Clinical Pharmacology for Caelyx
Mechanism Of Action
The active ingredient of CAELYX® (Pegylated Liposomal Doxorubicin Hydrochloride for
Injection) is doxorubicin HCl. The mechanism of action of doxorubicin HCl is thought to be
related to its ability to bind DNA and inhibit nucleic acid synthesis. Cell structure studies have
demonstrated rapid cell penetration and perinuclear chromatin binding, rapid inhibition of
mitotic activity and nucleic acid synthesis, and induction of mutagenesis and chromosomal
aberrations.
CAELYX® is doxorubicin HCl encapsulated in long-circulating STEALTH® liposomes.
Liposomes are microscopic vesicles composed of a phospholipid bilayer that are capable of
encapsulating active drugs. The STEALTH® liposomes of CAELYX® are formulated with
surface-bound methoxypolyethylene glycol (MPEG), a process often referred to as pegylation, to
protect liposomes from detection by the mononuclear phagocyte system (MPS) and to increase
blood circulation time.
Representation of a STEALTH® liposome:
STEALTH® liposomes have a half-life of approximately 73.9 hours in humans. They are stable
in blood, and direct measurement of liposomal doxorubicin shows that at least 90% of the drug
(the assay used cannot quantify less than 5-10% free doxorubicin) remains liposomeencapsulated
during circulation.
It is hypothesized that because of their small size (ca. 100 nm) and persistence in the circulation,
the pegylated CAELYX® liposomes are able to penetrate the altered and often compromised
vasculature of tumors. This hypothesis is supported by studies using colloidal gold-containing
STEALTH® liposomes, which can be visualized microscopically. Evidence of penetration of
STEALTH® liposomes from blood vessels and their entry and accumulation in tumors has been
seen in mice with C-26 colon carcinoma tumors. Once the STEALTH® liposomes distribute to
the tissue compartment, the encapsulated doxorubicin HCl becomes available. The exact
mechanism of release is not understood.
Pharmacokinetics
Population Pharmacokinetics
The pharmacokinetics of CAELYX® was evaluated in 120 patients from 10 different clinical
trials using the population pharmacokinetic approach. The pharmacokinetics of CAELYX® over
the dose range of 10 mg/m2 to 60 mg/m2 body surface, was best described by a two-compartment
non-linear model with zero-order input and Michaelis-Menten elimination. The mean intrinsic
clearance of CAELYX® was 0.030 L/h/m2 (range 0.008 to 0.152 L/h/m2) and the mean central
volume of distribution was 1.93 L/m2 (range 0.96 - 3.85 L/m2) approximating the plasma
volume. The apparent half-life ranged from 24 – 231 hours, with a mean of 73.9 hours. The
apparent non-linearity suggests that the clearance of CAELYX® is saturable, and that greater
than dose-proportional increases in exposure occur as the dose is increased.
Breast Cancer
The pharmacokinetics of CAELYX® determined in 18 patients with breast carcinoma were
similar to the pharmacokinetics determined in the larger population of 120 patients with various
cancers. The mean intrinsic clearance was 0.0160 L/h/m2 (range 0.0080 - 0.027 L/h/m2), the
mean central volume of distribution was 1.46 L/m2 (range 1.10 - 1.64 L/m2). The mean apparent
half-life was 71.5 hours (range 45.2 - 98.5 hours).
Ovarian Cancer
The pharmacokinetics of CAELYX® determined in 11 patients with ovarian carcinoma were
similar to the pharmacokinetics determined in the larger population of 120 patients with various
cancers. The mean intrinsic clearance was 0.021 L/h/m2 (range 0.009 – 0.041 L/h/m2), the mean
central volume of distribution was 1.95 L/m2 (range 1.67 – 2.40 L/m2). The mean apparent halflife
was 75.0 hours (range 36.1 – 125 hours).
AIDS-KS
The plasma pharmacokinetics, and tumor localization of CAELYX® were studied in 42 patients
with AIDS- related Kaposi’s sarcoma (KS) who received single doses of 10 or 20 mg/m2 body
surface, administered by a 30-minute infusion. Twenty-three of these patients received single
doses of both 10 and 20 mg/m2 body surface, with a 3-week wash-out period between doses.
The pharmacokinetic parameter values of CAELYX® are presented in the following table:
Table 11 - Pharmacokinetic Parameters in CAELYX®-Treated Patients
(Mean ± SD)
| Parameter (units) |
Dose |
10 mg/m2 body surface
(n=23) |
20 mg/m2 body surface
(n=23) |
| Peak Plasma Concentration (μg/mL) |
4.12 ± 0.215 |
8.34 ± 0.49 |
| Plasma Clearance (L/h/m2) |
0.0556 ± 0.01 |
0.041 ± 0.004 |
| Steady-State Volume of Distribution
(L/m2) |
2.83 ± 0.145 |
2.72 ± 0.120 |
| AUC (μg/mL•h) |
277 ± 32.9 |
590 ± 58.7 |
| First Phase (λ1) Half-Life (h) |
4.7 ± 1.1 |
5.2 ± 1.4 |
| Second Phase (λ2) Half-Life (h) |
52.3 ± 5.6 |
55.0 ± 4.8 |
Across this dosage range, CAELYX® displayed linear pharmacokinetics. Disposition occurred
in two phases after CAELYX® administration, with a relatively short first phase (~5 hours) and a
prolonged second phase (~55 hours) that accounted for the majority of the area under the curve
(AUC).
In contrast to the pharmacokinetics of doxorubicin, which displays a large volume of
distribution, the steady-state volume of distribution of CAELYX® indicated that CAELYX® was
confined mostly to the vascular fluid volume. Plasma protein binding of CAELYX® has not
been determined; however, the plasma protein binding of doxorubicin is approximately 70%.
Doxorubicinol, the major metabolite of doxorubicin, was detected at very low levels (range:
0.8 to 26.2 ng/mL) in the plasma of patients who received 10 or 20 mg/m2 (body surface) of
CAELYX®. The plasma clearance of CAELYX® was slow, with a mean clearance value of 0.042
L/h/m2 at a dose of 20 mg/m2 body surface.
