CLINICAL PHARMACOLOGY
Mechanism Of Action
Renin is secreted by the kidney
in response to decreases in blood volume and renal perfusion. Renin cleaves
angiotensinogen to form the inactive decapeptide angiotensin I (Ang I). Ang I
is converted to the active octapeptide angiotensin II (Ang II) by ACE and
non-ACE pathways. Ang II is a powerful vasoconstrictor and leads to the release
of catecholamines from the adrenal medulla and prejunctional nerve endings. It
also promotes aldosterone secretion and sodium reabsorption. Together, these
effects increase blood pressure. Ang II also inhibits renin release, thus
providing a negative feedback to the system. This cycle, from renin through
angiotensin to aldosterone and its associated negative feedback loop, is known
as the renin-angiotensin-aldosterone system (RAAS). Aliskiren is a direct renin
inhibitor, decreasing plasma renin activity (PRA) and inhibiting the conversion
of angiotensinogen to Ang I. Whether aliskiren affects other RAAS components,
e.g., ACE or non-ACE pathways, is not known.
All agents that inhibit the
RAAS, including renin inhibitors, suppress the negative feedback loop, leading
to a compensatory rise in plasma renin concentration. When this rise occurs
during treatment with ACEIs and ARBs, the result is increased levels of PRA.
During treatment with aliskiren, however, the effect of increased renin levels
is blocked so that PRA, Ang I and Ang II are all reduced, whether aliskiren is
used as monotherapy or in combination with other antihypertensive agents.
Pharmacodynamics
In placebo-controlled clinical
trials, PRA was decreased in a range of 50% to 80%. This reduction in PRA was
not dose-related and did not correlate with blood pressure reductions. The
clinical implications of the differences in effect on PRA are not known.
Pharmacokinetics
Aliskiren is poorly absorbed
(bioavailability about 2.5%) with an approximate accumulation half-life of 24
hours. Steady state blood levels are reached in about 7 to 8 days.
Absorption And Distribution
Following oral administration,
peak plasma concentrations of aliskiren are reached within 1 to 3 hours. When
taken with a high-fat meal, mean AUC and Cmax of aliskiren are decreased by 71%
and 85% respectively. In the clinical trials of aliskiren, it was administered
without requiring a fixed relation of administration to meals.
Metabolism And Elimination
About one-fourth of the
absorbed dose appears in the urine as parent drug. How much of the absorbed
dose is metabolized is unknown. Based on the in vitro studies, the major enzyme
responsible for aliskiren metabolism appears to be CYP3A4. Aliskiren does not
inhibit the CYP450 isoenzymes (CYP 1A2, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A) or
induce CYP3A4.
Transporters
Pgp (MDR1/Mdr1a/1b) was found
to be the major efflux system involved in intestinal absorption and elimination
via biliary excretion of aliskiren in preclinical studies. The potential for
drug interactions at the Pgp site will likely depend on the degree of
inhibition of this transporter.
Drug Interactions
The effect of coadministered
drugs on the pharmacokinetics of aliskiren and vice versa, were studied in
several single-and multiple-dose studies. Pharmacokinetic measures indicating
the magnitude of these interactions are presented in Figure 1 (impact of
coadministered drugs on aliskiren) and Figure 2 (impact of aliskiren on
coadministered drugs).
Figure 1: The Impact of Coadministered Drugs on the
Pharmacokinetics of Aliskiren
*Ketoconazole: A 400 mg once
daily dose was not studied, but would be expected to increase aliskiren blood
levels further.
**Ramipril, valsartan,
irbesartan: In general, avoid combined use of aliskiren with ACE inhibitors or
ARBs, particularly in patients with CrCl less than 60 mL/min [see DRUG
INTERACTIONS].
Warfarin: There was no clinically significant effect of a
single dose of warfarin 25 mg on the pharmacokinetics of aliskiren.
