Use with Immunosuppressant Drugs
LIVTENCITY has the potential to increase the drug concentrations of immunosuppressant drugs that are CYP3A4 and/or P-glycoprotein (P-gp) substrates where minimal concentration changes may lead to serious adverse events (including tacrolimus, cyclosporine, sirolimus and everolimus). Frequently monitor immunosuppressant drug levels throughout treatment with LIVTENCITY, especially following initiation and after discontinuation of LIVTENCITY and adjust the immunosuppressant dose, as needed [see Drug Interactions (7.3) and Clinical Pharmacology (12.3)].
Laboratory Abnormalities
Selected laboratory abnormalities reported in subjects with refractory (with or without genotypic resistance) CMV infections in Trial 303 are presented in Table 2.
Table 2: Selected Laboratory Abnormalities Reported in Trial 303| Laboratory Parameter | LIVTENCITY N=234 n (%) | IAT N=116 n (%) |
|---|
| Neutrophils (cells /µL) | | |
| <500 | 4 (2) | 4 (3) |
| ≥500 to <750 | 7 (3) | 7 (6) |
| ≥750 to <1,000 | 10 (4) | 6 (5) |
| Hemoglobin (g/dL) | | |
| <6.5 | 3 (1) | 1 (1) |
| ≥6.5 to <8.0 | 34 (15) | 23 (20) |
| ≥8.0 to <9.5 | 76 (32) | 33 (28) |
| Platelets (cells /µL) | | |
| <25,000 | 11 (5) | 6 (5) |
| ≥25,000 to <50,000 | 27 (12) | 10 (9) |
| ≥50,000 to <100,000 | 41 (18) | 20 (17) |
| Creatinine (mg/dL) | | |
| >2.5 | 16 (7) | 12 (10) |
| >1.5 to ≤2.5 | 78 (33) | 29 (25) |
Risk Summary
No adequate human data are available to establish whether LIVTENCITY poses a risk to pregnancy outcomes. In animal reproduction studies, embryo-fetal survival was decreased in rats, but not in rabbits, at maribavir exposures less than those observed in humans at the recommended human dose (RHD) (see Data).
The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.
Data
Animal Data
In a combined fertility and embryofetal development study, maribavir was administered to male and female rats at oral doses of 100, 200, or 400 mg/kg/day. Females were dosed for 15 consecutive days prior to pairing, throughout pairing, and up to gestation day (GD) 17, while males were dosed 29 days prior to mating and throughout mating. A decrease in the number of viable fetuses and increase in early resorptions and post-implantation losses were observed at ≥100 mg/kg/day (at exposures approximately half the human exposure at the RHD). Intermittent reduced body weight gain was observed in pregnant animals at ≥200 mg/kg/day. Maribavir had no effect on embryo-fetal growth or development at dose levels up to 400 mg/kg/day, at exposures similar to those observed in humans at the RHD.
No significant toxicological effects on embryo-fetal growth or development were observed in rabbits when maribavir was administered at oral doses up to 100 mg/kg/day from GD 8 to 20, at exposures approximately half the human exposure at the RHD.
In the pre-and postnatal developmental toxicity study maribavir was administered to pregnant rats at oral doses of 50, 150, or 400 mg/kg/day from GD 7 to postnatal day (PND) 21. A delay in developmental milestones was observed, including pinna detachment at doses ≥150 mg/kg/day and eye opening and preputial separation associated with reduced bodyweight gain of the offspring at 400 mg/kg/day. In addition, decreased fetal survival and litter loss was observed due to maternal toxicity and poor maternal care, respectively, at doses ≥150 mg/kg/day. No effects were observed at 50 mg/kg/day (which is estimated to be less than the human exposure at the RHD). No effects on number of offspring, proportion of males, number of live pups, or survival to PND 4 were observed at any dose in the offspring born to the second generation.
Risk Summary
It is not known whether maribavir or its metabolites are present in human or animal milk, affect milk production, or have effects on the breastfed infant. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for LIVTENCITY and any potential adverse effects to the breast-fed child.
Exposure-response
In dose-ranging studies that evaluated doses of 400 mg twice daily and twice daily doses of two and three times the recommended dose, no exposure-response relationship was observed for viral load or probability of unquantifiable plasma CMV DNA.