Kaposi’s sarcoma lesions and normal skin biopsies were obtained at 48 and 96 hours post
infusion of 10 or 20 mg/m2 (body surface) of CAELYX® in 22 patients. Significantly higher
doxorubicin concentrations were found in KS lesions than in normal skin biopsies at both
sampling times and dose levels. The median doxorubicin concentrations ranged from 2-fold to
20-fold higher in KS lesions than in normal skin.
Tissue Distribution
The concentration of CAELYX® in AIDS-KS lesions was a median of 21 times higher than in
normal skin at 48 hours post-treatment. Population pharmacokinetic analyses suggested that
there were small differences in the volume of distribution between tumor types, with the largest
volume of distribution in patients with AIDS-KS (2.24 L/m2), and the smallest volume of
distribution in patients with breast carcinoma (1.12 L/m2). The volume of distribution in the
ovarian carcinoma population is 1.56 L/m2.
Pharmacokinetics Of Caelyx® In Elderly Patients
The population-based pharmacokinetic analysis included patients from 21 to 73 years of age.
The results of this analysis suggested that age did not influence the pharmacokinetic profile of
CAELYX®.
Pharmacokinetics Of Caelyx® In Patients With Impaired Renal Function
As doxorubicin is metabolized by the liver and excreted in the bile, dose modification should not
be required with CAELYX®. Population-based analysis confirms that changes in renal function
over the range tested (estimated creatinine clearance 30-156 mL/min) do not alter the
pharmacokinetics of CAELYX®. No pharmacokinetic data are available in patients with
creatinine clearance of less than 30 mL/min.
Pharmacokinetics Of Caelyx® In Patients With Hepatic Insufficiency
Based upon population pharmacokinetics, bilirubin concentrations did not affect the
pharmacokinetics of CAELYX®. It should be noted however, that few patients with elevated
bilirubin were included in the analysis and that the highest bilirubin in the study was 4.0 mg/dL.
Until more data are available demonstrating the safety of CAELYX® in this patient population,
suggested dosing reductions mentioned under DOSAGE AND ADMINISTRATION should be
followed.
Clinical Trials
Breast Cancer
A phase III randomized, controlled parallel-group, open-label, multicentre study of CAELYX®
50 mg/m2 q 4 weeks vs, doxorubicin hydrochloride 60 mg/m2 q 3 weeks in patients with
metastatic breast cancer was completed in 509 patients.
The protocol-specified primary objective of demonstrating non-inferiority between CAELYX®
and doxorubicin was met, the hazard ratio (HR) for progression-free survival (PFS) was 1.00
(95% CI for HR= 0.82 - 1.22 ). The treatment HR for PFS when adjusted for prognostic
variables was consistent with PFS for the ITT population. Median PFS for CAELYX® was 6.9
months and for doxorubicin 7.8 months, not statistically significant.
Table 12 - Progression-Free Survival in Breast Cancer Patients
| |
Number of Subjects |
|
| |
n |
Censored |
Progresseda |
Median PFS |
P-valueb |
HR |
95% CI for HRc |
| CAELYX® |
254 |
52 |
202 |
6.9 months |
0.99 |
1.00 |
0.82-1.22 |
| Doxorubicin |
255 |
47 |
208 |
7.8 months |
a: Deaths within 4 months of last tumor evaluation indicating no progression are considered events.
b: Stratified log rank test to test superiority of CAELYX® to doxorubicin.
c: Adjusted for the interim analysis (95.01% CI provided). |
Figure #1: Kaplan-Meier Curve for Progression-free Survival in Breast Cancer Patients
Table 13 - Overall Survival in Breast Cancer Patients
| |
n |
Censored |
Dead |
Median
OS |
Pvaluea |
HR |
95% CI for HRb |
| CAELYX® |
254 |
110 |
144 |
21 months |
0.59 |
0.9 |
0.74-1.19 |
| Doxorubicin |
255 |
113 |
142 |
22 months |
a: Stratified log rank test to test superiority of CAELYX® to doxorubicin
b: Adjusted for the interim analysis (95.01% CI provided) |
Figure #2: Kaplan-Meier Curve for Overall Survival in Breast Cancer Patients
Table 14 - Objective Response to Treatment in Breast Cancer Patients
| |
Number (%) of Subjectsa |
CAELYX® (n=209) |
Doxorubicin (n=201) |
| Overall Response (CR+ PR) |
68 (33) |
77 (38) |
| Complete Response (CR) |
7 (3) |
9 (4) |
| Partial Response (PR) |
61 (29) |
68 (34) |
| Stable Disease (SD) |
52 (25) |
51 (25) |
| Progressive Disease (PD) |
37 (18) |
22 (11) |
| No assessment |
52 (25) |
51 (25) |
| a: Based on the number of subjects with measurable disease. |
In the breast cancer pivotal phase III trial comparing CAELYX® (50 mg/m2 every 4 weeks) to
doxorubicin (60 mg/m2 every 3 weeks), 10/254 patients randomized to receive CAELYX®
versus 48/255 patients randomized to receive doxorubicin met the protocol-defined criteria for
cardiotoxicity during treatment and/or follow-up. Cardiotoxicity was defined as a decrease of 20
percentage points or greater from baseline if the resting LVEF remained in the normal range or a
decrease of 10 percentage points or greater if the LVEF became abnormal (less than the lower
limit for normal). The risk of developing a cardiac event as a function of cumulative
anthracycline dose was significantly lower with CAELYX® than with doxorubicin (HR
[doxorubicin/CAELYX®] = 3.16, P<0.001). At cumulative doses greater than 450 mg/m2 there
were no cardiac events with CAELYX®. Patients were also assessed for signs and symptoms of
congestive heart failure (CHF). None of the 10 CAELYX® patients, who had cardiotoxicity by
LVEF criteria, developed signs and symptoms of CHF. In contrast, 10 of 48 doxorubicin
patients, who had cardiotoxicity by LVEF criteria, developed signs and symptoms of CHF.
