Trial Outcomes & Findings for A Study of Letermovir (MK-8228) to Evaluate Efficacy and Safety for Prevention of Cytomegalovirus Infection in Chinese Hematopoietic Stem Cell Transplant Recipients (MK-8228-045) (NCT NCT05763823)

Last Updated: 2025-03-25

Results Overview

Clinically significant CMV infection was defined as either one of the following: 1) initiation of anti-CMV pre-emptive therapy based on documented CMV viremia and the clinical condition of the participant or 2) onset of CMV end-organ disease. The percentage of participants with clinically significant CMV infection up to week 24 post-transplant is reported.

Recruitment status

COMPLETED

Study phase

PHASE3

Target enrollment

120 participants

Primary outcome timeframe

Up to Week 24 post-transplant (approximately 6 months)

Results posted on

2025-03-25

Participant Flow

Participant milestones

Participant milestones
Measure	Letermovir Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Overall Study STARTED	120
Overall Study COMPLETED	107
Overall Study NOT COMPLETED	13

Reasons for withdrawal

Reasons for withdrawal
Measure	Letermovir Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Overall Study Death	6
Overall Study Withdrawal by Parent/Guardian	1
Overall Study Withdrawal by Subject	6

Baseline Characteristics

A Study of Letermovir (MK-8228) to Evaluate Efficacy and Safety for Prevention of Cytomegalovirus Infection in Chinese Hematopoietic Stem Cell Transplant Recipients (MK-8228-045)

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Letermovir n=120 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Age, Continuous	37.8 Years STANDARD_DEVIATION 12.1 • n=99 Participants
Sex: Female, Male Female	45 Participants n=99 Participants
Sex: Female, Male Male	75 Participants n=99 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	0 Participants n=99 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	120 Participants n=99 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=99 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=99 Participants
Race (NIH/OMB) Asian	120 Participants n=99 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=99 Participants
Race (NIH/OMB) Black or African American	0 Participants n=99 Participants
Race (NIH/OMB) White	0 Participants n=99 Participants
Race (NIH/OMB) More than one race	0 Participants n=99 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=99 Participants

PRIMARY outcome

Timeframe: Up to Week 24 post-transplant (approximately 6 months)

Population: All allocated participants who received at least 1 dose of study treatment and have no detectable CMV viral deoxyribonucleic acid (DNA) when study intervention is initiated. Per protocol, participants who prematurely discontinued or had a missing outcome at the 24-week visit window were considered treatment failure (i.e. Non-completers equal failure \[NC=F\] approach was used).

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With Clinically Significant Cytomegalovirus (CMV) Infection up to Week 24 Post-Transplant	32 Percentage of Participants Interval 23.5 to 42.9

SECONDARY outcome

Timeframe: Up to 16 weeks

Population: All allocated participants who received at least one dose of study treatment.

An adverse event (AE) is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who experienced an AE is reported.

Outcome measures

Outcome measures
Measure	Letermovir n=120 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants Who Experienced an Adverse Event (AE)	99.2 Percentage of Participants Interval 95.4 to 100.0

SECONDARY outcome

Timeframe: Up to 14 weeks

Population: All allocated participants who received at least one dose of study treatment.

Outcome measures

Outcome measures
Measure	Letermovir n=120 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants Who Discontinue Study Treatment Due to an Adverse Event	0 Percentage of Participants

SECONDARY outcome

Timeframe: Up to 14 weeks post-transplant (99 days)

Population: All allocated participants who received at least 1 dose of study treatment and had no detectable CMV viral DNA when study intervention is initiated. Per protocol, participants who prematurely discontinued or had a missing outcome at the 14-week visit window were considered treatment failure (i.e. Non-completers equal failure \[NC=F\] approach was used).

Outcome measures

Outcome measures
Measure	Letermovir n=120 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With Clinically Significant CMV Infection up to Week 14 Post-Transplant	7.1 Percentage of Participants Interval 2.9 to 14.2

SECONDARY outcome

Timeframe: Up to 14 weeks post-transplant (99 days)

Initiation of anti-CMV preemptive therapy was based on documented CMV viremia and the clinical condition of the participant. The percentage of participants with initiation of anti-CMV preemptive anti-CMV therapy up to 14 weeks post-transplant is reported.

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With Preemptive Therapy for CMV Viremia up to Week 14 Post-Transplant	7.1 Percentage of Participants Interval 2.9 to 14.2

SECONDARY outcome

Timeframe: Up to 24 weeks post-transplant (approximately 6 months)

Population: All allocated participants who received at least 1 dose of study treatment and had no detectable CMV viral DNA when study intervention is initiated. Per protocol, participants who prematurely discontinued or had a missing outcome at the 24-week visit window were considered treatment failure (i.e. Non-completers equal failure \[NC=F\] approach was used).

