CLINICAL PHARMACOLOGY
Mechanism Of Action
Peramivir is an antiviral drug with activity against
influenza virus [see Microbiology].
Cardiac Electrophysiology
At twice the maximum recommended dose, RAPIVAB did not
prolong the QTc interval to any clinically relevant extent.
Pharmacokinetics
The pharmacokinetics of RAPIVAB was evaluated in Phase 1 trials
in adults. The pharmacokinetic parameters following intravenous administration
of RAPIVAB (0.17 to 2 times the recommended dose) showed a linear relationship
between dose and exposure parameters (Cmax and AUC).
Following intravenous administration of a single dose of
RAPIVAB 600 mg over 30 minutes, a maximum serum concentration (Cmax) of 46,800
ng/mL (46.8 μg/mL) was reached at the end of infusion. AUC0-∞ values
were 102,700 ng•hr/mL.
Distribution
In vitro binding of peramivir to human plasma proteins is
less than 30%.
Based on a population pharmacokinetic analysis, the
central volume of distribution was 12.56 L.
Metabolism And Elimination
Peramivir is not a substrate for CYP enzymes, does not
affect glucuronidation, and is not a substrate or inhibitor of P-glycoprotein
mediated transport.
Peramivir is not significantly metabolized in humans.
The elimination half-life of RAPIVAB following IV
administration to healthy subjects of 600 mg as a single dose is approximately
20 hours. The major route of elimination of RAPIVAB is via the kidney. Renal
clearance of unchanged peramivir accounts for approximately 90% of total
clearance. Negligible accumulation was observed following multiple doses,
either once or twice daily, for up to 10 days.
Specific Populations
Race
Pharmacokinetics of peramivir was evaluated primarily in
Caucasians and Asians. Based on a population pharmacokinetic analysis including
race as a covariate, volume of distribution was dependent on weight and Asian
race. No dose adjustment is required based on weight or Asian race.
Gender
Peramivir pharmacokinetics was similar in male and female
subjects.
Pediatric Patients
The pharmacokinetics of peramivir has been evaluated in a
study in pediatric subjects 2 to 17 years of age with acute uncomplicated
influenza. Pharmacokinetic sampling in this study was limited to approximately
3 hours after administration of peramivir. Pharmacokinetics of peramivir in
subjects 13 to 17 years of age was similar to those in adult subjects, with a Cmax
of 54,300 ng/mL and AUC0-last of 72,400 ng•h/mL after administration of a
single 600 mg dose. Pharmacokinetics of peramivir in subjects 2 to 12 years of
age (Cmax of 61,300 ng/mL and AUC0-last of 81,700 ng•h/mL) administered a
single 12 mg/kg dose was also similar to that in adult subjects administered a
single 600 mg dose.
Geriatric Patients
Peramivir pharmacokinetics in elderly subjects was
similar to non-elderly subjects. Peak concentrations of peramivir after a
single 4 mg/kg IV dose were approximately 10% higher in elderly subjects when
compared to young adults (22,647 vs 20,490 ng/mL, respectively). Exposure (AUC0-12)
to peramivir at steady state was roughly 34% higher in elderly subjects
compared to young adults (61,572 vs 46,000 ng•hr/mL, respectively). Dose
adjustment is not required for elderly patients.
Patients With Impaired Renal Function
A trial was conducted in adult subjects with various
degrees of renal impairment. When compared to a concurrent cohort with normal
renal function, no change in mean Cmax was observed (6 subjects per cohort).
However, mean AUC0-∞ after a single 2 mg/kg IV dose was increased by 28%,
by 302%, and by 412% in subjects with creatinine clearance 50-79, 3049, and
10-29 mL/min, respectively.
Hemodialysis was effective in reducing systemic exposure
of peramivir by 73% to 81%.
A reduced dose of RAPIVAB is recommended for patients
with creatinine clearance below 50 mL/min [see DOSAGE AND ADMINISTRATION].
The pharmacokinetics of peramivir has not been studied in
pediatric subjects with renal impairment. Given that the pharmacokinetics in
pediatric subjects is comparable to that observed in adults, the same
proportional dose reduction in pediatric patients is recommended [see DOSAGE
AND ADMINISTRATION].