Table 15 - Cardiac Toxicity During Treatment and Follow-Up in Breast Cancer Patients
| |
Number of Subjects |
CAELYX® (n=254) |
Doxorubicin (n=255) |
| Subjects developed cardiotoxicity (LVEF defined) |
10 |
48 |
| Cardiotoxicity (with signs & symptoms of CHF) |
0 |
10 |
| Cardiotoxicity (no signs & symptoms of CHF) |
10 |
38 |
Table 16 - Cumulative Anthracycline Dose and Cardiotoxicity in Breast Cancer Patients
Subgroups
| |
Number of Subjects |
| n |
Censored |
Cardiotoxicity
Events |
HR |
95% CI for
HR |
| ≥55 years old |
| CAELYX® |
159 |
153 |
6 |
2.04 |
0.81-5.18 |
| Doxorubicin |
152 |
134 |
18 |
| Prior Adjuvant Anthracycline |
| CAELYX® |
38 |
37 |
1 |
7.27 |
0.93-56.80 |
| Doxorubicin |
40 |
29 |
11 |
| Cardiac Risk Factor |
| CAELYX® |
122 |
117 |
5 |
2.7 |
1.01-7.18 |
| Doxorubicin |
121 |
100 |
21 |
Figure #3: Kaplan-Meier Curve for Rate of Cardiotoxicity vs. Cumulative Anthracycline
Dose in Breast Cancer Patients
In 418 patients with solid tumors (including a subset of patients with breast and ovarian cancers)
treated with CAELYX® at a dose of 50 mg/m2/cycle, the incidence of clinically significant
cardiac dysfunction was low. Only 13 of 88 patients (15%) with cumulative anthracycline dose
>400 mg/m2 body surface, had a clinically significant change in their LVEF (defined as LVEF
<45% or a decrease of at least 20 percentage points from baseline).
In addition, endomyocardial biopsies were performed in 8 solid tumor patients with cumulative
anthracycline dose of 509 mg/m2-1,680 mg/m2 body surface. The range of Billingham
cardiotoxicity scores was grades 0-1.5. These grading scores are consistent with no or mild
cardiotoxicity.
Table 17 - Most Common Treatment Related (≥5%) Adverse Events in Breast Cancer Patients
| |
Number (%) of Subjects |
CAELYX® (n=254) |
Doxorubicin (n=255) |
| All
Grades |
Grade 3 |
Grade 4 |
All Grades |
Grade 3 |
Grade 4 |
| PPE |
123 (48) |
42 (17) |
0 |
5 (2) |
0 |
0 |
| Nausea |
94 (37) |
8 (3) |
0 |
136 (53) |
12 (5) |
0 |
| Mucositis |
59 (23) |
10 (4) |
0 |
33 (13) |
5 (2) |
0 |
| Stomatitis |
55 (22) |
12 (5) |
0 |
38 (15) |
4 (2) |
0 |
| Alopecia |
51 (20) |
0 |
0 |
169 (66) |
0 |
0 |
| Vomiting |
48 (19) |
2 (<1) |
0 |
78 (31) |
11 (4) |
0 |
| Fatigue |
31 (12) |
2 (<1) |
0 |
40 (16) |
4 (2) |
0 |
| Anorexia |
27 (11) |
3 (1) |
0 |
26 (10) |
1(<1) |
0 |
| Asthenia |
26 (10) |
3 (1) |
0 |
32 (13) |
3 (1) |
0 |
| Rash |
25 (10) |
6 (2) |
0 |
4 (2) |
0 |
0 |
| Abdominal Pain |
21 (8) |
3 (1) |
0 |
11 (4) |
3 (1) |
0 |
| Constipation |
21 (8) |
2 (<1) |
0 |
24 (9) |
1 (<1) |
0 |
| Pigmentation Abnormal |
21 (8) |
1 (<1) |
0 |
6 (2) |
1 (<1) |
0 |
| Fever |
20 (8) |
0 |
0 |
18 (7) |
2 (<1) |
1 (<1) |
| Diarrhea |
18 (7) |
3 (1) |
0 |
20 (8) |
2 (<1) |
0 |
| Erythema |
18 (7) |
2 (<1) |
0 |
3 (1) |
0 |
0 |
| Weakness |
14 (6) |
1 (<1) |
0 |
20 (8) |
4 (2) |
0 |
| Mouth Ulceration |
13 (5) |
1 (<1) |
0 |
9 (4) |
0 |
0 |
| Anemia |
12 (5) |
2 (<1) |
1(<1) |
19 (7) |
3 (1) |
1(<1) |
| Neutropenia |
10 (4) |
3(1) |
1 (<1) |
25 (10) |
10 (4) |
9 (4) |
Ovarian Cancer
Pivotal Phase III Study
A phase III comparative study of CAELYX® versus topotecan in patients with epithelial ovarian
cancer following failure of first-line, platinum based chemotherapy was completed in 474
patients. All patients entered into this study had failed a first-line platinum-containing regimen,
usually a combination of platinum and paclitaxel, either used in combination or in sequence. A
small number of patients had received prior therapy with platinum alone.
Pivotal Phase III Study - Efficacy
For the protocol-specified primary endpoint of time to progression for the 416 (207 CAELYX®,
209 topotecan) evaluable patients (patients who were randomized, met enrolment criteria, and
received at least 2 cycles of study drug), the results of the study demonstrate therapeutic
equivalency of CAELYX® vs. topotecan. The median time to progression for evaluable patients
was 148 days for CAELYX® and 134 days for topotecan with a hazard ratio of 1.262, 90% CI
1.062-1.500, P=0.026.
The time to progression for the Intent to Treat (ITT) population n=474 (239 CAELYX®, 235
topotecan; patients who were randomized and received at least a partial dose of study drug)
favored CAELYX® over topotecan with a hazard ratio of 1.176, 90% CI 1.002-1.381, P=0.095.