In Phase 3 Trial 303 that evaluated a maribavir dose of 400 mg twice daily, increasing maribavir exposure was not associated with increased probability of confirmed plasma CMV DNA < LLOQ (lower limit of quantification) at Week 8.
Cardiac Electrophysiology
At three times the recommended dose (approximately twice the peak concentration observed following the recommended dose), LIVTENCITY does not prolong the QT interval to any clinically relevant extent.
Specific Populations
There were no clinically significant differences in the pharmacokinetics of maribavir based on age (18-79 years), gender, race (Caucasian, Black, Asian, or others), ethnicity (Hispanic/Latino or non-Hispanic/Latino), body weight (36 to 141 kg), mild to severe renal impairment (measured creatinine clearance ranging from 12 to 70 mL/min), or mild to moderate hepatic impairment (Child-Pugh Class A or B).
Pediatric Patients
The pharmacokinetics of maribavir in patients less than 18 years of age have not been evaluated.
Using modeling and simulation, the recommended dosing regimen is expected to result in comparable steady-state plasma exposures of maribavir in patients 12 years of age and older and weighing at least 35 kg as observed in adults [see Use in Specific Populations (8.4)].
Drug Interactions
Based on in vitro studies, the metabolism of maribavir is not mediated by CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP3A5, UGT1A4, UGT1A6, UGT1A10, or UGT2B15. The transport of maribavir is not mediated by organic anion transporting polypeptide (OATP)1B1, OATP1B3, or bile salt export pump (BSEP).
At clinically relevant concentrations, clinically significant interactions are not expected when LIVTENCITY is co-administered with substrates of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2E1, CYP2D6, CYP3A4; uridine diphosphate-glucuronosyltransferase (UGT)1A1, UGT1A4, UGT1A6, UGT1A9, UGT2B7; P-gp; BSEP; multidrug and toxin extrusion protein (MATE)1/2K; organic anion transporters (OAT)1 and OAT3; organic cation transporters (OCT)1 and OCT2; OATP1B1 and OATP1B3. In a clinical drug-drug interaction cocktail study, coadministration with maribavir had no effect on substrates of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4.
Drug interaction studies were performed with LIVTENCITY and other drugs likely to be co-administered for pharmacokinetic interactions. The effects of co-administration of other drugs on the pharmacokinetics of maribavir are summarized in Table 6, and the effects of maribavir on the pharmacokinetics of co-administered drugs are summarized in Table 7.
Dosing recommendations as a result of established and other potentially significant drug-drug interactions with LIVTENCITY are provided in Table 3 [see Drug Interactions (7.3)].
Table 6: Changes in Pharmacokinetics of LIVTENCITY in the Presence of Co-administered Drugs| Co-administered Drug and Regimen | LIVTENCITY Regimen | N | Geometric Mean Ratio (90% CI) of LIVTENCITY PK with/without Co-administered Drug [No Effect=1.00] |
|---|
| AUC | Cmax | Ctau tau is maribavir dosing interval: 12 hours |
|---|
| Anticonvulsants |
| Carbamazepine | 400 mg once daily | 800 mg twice daily / 400 mg twice daily | 200 | 1.40 (1.09, 1.67) | 1.53 (1.22, 1.79) | 1.05 (0.71, 1.40) |
| Phenobarbital | 100 mg once daily | 1,200 mg twice daily / 400 mg twice daily | 200 | 1.80 (1.18, 2.35) | 2.17 (1.69, 2.57) | 0.94 (0.22, 1.97) |
| Phenytoin | 300 mg once daily | 1,200 mg twice daily / 400 mg twice daily | 200 | 1.70 (1.06, 2.46) | 2.05 (1.49, 2.63) | 0.89 (0.26, 2.04) |
| Antimycobacterials |
| Rifampin | 600 mg once daily | 400 mg twice daily | 14 | 0.40 (0.36, 0.44) | 0.61 (0.52, 0.72) | 0.18 (0.14, 0.25) |
| Antifungals |
| Ketoconazole | 400 mg single dose | 400 mg single dose | 19 | 1.53 (1.44, 1.63) | 1.10 (1.01, 1.19) | - |
| Antacids |
| Aluminum hydroxide and magnesium hydroxide antacid | 20 mL Containing 800 mg aluminum hydroxide and 800 mg magnesium hydroxide single dose | 100 mg single dose | 15 | 0.89 (0.83, 0.96) | 0.84 (0.75, 0.94) | - |
Table 7: Drug Interactions: Changes in Pharmacokinetics for Co-administered Drug in the Presence of 400 mg Twice Daily LIVTENCITY| Co-administered Drug and Regimen | N | Geometric Mean Ratio (90% CI) of Co-administered Drug PK with/without LIVTENCITY [No Effect=1.00] |
