Mechanism of Action
Bevacizumab binds VEGF and prevents the interaction of VEGF
to its receptors (Flt-1 and KDR) on the surface of endothelial cells. The
interaction of VEGF with its receptors leads to endothelial cell proliferation
and new blood vessel formation in in vitro models of angiogenesis.
Administration of bevacizumab to xenotransplant models of colon cancer in nude
(athymic) mice caused reduction of microvascular growth and inhibition of
metastatic disease progression.
Pharmacokinetics
The pharmacokinetic profile of bevacizumab was assessed
using an assay that measures total serum bevacizumab concentrations (i.e., the
assay did not distinguish between free bevacizumab and bevacizumab bound to
VEGF ligand). Based on a population pharmacokinetic analysis of 491 patients
who received 1 to 20 mg/kg of Avastin weekly, every 2 weeks, or every 3 weeks,
the estimated half-life of bevacizumab was approximately 20 days (range
11-50 days). The predicted time to reach steady state was 100 days. The
accumulation ratio following a dose of 10 mg/kg of bevacizumab every 2 weeks
was 2.8.
The clearance of bevacizumab varied by body weight, gender,
and tumor burden. After correcting for body weight, males had a higher
bevacizumab clearance (0.262 L/day vs. 0.207 L/day) and a larger Vc (3.25 L vs.
2.66 L) than females. Patients with higher tumor burden (at or above median
value of tumor surface area) had a higher bevacizumab clearance (0.249 L/day
vs. 0.199 L/day) than patients with tumor burdens below the median. In Study 1,
there was no evidence of lesser efficacy (hazard ratio for overall survival) in
males or patients with higher tumor burden treated with Avastin as compared to
females and patients with low tumor burden. The relationship between
bevacizumab exposure and clinical outcomes has not been explored.
Animal Toxicology and/or Pharmacology
In cynomolgus monkeys, when bevacizumab was administered at
doses of 0.4 to 20 times the weekly human exposure, anatomical pathology
revealed several adverse effects on general growth and skeletal development,
fertility and wound healing capacity. Severe physeal dysplasia was consistently
reported in juvenile monkeys with open growth plates receiving 0.4 to 20 times
the human dose. The physeal dysplasia was characterized by a linear cessation
of growth line and chondrocyte hyperplasia which did not completely resolve
after the 4 to 12 weeks recovery period without drug exposure.
Rabbits dosed with bevacizumab exhibited reduced wound
healing capacity. Using full-thickness skin incision and partial thickness
circular dermal wound models, bevacizumab dosing resulted in reductions in
wound tensile strength, decreased granulation and re-epithelialization, and
delayed time to wound closure.
Reproductive and Developmental Toxicology
Pregnant rabbits dosed with 1 to 12 times the human dose of
bevacizumab every three days during the period of organogenesis (gestation day
6-18) exhibited teratogenic effects, decreases in maternal and fetal body
weights, and increased number of fetal resorptions. Teratogenic effects
included: reduced or irregular ossification in the skull, jaw, spine, ribs,
tibia and bones of the paws; meningocele; fontanel, rib and hindlimb
deformities; corneal opacity; and absent hindlimb phalanges. There are no data
available regarding the level of bevacizumab exposure in the offspring.
Clinical Studies
Metastatic Colorectal Cancer (mCRC)
Study 1
In this double-blind, active-controlled study, patients were
randomized (1:1:1) to IV bolus-IFL (irinotecan 125 mg/m², 5-FU 500 mg/m², and
leucovorin (LV) 20 mg/m² given once weekly for 4 weeks every 6 weeks) plus
placebo (Arm 1), bolus-IFL plus Avastin (5 mg/kg every 2 weeks) (Arm 2), or
5-FU/LV plus Avastin (5 mg/kg every 2 weeks) (Arm 3). Enrollment in Arm 3 was
discontinued, as pre-specified, when the toxicity of Avastin in combination
with the bolus-IFL regimen was deemed acceptable. The main outcome measure was
overall survival (OS).
Of the 813 patients randomized to Arms 1 and 2, the median
age was 60, 40% were female, 79% were Caucasian, 57% had an ECOG performance
status of 0, 21% had a rectal primary and 28% received prior adjuvant
chemotherapy. In 56% of the patients, the dominant site of disease was
extra-abdominal, while the liver was the dominant site in 38% of patients.
The addition of Avastin resulted in an improvement in
survival across subgroups defined by age ( < 65 yrs, ≥ 65 yrs) and
gender. Results are presented in Table 5 and Figure 1.
Table 5 : Study 1 Efficacy Results
| |
IFL + Placebo |
IFL + Avastin
5 mg/kg q 2 wks |
| Number of Patients |
411 |
402 |
| Overall Survivala |
| Median (months) |
15.6 |
20.3 |
| Hazard ratio |
|
0.66 |
| Progression-free Survivala |
| Median (months) |
6.2 |
10.6 |
| Hazard ratio |
|
0.54 |
| Overall Response Rateb |
| Rate (percent) |
35% |
45% |
| Duration of Response |
| Median (months) |
7.1 |
10.4 |
a p < 0.001 by stratified log rank test.
b p < 0.01 by χ² test. |
Figure 1 : Duration of Survival in Study 1
Among the 110 patients enrolled in Arm 3, median OS was 18.3
months, median progression-free survival (PFS) was 8.8 months, objective
response rate (ORR) was 39%, and median duration of response was 8.5 months.