The median time to progression was 113 days for CAELYX® and 119 days for topotecan.
Table 18 - Objective Response, Overall Response and Stratified by Platinum Sensitivity (ITT
Ovarian Cancer Population)
| |
CAELYX® (n=239) |
Topotecan (n=235) |
| Overall Response |
| n |
239 |
235 |
| Total |
47 (19.7%) |
40 (17%) |
| Complete |
9 (3.8%) |
11 (4.7%) |
| Partial |
38 (15.9%) |
29 (12.3%) |
| Platinum-Refractory |
| n |
130 |
124 |
| Total |
16 (12.3%) |
8 (6.5%) |
| Complete |
1 (0.8%) |
1 (0.8%) |
| Partial |
15 (11.5%) |
7 (5.6%) |
| Platinum-Sensitive |
| n |
109 |
111 |
| Total |
31 (28.4%) |
32 (28.8%) |
| Complete |
8 (7.3%) |
10 (9.0%) |
| Partial |
23 (21.1%) |
22 (19.8%) |
Figure #4 - Kaplan-Meier Curve of Progression-free Survival (Intent-to-treat Ovarian
Cancer Population)15
For the entire ITT population, overall survival for CAELYX® was at least equivalent to topotecan with ratio of
1.121 (90% CI 0.920-1.367, P=0.34) in favor of CAELYX®.
In the protocol-defined ITT population platinum-sensitive subgroup (patients who responded to
initial platinum-based therapy and had a progression-free interval of greater than 6 months off
treatment), both time to progression and overall survival were significantly in favor of
CAELYX® (Table 19).
Table 19 - Pivotal Phase III Study Protocol 30-49 (Ovarian Cancer Patients)
| Time to Progression for Platinum-Sensitive Subgroup of ITT population |
| Treatment |
n |
Median (days) |
Hazard Ratio (HR) |
90% CI for HR |
| CAELYX® |
109 |
202 |
1.349 |
1.065 - 1.709 |
| Topotecan |
111 |
163 |
| Overall Survival for Platinum-Sensitive Subgroup of ITT population |
| CAELYX® |
109 |
756 |
1.72 |
1.222 - 2.422 |
| Topotecan |
111 |
498 |
Figure #5 - Kaplan-Meier Curve of Progression-free Survival (Intent-to-treat Population;
Platinum-Sensitive Ovarian Cancer Patients).15
A consistent trend favouring CAELYX® was demonstrated across efficacy endpoints and
prognostic subgroups.
Pivotal Phase III Study - Safety
Overall, treatment-related adverse events observed with CAELYX® tended to be of mild or
moderate severity.
The most common drug-related adverse events associated with CAELYX® were PPE (Palmar-
Plantar Erythrodysesthesia) and stomatitis, and were severe in 23% and 8% of CAELYX®-
treated patients respectively. Both were easily managed with dose reduction or delays and were
seldom treatment-limiting or life-threatening.
The most common drug-related adverse events associated with topotecan were hematologic
toxicities (neutropenia, anemia, thrombocytopenia, leukopenia), nausea and alopecia.
Hematologic events, nausea, and alopecia were less frequent and less severe with CAELYX®
compared with topotecan. Hematologic toxicity with topotecan was frequently associated with
clinical sequelae, such as infection, or the need for transfusions or hematopoietic growth factors.
Table 20 - Most Frequently Reported Treatment-Related Adverse Events for Each Ovarian
Cancer Treatment Group - Phase III Study
| |
CAELYX® (n=239) |
Topotecan (n=235) |
| All Severities |
Grade III/IV Severity |
All Severities |
Grade III/IV Severity |
| Neutropenia |
84 (35%) |
29 (12%) |
191 (81%) |
178 (76%) |
| Anemia |
85 (36%) |
13 (5%) |
169 (72%) |
66 (28%) |
| Thrombocytopenia |
31 (13%) |
3 (1%) |
152 (65%) |
80 (34%) |
| Leukopenia |
87 (36%) |
24 (10%) |
149 (63%) |
117 (50%) |
| Alopecia |
38 (16%) |
3 (1%) |
115 (49%) |
14 (6%) |
| PPE* |
117 (49%) |
55 (23%) |
2 (1%) |
0 |
| Stomatitis |
95 (40%) |
20 (8%) |
35 (15%) |
1 (0.4%) |
| Nausea |
85 (36%) |
7 (3%) |
127 (54%) |
14 (6%) |
| * PPE = Palmar-plantar erythrodysesthesia |
There was no evidence of a relationship between cumulative CAELYX® dose and change from
baseline for LVEF (Left Ventricular Ejection Fraction).
When quality of life outcomes such as toxicity and progression are considered, CAELYX® is
always preferred over topotecan as demonstrated in the quality-adjusted survival analysis.
Although pain secondary to palmar-plantar erythrodysesthesia (PPE) is more common in
CAELYX® treated patients, this rarely resulted in study discontinuation.
AIDS-KS
Efficacy data on refractory patient population
CAELYX® was studied in an open-label, single-arm, multicenter study utilizing CAELYX® at
20 mg/m2 by intravenous infusion every three weeks generally until progression or intolerance
occurred. In an interim analysis, the treatment history of 383 patients was reviewed, and a
cohort of 77 patients was retrospectively identified as having disease progression on prior
systemic combination chemotherapy (at least 2 cycles of a regimen containing at least two of
three treatments: bleomycin, vincristine or vinblastine, or doxorubicin) or as being intolerant to
such therapy. Of the 77 patients selected, 66 had disease progression on conventional
chemotherapy prior to entering the trial and 11 could not continue systemic chemotherapy
because of intolerable toxicity. These 77 patients were predominantly white, homosexual males
with a mean age of 38 years.
Two analyses of tumor response were used to evaluate the effectiveness of CAELYX®:
- Indicator Lesion Assessment: A retrospective analysis was conducted based on analysis
of five indicator lesions. A partial response was defined as a decrease of ≥50% in the total
size of the indicator lesions compared to study entry, or a decrease of 50% in the number of
raised lesions.