Figure 2: The Impact of
Aliskiren on the Pharmacokinetics of Coadministered Drugs
*Furosemide: Patients receiving
furosemide could find its effects diminished after starting aliskiren. In
patients with heart failure, coadministration of aliskiren (300 mg/day) reduced
plasma AUC and Cmax of oral furosemide (60 mg/day) by 17% and 27%,
respectively, and reduced 24-hour urinary furosemide excretion by 29%. This
change in exposure did not result in statistically significant difference in
total urine volume and urinary sodium excretion over 24 hours. However, a
transient decrease in urinary sodium excretion and urine volume effects up to
12 hours were observed when furosemide was coadministered with aliskiren 300
mg/day.
**Ramipril, valsartan: In
general, avoid combined use of aliskiren with ACE inhibitors or ARBs,
particularly in patients with CrCl less than 60 mL/min [see DRUG
INTERACTIONS].
Special Populations
Renally Impaired Patients
Aliskiren was evaluated in
patients with varying degrees of renal insufficiency. The rate and extent of
exposure (AUC and Cmax) of aliskiren in subjects with renal impairment did not
show a consistent correlation with the severity of renal impairment. Adjustment
of the starting dose is not required in these patients [see WARNINGS AND
PRECAUTIONS].
The pharmacokinetics of
aliskiren following administration of a single oral dose of 300 mg was
evaluated in patients with End Stage Renal Disease (ESRD) undergoing
hemodialysis. When compared to matched healthy subjects, changes in the rate
and extent of aliskiren exposure (Cmax and AUC) in ESRD patients undergoing
hemodialysis were not clinically significant.
Timing of hemodialysis did not
significantly alter the pharmacokinetics of aliskiren in ESRD patients.
Therefore, no dose adjustment is warranted in ESRD patients receiving
hemodialysis.
Hepatically Impaired Patients
The pharmacokinetics of
aliskiren were not significantly affected in patients with mild to severe liver
disease. Consequently, adjustment of the starting dose is not required in these
patients.
Pediatric Patients
The pharmacokinetics of
aliskiren were evaluated in an 8-day pharmacokinetic study in 39 pediatric
hypertensive patients 6 to 17 years of age. Aliskiren was given as daily doses
of 2 or 6 mg/kg, administered as mini-tablets (3.125 mg oral pellets). The
pharmacokinetic parameters of aliskiren were similar to those in adults, and the
results of this study do not suggest that age or gender have any significant
effect on aliskiren systemic exposure in patients 6 to 17 years of age.
Exposure decreases with increase in body weight.
In an 8-week randomized double
blind study with aliskiren monotherapy in 267 pediatric hypertensive patients 6
to 17 years of age [see Clinical Studies], fasting trough aliskiren
concentrations at Day 28 demonstrated similar drug trough exposure levels to
those observed in other trials using similar aliskiren doses in both adults and
children.
Geriatric Patients
Exposure (measured by AUC) is
increased in elderly patients 65 years and older. Adjustment of the starting
dose is not required in these patients.
Race
The pharmacokinetic differences
between blacks, Caucasians, and Japanese are minimal.
Animal Toxicology And/Or Pharmacology
Reproductive Toxicology Studies
Reproductive toxicity studies of aliskiren hemifumarate
did not reveal any evidence of teratogenicity at oral doses up to 600 mg
aliskiren/kg/day (20 times the MRHD of 300 mg/day on a mg/m² basis) in pregnant
rats or up to 100 mg aliskiren/kg/day (7 times the MRHD on a mg/m² basis) in
pregnant rabbits. Fetal birth weight was adversely affected in rabbits at 50
mg/kg/day (3.2 times the MRHD on a mg/m² basis). Aliskiren was present in
placenta, amniotic fluid and fetuses of pregnant rabbits.
Juvenile Animal Studies
Juvenile toxicity studies
indicated increased systemic exposure to aliskiren 85-to 385-fold in 14-day and
8-day old rats respectively, compared with adult rats. The mdr1 gene expression
in juvenile rats was also significantly lower when compared to adult rats. The
increased aliskiren exposure in juvenile rats appears to be mainly attributed
to lack of maturation of P-gp. The overexposure in juvenile rats was associated
with high mortality. [see Use In Specific Populations].
