CLINICAL PHARMACOLOGY
Mechanism Of Action
PREVYMIS is an antiviral drug against CMV [see Microbiology].
Pharmacodynamics
Cardiac Electrophysiology
In a thorough QT trial in healthy subjects, letermovir at the therapeutic IV dose or at a dose of 2 times the approved IV dose did not prolong QTc to any clinically relevant extent.
Pharmacokinetics
The pharmacokinetic properties of letermovir are displayed in Table 4.
Table 4: Absorption, Distribution, Metabolism, Elimination (ADME), and Pharmacokinetic
Properties of PREVYMIS*
Pharmacokinetics in HSCT Recipients |
Treatment Regimen |
Steady-state median (90% prediction interval) AUC (ng•hr/mL) of PREVYMIS |
480 mg oral once daily, no cyclosporine |
34,400 (16,900, 73,700) |
480 mg IV once daily, no cyclosporine |
100,000 (65,300, 148,000) |
240 mg oral once daily, with cyclosporine |
60,800 (28,700, 122,000) |
240 mg IV once daily, with cyclosporine |
70,300 (46,200, 106,000) |
Pharmacokinetics in Healthy Subjects |
Treatment Regimen |
Steady-state geometric mean AUC and Cmax of PREVYMIS |
480 mg oral once daily |
Cmax: 13,000 ng/mL |
AUC: 71,500 ng•hr/mL |
Dose proportionality |
Greater than proportional following single and multiple oral or IV doses of PREVYMIS 240 mg and 480 mg |
Accumulation ratio† |
Cmax: 1.03 |
AUC: 1.22 |
Time to steady-state |
9-10 days |
Absorption |
Bioavailability |
Healthy subjects administered PREVYMIS without cyclosporine: 94% at an oral dose range of 240 mg to 480 mg |
HSCT recipients administered PREVYMIS without cyclosporine: 35% with 480 mg oral once daily |
HSCT recipients administered PREVYMIS with cyclosporine: 85% with 240 mg oral once daily |
Median Tmax (hr) |
1.5 to 3.0 hr |
Effect of food (relative to fasting) ‡ |
AUC: 99.63% [84.27% - 117.80%] |
Cmax: 129.82% [104.35% -161.50%] |
Distribution |
Mean steady-state volume of distribution |
45.5 L following IV administration in HSCT recipients |
% In vitro bound to human plasma proteins |
99% across the concentration range of 0.2 to 50 mg/L |
In vitro blood-to plasma ratio |
0.56 across the concentration range of 0.1 to 10 mg/L |
Metabolism |
In vitro metabolism |
UGT1A1/1A3 (minor) |
Drug-related component in plasma |
97% unchanged parent |
No major metabolites detected in plasma |
Elimination |
Route of elimination |
Hepatic uptake (OATP1B1/3) |
Mean terminal t1/2 (hr) |
12 hrs after dosing of PREVYMIS 480 mg IV once daily |
% of dose excreted in feces§ |
93% |
% of dose excreted in urine§ |
<2% |
% of unchanged drug excreted in feces§ |
70% |
* Values were obtained in studies of healthy subjects unless otherwise indicated.
† Based on geometric mean data.
‡ Values refer to geometric mean ratio [fed/fasted] percentage and 90% confidence interval back transformed from linear mixed-effects model performed on natural log-transformed values. The meal administered was a standard high fat and high calorie meal (33 grams protein, 65 grams carbohydrates, 58 grams fat; 920 total calories).
§ Single oral administration of radiolabeled letermovir in mass balance study. |
Specific Populations
Pediatric Population
The pharmacokinetics of letermovir in patients less than 18 years of age have not been evaluated.
Age, Gender, Race, And Weight
Age (18 to 78 years), gender, race (White vs. non-White), and body weight (up to 100 kg) did not have a clinically significant effect on the pharmacokinetics of letermovir.
