant recipients. We reviewed abdominal organ transplants recipients with CMV infection from the national transplant registry and identified patients treated with letermovir from electronic medical records. We report on letermovir treatment in one kidney and three simultaneous pancreas and kidney (SPK) transplant patients with refractory or ganciclovir-resistant CMV infection (UL54/ UL97 mutation). In SPK patients, persistent leukopenia undermined immunosuppressive and antiviral treatment, favoring life-threatening bacterial infections or ganciclovir resistance. All patients achieved viral clearance after letermovir monotherapy of 1.5-6 months. Letermovir was well tolerated and leukopenia resolved. Adjustments of calcineurin inhibitor doses were challenging. One acute rejection occurred because of under immunosuppression. After the end of treatment, recurrent low-grade CMV-DNAemia was common requiring reinitiating antiviral therapy to achieve viral clearance. To conclude, letermovir was a well-tolerated valuable option for the treatment of refractory or resistant CMV infection in kidney and pancreas transplantation.

Pharmacokinetics and Safety of Letermovir and Midazolam Coadministration in Healthy Subjects

Letermovir is a human cytomegalovirus (CMV) terminase inhibitor for the prophylaxis of CMV infection and disease in allogeneic hematopoietic stem-cell transplant recipients. In vitro studies have identified letermovir as a potential cytochrome P450 (CYP) 3A inhibitor. Thus, the effect of letermovir on the CYP3A isoenzyme-specific probe drug midazolam was investigated in a phase 1 trial. Healthy female subjects received single-dose intravenous (IV; 1 mg) and oral (2 mg) midazolam on days -4 and -2, respectively. Letermovir 240 mg once daily was administered on days 1 to 6, and further single doses of midazolam 1 mg IV and oral midazolam 2 mg were administered on days 4 and 6, respectively. Pharmacokinetics, tolerability, and safety were monitored throughout the trial. Following coadministration with letermovir, the least square means ratio for maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last measurable concentration was 172.4% and 225.3%, respectively, for oral midazolam, and 105.2% and 146.6%, respectively, for midazolam IV. The area under the plasma concentration-time curve from time 0 to the last measurable concentration ratio of midazolam to 1-hydroxymidazolam increased slightly in the presence of letermovir following IV (8.8-13.1; 49% increase) and oral (3.3-5.3; 59% increase) midazolam. Letermovir reached steady state, on average, by days 5 to 6. All treatments were generally well tolerated. Letermovir demonstrated moderate CYP3A inhibition.

Exposure-Response Analyses of Letermovir Following Oral and Intravenous Administration in Allogeneic Hematopoietic Cell Transplantation Recipients

The cytomegalovirus (CMV) viral terminase inhibitor letermovir is approved for prophylaxis of CMV infection and disease in adult CMV-seropositive allogeneic hematopoietic stem cell transplantation recipients. In a phase III trial (NCT02137772), letermovir significantly reduced clinically significant CMV infection (CS-CMVi) rate vs. placebo through Week 24 (primary end point) and Week 14 (secondary end point) post transplantation. Here, exposure-response relationships were investigated using efficacy and selected safety end points from the phase III trial to inform the proposed clinical dose. Post hoc exposure estimates were derived from a population pharmacokinetic model. No significant exposure dependencies were found for CS-CMVi through Week 24 or Week 14 among letermovir-treated participants. Evaluated covariates had no impact on exposure-efficacy relationships and letermovir plasma exposure did not affect time of CS-CMVi onset. There was no dependence between adverse event incidence and letermovir exposure. These results support current dosing recommendations in several countries and regions, including the United States and European Union.

Letermovir in lung transplant recipients with cytomegalovirus infection: A retrospective observational study

Letermovir is a new antiviral drug approved for the prophylaxis of CMV infection in allogeneic stem cell transplants. The aim of the study was to assess the therapeutic efficacy of letermovir in difficult to treat CMV infections in lung transplant recipients. All lung transplant recipients between March 2018 and August 2020, who have been treated with letermovir for ganciclovir-resistant or refractory CMV infection were included in the study and analysed retrospectively. In total, 28 patients were identified. CMV disease was present in 15 patients (53.6%). In 23 patients (82.1%), rapid response was noticed, and CMV-viral load could be significantly decreased (>1 log₁₀ ) after a median of 17 [14-27] days and cleared subsequently in all of these patients. Five patients (17.9%) were classified as non-responder. Thereof, development of a mutation of the CMV UL56 terminase (UL-56-Gen: C325Y) conferring letermovir resistance could be observed in three patients (60%). Common side effects were mild and mostly of gastrointestinal nature. Mild adjustments of the immunosuppressive drugs were mandatory upon treatment initiation with letermovir. In addition to other interventions, letermovir was effective in difficult to treat CMV infections in lung transplant recipients. However, in patients with treatment failure mutation conferring letermovir, resistance should be taken into account.

The addition of adjunctive letermovir to valganciclovir for refractory cytomegalovirus viremia in kidney transplant recipients

PURPOSE

Persistent viral replication resulting in ongoing cytomegalovirus (CMV) viremia despite adequate therapy is difficult to manage and associated with negative outcomes. We report a case series of kidney transplant recipients receiving adjunctive letermovir in combination with valganciclovir for refractory CMV.