Patients With Hepatic Impairment
The pharmacokinetics of peramivir in subjects with
hepatic impairment has not been studied. No clinically relevant alterations to
peramivir pharmacokinetics are expected in patients with hepatic impairment
based on the route of peramivir elimination.
Assessment Of Drug Interactions
The potential for CYP mediated interactions involving
RAPIVAB with other drugs is low, based on the known elimination pathway of
RAPIVAB, and data from in vitro studies indicating RAPIVAB does not induce or
inhibit cytochrome P450.
There was no evidence of drug-drug interactions when
RAPIVAB was administered with oral rimantadine, oseltamivir, or oral
contraceptives containing ethinyl estradiol and levonorgestrel; or when
peramivir IM was administered with oral probenecid.
RAPIVAB is primarily cleared in the urine by glomerular
filtration.
Microbiology
Mechanism Of Action
Peramivir is an inhibitor of influenza virus
neuraminidase, an enzyme that releases viral particles from the plasma membrane
of infected cells. The median neuraminidase inhibitory activities (IC50 values)
of peramivir in biochemical assays against influenza A/H1N1 virus, influenza
A/H3N2 virus, and influenza B virus clinical isolates were 0.16 nM (n=44; range
0.01-1.77 nM), 0.13 nM (n=32; range 0.05-11 nM), and 0.99 nM (n=39; range
0.04-54.2 nM), respectively, in a neuraminidase assay with a fluorescently
labeled MUNANA substrate.
Antiviral Activity
The antiviral activity of peramivir against laboratory
strains and clinical isolates of influenza virus was determined in cell
culture. The concentrations of peramivir required for inhibition of influenza
virus in cell culture varied depending on the assay method used and the virus
tested. The median 50% effective concentrations (EC50 values) of peramivir in
cell culture assays were 2.6 nM (n=13; range 0.09-21 nM), 0.08 nM (n=17; range
0.01-1.9 nM) and 4.8 nM (n=11; range 0.06-120 nM) for influenza A/H1N1 virus,
A/H3N2 virus, and B virus strains, respectively.
The relationship between the antiviral activity in cell
culture, inhibitory activity in the neuraminidase assay, and the inhibition of
influenza virus replication in humans has not been established.
Resistance
Cell Culture
Influenza A and B virus isolates with reduced
susceptibility to peramivir were recovered by serial passage of virus in cell
culture in the presence of increasing concentrations of peramivir. Reduced
susceptibility of influenza virus to inhibition by peramivir may be conferred
by amino acid substitutions in the viral neuraminidase or hemagglutinin
proteins (Table 4).
Table 4: Amino Acid Substitutions Selected by
Peramivir in Cell Culture Studies
Protein |
Type/Subtype |
A/H1N1* |
A/H3N2† |
B‡ |
HA§ |
D125S, R208K |
N63K, G78D, N145D, K189E |
T139N, G141E, R162M, D195N, T198N, Y319H |
NA |
N58D, I211T, H275Y |
- |
H273Y |
* Numbering based on A/California/04/2009
† Numbering based on A/Texas/50/2012
‡ Numbering based on B/Massachusetts/02/2012
§ Numbering begins after the predicted signal peptide. |
In vivo
Influenza A and B virus isolates with amino acid
substitutions associated with reduced susceptibility to peramivir were observed
in clinical isolates collected during clinical trials with peramivir (Table 5).
Amino acid substitutions have also been observed in viral isolates sampled
during community surveillance studies which may be associated with reduced
susceptibility to peramivir (Table 5). The clinical impact of this reduced
susceptibility is unknown and may be strain-dependent.