- Investigator Assessment: Investigator assessment of response was based on ACTG
criteria. Partial response was defined as no new lesions, sites of disease, or worsening
edema. In addition, one of the following criteria had to be fulfilled: (1) a 50% or greater
decrease in the number of all previously existing lesions; (2) a complete flattening of at least
50% of all previously raised lesions; (3) a 50% decrease in the sum of the products of the
largest perpendicular diameters of the indicator lesions; or (4) the patient met the criteria for
Clinical Complete Response except the patient had residual tumor-associated edema or
effusion.
Analyses of efficacy were conducted using both conventional (“best”) and “conservative”
response methodologies for the 77 refractory patients. According to the “conservative“ response
methodology (updated ACTG response criteria), patients had to meet the response criteria at a
minimum of two consecutive clinical evaluations, separated by a minimum of 21 days, with no
record of prior disease progression. The results obtained using both of these methodologies are
summarized below:
Table 21 - Best Response in Refractorya AIDS-KS
| |
Indicator Lesion Assessment |
Investigator Assessment |
| Number of Patients |
77 |
77 |
| Best Response |
|
|
| Complete |
0 |
1 ( 1.3%) |
| Partial |
52 (67.5%) |
43 (55.8%) |
| Stable |
20 (26.0%) |
29 (37.7%) |
| Progression |
5 (6.5%) |
4 ( 5.2%) |
| Time to PR and/or CR (days) |
|
|
| Median |
69 |
94 |
| Range |
1-351 |
1-280 |
| Duration of PR and/or
CR (days) |
|
|
| Median |
64 |
113 |
| Range |
1-211 |
15-368 |
aPatients with disease that progressed on prior combination chemotherapy or who were intolerant to such therapy.
PR = Partial response; CR = Complete response |
Table 22 - Best “Conservative” Response in Refractorya AIDS-KS
| |
Indicator Lesion Assessment |
Investigator Assessment |
| Number of Patients |
77 |
77 |
| Best Response |
| Complete |
0 |
1 ( 1.3%) |
| Partial |
26 (33.8%) |
33 (42.9%) |
| Stable |
19 (24.7%) |
22 (28.6%) |
| Progression |
32 (41.6%) |
21 (27.3%) |
| Time to PR and/or CR (days) |
| Median |
92 |
99 |
| Range |
1-414 |
1-304 |
| Duration of PR and/or
CR (days) |
| Median |
65 |
113 |
| Range |
22-211 |
21-368 |
a Patients with disease that progressed on prior combination chemotherapy or who were intolerant to such therapy.
PR = Partial response; CR = Complete response |
Controlled Trials
Two phase III, randomized, multicenter trials have been performed, comparing CAELYX® at a
dose of 20 mg/m2 with a combination chemotherapy regimen of 20 mg/m2 Adriamycin®, 10 U/m2
bleomycin and 1.0 mg vincristine (ABV) or 15 U/m2 bleomycin and 1.4 mg/m2 vincristine (BV)
in the treatment of severe AIDS-KS. Patients received up to 6 cycles of either treatment regimen
every 2 weeks (ABV-controlled) or 3 weeks (BV-controlled). Patients with extensive and
progressive cutaneous KS lesions or mucocutaneous disease and/or documented visceral disease
were enrolled in these studies. Most patients had between 10-50 lesions at baseline and CD4
counts of less than 50 cells per mm3 A total of 499 patients were treated in these two studies:
254 with CAELYX®, 125 with ABV, and 120 with BV.
The primary efficacy parameter used in studies 30-10 and 30-11 was overall clinical assessment
as determined by the investigator. Tumor response was to be classified as complete, clinically
complete, partial, stable disease, or progressive disease, based on a refinement of the ACTG
criteria published in 1989. In order to be classified as a “responder” (partial response (PR),
clinical complete response (CCR), or complete response (CR)), the patient must have had at least
two sequential investigator assessments, at least 28 days apart, that consistently confirmed the
response. Partial response was defined as above (see efficacy data on refractory patient
population; definition of investigator assessment). In conjunction with investigator assessment,
additional assessments were also made, among which, assessment of indicator lesion
characteristics and quality of life (QOL) questionnaires. Primary efficacy results are
summarized below:
Table 23 - Controlled Trials - Response Summary
| |
CAELYX® |
ABV |
BV |
| (N = 254) |
(N = 125) |
(N = 120) |
| Complete/Partial Response |
132 (52.0%) |
31 (24.8 %) |
28 (23.3%) |
| Time to CR/PR - Median (Days) |
43 |
50 |
64 |
| Duration - Median (Days) |
119 |
92 |
123 |
| CR = Complete response; PR = Partial response |
As evaluated by investigator assessment, the overall (complete/partial) response rate for
CAELYX® was significantly (P<0.001) superior to that of ABV and BV. In the CAELYX®
group, 8 patients (3.1%) achieved a clinical complete response and 124 patients (48.8%)
achieved a partial response. In the ABV group, no patients achieved a clinical complete
response and 31 (24.8%) achieved a partial response; in the BV group, 1 patient (0.8%) achieved
a clinical complete response and 27 (22.5%) achieved a partial response.
Response in both the CAELYX® patients and the control arms was associated with significant
improvements in the characteristics of the KS lesions, including a reduction in lesion thickness
and nodularity, improvement in lesion color, and resolution of lesion-associated edema.
CAELYX® patients also showed a mean decrease of indicator lesion size by 26.0% by the end of
treatment. ABV patients showed a mean decrease of 14.6%, whereas BV patients showed a
slight increase (0.2%). Compared to ABV and BV treatment, the response rates achieved by
CAELYX® also translated into improved QOL for patients.