|---|
| AUC | Cmax | Ctau |
|---|
| Immunosuppressants |
| Tacrolimus | stable dose, twice daily (total daily dose: 0.5-16 mg) | 20 | 1.51 (1.39, 1.65) | 1.38 (1.20, 1.57) | 1.57 (1.41, 1.74) |
| P-gp substrate |
| Digoxin | 0.5 mg single dose | 18 | 1.21 (1.10, 1.32) | 1.25 (1.13, 1.38) | - |
Mechanism of Action
The antiviral activity of maribavir is mediated by competitive inhibition of the protein kinase activity of human CMV enzyme pUL97, which results in inhibition of the phosphorylation of proteins. Maribavir inhibited wild-type pUL97 protein kinase in a biochemical assay with an IC50 value of 0.003 µM. Maribavir and its 5'-mono- and 5'-triphosphate derivatives at 100 µM had no significant effect on the incorporation of deoxynucleoside triphosphates by human CMV DNA polymerase. At a concentration of 100 µM, neither maribavir nor its 5′-triphosphate derivative inhibited CMV DNA polymerase delta, however the 5′-monophosphate derivative inhibited incorporation by polymerase delta of all 4 natural dNTPs by approximately 55%.
Antiviral Activity
Maribavir inhibited human CMV replication in virus yield reduction, DNA hybridization, and plaque reduction assays in human lung fibroblast cell line (MRC-5), human embryonic kidney (HEK), and human foreskin fibroblast (MRHF) cells. The EC50 values ranged from 0.03 to 2.2 µM depending on the cell line and assay endpoint. The cell culture antiviral activity of maribavir has also been evaluated against CMV clinical isolates. The median EC50 values were 0.1 µM (n=10, range 0.03-0.13 µM) and 0.28 µM (n=10, range 0.12-0.56 µM) using DNA hybridization and plaque reduction assays, respectively. No significant difference in EC50 values across the four human CMV glycoprotein B genotypes (N = 2, 1, 4, and 1 for gB1, gB2, gB3, and gB4, respectively) was seen.
Combination Antiviral Activity
When maribavir was tested in combination with other antiviral compounds, antagonism of the antiviral activity was seen in combination with ganciclovir. No antagonism was observed with cidofovir, foscarnet, letermovir and rapamycin at the drugs EC50 values. The pUL97 kinase activity inhibited by maribavir is necessary to activate valganciclovir/ganciclovir.
Viral Resistance
In Cell Culture
Selection of maribavir resistant virus in cell culture and genotypic plus phenotypic characterization of these has identified amino acid substitutions that confer reduced susceptibility to maribavir. Substitutions identified in pUL97 include L337M, V353A, L397R, T409M, and H411L/N/Y. These substitutions confer reductions in susceptibility that range from 3.5-fold to >200-fold. Substitutions were also identified in pUL27:R233S, W362R, W153R, L193F, A269T, V353E, L426F, E22stop, W362stop, 218delC, and 301-311del. These substitutions confer reductions in susceptibility that range from 1.7- to 4.8-fold.
In Clinical Studies
In Phase 2 Study 202 evaluating maribavir in 120 hematopoietic stem cell transplant (HSCT) or solid organ transplant (SOT) recipients with phenotypic resistance to valganciclovir/ganciclovir, DNA sequence analysis of a select region of pUL97 (amino acids 270 to 482) and pUL27 (amino acids 108 to 424) was performed on 34 paired virologic failure samples. There were 25 patients with treatment-emergent maribavir resistance-associated substitution(s) in pUL97 F342Y (4.5-fold reduction in susceptibility), T409M (78-fold reduction), H411L/Y (69- and 12-fold reduction) and/or C480F (224-fold reduction).
In Phase 3 Study 303 evaluating maribavir in patients with phenotypic resistance to valganciclovir/ganciclovir, DNA sequence analysis of the entire coding regions of pUL97 and pUL27 was performed on 134 paired sequences from maribavir-treated patients. The treatment-emergent pUL97 substitutions F342Y (4.5-fold), T409M (78-fold), H411L/N/Y (69-, 9-, and 12-fold, respectively), and/or C480F (224-fold) were detected in 58 subjects (47 subjects were on-treatment failures and 11 subjects were relapsers). One subject with the pUL27 L193F substitution (2.6-fold reduced susceptibility to maribavir) at baseline did not meet the primary endpoint.