METHODS

Adult patients receiving a kidney or kidney-pancreas transplant were included if they developed CMV viremia and initiated letermovir 480 mg daily as part of a dual therapy regimen with valganciclovir 900 mg twice daily between 1/9/2020 and 31/12/2020. Included patients received ≥90 days of valganciclovir and had a detectable viral load less than 1000 Iu/ml (log₁₀  < 3) at the time of letermovir initiation. The primary objective was to evaluate the impact of adjunctive letermovir on viral clearance to negativity. We also evaluated effect of letermovir on tacrolimus levels.

RESULTS

Eight patients were included. Letermovir was added 223 ± 105 days after initiation of CMV treatment with ganciclovir derivatives. Median viral load at initiation was 139.7 (range: 73-355) IU/ml and did not clear or change significantly after 2, 4 and 12 weeks of adjunctive letermovir (132.5 [range: 34.5-513] IU/ml vs. 68.7 [range: 34.5-574] IU/ml vs. 78.3 [range: 34.5-347] IU/ml, p > 0.05). Tacrolimus was reduced by ∼30% in anticipation of a letermovir-tacrolimus drug interaction. Despite this reduction, mean tacrolimus serum levels two weeks after adjunctive letermovir increased by 43% (5.6 ± 1.6 ng/ml vs 8.0 ± 4.6 ng/ml).

CONCLUSION

In kidney and kidney-pancreas recipients with refractory CMV, the use of adjunctive letermovir did not result in viral clearance. Additionally, despite a mean tacrolimus dose reduction of 30% at letermovir initiation, serum concentrations increased by over 40%. Further investigation into the optimal approach to refractory CMV is needed.

Letermovir treatment of cytomegalovirus infection or disease in solid organ and hematopoietic cell transplant recipients

BACKGROUND

Few options are available for cytomegalovirus (CMV) treatment in transplant recipients resistant, refractory, or intolerant to approved agents. Letermovir (LET) is approved for prophylaxis in hematopoietic cell transplant (HCT) recipients, but little is known about efficacy in CMV infection. We conducted an observational study to determine the patterns of use and outcome of LET treatment of CMV infection in transplant recipients.

METHODS

Patients who received LET for treatment of CMV infection were identified at 13 transplant centers. Demographic and outcome data were collected.

RESULTS

Twenty-seven solid organ and 21 HCT recipients (one dual) from 13 medical centers were included. Forty-five of 47 (94%) were treated with other agents prior to LET, and 57% had a history of prior CMV disease. Seventy-seven percent were intolerant to other antivirals; 32% were started on LET because of resistance concerns. Among 37 patients with viral load < 1000 international units (IU)/ml at LET initiation, two experienced >1 log rise in viral load by week 12, and no deaths were attributed to CMV. Ten patients had viral load > 1000 IU/ml at LET initiation, and six of 10 (60%) had a CMV viral load < 1000 IU/ml at completion of therapy or last known value. LET was discontinued in two patients for an adverse event.

CONCLUSIONS

Patients treated with LET with viral load < 1000 IU/ml had good virologic outcomes. Outcomes were mixed when LET was initiated at higher viral loads. Further studies on combination therapy or alternative LET dosing are needed.

Letermovir and Maribavir for the Treatment and Prevention of Cytomegalovirus Infection in Solid Organ and Stem Cell Transplant Recipients

Until recently, available drugs for cytomegalovirus (CMV) prevention and treatment in transplant patients included (val)ganciclovir, foscarnet, and cidofovir. Use of these drugs is limited by toxicity and the development of resistance. The 2017 approval of letermovir for prevention of CMV after stem cell transplant marked the first approval of an anti-CMV agent since 2003. The role of letermovir in treatment of established CMV infection or disease remains largely unstudied, although early reports suggest that a low barrier to resistance will likely limit efficacy as primary therapy for patients with refractory or resistant disease. The investigational agent maribavir has shown promise as preemptive treatment; in patients with refractory or resistant disease the emergence of resistance while on treatment has been observed and ongoing studies will define efficacy in this population. Both agents have unique mechanisms of action limiting cross resistance, and neither exhibit myelotoxicity or nephrotoxicity.

Drug interaction between letermovir and voriconazole after allogeneic hematopoietic cell transplantation

Letermovir has been approved for the prevention of cytomegalovirus (CMV) infection after allogeneic hematopoietic stem cell transplantation (HCT). Letermovir is a cytochrome P450 (CYP) 2C19 inducer. Voriconazole, which is a broad-spectrum triazole antifungal agent, is mainly metabolized by CYP2C19. Thus, voriconazole trough concentration may decrease due to the drug interaction between voriconazole and letermovir. This study aimed to clarify the effects of letermovir on voriconazole trough concentration in allogeneic HCT recipients. We retrospectively examined voriconazole trough concentration in 24 allogeneic HCT recipients who had letermovir for prevention of CMV infection. The median voriconazole C/D ratios significantly decreased after starting letermovir from 0.25 L/kg to 0.11 L/kg (p < 0.01), and increased after discontinuing letermovir from 0.15 L/kg to 0.24 L/kg (p = 0.02). The median fold change of voriconazole trough concentration during letermovir administration was 0.40. Our results suggest that voriconazole trough concentration decreases when voriconazole is combined with letermovir in allogeneic HCT recipients. Therefore, close therapeutic drug monitoring of voriconazole trough concentration is warranted in allogeneic HCT recipients after starting or discontinuing letermovir.

