CLINICAL PHARMACOLOGY
Sandostatin LAR Depot is a
long-acting dosage form consisting of microspheres of the biodegradable glucose
star polymer, D,L-lactic and glycolic acids copolymer, containing octreotide.
It maintains all of the clinical and pharmacological characteristics of the
immediate-release dosage form Sandostatin Injection with the added feature of
slow release of octreotide from the site of injection, reducing the need for
frequent administration. This slow release occurs as the polymer biodegrades,
primarily through hydrolysis. Sandostatin LAR Depot is designed to be injected
intramuscularly (intragluteally) once every 4 weeks.
Mechanism Of Action
Octreotide exerts pharmacologic
actions similar to the natural hormone, somatostatin. It is an even more potent
inhibitor of growth hormone, glucagon, and insulin than somatostatin. Like
somatostatin, it also suppresses LH response to GnRH, decreases splanchnic
blood flow, and inhibits release of serotonin, gastrin, vasoactive intestinal
peptide, secretin, motilin, and pancreatic polypeptide.
By virtue of these
pharmacological actions, octreotide has been used to treat the symptoms
associated with metastatic carcinoid tumors (flushing and diarrhea), and
Vasoactive Intestinal Peptide (VIP) secreting adenomas (watery diarrhea).
Pharmacodynamics
Octreotide substantially
reduces and in many cases can normalize growth hormone and/or IGF-1
(somatomedin C) levels in patients with acromegaly.
Single doses of Sandostatin
Injection given subcutaneously have been shown to inhibit gallbladder
contractility and to decrease bile secretion in normal volunteers. In
controlled clinical trials, the incidence of gallstone or biliary sludge
formation was markedly increased [see WARNINGS AND PRECAUTIONS].
Octreotide may cause clinically
significant suppression of thyroid-stimulating hormone (TSH).
Pharmacokinetics
Sandostatin Injection
According to data obtained with the immediate-release
formulation, Sandostatin Injection solution, after subcutaneous injection,
octreotide is absorbed rapidly and completely from the injection site. Peak
concentrations of 5.2 ng/mL (100-mcg dose) were reached 0.4 hours after dosing.
Using a specific radioimmunoassay, intravenous and subcutaneous doses were
found to be bioequivalent. Peak concentrations and area-under-the-curve (AUC)
values were dose proportional both after subcutaneous or intravenous single
doses up to 400 mcg and with multiple doses of 200 mcg 3 times daily (600
mcg/day). Clearance was reduced by about 66% suggesting nonlinear kinetics of
the drug at daily doses of 600 mcg/day compared to 150 mcg/day. The relative
decrease in clearance with doses above 600 mcg/day is not defined.
In healthy volunteers, the distribution of octreotide
from plasma was rapid (tα½=0.2 h), the volume of distribution (Vdss) was
estimated to be 13.6 L and the total body clearance was 10 L/h.
In blood, the distribution of octreotide into the
erythrocytes was found to be negligible and about 65% was bound in the plasma
in a concentration-independent manner. Binding was mainly to lipoprotein and,
to a lesser extent, to albumin.
The elimination of octreotide from plasma had an apparent
half-life of 1.7 hours, compared with the 1-3 minutes with the natural hormone,
somatostatin. The duration of action of subcutaneously administered Sandostatin
Injection solution is variable but extends up to 12 hours depending upon the
type of tumor, necessitating multiple daily dosing with this immediate-release
dosage form. About 32% of the dose is excreted unchanged into the urine. In an
elderly population, dose adjustments may be necessary due to a significant increase
in the half-life (46%) and a significant decrease in the clearance (26%) of the
drug.
In patients with acromegaly, the pharmacokinetics differ
somewhat from those in healthy volunteers. A mean peak concentration of 2.8
ng/mL (100-mcg dose) was reached in 0.7 hours after subcutaneous dosing. The
Vdss was estimated to be 21.6 ± 8.5 L and the total body clearance was
increased to 18 L/h. The mean percent of the drug bound was 41.2%. The
disposition and elimination half-lives were similar to normals.
The half-life in renal-impaired patients was slightly
longer than normal subjects (2.4-3.1 h versus 1.9 h). The clearance in
renal-impaired patients was 7.3-8.8 L/h as compared to 8.3 L/h in healthy
subjects. In patients with severe renal failure requiring dialysis, clearance
was reduced to about half that found in healthy subjects (from approximately 10
L/h to 4.5 L/h).