Clinical Studies
Aliskiren Monotherapy
The antihypertensive effects of
Tekturna have been demonstrated in 6 randomized, double-blind,
placebo-controlled 8week clinical trials in patients with mild-to-moderate
hypertension. The placebo response and placebo-subtracted changes from baseline
in seated trough cuff blood pressure are shown in Table 2.
Table 2: Reductions in
Seated Trough Cuff Blood Pressure (mmHg systolic/diastolic) in the
Placebo-Controlled Studies
Study |
Placebo mean change |
Aliskiren daily dose, mg |
75 |
150 |
300 |
600 |
Placebo-subtracted |
Placebo-subtracted |
Placebo-subtracted |
Placebo-subtracted |
1 |
2.9/3.3 |
5.7/4* |
5.9/4.5* |
11.2/7.5* |
- |
2 |
5.3/6.3 |
- |
6.1/2.9* |
10.5/5.4* |
10.4/5.2* |
3 |
10/8.6 |
2.2/1.7 |
2.1/1.7 |
5.1/3.7* |
-- |
4 |
7.5/6.9 |
1.9/1.8 |
4.8/2* |
8.3/3.3* |
-- |
5 |
3.8/4.9 |
-- |
9.3/5.4* |
10.9/6.2* |
12.1/7.6* |
6 |
4.6/4.1 |
-- |
-- |
8.4/4.9† |
-- |
*pvalue less than 0.05 versus
placebo by ANCOVA with Dunnett's procedure for multiple comparisons
†p value less than 0.05 versus placebo by ANCOVA for the pairwise comparison. |
The studies included
approximately 2,730 patients given doses of 75 to 600 mg of aliskiren and 1,231
patients given placebo. As shown in Table 1, there is some increase in response
with administered dose in all studies, with reasonable effects seen at 150mg to
300 mg, and no clear further increases at 600 mg. A substantial proportion (85%
to 90%) of the blood pressure-lowering effect was observed within 2 weeks of
treatment. Studies with ambulatory blood pressure monitoring showed reasonable
control throughout the interdosing interval; the ratios of mean daytime to mean
nighttime ambulatory BP range from 0.6 to 0.9.
Patients in the
placebo-controlled trials continued open-label aliskiren for up to 1 year. A
persistent blood pressure-lowering effect was demonstrated by a randomized
withdrawal study (patients randomized to continue drug or placebo), which
showed a statistically significant difference between patients kept on
aliskiren and those randomized to placebo. With cessation of treatment, blood
pressure gradually returned toward baseline levels over a period of several
weeks. There was no evidence of rebound hypertension after abrupt cessation of
therapy.
Aliskiren lowered blood
pressure in all demographic subgroups, although black patients tended to have
smaller reduction than Caucasians and Asians, as has been seen with ACEIs and
ARBs.
There are no studies of
Tekturna or members of the direct renin inhibitors demonstrating reductions in
cardiovascular risk in patients with hypertension.
Aliskiren In Combination With Other
Antihypertensives
Hydrochlorothiazide (HCTZ)
Aliskiren 75, 150, and 300 mg
and HCTZ 6.25, 12.5, and 25 mg were studied alone and in combination in an
8-week, 2,776-patient, randomized, double-blind, placebo-controlled,
parallel-group, 15-arm factorial study. Blood pressure reductions with the
combinations were greater than the reductions with the monotherapies as shown
in Table 3.