Cross Resistance
Cross-resistance has been observed between maribavir and ganciclovir/valganciclovir in cell culture and in clinical studies.
pUL97 valganciclovir/ganciclovir resistance-associated substitutions F342S/Y, K355del, V356G, D456N, V466G, C480R, P521L, and Y617del reduce susceptibility to maribavir >4.5-fold. Other vGCV/GCV resistance pathways have not been evaluated for cross-resistance to maribavir. pUL54 DNA polymerase substitutions conferring resistance to vGCV/GCV, cidofovir, or foscarnet remained susceptible to maribavir.
Substitutions pUL97 F342Y and C480F are maribavir treatment-emergent resistance-associated substitutions that confer >1.5-fold reduced susceptibility to vGCV/GCV, a fold reduction that is associated with phenotypic resistance to vGCV/GCV. The clinical significance of this cross-resistance to vGCV/GCV for these substitutions has not been determined. Maribavir resistant virus remained susceptible to cidofovir and foscarnet. Additionally, there are no reports of any pUL27 maribavir resistance-associated substitutions being evaluated for vGCV/GCV, cidofovir, or foscarnet cross-resistance. Given the lack of resistance-associated substitutions for these drugs mapping to pUL27, cross-resistance is not expected for pUL27 maribavir substitutions.
Mutagenicity
Maribavir was negative in a bacterial mutation assay and the in vivo rat bone marrow micronucleus assay. Maribavir was positive in the absence of metabolic activation in the mouse lymphoma assay, and the results were equivocal in the presence of metabolic activation.
Impairment of Fertility
Although decreased sperm straight line velocity was observed in males (at maribavir exposures less than those observed in humans at the RHD), there were no effects on fertility in males or females in a combined oral fertility and embryo-fetal study in rats administered maribavir at up to 400 mg/kg/day [see Use in Specific Populations (8.1)].
Primary Efficacy Endpoint
The primary efficacy endpoint was confirmed CMV DNA level < LLOQ (i.e. <137 IU/mL) as assessed by COBAS® AmpliPrep/COBAS® TaqMan® CMV test) at the end of Week 8. The key secondary endpoint was CMV DNA level < LLOQ and CMV infection symptom control at the end of Study Week 8 with maintenance of this treatment effect through Study Week 16.
For the primary endpoint, LIVTENCITY was statistically superior to IAT (56% vs. 24%, respectively), as shown in Table 9.
Table 9: Primary Efficacy Endpoint Analysis at Week 8 (Randomized Set) in Trial 303 | LIVTENCITY 400 mg | IAT |
|---|
| Twice Daily N=235 n (%) | N=117 n (%) |
|---|
| CI=confidence interval; CMV=cytomegalovirus; IAT=investigator-assigned anti-CMV treatment; N=number of patients. |
| Primary Endpoint: Confirmed CMV DNA Level < LLOQ at Week 8 Confirmed CMV DNA level < LLOQ at the end of Week 8 (2 consecutive samples separated by at least 5 days with DNA levels < LLOQ [ie, <137 IU/mL]). | | |
| Responders | 131 (56) | 28 (24) |
| Adjusted difference in proportion of responders (95% CI) | 33 (23, 43) | |
| p-value: adjusted | <0.001 | |
The reasons for failure to meet the primary endpoint are summarized in Table 10.
Table 10: Analysis of Failures for Primary Efficacy Endpoint| Outcome at Week 8 | LIVTENCITY N=235 n (%) | IAT N=117 n (%) |
|---|
| CMV=Cytomegalovirus, IAT=Investigator-assigned anti-CMV Treatment, MBV=maribavir. |
| Percentages are based on the number of subjects in the Randomized Set. |
| Responders (Confirmed DNA Level < LLOQ) Confirmed CMV DNA level < LLOQ at the end of Week 8 (2 consecutive samples separated by at least 5 days with DNA levels < LLOQ [ie, <137 IU/mL]). | 131 (56) | 28 (24) |
| Non-responders: | 104 (44) | 89 (76) |
| Due to virologic failure: | 80 (34) | 42 (36) |
- •CMV DNA never < LLOQ
- •CMV DNA breakthrough
| 48 (20) 32 (14) | 35 (30) 7 (6) |
| Due to drug/study discontinuation: | 21 (9) | 44 (38) |
- •Adverse events
- •Deaths
- •Withdrawal of consent
- •Other reasons
Other reasons= other reasons not including adverse events, deaths and lack of efficacy, withdrawal of consent, and non-compliance.