Patients with liver cirrhosis showed prolonged
elimination of drug, with octreotide half-life increasing to 3.7 h and total
body clearance decreasing to 5.9 L/h, whereas patients with fatty liver disease
showed half-life increasing to 3.4 h and total body clearance of 8.4 L/h. In
normal subjects, octreotide half-life is 1.9 h and the clearance is 8.3 L/h
which is comparable with the clearance in fatty-liver patients.
Sandostatin LAR Depot
The magnitude and duration of octreotide serum
concentrations after an intramuscular injection of the long-acting depot
formulation Sandostatin LAR Depot reflect the release of drug from the
microsphere polymer matrix. Drug release is governed by the slow biodegration
of the microspheres in the muscle, but once present in the systemic
circulation, octreotide distributes and is eliminated according to its known
pharmacokinetic properties which are as follows.
After a single IM injection of the long-acting depot
dosage form Sandostatin LAR Depot in healthy volunteer subjects, the serum
octreotide concentration reached a transient initial peak of about 0.03
ng/mL/mg within 1 hour after administration progressively declining over the
following 3-5 days to a nadir of < 0.01 ng/mL/mg, then slowly increasing and
reaching a plateau about 2-3 weeks postinjection. Plateau concentrations were
maintained over a period of nearly 2-3 weeks, showing dose proportional peak concentrations
of about 0.07 ng/mL/mg. After about 6 weeks postinjection, octreotide
concentration slowly decreased, to < 0.01 ng/mL/mg by Weeks 12 to 13,
concomitant with the terminal degradation phase of the polymer matrix of the
dosage form. The relative bioavailability of the long-acting release
Sandostatin LAR Depot compared to immediate-release Sandostatin Injection
solution given subcutaneously was 60%-63%.
In patients with acromegaly, the octreotide
concentrations after single doses of 10 mg, 20 mg, and 30 mg Sandostatin LAR
Depot were dose proportional. The transient Day 1 peak, amounting to 0.3 ng/mL,
0.8 ng/mL, and 1.3 ng/mL, respectively, was followed by plateau concentrations
of 0.5 ng/mL, 1.3 ng/mL, and 2.0 ng/mL, respectively, achieved about 3 weeks
postinjection. These plateau concentrations were maintained for nearly 2 weeks.
Following multiple doses of Sandostatin LAR Depot given
every 4 weeks, steady-state octreotide serum concentrations were achieved after
the third injection. Concentrations were dose proportional and higher by a
factor of approximately 1.6 to 2.0 compared to the concentrations after a
single dose. The steady-state octreotide concentrations were 1.2 ng/mL and 2.1
ng/mL, respectively, at trough and 1.6 ng/mL and 2.6 ng/mL, respectively, at
peak with 20 mg and 30 mg Sandostatin LAR Depot given every 4 weeks. No
accumulation of octreotide beyond that expected from the overlapping release
profiles occurred over a duration of up to 28 monthly injections of Sandostatin
LAR Depot. With the long-acting depot formulation Sandostatin LAR Depot
administered IM every 4 weeks the peak-to-trough variation in octreotide
concentrations ranged from 44%-68%, compared to the 163%-209% variation
encountered with the daily subcutaneous three times daily regimen of
Sandostatin Injection solution.
In patients with carcinoid tumors, the mean octreotide
concentrations after 6 doses of 10 mg, 20 mg, and 30 mg Sandostatin LAR Depot
administered by IM injection every 4 weeks were 1.2 ng/mL, 2.5 ng/mL, and 4.2
ng/mL, respectively. Concentrations were dose proportional and steady-state
concentrations were reached after 2 injections of 20 mg and 30 mg and after 3
injections of 10 mg.
Sandostatin LAR Depot has not been studied in patients
with renal impairment.
Sandostatin LAR Depot has not been studied in patients
with hepatic impairment.
Reproductive Toxicology Studies
Reproduction studies have been performed in rats and
rabbits at doses up to 16x the highest recommended human dose based on body
surface area and have revealed no evidence of harm to the fetus due to
octreotide.
Clinical Studies
Acromegaly
The clinical trials of Sandostatin LAR Depot were
performed in patients who had been receiving Sandostatin Injection for a period
of weeks to as long as 10 years. The acromegaly studies with Sandostatin LAR
Depot described below were performed in patients who achieved GH levels of
< 10 ng/mL (and, in most cases < 5 ng/mL) while on subcutaneous Sandostatin
Injection. However, some patients enrolled were partial responders to
subcutaneous Sandostatin Injection, i.e., GH levels were reduced by > 50% on
subcutaneous Sandostatin Injection compared to the untreated state, although
not suppressed to < 5 ng/mL.