Table 3: Placebo-Subtracted
Reductions in Seated Trough Cuff Blood Pressure (mmHg systolic/diastolic) in
Combination with Hydrochlorothiazide
Aliskiren, mg |
Placebo mean change |
Hydrochlorothiazide, mg |
0 |
6.25 |
12.5 |
25 |
Placebo- subtracted |
Placebo- subtracted |
Placebo- subtracted |
Placebo- subtracted |
0 |
7.5/6.9 |
-- |
3.5/2.1 |
6.4/3.2 |
6.8/2.4 |
75 |
-- |
1.9/1.8 |
6.8/3.8 |
8.2/4.2 |
9.8/4.5 |
150 |
-- |
4.8/2 |
7.8/3.4 |
10.1/5 |
12/5.7 |
300 |
-- |
8.3/3.3 |
-- |
12.3/7 |
13.7/7.3 |
Valsartan
Aliskiren 150 mg and 300 mg and
valsartan 160 mg and 320 mg were studied alone and in combination in an 8-week,
1,797-patient, randomized, double-blind, placebo-controlled, parallel-group,
4-arm, dose-escalation study. The dosages of aliskiren and valsartan were started
at 150 mg and 160 mg, respectively, and increased at 4 weeks to 300 mg and 320
mg, respectively. Seated trough cuff blood pressure was measured at baseline,
4, and 8 weeks. Blood pressure reductions with the combinations were greater
than the reductions with the monotherapies as shown in Table 4. In general, the
combination of aliskiren and angiotensin receptor blocker should be avoided [see
CONTRAINDICATIONS, WARNINGS AND PRECAUTIONS, and DRUG
INTERACTIONS].
Table 4: Placebo-Subtracted
Reductions in Seated Trough Cuff Blood Pressure (mmHg systolic/diastolic) in
Combination with Valsartan
Aliskiren, mg |
Placebo mean change |
Valsartan, mg |
0 |
160 |
320 |
0 |
4.6/4.1* |
-- |
5.6/3.9 |
8.2/5.6 |
150 |
-- |
5.4/2.7 |
10.0/5.7 |
-- |
300 |
-- |
8.4/4.9 |
-- |
12.6/8.1 |
*The placebo change is 5.2/4.8 for week 4 endpoint which was used for the
dose groups containing aliskiren 150 mg or valsartan 160 mg. |
Amlodipine
Aliskiren 150 mg and 300 mg and
amlodipine besylate 5 mg and 10 mg were studied alone and in combination in an
8week, 1,685-patient, randomized, double-blind, placebo-controlled,
multifactorial study. Treatment with aliskiren and amlodipine resulted overall
in significantly greater reductions in diastolic and systolic blood pressure
compared to the respective monotherapy components as shown in Table 5.
Table 5: Placebo-Subtracted
Reductions in Seated Trough Cuff Blood Pressure (mmHg systolic/diastolic) in
Combination with Amlodipine
Aliskiren, mg |
Placebo mean change |
Amlodipine, mg |
0 |
5 |
10 |
0 |
6.8/5.4 |
-- |
9.0/5.6 |
14.3/8.5 |
150 |
-- |
3.9/2.6 |
13.9/8.6 |
17.1/10.8 |
300 |
-- |
8.6/4.9 |
15.0/9.6 |
16.4/11.1 |
Aliskiren In Patients With Diabetes
Treated With ARB Or ACEI (ALTITUDE study)
Patients with diabetes with
renal disease (defined either by the presence of albuminuria or reduced GFR)
were randomized to aliskiren 300 mg daily (n=4296) or placebo (n=4310). All
patients were receiving background therapy with an ARB or ACEI. The primary
efficacy outcome was the time to the first event of the primary composite
endpoint consisting of cardiovascular death, resuscitated sudden death,
nonfatal myocardial infarction, nonfatal stroke, unplanned hospitalization for
heart failure, onset of end stage renal disease, renal death, and doubling of
serum creatinine concentration from baseline sustained for at least 1 month.
After a median follow-up of about 32 months, the trial was terminated early for
lack of efficacy. Higher risk of renal impairment, hypotension and hyperkalemia
was observed in aliskiren compared to placebo-treated patients, as shown in
Table 6.