Letermovir for the compassionate therapeutic use of cytomegalovirus infection

PURPOSE

Data on the efficacy, dosing and safety of letermovir for the compassionate therapeutic use of CMV infections are limited.

METHODS

Clinical and virological efficacy of letermovir was assessed in a retrospective single-centre study of patients who received letermovir for the compassionate therapeutic use of CMV infections.

RESULTS

Letermovir initiation yielded prompt treatment response in 7 out of 9 patients (77.7%).

CONCLUSION

Letermovir may be an effective and well tolerated option in the compassionate treatment of CMV infections, although recurrence of CMV and emergence of resistance may be issues.

Advances in the Development of Therapeutics for Cytomegalovirus Infections

The development of therapeutics for cytomegalovirus (CMV) infections, while progressing, has not matched the pace of new treatments of human immunodeficiency virus (HIV) infections; nevertheless, recent developments in the treatment of CMV infections have resulted in improved human health and perhaps will encourage the development of new therapeutic approaches. First, the deployment of ganciclovir and valganciclovir for both the prevention and treatment of CMV infections and disease in transplant recipients has been further improved with the licensure of the efficacious and less toxic letermovir. Regardless, late-onset CMV disease, specifically pneumonia, remains problematic. Second, the treatment of congenital CMV infections with valganciclovir has beneficially improved both hearing and neurologic outcomes, both fundamental advances for these children. In these pediatric studies, viral load was decreased but not eliminated. Thus, an important lesson learned from studies in both populations is the need for new antiviral agents and the necessity for combination therapies as has been shown to be beneficial in the treatment of HIV infections, among others. The development of monoclonal antibodies, sirtuins, and cyclopropovir may provide new treatment options.

Case Report: Management of a Multidrug-Resistant CMV-Strain in a Renal Transplant Recipient by High-Dose CMV-Specific Immunoglobulins, Modulation in Immunosuppression, and Induction of CMV-Specific Cellular Immunity

The management of multidrug-resistant strains of cytomegalovirus after solid organ transplantation is challenging. This case report demonstrates the successful treatment of a multidrug-resistant strain of cytomegalovirus that may represent a valuable option for problematic cases. This report illustrates the emergence of a multidrug-resistant cytomegalovirus (CMV) UL54 mutant strain in a renal transplant recipient with severe lymphopenia and thrombocytopenia. We show that the combined treatment with high-dose intravenous cytomegalovirus-specific immunoglobulins (CMV-IVIG) after the switch to a mammalian target of rapamycin (mTOR)-inhibitor and cyclosporine A was a successful treatment alternative to direct antiviral treatment with high-dose ganciclovir and foscarnet. This treatment was associated with a quantitative induction of CMV-specific CD4 and CD8 T cells that showed maturation in phenotype and functionality with decreasing viral load. Our case report illustrates that high-dose CMV-IVIG and conversion of immunosuppressive drugs to mTOR inhibitors and cyclosporine A can be a successful treatment in a situation where the use of direct antiviral drugs was considered insufficient.

Population pharmacokinetics of letermovir following oral and intravenous administration in healthy participants and allogeneic hematopoietic cell transplantation recipients

Letermovir is indicated for prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients. Two‐stage population pharmacokinetic (PK) modeling of letermovir was conducted to support dose rationale and evaluate the impact of intrinsic/extrinsic factors. Data from healthy phase I study participants over a wide dose range were modeled to evaluate the effects of selected intrinsic factors, including pharmacogenomics; next, phase III HSCT‐recipient data at steady‐state following clinical doses were modeled. The model in HSCT recipients adequately described letermovir PK following both oral or i.v. administration, and was consistent with the healthy participant model at steady‐state clinical doses. Intrinsic factor effects were not clinically meaningful. These staged analyses indicate that letermovir PK in HSCT recipients and healthy participants differ only with respect to bioavailability and absorption rate. The HSCT recipient model was suitable for predicting exposure for exposure–response analysis supporting final dose selection.

Cytomegalovirus management after allogeneic hematopoietic stem cell transplantation: A mini-review

Because of the high incidence of cytomegalovirus (CMV) seropositivity in the population, CMV infection is a common and severe complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in Taiwan. Here we propose a CMV management strategy for patients undergoing allo-HSCT from the Taiwanese perspective, which focuses on the epidemiology, diagnosis, monitoring, prophylaxis, and treatment of CMV infection after allo-HSCT. In terms of CMV monitoring, weekly CMV monitoring with the COBAS® AmpliPrep system is the standard approach because the pp65 CMV antigenemia assay has a lower sensitivity than CMV monitoring with the COBAS® AmpliPrep system. However, pp65 CMV antigenemia assay has a better correlation with clinical symptoms in immunocompromised patients. A 14-week prophylactic course of letermovir is recommended for allo-HSCT recipients in Taiwan, especially for recipients of hematopoietic stem cells from mismatched unrelated and haploidentical donors. Preemptive ganciclovir therapy should be initiated when the CMV viral load exceeds 1000 copies/mL, and should not be discontinued until CMV DNA is no longer detected in the blood. For allo-HSCT recipients who have CMV-related diseases, ganciclovir with or without CMV-specific intravenous immunoglobulin is the standard of care. The limited availability of foscarnet, an alternative for patients who are not responsive to or cannot tolerate ganciclovir, is a crucial issue in Taiwan. For pediatric allo-HSCT recipients, more data are needed to propose a CMV management recommendation.