Sandostatin LAR Depot was evaluated in three clinical
trials in acromegalic patients.
In two of the clinical trials, a total of 101 patients
were entered who had, in most cases, achieved a GH level < 5 ng/mL on
Sandostatin Injection given in doses of 100 mcg or 200 mcg three times daily.
Most patients were switched to 20 mg or 30 mg doses of Sandostatin LAR Depot
given once every 4 weeks for up to 27 to 28 injections. A few patients received
doses of 10 mg and a few required doses of 40 mg. Growth hormone and IGF-1
levels were at least as well controlled with Sandostatin LAR Depot as they had
been on Sandostatin Injection and this level of control remained for the entire
duration of the trials.
A third trial was a 12-month study that enrolled 151
patients who had a GH level < 10 ng/mL after treatment with Sandostatin
Injection (most had levels < 5 ng/mL). The starting dose of Sandostatin LAR
Depot was 20 mg every 4 weeks for 3 doses. Thereafter, patients received 10 mg,
20 mg, or 30 mg every 4 weeks, depending upon the degree of GH suppression [see
DOSAGE AND ADMINISTRATION]. Growth hormone and IGF-1 were at least as
well controlled on Sandostatin LAR Depot as they had been on Sandostatin
Injection.
Table 5 summarizes the data on hormonal control (GH and
IGF-1) for those patients in the first two clinical trials who received all 27
to 28 injections of Sandostatin LAR Depot.
Table 5: Hormonal Response in Acromegalic Patients
Receiving 27 to 28 Injections During1 Treatment
with Sandostatin LAR Depot
Mean Hormone Level |
Sandostatin Injection S.C. |
Sandostatin LAR Depot |
n |
% |
n |
% |
GH < 5.0 ng/mL |
69/88 |
78 |
73/88 |
83 |
< 2.5 ng/mL |
44/88 |
50 |
41/88 |
47 |
< 1.0 ng/mL |
6/88 |
7 |
10/88 |
11 |
IGF-1 normalized |
36/88 |
41 |
45/88 |
51 |
GH < 5.0 ng/mL + IGF-1 normalized |
36/88 |
41 |
45/88 |
51 |
< 2.5 ng/mL + IGF-1 normalized |
30/88 |
34 |
37/88 |
42 |
< 1.0 ng/mL + IGF-1 normalized |
5/88 |
6 |
10/88 |
11 |
1Average of monthly levels of GH and IGF-1
over the course of the trials. |
For the 88 patients in Table 5,
a mean GH level of < 2.5 ng/mL was observed in 47% receiving Sandostatin LAR
Depot. Over the course of the trials, 42% of patients maintained mean growth
hormone levels of < 2.5 ng/mL and mean normal IGF-1 levels.
Table 6 summarizes the data on
hormonal control (GH and IGF-1) for those patients in the third clinical trial
who received all 12 injections of Sandostatin LAR Depot.
Table 6: Hormonal Response in Acromegalic Patients
Receiving 12 Injections During1 Treatment with Sandostatin LAR Depot
Mean Hormone Level |
Sandostatin Injection S.C. |
Sandostatin LAR Depot |
n |
% |
n |
% |
GH < 5.0 ng/mL |
116/122 |
95 |
118/122 |
97 |
< 2.5 ng/mL |
84/122 |
69 |
80/122 |
66 |
< 1.0 ng/mL |
25/122 |
21 |
28/122 |
23 |
IGF-1 normalized |
82/122 |
67 |
82/122 |
67 |
GH < 5.0 ng/mL + IGF-1 normalized |
80/122 |
66 |
82/122 |
67 |
< 2.5 ng/mL + IGF-1 normalized |
65/122 |
53 |
70/122 |
57 |
< 1.0 ng/mL + IGF-1 normalized |
23/122 |
19 |
27/122 |
22 |
1Average of monthly levels of GH and IGF-1
over the course of the trial |
For the 122 patients in Table
6, who received all 12 injections in the third trial, a mean GH level of
< 2.5 ng/mL was observed in 66% receiving Sandostatin LAR Depot. Over the
course of the trial, 57% of patients maintained mean growth hormone levels of
< 2.5 ng/mL and mean normal IGF-1 levels. In comparing the hormonal response
in these trials, note that a higher percentage of patients in the third trial
suppressed their mean GH to < 5 ng/mL on subcutaneous Sandostatin Injection,
95%, compared to 78% across the two previous trials.