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With Preemptive Therapy for CMV Viremia up to Week 24 Post-Transplant	32.7 Percentage of Participants Interval 23.5 to 42.9

SECONDARY outcome

Timeframe: Up to 14 weeks post-transplant (99 days)

CMV end-organ disease met per-protocol diagnostic criteria for CMV-pneumonia, gastrointestinal disease, hepatitis, central nervous system disease, retinitis, nephritis, cystitis, myocarditis, pancreatitis, or other disease categories. Only Clinical Adjudication Committee-confirmed CMV end-organ disease will be included in this analysis. The percentage of participants with CMV end-organ disease up to 14 weeks post-transplant is reported.

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With CMV End-organ Disease up to Week 14 Post-Transplant	6.1 Percentage of Participants Interval 2.3 to 12.9

SECONDARY outcome

Timeframe: Up to 24 weeks post-transplant (approximately 6 months)

Population: All allocated participants who received at least 1 dose of study treatment and had no detectable CMV viral DNA when study intervention is initiated. Per protocol, participants who prematurely discontinued or had a missing outcome at the 24-week visit window were considered treatment failure (i.e. Non-completers equal failure \[NC=F\] approach was used).

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With CMV End-organ Disease up to Week 24 Post-Transplant	11.2 Percentage of Participants Interval 5.7 to 19.2

SECONDARY outcome

Timeframe: Up to 14 weeks post-transplant (99 days)

Population: All allocated participants who received at least 1 dose of study treatment and had no detectable CMV viral DNA when study intervention is initiated.

The percentage of participants who died due to any cause up to 14 weeks post-transplant is reported.

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With All-Cause Mortality up to Week 14 Post-Transplant	5.1 Percentage of Participants Interval 1.7 to 11.5

SECONDARY outcome

Timeframe: Up to 24 weeks post-transplant (approximately 6 months)

Population: All allocated participants who received at least 1 dose of study treatment and had no detectable CMV viral DNA when study intervention is initiated.

The percentage of participants who died due to any cause up to 24 weeks post-transplant is reported.

Outcome measures

Outcome measures
Measure	Letermovir n=98 Participants Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Percentage of Participants With All-cause Mortality up to Week 24 Post-Transplant	6.1 Percentage of Participants Interval 2.3 to 12.9

Adverse Events

Letermovir

Serious events: 70 serious events

Other events: 118 other events

Deaths: 8 deaths

Serious adverse events

Serious adverse events
Measure	Letermovir n=120 participants at risk Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Blood and lymphatic system disorders Anaemia	2.5% 3/120 • Number of events 4 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Atypical haemolytic uraemic syndrome	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Pancytopenia	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Thrombocytopenia	3.3% 4/120 • Number of events 4 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Thrombotic microangiopathy	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Diarrhoea	1.7% 2/120 • Number of events 3 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Dysbiosis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Gastrooesophageal reflux disease	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
General disorders Multiple organ dysfunction syndrome	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
General disorders Pyrexia	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
General disorders Sudden cardiac death	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Hepatobiliary disorders Hepatic failure	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Hepatobiliary disorders Hepatic function abnormal	2.5% 3/120 • Number of events 3 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Hepatobiliary disorders Liver injury	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Acute graft versus host disease	11.7% 14/120 • Number of events 16 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Acute graft versus host disease in intestine	3.3% 4/120 • Number of events 4 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Acute graft versus host disease in skin	0.83% 1/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Chronic graft versus host disease in intestine	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Graft versus host disease	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Bacterial infection	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Coronavirus infection	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Cystitis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Cytomegalovirus infection	5.8% 7/120 • Number of events 7 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Cytomegalovirus viraemia	3.3% 4/120 • Number of events 4 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Epstein-Barr viraemia	5.0% 6/120 • Number of events 6 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Epstein-Barr virus infection	6.7% 8/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Febrile infection	2.5% 3/120 • Number of events 3 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Gastroenteritis	2.5% 3/120 • Number of events 3 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Gastrointestinal infection	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Herpes zoster	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Infection	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Influenza	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Klebsiella sepsis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Pneumonia	14.2% 17/120 • Number of events 20 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Pneumonia fungal	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Pulmonary tuberculosis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Septic shock	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Sinusitis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Upper respiratory tract infection	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Blood creatinine increased	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Platelet count decreased	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Electrolyte imbalance	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Musculoskeletal and connective tissue disorders Synovitis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Acute lymphocytic leukaemia recurrent	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Acute lymphocytic leukaemia refractory	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Acute myeloid leukaemia	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Acute myeloid leukaemia recurrent	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Acute promyelocytic leukaemia	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Chronic myeloid leukaemia	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Post transplant lymphoproliferative disorder	1.7% 2/120 • Number of events 2 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Nervous system disorders Altered state of consciousness	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Nervous system disorders Cerebrovascular disorder	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Renal and urinary disorders Cystitis haemorrhagic	10.0% 12/120 • Number of events 12 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Renal and urinary disorders Renal failure	2.5% 3/120 • Number of events 3 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Respiratory, thoracic and mediastinal disorders Pleural effusion	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Vascular disorders Axillary vein thrombosis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Vascular disorders Shock	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Vascular disorders Subclavian vein thrombosis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Vascular disorders Venous thrombosis	0.83% 1/120 • Number of events 1 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.