Table 5: Neuraminidase Amino Acid Substitutions
Associated with Reduced Susceptibility to Peramivir in Clinical Virus Isolates
Protein |
|
Type / Subtype |
|
Influenza A/H1N1* |
Influenza A/H3N2† |
Influenza B‡ |
NA |
Clinical Trial |
R152K, H275Y |
R292K, N294S |
- |
Community Surveillance Studies |
G147R, I223R/V, S247N, H275Y |
E119V, Q136K, D151A/E/G/N/V |
P139S, D197E/N/Y, I221T/V, R374K |
* Numbering based on A/California/04/2009
† Numbering based on A/Texas/50/2012
‡ Numbering based on B/Massachusetts/02/2012 |
Circulating seasonal influenza strains expressing
neuraminidase resistance-associated substitutions have been observed in
individuals who have not received RAPIVAB. Prescribers should consider
available information from the CDC on influenza virus drug susceptibility
patterns and treatment effects when deciding whether to use RAPIVAB.
Cross Resistance
Cross-resistance between peramivir, oseltamivir and
zanamivir was observed in neuraminidase biochemical assays and cell culture
assays. The amino acid substitutions that resulted in reduced susceptibility to
peramivir and either oseltamivir or zanamivir are summarized in Table 6. The
clinical impact of this reduced susceptibility is unknown and may be
strain-dependent.
Table 6: Summary of Amino Acid Substitutions with
Cross-Resistance between Peramivir and Oseltamivir or Zanamivir in
Susceptibility Assays
|
|
Type/ Subtype |
Protein |
A/H1N1* |
A/H3N2† |
B‡ |
Oseltamivir |
HA§ |
- |
N63K, N145D |
- |
NA |
E119V, D151G/N, R152K, Y155H, D199G, I223R/T/V, S247N, G249R+I267V, H275Y, N295S, Q313R, R368K, I427T |
E119I/V, I222V, S247P, R292K, N294S |
P139S, G140R, D197E/N/Y, I221T/V, H273Y, R374K, G407S |
Zanamivir |
HA§ |
- |
N63K, N145D |
- |
NA |
Q136K, R152K, Y155H, D199G, I223T, S247N, G249R+I267V, N295S, Q313R, R368K, I427T |
E119G/V, T148I, D151A/G/N/V, I222V, S247P, R292K, N294S |
E117A/D/G, P139S, R150K, D197E/N/Y, R292K, R374K, G407S |
* Numbering based on A/California/04/2009
† Numbering based on A/Texas/50/2012
‡ Numbering based on B/Massachusetts/02/2012
§ Numbering begins after the predicted signal peptide. |
No single amino acid substitution has been identified
that could confer cross-resistance between the neuraminidase inhibitor class
(peramivir, oseltamivir, zanamivir) and the M2 ion channel inhibitor class
(amantadine, rimantadine). However, a virus may carry a neuraminidase inhibitor
resistance-associated substitution in neuraminidase and an M2 ion channel
inhibitor resistance-associated substitution in M2 and may therefore be
resistant to both classes of inhibitors. The clinical relevance of phenotypic
cross-resistance evaluations has not been established and may be
strain-dependent.
Immune Response
No influenza vaccine/peramivir interaction study has been
conducted.
Animal Toxicology And/Or Pharmacology
Peramivir caused renal tubular necrosis and abnormal
renal function in rabbits. Toxicities included tubular dilatation and necrosis
with protein casts in cortical areas, dilated tubules with mineralization in
corticomedullary junction areas, and multifocal tubular regeneration. The
rabbit appeared to be the sensitive species for peramivir renal toxicity, which
was noted at exposures approximately 2-to 4-fold those in humans at the
clinically recommended dose.
Clinical Studies
Acute Uncomplicated Influenza In Adults
Study 621 was a randomized, multicenter, blinded trial
conducted in Japan that evaluated a single intravenous administration of
RAPIVAB 300 mg, RAPIVAB 600 mg, or placebo administered over 30 minutes in
subjects 20 to 65 years of age with acute uncomplicated influenza. Subjects
were eligible if they had fever greater than or equal to 38°C (axillary) and a
positive rapid antigen test for influenza virus, accompanied by at least two
symptoms (cough, nasal symptoms, sore throat, myalgia, chills/sweats, malaise,
fatigue, or headache). In addition, all subjects enrolled were allowed to take
fever-reducing medications.