Cardiotoxicity
An increased incidence of congestive heart failure is associated with doxorubicin therapy at
cumulative lifetime doses >450 mg/m2 body surface, or at lower doses for patients with cardiac
risk factors. Endomyocardial biopsies on ten AIDS-KS patients receiving cumulative doses of
CAELYX® greater than 460 mg/m2 body surface, indicate no evidence of anthracycline-induced
cardiomyopathy in 5 patients, minimal myocardial cell damage (<5%) in 4 patients and in 1
patient cell damage was >6-15%. The recommended dose of CAELYX® for AIDS-KS patients
is 20 mg/m2 body surface, every two-to-three weeks. The cumulative dose at which
cardiotoxicity would become a concern for these AIDS-KS patients (>400 mg/m2 body surface)
would require more than 20 courses of CAELYX® therapy over 40 to 60 weeks.
Detailed Pharmacology
Animal Pharmacology
Therapeutic Efficacy Of Caelyx®
The efficacy of CAELYX®, equivalent doses of conventionally formulated doxorubicin
hydrochloride and doxorubicin hydrochloride encapsulated in conventional liposomes have been
compared in a variety of murine tumor models including several human xenograft models. In
every model examined, CAELYX® was more effective than the same dose of doxorubicin
hydrochloride in inhibiting or halting tumor growth, in effecting cures and/or in prolonging the
survival of tumor-bearing animals; and in no case was CAELYX® less effective than
doxorubicin hydrochloride. CAELYX® was more active in both solid and dispersed tumors and
was more effective than doxorubicin hydrochloride in preventing spontaneous metastases from
intramammary implants of two different mammary tumors in mice. In two tumor models in
which they were compared, CAELYX® was also more effective than the same dose of
doxorubicin hydrochloride encapsulated in non-pegylated liposomes, demonstrating the impact
of the long-circulating liposome.
Pharmacokinetics
Single dose studies were performed in rats and dogs, and multiple dose pharmacokinetic studies
were also conducted in rats, rabbits and dogs to characterize the plasma pharmacokinetics of
CAELYX®.
The plasma pharmacokinetics of CAELYX® and doxorubicin were found to be significantly
different in all species evaluated. The plasma concentration of doxorubicin was up to 2000-fold
higher in CAELYX®-treated animals after intravenous injection of equivalent doses of
CAELYX® and doxorubicin hydrochloride. Plasma concentration by time data were best fit with
a bi-exponential curve, with a relatively short first phase (half-life = 1 to 3 hours), and a more
prolonged second phase, which represented the majority of the AUC (area-under- the-curve), and
a half-life ranging from 20 to 30 hours. The volume of distribution was smaller and clearance
was substantially decreased when compared to doxorubicin hydrochloride. Although plasma
concentration and AUC were dose-dependent, CAELYX® disposition kinetics were independent
of dose. No evidence of drug accumulation was seen in dogs treated with up to 1.0 mg/kg of
CAELYX® every three weeks. The plasma pharmacokinetics of CAELYX® in rats did not
change with repeated dosing.
Despite the higher plasma concentration of doxorubicin after CAELYX® treatment, the stability
of the STEALTH® liposome and its low rate of doxorubicin release (leakage) in plasma results in
very low levels of free (non-liposomal) doxorubicin hydrochloride in the bloodstream. Virtually
the entire CAELYX® dose administered to animals can be accounted for in the plasma in 2-5
minutes after treatment, suggesting that no sudden burst of drug release occurs after drug
injection, as has been reported for conventional, non-STEALTH® liposomal formulations of
doxorubicin hydrochloride. Direct measurements of the amount of liposomal drug in the plasma
shows that more than 90% to 95% of the doxorubicin, remains encapsulated in liposomes.
Tissue levels of doxorubicin were determined in tumor-bearing mice and in non-tumor-bearing
rats and dogs. In the tumor model studies, tumor AUC’s in CAELYX®-treated animals ranged
from 7-fold higher in a murine C26 colon carcinoma model to 25-fold greater in the human
prostatic xenograft than in mice treated with the same dose of doxorubicin hydrochloride.
Tumor and normal tissue levels of doxorubicin continued to rise for at least 24 hours in
CAELYX®-treated mice, but peaked after 1-4 hours in animals that received doxorubicin
hydrochloride, declining rapidly thereafter.
Doxorubicin concentrations persisted in the tissues in CAELYX®-treated animals, owing to the
slower clearance of liposome-associated drug, resulting in significantly higher tissue AUC’s. It
is known that doxorubicin-associated toxicity, particularly cardiotoxicity, is associated with the
high peak concentrations of doxorubicin, but not with AUC. Treatment regimens that minimize
peak doxorubicin plasma concentrations, but maintain cumulative AUC, are associated with
reduced risk of cardiomyopathy and do not compromise anti-tumor activity. The reduced cardiac
tissue concentrations in CAELYX®-treated animals correlate well with the observation that
CAELYX® is less cardiotoxic than doxorubicin hydrochloride in animals (see Toxicology,
Special Studies, Cardiotoxicity).
The higher AUC's in the tissues also did not correlate with increased toxicity, with the exception
of cutaneous lesions. Doxorubicin concentrations were higher at sites of cutaneous lesions than
in normal skin, with levels falling rapidly after treatment stopped and nearing the concentrations
found in normal skin by the end of the recovery period. It could not be determined if lesions
formed because of increased doxorubicin concentrations, or whether doxorubicin concentration
was secondarily increased as a result of extravasation of CAELYX® at pre-existing sites of tissue
damage. Studies in dogs have demonstrated that the incidence and severity of the cutaneous
lesions is related to dose intensity, with lower dose levels associated with decreased lesion
formation (see Toxicology, Special Studies, Dermal Lesion Development).
Toxicology
Acute Toxicity
In single dose studies, the acute toxicity of CAELYX® was similar for mice, rats, and dogs. In
the rat, the incidence and severity of clinical observations were dose-related and included tail and
footpad lesions, swelling and inflammation of the penis and scrotum, rough haircoat, alopecia,
hypoactivity, hunched posture, respiratory distress, and reduced body weight gain. Reversible
myelotoxicity was noted based on decreased RBC, WBC, hemoglobin, and hematocrit.
Increases occurred in BUN and cholesterol levels.