Renal Impairment
Letermovir AUC was approximately 1.9- and 1.4-fold higher in subjects with moderate (eGFR greater than or equal to 30 to 59 mL/min/1.73m2) and severe (eGFR less than 30 mL/min/1.73m2) renal impairment, respectively, compared to healthy subjects.
Hydroxypropyl betadex present in the intravenous letermovir formulation is mainly eliminated by glomerular filtration. Decreased elimination of hydroxypropyl betadex has been reported in the literature in patients with severe renal impairment.
Hepatic Impairment
Letermovir AUC was approximately 1.6- and 3.8-fold higher in subjects with moderate (Child-Pugh Class B [CP-B], score of 7-9) and severe (Child-Pugh Class C [CP-C], score of 10-15) hepatic impairment, respectively, compared to healthy subjects.
Drug Interaction Studies
Drug interaction studies were performed in healthy subjects with PREVYMIS and drugs likely to be co-administered or drugs commonly used as probes for pharmacokinetic interactions (see Table 5 and Table 6).
In vitro results indicate that letermovir is a substrate of drug metabolizing enzymes CYP3A, CYP2D6, UGT1A1, and UGT1A3, and transporters OATP1B1/3 and P-gp. Oxidative metabolism is considered to be a minor elimination pathway based on in vivo human data. Inhibitors of OATP1B1/3 may result in increases in letermovir plasma concentrations. Changes in letermovir plasma concentrations due to inhibition of P-gp or UGTs are not anticipated to be clinically relevant.
Based on in vitro studies, the metabolism of letermovir is not mediated by CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2E1, CYP4A11, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, UGT2B7, UGT2B15, or UGT2B17. The transport of letermovir is not mediated by OATP2B1, OCT1, OAT1, BCRP, or MRP2 in vitro.
Letermovir is a time-dependent inhibitor and inducer of CYP3A in vitro. Co-administration of PREVYMIS with midazolam resulted in increased exposure of midazolam, indicating that the net effect of letermovir on CYP3A is moderate inhibition (see Table 6). Based on these results, co-administration of PREVYMIS with CYP3A substrates may increase the plasma concentrations of the CYP3A substrates [see CONTRAINDICATIONS, WARNINGS AND PRECAUTIONS, DRUG INTERACTIONS, and Table 3]. Letermovir is a reversible inhibitor of CYP2C8 in vitro. When co-administered with PREVYMIS, plasma concentrations of CYP2C8 substrates are predicted to be increased [see Table 3 in DRUG INTERACTIONS]. Co-administration of PREVYMIS reduced the exposure of voriconazole, most likely due to the induction of voriconazole elimination pathways, CYP2C9 and CYP2C19. Co-administration of PREVYMIS with CYP2C9 and CYP2C19 substrates may decrease the plasma concentrations of the CYP2C9 and CYP2C19 substrates [see Table 3 in DRUG INTERACTIONS]. Letermovir is an inducer of CYP2B6 in vitro; the clinical relevance is unknown.
Letermovir inhibited efflux transporters P-gp, breast cancer resistance protein (BCRP), bile salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2), OAT3, and hepatic uptake transporter OATP1B1/3 in vitro. Co-administration of PREVYMIS with substrates of OATP1B1/3 transporters (e.g. atorvastatin, a known substrate of CYP3A, OATP1B1/3, and potentially BCRP) may result in a clinically relevant increase in plasma concentrations of OATP1B1/3 substrates [see Table 3 in DRUG INTERACTIONS]. There were no clinically relevant changes in plasma concentrations of digoxin, a P-gp substrate, or acyclovir, an OAT3 substrate, following co-administration with PREVYMIS in clinical studies (see Table 6). The effect of letermovir on BCRP, BSEP, and MRP2 substrates was not evaluated in clinical studies; the clinical relevance is unknown.
