CLINICAL PHARMACOLOGY
Mechanism Of Action
Angiotensin II raises blood pressure by vasoconstriction
and increased aldosterone release. Direct action of angiotensin II on the
vessel wall is mediated by binding to the G-protein-coupled angiotensin II
receptor type 1 on vascular smooth muscle cells, which stimulates Ca2+/calmodulin-dependent
phosphorylation of myosin and causes smooth muscle contraction.
Pharmacodynamics
For the 114 (70%) patients in the GIAPREZA arm who
reached the target MAP at Hour 3, the median time to reach the target MAP
endpoint was approximately 5 minutes. GIAPREZA is titrated to effect for each
individual patient.
Pharmacokinetics
Following intravenous infusion of angiotensin II in
adults with septic or other distributive shock, serum levels of angiotensin II
are similar at Baseline and Hour 3 after intravenous infusion. After 3 hours of
treatment, however, the serum level of angiotensin I (the angiotensin II precursor
peptide) is reduced by approximately 40%.
Distribution
No specific studies were conducted that examined the
distribution of GIAPREZA.
Metabolism And Excretion
No specific studies were conducted that examined the
metabolism and excretion of GIAPREZA.
The plasma half-life of IV administered angiotensin II is
less than one minute. It is metabolized by aminopeptidase A and angiotensin
converting enzyme 2 to angiotensin-(2-8) [angiotensin III] and
angiotensin-(1-7), respectively in plasma, erythrocytes and many of the major
organs (i.e., intestine, kidney, liver and lung). Angiotensin II type 1
receptor (AT1) mediated activity of angiotensin III is approximately 40% of
angiotensin II; however, aldosterone synthesis activity is similar to
angiotensin II. Angiotensin-(1-7) exerts the opposite effects of angiotensin II
on AT1 receptors and causes vasodilation.
Specific Populations
No formal pharmacokinetic studies were conducted with
GIAPREZA in the following specific populations.
Renal Impairment
The clearance of angiotensin II is not dependent on renal
function. Therefore, the pharmacokinetics of GIAPREZA are not expected to be
influenced by renal impairment.
Hepatic Impairment
The clearance of angiotensin II is not dependent on
hepatic function. Therefore, the pharmacokinetics of GIAPREZA are not expected
to be influenced by hepatic impairment.
Age
The effect of age was analyzed in the 163 patients
receiving GIAPREZA in ATHOS-3. There were no significant differences in
pharmacokinetics between age groups (< 65 years / ≥ 65 years).
Male And Female Patients
The effect of sex was analyzed in the 163 patients
receiving GIAPREZA in ATHOS-3. There were no significant differences in
pharmacokinetics between male and female patients.
Animal Toxicology And/Or Pharmacology
No animal toxicology studies were conducted with
GIAPREZA.
Safety Pharmacology
In a cardiovascular safety pharmacology study in
normotensive dogs, GIAPREZA doses of 150, 450, and 1800 ng/kg (5, 15 and 60
ng/kg/min) were infused intravenously for 30 minutes each. At ≥ 450 ng/kg,
GIAPREZA caused significantly elevated MAP and systemic vascular resistance, as
expected. The 1800 ng/kg dose also caused increased heart rate, increased systemic
vascular resistance, increased left ventricular systolic and end-diastolic
pressures, and PR interval prolongation. GIAPREZA did not significantly alter
respiratory rate or cause electrocardiographic changes in QRS duration or QTc.
Clinical Studies
ATHOS-3
The Angiotensin II for the Treatment of High-Output Shock
(ATHOS-3) trial was a double-blind study in which 321 adults with septic or
other distributive shock who remained hypotensive despite fluid and vasopressor
therapy were randomized 1:1 to GIAPREZA or placebo. Doses of GIAPREZA or
placebo were titrated to a target mean arterial pressure (MAP) of ≥ 75
mmHg during the first 3 hours of treatment while doses of other vasopressors
were maintained. From Hour 3 to Hour 48, GIAPREZA or placebo were titrated to
maintain MAP between 65 and 70 mmHg while reducing doses of other vasopressors.
The primary endpoint was the percentage of subjects who achieved either a MAP ≥
75 mmHg or a ≥ 10 mmHg increase in MAP without an increase in baseline
vasopressor therapy at 3 hours. 91% of subjects had septic shock; the remaining
subjects had other forms of distributive shock such as neurogenic shock. At the
time of study drug administration, 97% of subjects were receiving
norepinephrine, 67% vasopressin, 15% phenylephrine, 13% epinephrine, and 2% dopamine.
83% of subjects had received two or more vasopressors and 47% three or more vasopressors
prior to study drug administration. 61% of subjects were male, 80% were White, 10%
were Black, and 10% were other races. The median age of subjects was 64 years (range:
22-89 years). Patients requiring high doses of steroids, patients with a
history of asthma or bronchospasm, and patients with Raynaud's syndrome were
not included.
The primary endpoint was achieved by 70% of patients
randomized to GIAPREZA compared to 23% of placebo subjects; p < 0.0001 (a
treatment effect of 47%). Figure 1 shows the results in all patients and in
selected subgroups.
Figure 1: ATHOS-3: Primary Endpoint - Overall Result
and Results in Selected Subgroups
NE Equiv = norepinephrine equivalent dose: the sum of all
vasopressors doses with each vasopressor dose converted to the clinically
equivalent norepinephrine dose
Note: The figure above presents effects in various
subgroups, all of which are baseline characteristics. The 95% confidence limits
that are shown do not take into account the number of comparisons made, and may
not reflect the effect of a particular factor after adjustment for all other
factors. Apparent homogeneity or heterogeneity among groups should not be
over-interpreted.
In the GIAPREZA-treated group, the median time to reach
the target MAP endpoint was 5 minutes. The effect on MAP was sustained for at
least the first three hours of treatment. The median dose of GIAPREZA was 10
ng/kg/min at 30 minutes. Of the 114 responders at Hour 3, only 2 (1.8%) received
more than 80 ng/kg/min.
Patients were not necessarily on maximum doses of other
vasopressors at the time of randomization. The effect of GIAPREZA when added to
maximum doses of other vasopressors is unknown.
Mortality through Day 28 was 46% on GIAPREZA and 54% on
placebo (hazard ratio 0.78; 95% confidence interval 0.57 - 1.07).