| 8 (3) 10 (4) 1 (<1) 2 (1) | 26 (22) 3 (3) 9 (8) 6 (5) |
| Due to other reasons but remained on study Includes subjects who completed study assigned treatment and were non-responders. | 3 (1) | 3 (3) |
The treatment effect of LIVTENCITY was consistent across transplant type, age group, and the presence of CMV syndrome/disease at baseline. However, LIVTENCITY was less effective against subjects with increased CMV DNA levels (≥50,000 IU/mL) and subjects with absence of genotypic resistance (see Table 11).
Table 11: Responders by Subgroup in Trial 303 | LIVTENCITY 400 mg Twice Daily | IAT |
|---|
| N=235 | N=117 |
|---|
| n/N | % | n/N | % |
|---|
| Transplant type |
| SOT | 79/142 | 56 | 18/69 | 26 |
| HSCT | 52/93 | 56 | 10/48 | 21 |
| Baseline CMV DNA viral load |
| Low (<9,100 IU/mL) | 95/153 | 62 | 21/85 | 25 |
| Intermediate (≥9,100 to <91,000 IU/mL) | 32/68 | 47 | 5/25 | 20 |
| ≥9,100 to <50,000 IU/mL | 29/59 | 49 | 4/20 | 20 |
| ≥50,000 to <91,000 IU/mL | 3/9 | 33 | 1/5 | 20 |
| High (≥91,000 IU/mL) | 4/14 | 29 | 2/7 | 29 |
| Genotypic resistance to other anti-CMV agents |
| Yes | 76/121 | 63 | 14/69 | 20 |
| No | 42/96 | 44 | 11/34 | 32 |
| CMV syndrome/disease at baseline |
| Yes | 10/21 | 48 | 1/8 | 13 |
| No | 121/214 | 57 | 27/109 | 25 |
| Age Group |
| 18 to 44 years | 28/55 | 51 | 8/32 | 25 |
| 45 to 64 years | 71/126 | 56 | 19/69 | 28 |
| ≥65 years | 32/54 | 59 | 1/16 | 6 |
Secondary Endpoints
Table 12 shows results of the secondary endpoint, achievement of CMV DNA level < LLOQ and symptom controla at Week 8 with maintenance through Week 16.
Table 12. Achievement of CMV DNA Level < LLOQ and CMV Infection Symptom Control at Week 8, With Maintenance Through Week 16CMV infection symptom control was defined as resolution or improvement of tissue-invasive disease or CMV syndrome for symptomatic patients at baseline, or no new symptoms for patients who were asymptomatic at baseline
| LIVTENCITY 400 mg | IAT |
|---|
| Twice Daily N=235 n (%) | N=117 n (%) |
|---|
| Responders | 44 (19) | 12 (10) |
| Adjusted difference in proportion of responders (95% CI) | 9 (2,17) | |
| p-value: adjusted | 0.013 | |
Virologic relapse during follow-up period: After the end of treatment phase, 65/131 (50%) of subjects in the LIVTENCITY group and 11/28 (39%) subjects in the IAT group who achieved CMV DNA level < LLOQ experienced virologic relapse during the follow-up period. Most of the relapses 58/65 (89%) in LIVTENCITY group and 11/11 (100% in IAT group)] occurred within 4 weeks after study drug discontinuation; and the median time to relapse after CMV DNA level < LLOQ was 15 days (range 7, 71) in the LIVTENCITY group and 15 days (range 7, 29) in the IAT group [see Warnings and Precautions (5.2) and Microbiology (12.4)].
New onset symptomatic CMV infection: For the entire study period, a similar percentage of subjects in each treatment group developed new onset symptomatic CMV infection (LIVTENCITY 6% [14/235]; IAT 6% [7/113]).
Overall mortality: All-cause mortality was assessed for the entire study period. A similar percentage of subjects in each treatment group died during the trial (LIVTENCITY 11% [27/235]; IAT 11% [13/117]).
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