Primary endpoint results
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Clinically significant CMV infection at week 24 in HSCT patients
PREVYMIS demonstrated significant efficacy vs placebo in the primary endpoint: Clinically significant CMV infectiona at week 24 (NC=F approach)b

(a) Clinically significant CMV infection was defined as either the occurrence of CMV end-organ disease or initiation of anti-CMV PET, based on documented CMV viremia and the clinical condition of the patient. Viremia was determined using the Roche COBAS® AmpliPrep/COBAS TaqMan® assay; lower limit of quantification was 137 IU/mL, which is approximately 150 copies/mL.
(b) The Noncompleter=Failure (NC=F) approach was used in which patients who discontinued from the study prior to week 24 post-transplant or had a missing outcome at week 24 post-transplant were counted as failures.
(c) The categories of failure are mutually exclusive and based on the hierarchy of categories in the order listed.
(d) Through week 14, 8% of subjects in the PREVYMIS group and 39% of subjects in the placebo group experienced clinically significant CMV infection.
(e) Reasons for discontinuation included adverse event (AE), death, lost to follow-up, physician decision, and withdrawal by subject.
Rate of clinically significant CMV infection
Significantly lower rate of onset of clinically significant CMVf infection for PREVYMIS vs placebo1,g

(f) Clinically significant CMV infection was defined as either the occurrence of CMV end-organ disease or initiation of anti-CMV PET, based on documented CMV viremia and the clinical condition of the patient. Viremia was determined using the Roche COBAS® AmpliPrep/COBAS TaqMan® assay; lower limit of quantification was 137 IU/mL, which is approximately 150 copies/mL.
(g) Included patients who received at least 1 dose of study drug and excluded patients with detectable CMV DNA at baseline.
Factors associated with clinically significant CMV infection between week 14 and week 24 post-transplant among PREVYMIS patients included:
- High-risk stratum for CMV reactivation at baseline
- Having GVHD
- Steroid use at any time after randomization
High- and low-risk strata
Efficacy results were consistent across high- and low-risk strata for CMV reactivation.


Copyright © 2017 Massachusetts Medical Society. Reprinted with permission from Massachusetts Medical Society.1
Overview of CMV-seropositive recipients [R+] status and additional risk factors at baseline

Baseline data collected at randomization in the phase 3 trial.
The majority of patients in the phase 3 trial were R+ with no additional risk factors at baseline. Thirty percent of patients were R+ with ≥1 of the following additional risk factors and were placed in the high-risk stratum:
- Related donor with human leukocyte antigen (HLA) mismatch
- Haploidentical donor
- Unrelated donor with HLA mismatch
- Use of umbilical cord blood
- Use of ex vivo T-cell–depleted grafts
- GVHD requiring systemic corticosteroids
Reference
- Marty FM, Ljungman P, Chemaly RF, et al. Letermovir prophylaxis for cytomegalovirus in hematopoietic-cell transplantation. N Engl J Med. 2017;377(25):2433–2444.