Based on in vitro results letermovir is not an inhibitor of CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, UGT1A4, UGT1A6, UGT1A9, or UGT2B7 and is not an inducer of CYP1A2. Letermovir is not an inhibitor of OATP2B1, OCT1, OCT2, or OAT1 in vitro.
Table 5: Drug Interactions: Changes in Pharmacokinetics of Letermovir in the Presence of Co-administered Drug
Co-administered Drug |
Regimen of Co-administered Drug |
Letermovir Regimen |
Geometric Mean Ratio [90% CI] of Letermovir PK with/without Co-administered Drug (No Effect=1.00) |
AUC |
Cmax |
C24hr* |
Antifungals |
fluconazole |
400 mg single dose PO |
480 mg single dose PO |
1.11 (1.01, 1.23) |
1.06 (0.93, 1.21) |
1.28 (1.15, 1.43) |
Antimycobacterials |
rifampin |
600 mg single dose PO |
480 mg single dose PO |
2.03 (1.84, 2.26) |
1.59 (1.46, 1.74) |
2.01 (1.59, 2.54) |
600 mg single dose IV |
480 mg single dose PO |
1.58 (1.38, 1.81) |
1.37 (1.16, 1.61) |
0.78 (0.65, 0.93) |
600 mg once daily PO |
480 mg once daily PO |
0.81 (0.67, 0.98) |
1.01 (0.79, 1.28) |
0.14 (0.11, 0.19) |
600 mg once daily PO (24 hours after rifampin)† |
480 mg once daily PO |
0.15 (0.13, 0.17) |
0.27 (0.22, 0.31) |
0.09 (0.06, 0.12) |
Immunosuppressants |
cyclosporine |
200 mg single dose PO |
240 mg once daily PO |
2.11 (1.97, 2.26) |
1.48 (1.33, 1.65) |
2.06 (1.81, 2.35) |
mycophenolate mofetil |
1 g single dose PO |
480 mg once daily PO |
1.18 (1.04, 1.32) |
1.11 (0.92, 1.34) |
1.39 (1.12, 1.74) |
tacrolimus |
5 mg single dose PO |
80 mg twice daily PO |
1.02 (0.97, 1.07) |
0.92 (0.84, 1.00) |
1.02 (0.93, 1.12) |
Abbreviations: PO= oral
* C12hr for tacrolimus
†These data are the effect of rifampin on letermovir 24 hours after final rifampin dose. |
Table 6: Drug Interactions: Changes in Pharmacokinetics for Co-administered Drug in the
Presence of Letermovir
Co-administered Drug |
Regimen ofCo-administered Drug |
Letermovir Regimen |
Geometric Mean Ratio [90% CI] of Co-administered Drug PK with/without Letermovir (No Effect=1.00) |
AUC |
Cmax |
C24hr* |
CYP3A Substrates |
midazolam |
1 mg single dose IV |
240 mg once daily PO |
1.47 (1.37, 1.58) |
1.05 (0.94, 1.17) |
2.74 (2.16, 3.49) |
2 mg single dose PO |
240 mg once daily PO |
2.25 (2.04, 2.48) |
1.72 (1.55, 1.92) |
Not available |
P-gp Substrates |
digoxin |
0.5 mg single dose PO |
240 mg twice daily PO |
0.88 (0.80, 0.96) |
0.75 (0.63, 0.89) |
0.90 (0.84, 0.96) |
Immunosuppressants |
cyclosporine |
50 mg single dose PO |
240 mg once daily PO |
1.66 (1.51, 1.82) |
1.08 (0.97, 1.19) |
2.19 (1.80, 2.66) |
mycophenolate mofetil |
1 g single dose PO |
480 mg once daily PO |
1.08 (0.97, 1.20) |
0.96 (0.82, 1.12) |
1.04 (0.86, 1.27) |
tacrolimus |
5 mg single dose PO |
480 mg once daily PO |
2.42 (2.04, 2.88) |
1.57 (1.32, 1.86) |
2.53 (2.12, 3.03) |
sirolimus |
2 mg single dose PO |
480 mg once daily PO |
3.40 (3.01, 3.85) |
2.76 (2.48, 3.06) |
3.15 (2.80, 3.55) |
Antifungals and Antivirals |
acyclovir |
400 mg single dose PO |
480 mg once daily PO |
1.02 (0.87, 1.2) |
0.82 (0.71, 0.93) |
1.13 (0.94, 1.36) |
fluconazole |
400 mg single dose PO |
480 mg single dose PO |
1.03 (0.99, 1.08) |
0.95 (0.92, 0.99) |
1.04 (1.00, 1.08) |
posaconazole |
300 mg single dose PO |
480 mg once daily PO |