Progress and Challenges in the Prevention, Diagnosis, and Management of Cytomegalovirus Infection in Transplantation

Hosts with compromised or naive immune systems, such as individuals living with HIV/AIDS, transplant recipients, and fetuses, are at the highest risk for complications from cytomegalovirus (CMV) infection. Despite substantial progress in prevention, diagnostics, and treatment, CMV continues to negatively impact both solid-organ transplant (SOT) and hematologic cell transplant (HCT) recipients. In this article, we summarize important developments in the field over the past 10 years and highlight new approaches and remaining challenges to the optimal control of CMV infection and disease in transplant settings.

Single-center experience with use of letermovir for treatment of CMV infection in stem cell transplant recipients

The approval of letermovir provided a new option for cytomegalovirus (CMV) prophylaxis in CMV seropositive allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Data are limited on the use of letermovir for the treatment of CMV infection. We performed a single-center retrospective review of allo-HSCT recipients who received letermovir off-label for treatment of CMV infection (CMV DNAemia and CMV disease) from November 2017 until November 2019. Fifteen patients were included, 14 of which received letermovir for treatment of CMV DNAemia. The median duration from transplant to CMV DNAemia was 41 days and median duration of letermovir therapy was 53 days (IQR, 43-59). Median time to first undetectable CMV viral load from the start of letermovir was 16 days (IQR, 13-21). No significant correlation was noted between the time to CMV DNA clearance and either CMV DNA at the time of starting letermovir (r = -.12, 95% CI: -0.63-0.46; P = .69) or CMV DNA peak (r = .04, 95% CI: -0.51-0.58, P = .87). Three patients had late reactivation of CMV after completion of letermovir (20%) after 87 days (IQR, 68-103) of therapy cessation. Clinical failure or treatment intolerance occurred in two patients (14%). One patient failed to achieve an undetectable viral load. In another patient, letermovir was discontinued due to documented therapy-related thrombocytopenia. Our analysis suggests that letermovir might have a potential role for the treatment of CMV infection in select patients with contraindication or intolerance to more validated therapies.

DNA Encapsidation and Capsid Assembly Are Underexploited Antiviral Targets for the Treatment of Herpesviruses

Although there are effective nucleoside analogs to treat HSV, VZV, and HCMV disease, herpesvirus infections continue to contribute to significant morbidity and mortality. Acyclovir is the drug of choice for HSV encephalopathy, yet there is an estimated 6-19% mortality rate with half of the survivors experiencing moderate to severe chronic neurological deficits. For VZV, current treatments are inadequate to prevent acute and persistent pain due to zoster. Treatment of HCMV with GCV requires close monitoring particularly in patients with impaired renal function and there are no approved treatments for congenital HCMV infections. New therapeutic options to control cytomegalovirus reactivation in bone marrow and stem cell transplant patients are needed to improve patient outcome. No successful chemotherapeutic options are available for EBV, HHV-6, 7, and 8. Drug resistance is a concern for HCMV, HSV, and VZV since approved drugs share common mechanisms of action. Targeting DNA encapsidation or capsid assembly provide additional options for the development of non-nucleoside, small molecule anti-herpesviral drugs.

Prevention and Management of CMV Infections after Liver Transplantation: Current Practice in German Transplant Centers

Human cytomegalovirus (CMV) remains a major cause of mortality and morbidity in human liver transplant recipients. Anti-CMV therapeutics can be used to prevent or treat CMV in liver transplant recipients, but their toxicity needs to be balanced against the benefits. The choice of prevention strategy (prophylaxis or preemptive treatment) depends on the donor/recipient sero-status but may vary between institutions. We conducted a series of consultations and roundtable discussions with German liver transplant center representatives. Based on 20 out of 22 centers, we herein summarize the current approaches to CMV prevention and treatment in the context of liver transplantation in Germany. In 90% of centers, transient prophylaxis with ganciclovir or valganciclovir was standard of care in high-risk (donor CMV positive, recipient CMV naive) settings, while preemptive therapy (based on CMV viremia detected during (bi) weekly PCR testing for circulating CMV-DNA) was preferred in moderate- and low-risk settings. Duration of prophylaxis or intense surveillance was 3-6 months. In the case of CMV infection, immunosuppression was adapted. In most centers, antiviral treatment was initiated based on PCR results (median threshold value of 1000 copies/mL) with or without symptoms. Therefore, German transplant centers report similar approaches to the prevention and management of CMV infection in liver transplantation.