Other adverse events

Other adverse events
Measure	Letermovir n=120 participants at risk Chinese HSCT recipients received 240 mg of Letermovir \[for participants on Cyclosporin A (CsA)\] or 480 mg of Letermovir (for participants not on CsA) either orally or IV once daily through week 14 (99 days) post-transplant.
Blood and lymphatic system disorders Coagulopathy	6.7% 8/120 • Number of events 11 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Hypofibrinogenaemia	6.7% 8/120 • Number of events 10 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Abdominal pain	5.8% 7/120 • Number of events 11 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Abdominal pain upper	5.8% 7/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Constipation	8.3% 10/120 • Number of events 11 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Diarrhoea	20.8% 25/120 • Number of events 36 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Haemorrhoids	11.7% 14/120 • Number of events 15 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Mouth ulceration	6.7% 8/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Nausea	22.5% 27/120 • Number of events 32 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Stomatitis	9.2% 11/120 • Number of events 13 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Vomiting	30.8% 37/120 • Number of events 65 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
General disorders Asthenia	6.7% 8/120 • Number of events 9 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
General disorders Pyrexia	26.7% 32/120 • Number of events 48 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Hepatobiliary disorders Hepatic function abnormal	10.8% 13/120 • Number of events 14 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Acute graft versus host disease	13.3% 16/120 • Number of events 16 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations COVID-19	9.2% 11/120 • Number of events 14 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Conjunctivitis	7.5% 9/120 • Number of events 9 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Cystitis	5.8% 7/120 • Number of events 7 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Epstein-Barr virus infection	16.7% 20/120 • Number of events 27 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Infection	5.8% 7/120 • Number of events 7 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Pneumonia	9.2% 11/120 • Number of events 11 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Upper respiratory tract infection	15.8% 19/120 • Number of events 22 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Urinary tract infection	10.0% 12/120 • Number of events 14 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Alanine aminotransferase increased	8.3% 10/120 • Number of events 12 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Aspartate aminotransferase increased	7.5% 9/120 • Number of events 15 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Blood creatinine increased	6.7% 8/120 • Number of events 13 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Blood lactate dehydrogenase increased	13.3% 16/120 • Number of events 23 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Gamma-glutamyltransferase increased	10.0% 12/120 • Number of events 15 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Neutrophil count decreased	13.3% 16/120 • Number of events 31 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Platelet count decreased	16.7% 20/120 • Number of events 25 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations Weight decreased	10.0% 12/120 • Number of events 12 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Investigations White blood cell count decreased	22.5% 27/120 • Number of events 53 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Decreased appetite	5.8% 7/120 • Number of events 9 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Electrolyte imbalance	8.3% 10/120 • Number of events 11 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypercholesterolaemia	5.8% 7/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hyperglycaemia	7.5% 9/120 • Number of events 18 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hyperlipidaemia	15.0% 18/120 • Number of events 24 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypertriglyceridaemia	6.7% 8/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hyperuricaemia	5.8% 7/120 • Number of events 9 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypoalbuminaemia	13.3% 16/120 • Number of events 23 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypocalcaemia	5.8% 7/120 • Number of events 8 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypokalaemia	32.5% 39/120 • Number of events 66 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypomagnesaemia	10.8% 13/120 • Number of events 19 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hyponatraemia	16.7% 20/120 • Number of events 36 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Hypoproteinaemia	15.8% 19/120 • Number of events 27 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Musculoskeletal and connective tissue disorders Back pain	5.8% 7/120 • Number of events 7 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Nervous system disorders Headache	8.3% 10/120 • Number of events 12 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Psychiatric disorders Insomnia	9.2% 11/120 • Number of events 12 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Renal and urinary disorders Cystitis haemorrhagic	15.8% 19/120 • Number of events 19 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Renal and urinary disorders Renal failure	6.7% 8/120 • Number of events 10 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Respiratory, thoracic and mediastinal disorders Cough	12.5% 15/120 • Number of events 17 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Skin and subcutaneous tissue disorders Rash	21.7% 26/120 • Number of events 27 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.
Vascular disorders Hypertension	10.8% 13/120 • Number of events 16 • Up to 6 months All cause mortality is reported for all allocated participants. Serious adverse events and other adverse events are reported for all allocated participants who received at least 1 dose of study treatment.

Additional Information

Senior Vice President, Global Clinical Development

Merck Sharp & Dohme LLC

Phone: 1-800-672-6372

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee If publication activity is not directed by the Sponsor, the investigator agrees to submit all manuscripts or abstracts to the Sponsor before submission. Authorship will be determined by mutual agreement and in line with International Committee of Medical Journal Editors authorship requirements.
Publication restrictions are in place

Restriction type: OTHER