Study treatment was started within 48 hours of onset of
symptoms. Subjects participating in the trial were required to self-assess
their influenza symptoms as “none’, ‘mild’, ‘moderate’, or ‘severe’ twice
daily. The primary endpoint, time to alleviation of symptoms, was defined as
the number of hours from initiation of study drug until the start of the 24
hour period in which all seven symptoms of influenza (cough, sore throat, nasal
congestion, headache, feverishness, myalgia and fatigue) were either absent or
present at a level no greater than mild for at least 21.5 hours.
The overall efficacy population, consisting of subjects
with confirmed influenza and administered study drug, totaled 297 subjects.
Among the 98 subjects enrolled in the RAPIVAB 600 mg dose group, the mean age
was 34 years; 55% were male; 34% were smokers; 99% were infected with influenza
A virus and 1% were infected with influenza B virus. The majority of subjects
(53%) had influenza illness lasting less than 24 hours at the time of
presentation.
Overall, subjects receiving RAPIVAB 600 mg experienced
alleviation of their combined influenza symptoms a median of 21 hours sooner
than those receiving placebo. The median time to recovery to normal temperature
(less than 37°C) in the 600 mg group was approximately 12 hours sooner compared
to placebo.
Insufficient numbers of subjects infected with influenza
B virus were enrolled to determine efficacy of RAPIVAB in this influenza type.
Acute Uncomplicated Influenza In Pediatric Subjects
Study 305 was a randomized, multicenter, open-label,
active-controlled trial to evaluate the safety, pharmacokinetics and efficacy
of a single intravenous dose of RAPIVAB administered for a minimum of 15
minutes in subjects 2 to 17 years of age with acute uncomplicated influenza who
had fever greater than or equal to 37.8°C (oral) with at least one respiratory
symptom (cough or rhinitis) or a positive influenza rapid antigen test. Study
treatment was started within 48 hours of onset of symptoms. Subjects were
randomized to receive RAPIVAB 600 mg (13 to 17 years of age), RAPIVAB 12 mg/kg
up to a maximum dose of 600 mg (2 to 12 years of age), or oral oseltamivir BID
for 5 days. In addition, all enrolled subjects were allowed to take
fever-reducing medications.
The overall efficacy population, consisting of subjects
with confirmed influenza who were administered study drug, totaled 84 subjects.
Among the 69 subjects treated with RAPIVAB, the median age was 7.9 years; 55%
were male; 58% were infected with influenza A virus, 36% were infected with
influenza B virus, and 6% were co-infected with influenza A and B viruses.
The primary endpoint was the safety of peramivir compared
to oseltamivir as measured by adverse events, laboratory analysis, vital signs
and physical exams. Secondary endpoints included efficacy outcomes such as time
to resolution of influenza symptoms and time to resolution of fever; however,
the trial was not powered to detect statistically significant differences in
these secondary endpoints.
Subjects receiving RAPIVAB experienced a median time to
alleviation of their combined influenza symptoms of 79 hours (interquartile
range: 34-122 hours) compared to 107 hours (interquartile range: 57-145 hours)
in subjects receiving oseltamivir. The median time to recovery to normal
temperature (less than 37°C) was 40 hours (interquartile range: 19-68 hours)
and 28 hours (interquartile range: 15-41 hours) in subjects receiving RAPIVAB
and oseltamivir, respectively [see Use In Specific Populations].
Serious Influenza Requiring Hospitalization
The efficacy of RAPIVAB could not be established in
patients with serious influenza requiring hospitalization [see INDICATIONS AND USAGE].
A randomized, double-blind, multicenter,
placebo-controlled trial (Study 301) was conducted in 398 subjects with serious
influenza requiring hospitalization. Subjects were randomized to receive
RAPIVAB 600 mg daily for 5 days plus standard of care versus standard of care
plus placebo within 72 hours of start of symptoms. The primary endpoint was
time to clinical resolution defined as the time in hours from initiation of
study treatment until resolution of at least 4 of 5 signs (temperature, oxygen
saturation, respiration rate, heart rate, or systolic blood pressure),
maintained for at least 24 hours. RAPIVAB plus standard of care did not improve
median time to clinical resolution compared with standard of care alone.