Maribavir for Refractory or Resistant Cytomegalovirus Infections in Hematopoietic-cell or Solid-organ Transplant Recipients: A Randomized, Dose-ranging, Double-blind, Phase 2 Study

Background

Cytomegalovirus (CMV) infections that are refractory or resistant (RR) to available antivirals ([val]ganciclovir, foscarnet, cidofovir) are associated with higher mortality in transplant patients. Maribavir is active against RR CMV strains.

Methods

Hematopoietic-cell or solid-organ transplant recipients ≥12 years old with RR CMV infections and plasma CMV deoxyribonucleic acid (DNA) ≥1000 copies/mL were randomized (1:1:1) to twice-daily dose-blinded maribavir 400, 800, or 1200 mg for up to 24 weeks. The primary efficacy endpoint was the proportion of patients with confirmed undetectable plasma CMV DNA within 6 weeks of treatment. Safety analyses included the frequency and severity of treatment-emergent adverse events (TEAEs).

Results

From July 2012 to December 2014, 120 patients were randomized and treated (40 per dose group): 80/120 (67%) patients achieved undetectable CMV DNA within 6 weeks of treatment (95% confidence interval, 57–75%), with rates of 70%, 63%, and 68%, respectively, for maribavir 400, 800, and 1200 mg twice daily. Recurrent on-treatment CMV infections occurred in 25 patients; 13 developed mutations conferring maribavir resistance. Maribavir was discontinued due to adverse events in 41/120 (34%) patients, and 17/41 discontinued due to CMV infections. During the study, 32 (27%) patients died, 4 due to CMV disease. Dysgeusia was the most common TEAE (78/120; 65%) and led to maribavir discontinuation in 1 patient. Absolute neutrophil counts <1000/µL were noted in 12/106 (11%) evaluable patients, with rates similar across doses.

Conclusions

Maribavir ≥400 mg twice daily was active against RR CMV infections in transplant recipients; no new safety signals were identified.

Clinical Trials Registration

NCT01611974.

Letermovir and its role in the prevention of cytomegalovirus infection in seropositive patients receiving an allogeneic hematopoietic cell transplant

Cytomegalovirus (CMV) reactivation is one of the most common infections affecting allogeneic hematopoietic cell transplant recipients. Although available anti-CMV therapies have been evaluated for the prevention of CMV reactivation, their toxicity profile makes them unfavorable for use as primary prophylaxis; thus, they are routinely reserved for the treatment of CMV viremia or CMV end-organ disease. Pre-emptive CMV monitoring strategies have been widely accepted, and although they have been helpful in early detection, they have not affected the overall morbidity and mortality associated with CMV. Letermovir is a novel agent that was approved for primary prophylaxis in CMV-seropositive adult allogeneic hematopoietic cell transplant recipients. This review focuses on letermovir’s novel mechanism; clinical trials supporting its United States Food and Drug Administration (FDA) approval and subsequent follow-up analyses; clinical considerations, with an emphasis on pharmacology; and lessons learned from solid organ transplant recipients, as well as potential future directions.

Compassionate Use of Letermovir in a 2-Year-Old Immunocompromised Child With Resistant Cytomegalovirus Disease

Little information on the efficacy and pharmacokinetics of letermovir among immunocompromised children is currently available. We describe here the use of letermovir in a 2-year-old immunocompromised child with ganciclovir-resistant cytomegalovirus disease who required extracorporeal membrane oxygenation. Detailed information on therapeutic-drug-monitoring measures and dosage adjustments for letermovir is provided.

Letermovir as Salvage Therapy for Cytomegalovirus Infection in Transplant Recipients

BACKGROUND

Letermovir, a new viral terminase complex inhibitor, has been approved for the prevention of cytomegalovirus (CMV) infection in hematopoietic stem cell transplant patients. However, data on the efficacy and safety of letermovir for the treatment of CMV infection in transplant recipients remain scarce.

METHODS

We performed a single-center retrospective study of stem cell and organ transplant recipients who received letermovir for the treatment of CMV infection from November 2017 to October 2018.

RESULTS

Six patients were included, and 5 were evaluable. All received letermovir in the context of a refractory or resistant CMV infection including asymptomatic CMV viremia (n = 3), CMV syndrome (n = 1), and CMV pneumonitis and colitis (n = 1). The 3 asymptomatic patients experienced a decrease of the viral load (VL) to <200 IU/mL after letermovir therapy. One patient displayed a partial VL response (2-log of VL reduction) but a good clinical response, and one who received a suboptimal dose of letermovir experienced an increase of viremia. There were no treatment-related adverse effects.

CONCLUSIONS

We demonstrate mixed efficacy in patients with refractory CMV infection suggesting that letermovir may be a useful therapeutic adjunct, potentially in combination with other antivirals.