In all three trials, GH, IGF-1,
and clinical symptoms were similarly controlled on Sandostatin LAR Depot as
they had been on Sandostatin Injection.
Of the 25 patients who
completed the trials and were partial responders to Sandostatin Injection (GH
> 5.0 ng/mL but reduced by > 50% relative to untreated levels), 1 patient
(4%) responded to Sandostatin LAR Depot with a reduction of GH to < 2.5 ng/mL
and 8 patients (32%) responded with a reduction of GH to < 5.0 ng/mL.
Two open-label clinical studies
investigated a 48-week treatment with Sandostatin LAR Depot in 143 untreated
(de novo) acromegalic patients. The median reduction in tumor volume was 20.6%
in Study 1 (49 patients) at 24 weeks and 24.5% in Study 2 (94 patients) at 24
weeks and 36.2% at 48 weeks.
Carcinoid Syndrome
A 6-month clinical trial of
malignant carcinoid syndrome was performed in 93 patients who had previously
been shown to be responsive to Sandostatin Injection. Sixty-seven (67) patients
were randomized at baseline to receive double-blind doses of 10 mg, 20 mg, or
30 mg Sandostatin LAR Depot every 28 days and 26 patients continued, unblinded,
on their previous Sandostatin Injection regimen (100-300 mcg three times
daily).
In any given month after steady-state
levels of octreotide were reached, approximately 35%-40% of the patients who
received Sandostatin LAR Depot required supplemental subcutaneous Sandostatin
Injection therapy usually for a few days, to control exacerbation of carcinoid
symptoms. In any given month, the percentage of patients randomized to
subcutaneous Sandostatin Injection who required supplemental treatment with an
increased dose of Sandostatin Injection was similar to the percentage of
patients randomized to Sandostatin LAR Depot. Over the 6-month treatment
period, approximately 50%-70% of patients who completed the trial on
Sandostatin LAR Depot required subcutaneous Sandostatin Injection supplemental
therapy to control exacerbation of carcinoid symptoms although steady-state serum
Sandostatin LAR Depot levels had been reached.
Table 7 presents the average
number of daily stools and flushing episodes in malignant carcinoid patients.
Table 7: Average Number of
Daily Stools and Flushing Episodes in Patients with Malignant Carcinoid
Syndrome
Treatment |
Daily Stools (Average Number) |
Daily Flushing Episodes (Average Number) |
n |
Baseline |
Last Visit |
Baseline |
Last Visit |
Sandostatin Injection S.C. |
26 |
3.7 |
2.6 |
3.0 |
0.5 |
Sandostatin LAR Depot |
10 mg |
22 |
4.6 |
2.8 |
3.0 |
0.9 |
20 mg |
20 |
4.0 |
2.1 |
5.9 |
0.6 |
30 mg |
24 |
4.9 |
2.8 |
6.1 |
1.0 |
Overall, mean daily stool
frequency was as well controlled on Sandostatin LAR Depot as on Sandostatin
Injection (approximately 2-2.5 stools/day).
Mean daily flushing episodes
were similar at all doses of Sandostatin LAR Depot and on Sandostatin Injection
(approximately 0.5-1 episode/day).
In a subset of patients with
variable severity of disease, median 24 hour urinary 5-HIAA (5-hydroxyindole
acetic acid) levels were reduced by 38%-50% in the groups randomized to
Sandostatin LAR Depot.
The reductions are within the
range reported in the published literature for patients treated with octreotide
(about 10%-50%).
Seventy-eight (78) patients
with malignant carcinoid syndrome who had participated in this 6-month trial,
subsequently participated in a 12-month extension study in which they received
12 injections of Sandostatin LAR Depot at 4-week intervals. For those who
remained in the extension trial, diarrhea and flushing were as well controlled
as during the 6-month trial. Because malignant carcinoid disease is
progressive, as expected, a number of deaths (8 patients: 10%) occurred due to disease
progression or complications from the underlying disease. An additional 22% of
patients prematurely discontinued Sandostatin LAR Depot due to disease
progression or worsening of carcinoid symptoms.