0.98 (0.82, 1.17) |
1.11 (0.95, 1.29) |
1.10 (0.94, 1.30) |
voriconazole |
200 mg twice daily PO |
480 mg once daily PO |
0.56 (0.51, 0.62) |
0.61 (0.53, 0.71) |
0.49 (0.42, 0.57) |
HMG-CoA Reductase Inhibitors |
atorvastatin |
20 mg single dose PO |
480 mg once daily PO |
3.29 (2.84, 3.82) |
2.17 (1.76, 2.67) |
3.62 (2.87, 4.55) |
Oral Contraceptives |
ethinyl estradiol
(EE)
/levonorgestrel (LNG) |
0.03 mg EE single dose PO |
480 mg once daily PO |
1.42 (1.32, 1.52) |
0.89 (0.83, 0.96) |
1.57 (1.45, 1.70) |
0.15 mg LNG single dose PO |
1.36 (1.30, 1.43) |
0.95 (0.86, 1.04) |
1.38 (1.32, 1.46) |
Abbreviations: PO=oral
* C12hr reported for voriconazole. |
Microbiology
Mechanism Of Action
Letermovir inhibits the CMV DNA terminase complex (pUL51, pUL56, and pUL89) which is required for viral DNA processing and packaging. Biochemical characterization and electron microscopy demonstrated that letermovir affects the production of proper unit length genomes and interferes with virion maturation. Genotypic characterization of virus resistant to letermovir confirmed that letermovir targets the terminase complex.
Antiviral Activity
The median EC50 value of letermovir against a collection of clinical CMV isolates in a cell-culture model of infection was 2.1 nM (range = 0.7 nM to 6.1 nM, n = 74). There was no significant difference in EC50 value by CMV gB genotype (gB1=29; gB2=27; gB3=11; and gB4=3).
Combination Antiviral Activity
No antagonism of the antiviral activity was seen when letermovir was combined with CMV DNA polymerase inhibitors (cidofovir, foscarnet, or ganciclovir).
Viral Resistance
In Cell Culture
CMV mutants with reduced susceptibility to letermovir have been selected in cell culture and the resistance mutations map to UL56. Resistance-associated substitutions occur between amino acid positions pUL56 231 and 369 (V231A/L, V236L/M, E237D, L241P, T244K/R, L257I, F261C/L/S, Y321C, C325F/R/Y, M329T, R369G/M/S). EC50 values for virus expressing these substitutions are 13- to 5,870fold higher than those for the wild-type reference virus.
In Clinical Studies
In a Phase 2b trial evaluating letermovir or placebo in 131 HSCT recipients, DNA sequence analysis of a select region of UL56 (amino acids 231 to 369) was performed on samples obtained from 12 letermovir treated subjects who experienced prophylaxis failure and for whom on-treatment samples were available for analysis. One subject had a letermovir resistance substitution, pUL56 V236M.
In a Phase 3 trial (P001), DNA sequence analysis of the entire coding regions of UL56 and UL89 was performed on samples obtained from 28 letermovir-treated subjects who had received at least one dose of study drug and experienced prophylaxis failure and for whom samples were available for analysis. Two subjects were identified as having a letermovir-resistance substitution, pUL56 V236M or C325W. These substitutions were identified from on-treatment samples [see Clinical Studies]. A virus from a third subject who experienced prophylaxis failure had a pUL56 E237G substitution at low frequency (<5%), and while pUL56 E237D was associated with resistance in cell culture, the clinical significance of this substitution at this frequency is unknown.