Tacrolimus Concentration after Letermovir Initiation in Hematopoietic Stem Cell Transplantation Recipients Receiving Voriconazole: A Retrospective, Observational Study

Letermovir (LMV) is a new antiviral drug used to prevent cytomegalovirus infection in hematopoietic stem cell transplantation (HSCT) recipients. It has been reported to increase tacrolimus (TAC) exposure and decrease voriconazole (VRCZ) exposure in healthy participants. However, VRCZ inhibits the metabolism of TAC. Thus, the effects of LMV on TAC exposure in patients receiving VRCZ are unknown. This retrospective, observational, single-center study was conducted between May 2018 and April 2019. The TAC concentration/dose (C/D) ratio, VRCZ concentration, and VRCZ C/D ratio for 7 days before and for the first and second 7-day periods after the initiation of LMV administration were evaluated. Fourteen HSCT recipients receiving VRCZ were enrolled. There was no significant difference in the TAC C/D ratio for 7 days before and for the first and second 7-day periods after initiating LMV administration (median: 866 [IQR: 653-953], 842 [IQR: 636-1031], and 906 [IQR: 824-1210] [ng/mL]/[mg/kg], respectively). In contrast, the VRCZ C/D ratio and concentration for the first and second 7-day periods after LMV initiation were significantly lower than those before initiating LMV administration (mean 1.11 ± 0.07, 0.12 ± 0.08, and 0.22 ± 0.12 [μg/mL]/[mg/kg] and 0.7 ± 0.5, 0.8 ± 0.5, and 1.3 ± 0.7 μg/mL, respectively; n = 12). This can be explained by the increase in TAC concentration caused by CYP3A4 inhibition due to LMV and by the decrease in TAC concentration ascribed to the decrease in VRCZ concentration by CYP2C19 induction due to LMV. These results suggest that it is unnecessary to adjust the dose of TAC based on LMV initiation; however, it is necessary to adjust the dose of TAC based on conventional TAC concentration measurements.

CMV Prevention and Treatment in Transplantation: What's New in 2019

PURPOSE OF REVIEW

Transplant recipients are at risk for cytomegalovirus (CMV) infection and associated morbidity and mortality. We summarize recently introduced or currently investigated modalities for prevention and treatment of CMV infection in hematopoietic cell (HCT) and solid organ transplant (SOT) recipients.

RECENT FINDINGS

Letermovir was recently approved for CMV prevention in HCT recipients. Data from real world studies support its role to improve outcomes in this population. Letermovir is currently under investigation for broader patient populations and indications. Maribavir is in late stages of development for CMV treatment and may provide a safer alternative to currently available anti-CMV drugs. Promising CMV vaccine candidates and adoptive cell therapy approaches are under evaluation. CMV immune monitoring assays are predicted to play a more central role in our clinical decision making. In recent years, major advances have been made in CMV prevention and treatment in transplant recipients. Rigorous research is ongoing and is anticipated to further impact our ability to improve outcomes in this population.

CMV infection management in transplant patients in Italy

Transplant represents an effective strategy in the management of chronic organ dysfunction. Nonetheless, life threatening risks remain, especially in the post-transplant; among them, human cytomegalovirus (CMV) is a major concern, currently causing active infections in at least one-third of transplant recipients. Microbiologist and transplant scientific societies redefined guidance on CMV disease prevention and the best use for universal prophylaxis and pre-emptive virological monitoring. Developments in molecular diagnostic supported the spread of the pre-emptive strategy, and quantitative Real Time-PCR assays has unravelled the potential of viral load measurement as a predictor of the infection development in CMV post-transplant management. However, despite the WHO 1st CMV International Standard, the standardization of diagnostic and clinical practice has been limited by the absence of algorithms for calculating conversion factor to International Units and the lack of shared monitoring procedure, both at national and international level. At a regional level, the Italian scientific societies, AMCLI (Italian Clinical Microbiologist Association), SITO (Organ Transplant Italian Society), GITMO (Italian Group for Bone Marrow Transplant), recently tried to define a consensus for post-transplant monitoring. The concerted practice encompasses molecular quantitative PCR assays technical aspects and endorses the relevance of immunologic monitoring for improvement in patient risk stratification and prognosis. Here, we provide an overview of the state of the art of CMV management strategies, with a specific focus on the clinical practices and on the scientific societies' initiatives that aim to implement international standardization guidelines at a national level.

Infectious Complications Following Kidney Transplantation-A Focus on Hepatitis C Infection, Cytomegalovirus Infection and Novel Developments in the Gut Microbiota

The incidence of infectious complications, compared with the general population and the pre-transplant status of the recipient, increases substantially following kidney transplantation, causing significant morbidity and mortality. The potent immunosuppressive therapy given to prevent graft rejection in kidney transplant recipients results in an increased susceptibility to a wide range of opportunistic infections including bacterial, viral and fungal infections. Over the last five years, several advances have occurred that may have changed the burden of infectious complications in kidney transplant recipients. Due to the availability of direct-acting antivirals to manage donor-derived hepatitis C infection, this has opened the way for donors with hepatitis C infection to be considered in the donation process. In addition, there have been the development of medications targeting the growing burden of resistant cytomegalovirus, as well as the discovery of the potentially important role of the gastrointestinal microbiota in the pathogenesis of post-transplant infection. In this narrative review, we will discuss these three advances and their potential implications for clinical practice.