Dogs were the most sensitive species. Treatment-related toxicity included dermal toxicity,
reversible myelotoxicity, hematologic changes, increased BUN, gastrointestinal toxicity, body
weight loss, reversible cutaneous lesions, and alopecia. Myelotoxicity was less severe compared
with the doxorubicin hydrochloride group.
In a single dose study, MPEG-DSPE micelles, a component of the CAELYX® liposome
formulation, had no acute toxic effects in mice when administered at a lipid dose approximately
30-fold that found in the dose of 20 mg/m2 recommended for humans.
Long-Term Toxicity
The toxicity of CAELYX® following repeated administration was similar in rats and dogs and an
extension of the findings in the acute studies. Treatment-related effects included dermatologic
toxicity, body weight and food consumption changes, alopecia, myelotoxicity (bone marrow
cellularity changes), and hematologic effects (leukopenia and lower erythron mass). Dogs also
showed gastrointestinal toxicity and no pathologic signs of toxicity. In the long-term studies,
CAELYX® was compared with non-liposomal doxorubicin hydrochloride:
Table 24 - Comparative Long-term Toxicity Studies
| Species |
No./Sex |
No. of Doses |
Dose (mg/kg) |
CONCLUSIONS |
| Rat |
Groups of 30 15 Female 15 Male |
13 dose q3d |
CAELYX®0.25, 1.0, 1.5 Dox HCl1 |
- Dosing halted in 1.5 mg/kg CAELYX® group due to effect of dermal lesions on general health. Death of 1/10 males related to this toxicity.
- CAELYX® induced dermal lesions at ≥1 mg/kg; readily reversible upon cessation of treatment.
- CAELYX® less cardiotoxic, haemotoxic and nephrotoxic than equivalent dose of doxorubicin hydrochloride.
- Other adverse effects similar in nature, incidence and severity in CAELYX® and doxorubicin hydrochloride groups.
- No effect of placebo liposomes.
|
| Dog |
Groups of6 Male |
4 dose q7d |
CAELYX®1 Dox-HCl 1 |
- 1 CAELYX® and 1 Dox-HCl animal died during treatment.
- Myelotoxicity milder in CAELYX® groups, with later onset, less severe changes and quicker recovery.
- CAELYX® induced adverse inflammatory lesions of feet and legs; readily reversed upon cessation of treatment.
- Other adverse effects comparable in CAELYX® and Dox-HCl treatment.
- Dogs given placebo liposomes exhibited transient hypoactivity, flushing, emesis, prostration during 2nd dose. Reduced in incidence and severity at 3rd and 4th doses.
|
| Dog |
Groups of 6 Female 6 Male |
10 dose q21d |
CAELYX® 0.25, 0.75,1.0Dox-HCl 1.0 |
- Mild to moderate cardiomyopathy in all dogs treated with non-liposomal doxorubicin hydrochloride that worsened during the recovery period.
- No evidence of cardiotoxicity in any CAELYX®- treated dog at interim or final necropsy.
- Bone marrow hypocellularity in ribs and femur of doxorubicin hydrochloride-treated animals, with mild decreases in WBC count. Both resolved in 4-week recovery period. WBC depression only in CAELYX® groups, also resolved in recovery period
- Alopecia and mild dermal ulcers seen in 0.75 and 1.0 mg/kg CAELYX® groups. Ulcers healed, but alopecia only partially resolved during recovery.
- Placebo liposome effect (hypoactivity, emesis, etc.) could be controlled by reducing dose rate from 2.0 to 0.5 mL/min.
|
Carcinogenicity And Mutagenicity
Doxorubicin, the active component of CAELYX®, is both mutagenic and carcinogenic so
conducting carcinogenicity and mutagenicity studies was not deemed necessary. Four studies
were carried out with STEALTH® placebo liposome to confirm their lack of mutagenicity and
genotoxicity.
Negative results were obtained in the Ames, the L5178Y mouse lymphoma, and chromosomal
aberration assays in vitro, and the mouse bone marrow micronucleus assay in vivo.
Nephrotoxicity
Cynomolgus monkeys (3/sex) were administered a single intravenous dose of CAELYX®
(Doxil® formulation) of 10 mg/kg (120 mg/m²; approximately two times the clinical dose) and
followed for 28 days as a comparator arm in an acute toxicity study with an investigational
doxorubicin formulation. Three male and 1 female monkeys were sacrificed on Day 11 or 15 in
poor condition attributable to renal toxicity. Renal toxicity reflected in increased serum
creatinine and blood urea nitrogen levels included tubular and/or glomerular changes and
presented as renal hemorrhage and/or edema (cortex, pelvis or papilla), distal tubular dilatation,
tubular protein casts, hypertrophy of the Bowman’s capsular epithelial cells, interstitial
neutrophil infiltration, and/or necrosis of renal adipose tissue. Renal toxicity has been observed
with even lower single doses of doxorubicin HCl in rats and rabbits. However, since an
evaluation of the post-marketing safety database for CAELYX® in patients has not suggested a
significant nephrotoxicity liability of CAELYX®, these findings in monkeys may not have
relevance to patient risk assessment.
Reproduction And Teratology
The potential developmental toxicity of CAELYX® was evaluated in rats and rabbits. In the first
study, intravenous bolus injections of CAELYX® 0.1, 0.5, or 1.0 mg/kg was administered on
gestation days 6, 9, 12, and 15; or STEALTH® placebo liposomes or saline on the same
treatment schedule. An additional group received doxorubicin 0.2 or 0.4 mg/kg daily between
gestation days 6 and 15. Equivalent maternal toxicity occurred in the CAELYX® 0.5 and 1.0
mg/kg groups and in the doxorubicin groups. CAELYX® 1.0 mg/kg induced decreased fetal
weights, increases in fetal resorptions, and retarded ossification of caudal vertebrae and xiphoid
centers in the fetuses. No adverse effects were seen in dams or fetuses in the placebo liposome
or CAELYX® 0.1 mg/kg groups.