Cross Resistance
Cross resistance is not likely with drugs outside of this class. Letermovir is fully active against viral populations with substitutions conferring resistance to CMV DNA polymerase inhibitors (cidofovir, foscarnet, and ganciclovir). These DNA polymerase inhibitors are fully active against viral populations with substitutions conferring resistance to letermovir.
Animal Toxicology And/Or Pharmacology
Testicular toxicity in rats observed at ≥180 mg/kg/day (greater than or equal to 3 times the human exposure at the RHD) was characterized by decreased testis weight, bilateral seminiferous tubular degeneration, decreased sperm count and motility, and resultant decreased male fertility. Male reproductive system toxicities were not observed in either a monkey testicular toxicity study up to 240 mg/kg/day (approximately 2 times higher than human exposure at the RHD), or a general toxicology study in mice up to 250 mg/kg/day (approximately 3 times higher than human exposure at the RHD).
Clinical Studies
Adult CMV-Seropositive Recipients [R+] Of An Allogeneic Hematopoietic Stem Cell Transplant
To evaluate PREVYMIS prophylaxis as a preventive strategy for CMV infection or disease in transplant recipients at high risk for CMV reactivation, the efficacy of PREVYMIS was assessed in a multicenter, double-blind, placebo-controlled Phase 3 Trial (P001, NCT02137772) in adult CMV-seropositive recipients [R+] of an allogeneic hematopoietic stem cell transplant (HSCT). Subjects were randomized (2:1) to receive either PREVYMIS at a dose of 480 mg once daily adjusted to 240 mg when co-administered with cyclosporine, or placebo. Randomization was stratified by investigational site and risk level for CMV reactivation at the time of study entry. Study drug was initiated after HSCT (at any time from Day 0 to Day 28 post-transplant) and continued through Week 14 post-transplant. Study drug was administered either orally or intravenously; the dose of PREVYMIS was the same regardless of the route of administration. Subjects received CMV DNA monitoring weekly until post-transplant Week 14 and then bi-weekly until post-transplant Week 24, with initiation of standard-of-care CMV pre-emptive therapy if CMV viremia was considered clinically significant. Subjects had continued follow-up through Week 48 post-transplant.
Among the 565 treated subjects, 70 subjects were found to have CMV viremia prior to study drug initiation and were therefore excluded from the efficacy analyses. The efficacy population consisted of 325 subjects who received PREVYMIS (including 91 subjects who received at least one IV dose) and 170 who received placebo (including 41 subjects who received at least one IV dose). The IV formulation of PREVYMIS was used at investigators’ discretion in subjects who were unable to take oral therapy (e.g., unable to tolerate oral intake). The median time to starting study drug was 8 days after transplantation. Thirty-four percent (34%) of subjects were engrafted at baseline. The median age was 55 years (range: 18 to 76 years); 57% were male; 84% were White; 9% were Asian; 2% were Black or African American; and 7% were Hispanic or Latino.
At baseline, 30% of all subjects had one or more of the following factors associated with increased risk for CMV reactivation (high risk stratum): Human Leukocyte Antigen (HLA)-related donor with at least one mismatch at one of the following three HLA-gene loci: HLA-A, -B or –DR; haploidentical donor; unrelated donor with at least one mismatch at one of the following four HLA-gene loci: HLA-A, -B, -C and -DRB1; use of umbilical cord blood as stem cell source; use of ex vivo T-cell-depleted grafts; Grade 2 or greater Graft-Versus-Host Disease (GVHD) requiring systemic corticosteroids. The remaining 70% of subjects did not meet any of these high risk stratum criteria and were therefore included in the low risk stratum. Additionally, 48% of subjects received a myeloablative regimen, 51% were receiving cyclosporine, and 43% were receiving tacrolimus. The most common primary reasons for transplant were acute myeloid leukemia (38%), myelodysplastic syndrome (16%), and lymphoma (12%).