Single-center experience with use of letermovir for CMV prophylaxis or treatment in thoracic organ transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection is common in thoracic organ transplant recipients. Valganciclovir and ganciclovir are used for both prophylaxis and treatment of this infection, but intolerance and treatment failure are common. Letermovir has been demonstrated to reduce the risk of CMV infection when used for prophylaxis in allogeneic hematopoietic cell transplantation. However, there are no data on its efficacy in thoracic organ transplantation.

METHODS

We examined the use of letermovir for either CMV prophylaxis (primary and secondary) or treatment in heart and lung transplant recipients at our institution from February 1, 2018, through December 31, 2018.

RESULTS

Nine total patients received letermovir at our institution (8 lung transplant, 1 heart transplant) during the study period. Letermovir was prescribed for CMV prophylaxis in eight patients (primary prophylaxis in two patients and secondary prophylaxis in 6 patients), and for treatment of CMV DNAemia in two cases. One patient received letermovir for both secondary prophylaxis and treatment on separate occasions. Three out of 8 (37.5%) patients receiving letermovir for prophylaxis developed CMV DNAemia during prophylaxis. One patient treated for CMV disease had clinical failure with a sharp rise in serum CMV DNA PCR. The other patient treated for low-grade CMV DNAemia initially had a slight rise in CMV DNA PCR, but has since had a sustained response. No major side effects were experienced, and 2 patients reported minor side effects.

CONCLUSION

Letermovir was well tolerated with only minor side effects reported; however, the rate of development of CMV DNAemia on prophylaxis was considerable. Further study of the dosing and efficacy of letermovir for CMV prophylaxis or treatment in thoracic organ transplant recipients is warranted.

Safety considerations with current and emerging antiviral therapies for cytomegalovirus infection in transplantation

Introduction: Human cytomegalovirus (HCMV) is a major contributor of morbidity and mortality, and its management is essential for the successful outcome of solid organ and hematopoietic stem cell transplantation. Areas covered: This review discusses the safety profiles of currently available and emerging antiviral drugs and the other strategies for HCMV prevention and treatment after transplantation. Expert opinion: Strategies for management of HCMV rely largely on the use of antiviral agents that inhibit viral DNA polymerase (ganciclovir/valganciclovir, foscarnet, and cidofovir/brincidofovir) and viral terminase complex (letermovir), with different types and degrees of adverse effects. An investigational agent, maribavir, exerts its anti-CMV effect through UL97 inhibition, and its safety profile is under clinical evaluation. In choosing the antiviral medication to use, it is important to consider these safety profiles in addition to overall efficacy. In addition to antiviral drugs, reduction of immunosuppression is often generally needed in the management of HCMV infection, but with a potential risk of allograft rejection or graft-versus-host disease. The use of HCMV-specific or non-specific intravenous immunoglobulins remains debated, while adoptive HCMV-specific T cell therapy remains investigational, and associated with unique set of adverse effects.

An update on the treatment of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Introduction: Human Cytomegalovirus (CMV) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Standard treatment options have for long been limited to a small number of effective drugs with significant toxicities.Areas covered: In this manuscript, the authors update a previous review summarizing recent developments in the virology lab and their possible implications for treatment strategies at bedside. In particular, the authors focused on new antiviral drugs already available and under investigation in clinical trials and innovative immunotherapeutic approaches, including adoptive T-cell therapy and vaccines.Expert opinion: Broader knowledge of CMV biology and its relationship with the host immune system is greatly contributing to the development of novel therapeutic approaches. The availability of new drugs, the improved techniques for virological testing and the more accurate patient risk stratification allow to better individualize treatment, limiting toxicity while sparing antiviral effects. The role of immunotherapy is clearly emerging and will further expand our treatment armamentarium.

An overview of letermovir: a cytomegalovirus prophylactic option

Introduction: Human cytomegalovirus (HCMV) or human herpesvirus 5 (HHV-5) is a β-herpesvirus that causes widespread infection in nearly all members of the human population worldwide. Its persistence in humans after primary infection in a latent phase as well as a partial non-protective immune response is the basis for repeated re-activation/re-infection episodes occurring both in immunocompetent and immunocompromised subjects. In the latter patient populations, which include hematopoietic stem cell transplant (HSCT) recipients, HCMV reactivation episodes may be particularly severe, leading to both systemic and end-organ diseases. Since the 90s, at least four antiviral drugs targeting the DNA polymerase complex have been developed for the prevention and treatment of HCMV infections in transplant recipients, used as first-line (ganciclovir and valganciclovir) and second-line therapy (foscarnet and cidofovir). However, due to their toxicity and drug-resistance induction, new drugs with different targets were needed. Areas covered: In 2017, a new drug named letermovir (LTV), which targets the HCMV DNA terminase complex, was licensed for prophylaxis of HCMV infections in HSCT recipients. This is the focus of this review. Expert opinion: LTV safety and efficacy are promising. However, long-term adverse events and the emergence of drug-resistant HCMV strains must be investigated in extended clinical trials prior to drawing final conclusions.

Role of letermovir for prevention of cytomegalovirus infection after allogeneic haematopoietic stem cell transplantation

PURPOSE OF REVIEW

Cytomegalovirus (CMV) infection is a common opportunistic infection after allogeneic haematopoietic stem cell transplantation (HSCT). CMV surveillance-preemptive therapy is the current preferred approach for preventing CMV disease after HSCT. In contrast, antiviral prophylaxis is not commonly used due to myelosuppressive effects of valganciclovir. In this article, the role of the newly approved antiviral compound, letermovir, is reviewed.