Table 6: Incidence of
Selected Adverse Events During the Treatment Phase in ALTITUDE
|
Aliskiren
N=4272 |
Placebo
N=4285 |
Serious Adverse Events* (%) |
Adverse Events (%) |
Serious Adverse Events* (%) |
Adverse Events (%) |
Renal impairment† |
5.7 |
14.5 |
4.3 |
12.4 |
Hypotension†† |
2.3 |
19.9 |
1.9 |
16.3 |
Hyperkalemia††† |
1.0 |
38.9 |
0.5 |
28.8 |
†renal failure, renal failure
acute, renal failure chronic, renal impairment
††dizziness, dizziness postural, hypotension, orthostatic hypotension,
presyncope, syncope
†††Given the variable baseline potassium levels of patients with renal
insufficiency on dual RAAS therapy, the reporting of adverse event of
hyperkalemia was at the discretion of the investigator.
* A Serious Adverse Event (SAE) is defined as: an event which is fatal or
life-threatening, results in persistent or significant disability/incapacity,
constitutes a congenital anomaly/birth defect, requires inpatient
hospitalization or prolongation of existing hospitalization, or is medically
significant (i.e., defined as an event that jeopardizes the patient or may
require medical or surgical intervention to prevent one of the outcomes
previously listed). |
The risk of stroke (3.4% aliskiren versus 2.7% placebo) and death (8.4% aliskiren versus 8.0% placebo)
were also numerically higher in aliskiren treated patients.
Pediatric Hypertension
The efficacy of aliskiren was evaluated in an 8-week
randomized, double-blind trial in 267 pediatric hypertensive patients 6 to 17
years of age (Study CSPP100A2365; NCT01150357). The majority of patients (82%)
had primary hypertension, 59% had a BMI ≥95th percentile, 20% had an
estimated GFR between 60 and 90 mL/min/1.73m² and < 2% had an estimated GFR
< 60 mL/min/1.73m². The mean age was 11.8 years and 74% of patients were Caucasian.
In the initial 4week,dose-response phase of the trial patients were randomized
to weight-based low, mid and high dosing groups as shown in the table 7 below.
At the end of this phase, patients entered a 4-week randomized withdrawal phase
in which they were re-randomized in each weight category in a 1:1 ratio to
continue the same dose of aliskiren or take placebo.
Table 7: Dosing groups based
on weight categories in dose-response phase
Weight Category |
Dosing Groups |
Low Dose |
Mid Dose |
High Dose |
20 to 50 kg |
6.25 mg |
37.5 mg |
150 mg |
50 to 80 kg |
12.5 mg |
75 mg |
300 mg |
80 to 150 kg |
25 mg |
150 mg |
600 mg |
During the initial
dose-response phase, aliskiren reduced both systolic and diastolic blood
pressure in a weight-based dose-dependent manner. Sitting systolic blood
pressure, the trial's primary endpoint, was reduced by 4.8, 5.6 and 8.7 mmHg
from baseline in the low, medium and high dose groups, respectively. In the
randomized withdrawal phase , the mean difference between the high dose group
of aliskiren and placebo in the mean change in sitting systolic blood pressure
was -2.7 mmHg.
Following the 8-week trial, 208
subjects were enrolled in a 52-week extension trial in which patients were
randomized in a 1:1 ratio (irrespective of whether they were on placebo or
aliskiren at the end of the 8-week study) to receive either aliskiren or
enalapril (CSPP100A2365E1; NCT01151410). The extension study included 3 dose
levels based on weight; optional dose up-titrations were allowed during the
study to control blood pressure as shown in table 8 below.
Table 8: Dose levels based on weight categories in
extension study
|
Aliskiren |
Enalapril |
Dose at randomization |
1st uptitration |
2nd uptitration |
Dose at randomization |
1st uptitration |
2nd uptitration |
Greater than or equal to 20 kg to less than 50 kg |
37.5 mg |
75 mg |
150 mg |
2.5 mg |
5 mg |
10 mg |
Greater than or equal to 50 kg to less than 80 kg |
75 mg |
150 mg |
300 mg |
5 mg |
10 mg |
20 mg |
Greater than or equal to 80 kg to less than or equal to 150 kg |
150 mg |
300 mg |
600 mg |
10 mg |
20 mg |
40 mg |
At the end of 52 weeks, reductions in blood pressure from baseline were similar in patients receiving
aliskiren (7.6/3.9 mmHg) and enalapril (7.9/4.9 mmHg).