Clinically Significant CMV Infection
The primary efficacy endpoint of Trial P001 was the incidence of clinically significant CMV infection through Week 24 post-transplant (prophylaxis failure). Clinically significant CMV infection was defined as the occurrence of either CMV end-organ disease, or initiation of anti-CMV pre-emptive therapy (PET) based on documented CMV viremia (using the Roche COBAS® AmpliPrep/COBAS TaqMan® assay, LLoQ is 137 IU/mL, which is approximately 150 copies/mL) and the clinical condition of the subject. The protocol-specified guidance for CMV DNA thresholds for the initiation of PET during the treatment period was ≥ 150 copies/mL or > 300 copies/mL for subjects in the high and low risk strata, respectively. From Week 14 through Week 24, the threshold was >300 copies/mL for both high and low risk strata subjects. The Non-Completer=Failure (NC=F) approach was used, where subjects who discontinued from the trial prior to Week 24 post-transplant or had a missing outcome at Week 24 post-transplant were counted as failures.
Efficacy results from Trial P001 are shown in Table 7.
Table 7: Trial P001 Efficacy Results in HSCT Recipients (NC=F Approach, FAS Population)
Through Week 24
Parameter |
Letermovir (N=325) |
Placebo (N=170) |
Proportion of subjects who failed prophylaxis |
38% |
61% |
Reasons for failures* |
|
|
Clinically significant CMV infection by Week 24† |
18% |
42% |
Initiation of PET based on documented CMV viremia |
16% |
40% |
CMV end-organ disease |
2% |
2% |
Discontinued from study before Week 24‡ |
17% |
16% |
Missing outcome in Week 24 visit window |
3% |
3% |
Stratum-adjusted treatment difference (Letermovir-Placebo)§ |
Difference (95% CI) |
-23.5
(-32.5, -14.6)¶ |
|
* The categories of failure are mutually exclusive and based on the hierarchy of categories in the order listed.
† Through Week 14, 8% of subjects in the PREVYMIS group and 39% of subjects in the placebo group experienced clinically significant CMV infection.
‡ Reasons for discontinuation included adverse event, death, lost to follow-up, physician decision, and withdrawal by subject.
§ 95% CI and p-value for the treatment differences in percent response were calculated using stratum-adjusted Mantel-Haenszel method with the difference weighted by the harmonic mean of sample size per arm for each stratum (high or low risk).
¶ p-value <0.0001. Note: FAS=Full analysis set; FAS includes randomized subjects who received at least one dose of study medication, and excludes subjects with detectable CMV DNA at baseline. Approach to handling missing values: Non-Completer=Failure (NC=F) approach. With NC=F approach, failure was defined as all subjects who developed clinically significant CMV infection or prematurely discontinued from the study or had a missing outcome through Week 24 post-transplant visit window. |
Efficacy results were consistent across high and low risk strata for CMV reactivation. The time to clinically significant CMV infection is shown in Figure 1.
Figure 1: P001: Kaplan-Meier Plot of Time to Onset of Clinically Significant CMV Infection Through Week 24 Post-Transplant in HSCT Recipients (FAS Population)
Post-hoc analysis demonstrated that among PREVYMIS-treated subjects, inclusion in the high risk stratum for CMV reactivation at baseline, occurrence of GVHD, and steroid use at any time after randomization may be associated with the development of clinically significant CMV infection between Week 14 and Week 24 post-transplant.
Mortality
The Kaplan-Meier event rate for all-cause mortality in the letermovir vs. placebo groups was 12% vs. 17% at Week 24 post-transplant, and 24% vs. 28% at Week 48 post-transplant.