The embryotoxicity of CAELYX® was confirmed in the study in pregnant New Zealand White
rabbits administered intravenous injections of CAELYX® 0.5, 1.5, or 2.5 mg/kg on gestation
days 6, 9, 12, 15, and 18. All doses were maternally toxic. Four females that died (3 and 1 in the
high- and mid-dose groups, respectively), surviving females in the mid- and high-dose groups (4
and 2, respectively), and 4 females (low-dose group) who aborted prior to the end of the study all
had 100% resorbed conceptuses. The uterine of another female (low-dose group) who aborted
prior to the end of the study consisted of 3 normal conceptuses, 4 late resorptions, and 5 early
resorptions. CAELYX® is both embryotoxic and an abortifacient in rabbits.
Special Studies
Local Tolerance
Two single dose studies were conducted to examine the potential of CAELYX® to cause injury if
accidentally extravasated. Rabbits received single intravenous or subcutaneous injections of 0.1
or 1.0 mL of undiluted CAELYX® 2.0 mg/mL, doxorubicin hydrochloride 2.0 mg/mL, or
STEALTH® placebo liposomes. Histopathological evaluation of the intravenous injection sites
revealed that CAELYX®, doxorubicin hydrochloride, and placebo liposomes were well tolerated
with no gross or microscopic evidence of irritation.
In contrast, histopathological evaluation of the subcutaneous injection sites showed reversible
mild to moderate dose-related inflammation at CAELYX® injections sites compared to moderate
to severe inflammation and necrosis at doxorubicin hydrochloride injection sites that showed no
signs of resolution during a 4-week recovery period.
Hemolytic Potential
The hemolytic potential of CAELYX® and STEALTH® placebo liposomes in human blood was
assessed in vitro, as well as their compatibility with human serum and plasma. Neither
CAELYX® 1.0 mg/mL nor empty STEALTH® liposomes induced hemolysis of human
erythrocytes, nor did either cause coagulation or precipitation of human serum or plasma.
Lysophosphatidylcholine (LPC) is a degradation product of the phosphatidylcholine component
of the liposomes. An additional hemolytic potential study using CAELYX® formulations
prepared with 0 mg/mL, 0.5 mg/mL, or 0.88 mg/mL LPC caused no hemolysis of rat blood cells.
Dermal Lesion Development
The effect of peak dosage and dose frequency on dermal lesion development and
myelosuppression was studied in dogs. CAELYX® 0.5, 1.0, 1.5 mg/kg was administered q7d,
q14d, or q28d by intravenous (cephalic) catheter for 6-12 weeks. The higher dose intensities
with lower dose frequency (1.0 mg/kg q14d and 1.5 mg/kg q28d) produced minimal evidence of
cyclic depression of hemoglobin and hematocrit. In both groups, the hemoglobin and hematocrit
values recovered to prestudy values at the end of the study. The onset of lesions occurred within
1 to 2 weeks after initiation of treatment and began to heal at rates that varied depending on
lesion severity and dose frequency.
Myelosuppression was mild with all treatment regimens and no evidence of treatment-related
leukopenia was observed. Dosages of 0.5 mg/kg given every 2 or 4 weeks were tolerated much
better than the weekly doses at 0.5 mg/kg. Comparison of groups that received 0.5
mg/kg/treatment showed clear dose frequency-related effects on lesion development, lesion
severity, and general toxicity. Integration of current results with previous studies showed a
similar frequency-dependent effect with 1.0 mg/kg; weekly and every 2-week regimens produced
severe toxicity while a 3-week dose cycle was better tolerated.
Cardiotoxicity
Cardiotoxicity is frequently observed in animals and man administered non-liposomal
doxorubicin. However, in studies with CAELYX® in rats and dogs it was observed that
cardiotoxicity was either absent or present at a substantially decreased incidence and severity. A
multiple-dose study was carried out to evaluate the relative cardiotoxicity of CAELYX® and
doxorubicin hydrochloride administered to male rabbits by intravenous injection q5d for targeted
cumulative dosages of 14 or 21 mg/kg. Treatment was interrupted twice for 26 days to allow
recovery from short-term toxicities unrelated to cardiotoxicity. Necropsies were conducted 1, 5,
and 13 weeks after the 14th dose and 13 weeks after the 21st dose; hearts were examined for
histopathological changes at each point. Lesion severity and incidence at five sites within the
heart were also utilized to calculate a cardiotoxicity score for each animal.
Nine early deaths occurred in the CAELYX® group, 3 due to cardiotoxicity and 5 due to
generalized stress secondary to dermal lesions; 5 early deaths occurred in the doxorubicin
hydrochloride group, all with evidence of cardiotoxicity. Cardiac lesions were more severe and
frequent in the doxorubicin hydrochloride group: overall, 4/25 (16%) CAELYX®-treated
animals with cardiotoxicity compared to 10/15 (67%) doxorubicin hydrochloride-treated
animals. The decreased cardiotoxicity was not due to increased latency of the lesion; there was
no significant increase in lesion incidence or severity with time post-treatment. Cardiomyopathy
increased in evidence and severity with time after treatment in the doxorubicin hydrochloride
treatment group. Up to 50% more CAELYX® (21 mg/kg cumulative dose) could be given
without incurring increased cardiotoxicity compared to doxorubicin hydrochloride (14 mg/kg
cumulative dose).
STEALTH® Liposome Placebo
In addition to the mutagenicity and developmental studies, and the acute and long-term studies in
which placebo liposomes were used as controls, STEALTH® Liposome Placebo was evaluated
for its potential to induce cardiovascular changes in dogs and neurobehavioral changes in rats. In
the cardiovascular study, dogs showed a significant decrease in blood pressure (19-70%)
immediately after the start of dosing followed by a rapid partial recovery after the end of dosing,
and a return to normal values within 4-6 hours post-dose. Compensating acceleration in heart
rate was not seen. The dose rate did not affect the extent of hypotension, but inversely affected
the duration. In the rat study, placebo liposomes did not induce any adverse neurobehavioral
effects or evidence of neurotoxicity.