RECENT FINDINGS

Letermovir inhibits CMV by interfering viral terminase complex. In a phase 3 randomized placebo-controlled clinical study that enrolled 495 CMV-seropositive HSCT recipients, the primary end point of clinically significant CMV infection was significantly reduced by letermovir prophylaxis. Letermovir was well tolerated without risk of myelotoxicity and nephrotoxicity. Experimental in-vitro data suggest that letermovir may possess low genetic barrier to resistance. In prophylaxis trials, two breakthrough infections were reported due to selection of CMV UL56 V236M mutation.

SUMMARY

Letermovir is an important addition to the current strategies for CMV prevention after allogeneic HSCT. Its favourable efficacy and safety profile re-opens door for antiviral prophylaxis another first-line option, similar to CMV surveillance-preemptive therapy, for preventing CMV in allogeneic HSCT recipients.

Letermovir for the prevention of cytomegalovirus infection and disease in transplant recipients: an evidence-based review

Cytomegalovirus (CMV) is a leading opportunistic infection in immune compromised patients, including allogeneic hematopoietic stem cell (HSCT) or solid organ transplant (SOT) recipients, where primary infection or reactivation is associated with increased morbidity and mortality. Antiviral drugs are the mainstay for the prevention of CMV infection and disease, most commonly with valganciclovir. However, valganciclovir use is often associated with adverse drug reactions, most notably leukopenia and neutropenia, and its widespread use has led to emergence of antiviral resistance. Foscarnet and cidofovir, however, are associated with nephrotoxicity. Letermovir, a novel CMV viral terminase inhibitor drug, was recently approved for CMV prophylaxis in allogeneic HSCT recipients. It has a favorable pharmacokinetic and tolerability profile. The aim of this paper is to review the evidence supporting the use of letermovir in allogeneic HSCT recipients, and how the drug impacts our contemporary clinical practice. In addition, we discuss the ongoing clinical trial of letermovir for the prevention of CMV in SOT recipients. The use of letermovir for treatment of CMV infection and disease is not yet approved. However, because of a unique mechanism of activity, we provide our perspective on the potential role of letermovir in the treatment of ganciclovir-resistant CMV infection and disease. Furthermore, drug-resistant CMV has emerged during use of letermovir for prophylaxis and treatment. Caution is advised on its use in order to preserve its therapeutic lifespan.

New Developments in the Management of Cytomegalovirus Infection After Transplantation

Cytomegalovirus (CMV) continues to be one of the most important pathogens that universally affect solid organ and allogeneic hematopoietic stem cell transplant recipients. Lack of effective CMV-specific immunity is the common factor that predisposes to the risk of CMV reactivation and clinical disease after transplantation. Antiviral drugs are the cornerstone for prevention and treatment of CMV infection and disease. Over the years, the CMV DNA polymerase inhibitor, ganciclovir (and valganciclovir), have served as the backbone for management, while foscarnet and cidofovir are reserved for the management of CMV infection that is refractory or resistant to ganciclovir treatment. In this review, we highlight the role of the newly approved drug, letermovir, a viral terminase inhibitor, for CMV prevention after allogeneic hematopoietic stem cell transplantation. Advances in immunologic monitoring may allow for an individualized approach to management of CMV after transplantation. Specifically, the potential role of CMV-specific T-cell measurements in guiding the need for the treatment of asymptomatic CMV infection and the duration of treatment of CMV disease is discussed. The role of adoptive immunotherapy, using ex vivo-generated CMV-specific T cells, is highlighted. This article provides a review of novel drugs, tests, and strategies in optimizing our current approaches to prevention and treatment of CMV in transplant recipients.

From academic research to founding a company: the story of AiCuris

This contribution describes the experiences with three careers: leading and building an academic research institute, heading a research area in a multinational pharma company and founding and leading a biotech company, which saw its first drug successfully enter the market in its 11thyear of existence. The three positions had very different challenges, the common denominator for success was good and innovative science. However, research in a commercial environment, in addition to scientific excellence, also means to demonstrate the likely commercial success of the particular research. The most challenging, but at the same time the most interesting mission was the foundation of a new company, securing the financial means and developing the drugs, which had been discovered, in the clinics.

Donor-derived Viral Infections in Liver Transplantation

Donor-derived infections are defined as any infection present in the donor that is transmitted to 1 or more recipients. Donor-derived infections can be categorized into 2 groups: "expected" and "unexpected" infections. Expected transmissions occur when the donor is known to have an infection, such as positive serology for cytomegalovirus, Epstein Barr virus, or hepatitis B core antibody, at the time of donation. Unexpected transmissions occur when a donor has no known infection before donation, but 1 or more transplant recipients develop an infection derived from the common donor. Unexpected infections are estimated to occur in far less than 1% of solid organ transplant recipients. We will review the epidemiology, risk factors, and approaches to prevention and management of donor-derived viral infectious disease transmission in liver transplantation.