Study 2
Study 2 was a randomized, open-label, active-controlled
trial in patients who were previously treated with irinotecan +/- 5-FU for
initial therapy for metastatic disease or as adjuvant therapy. Patients were
randomized (1:1:1) to IV FOLFOX4 (Day 1: oxaliplatin 85 mg/m² and LV 200 mg/m²
concurrently, then 5-FU 400 mg/m² bolus followed by 600 mg/m² continuously; Day
2: LV 200 mg/m², then 5-FU 400 mg/m² bolus followed by 600 mg/m² continuously;
repeated every 2 weeks), FOLFOX4 plus Avastin (10 mg/kg every 2 weeks prior to
FOLFOX4 on Day 1), or Avastin monotherapy(10 mg/kg every 2 weeks). The main
outcome measure was OS.
The Avastin monotherapy arm was closed to accrual after
enrollment of 244 of the planned 290 patients following a planned interim
analysis by the data monitoring committee based on evidence of decreased
survival compared to FOLFOX4 alone.
Of the 829 patients randomized to the three arms, the median
age was 61 years, 40% were female, 87% were Caucasian, 49% had an ECOG
performance status of 0, 26% received prior radiation therapy, and 80% received
prior adjuvant chemotherapy, 99% received prior irinotecan, with or without
5-FU as therapy for metastatic disease, and 1% received prior irinotecan and
5-FU as adjuvant therapy.
The addition of Avastin to FOLFOX4 resulted in significantly
longer survival as compared to FOLFOX4 alone (median OS 13.0 months vs. 10.8
months; hazard ratio 0.75 [95% CI 0.63, 0.89], p = 0.001 stratified log rank
test) with clinical benefit seen in subgroups defined by age ( < 65 yrs,
≥ 65 yrs) and gender. PFS and ORR based on investigator assessment were
higher in the Avastin plus FOLFOX4 arm.
Study 3
The activity of Avastin in combination with bolus or
infusional 5-FU/LV was evaluated in a single arm study enrolling 339 patients
with mCRC with disease progression following both irinotecan- and
oxaliplatin-containing chemotherapy regimens. Seventy-three percent of patients
received concurrent bolus 5-FU/LV. One objective partial response was verified
in the first 100 evaluable patients for an overall response rate of 1% (95% CI
0-5.5%).
Unresectable Non–Squamous Non–Small Cell Lung Cancer (NSCLC)
Study 4
The safety and efficacy of Avastin as first-line treatment
of patients with locally advanced, metastatic, or recurrent non–squamous NSCLC
was studied in a single, large, randomized, active-controlled, open-label,
multicenter study.
Chemotherapy-naïve patients with locally advanced,
metastatic or recurrent non–squamous NSCLC were randomized (1:1) to receive six
21-day cycles of paclitaxel 200 mg/m² and carboplatin AUC=6.0, by IV on day 1
(PC) or PC in combination with Avastin 15 mg/kg by IV on day 1 (PC plus
Avastin). After completion or upon discontinuation of chemotherapy, patients in
the PC plus Avastin arm continued to receive Avastin alone until disease
progression or until unacceptable toxicity. Patients with predominant squamous
histology (mixed cell type tumors only), central nervous system (CNS)
metastasis, gross hemoptysis ( ≥ ½ tsp of red blood), unstable angina, or
receiving therapeutic anticoagulation were excluded. The main outcome measure
was duration of survival.
Of the 878 patients randomized, the median age was 63, 46%
were female, 43% were ≥ age 65, and 28% had ≥ 5% weight loss at
study entry. Eleven percent had recurrent disease and of the 89% with newly
diagnosed NSCLC, 12% had Stage IIIB with malignant pleural effusion and 76% had
Stage IV disease.
The results are presented in Figure 2. OS was statistically
significantly higher among patients receiving PC plus Avastin compared with
those receiving PC alone; median OS was 12.3 months vs. 10.3 months [hazard
ratio 0.80 (repeated 95% CI 0.68, 0.94), final p- value 0.013, stratified
log-rank test]. Based on investigator assessment which was not independently
verified, patients were reported to have longer PFS with Avastin in combination
with PC compared to PC alone.
Figure 2 : Duration of Survival in Study 4
In an exploratory analyses across patient subgroups, the
impact of Avastin on OS was less robust in the following: women [HR = 0.99 (95%
CI: 0.79, 1.25)], age ≥ 65 years [HR = 0.91 (95% CI: 0.72, 1.14)] and
patients with ≥ 5% weight loss at study entry [HR = 0.96 (95% CI: 0.73,
1.26)].
Metastatic Breast Cancer (MBC)
Study 5
The efficacy and safety of Avastin as first-line treatment
of patients with MBC was studied in a single, open-label, randomized,
multicenter study. Patients who had not received chemotherapy for locally
recurrent or MBC were randomized (1:1) to receive paclitaxel (90 mg/m² IV once
weekly for 3 out of 4 weeks) alone or in combination with Avastin (10 mg/kg IV
infusion every 2 weeks). Patients were treated until disease progression or
unacceptable toxicity. In situations where paclitaxel was discontinued or held,
treatment with Avastin alone could be continued until disease progression.
Patients with breast cancer overexpressing HER2 were not eligible unless they
had received prior therapy with trastuzumab.
Prior hormonal therapy for the treatment of metastatic
disease was allowed, as was prior adjuvant chemotherapy or hormonal therapy.
Adjuvant taxane therapy, if received, must have been completed 12 or more
months prior to study entry. Patients with central nervous system metastasis
were excluded. The main outcome measure of the study was PFS as assessed by
independent radiographic review. Secondary outcome measures were OS and ORR.
Of the 722 patients randomized, the median age was 55 years,
76% were white, 55% were postmenopausal, and 64% were ER and/or PR positive.
Patient characteristics were similar across treatment arms. Thirty-six percent
had received prior hormonal therapy for advanced disease, and 66% had received
adjuvant chemotherapy, including 20% with prior taxane use and 50% with prior
anthracycline use. Efficacy results are summarized in Table 6.
Table 6 : Avastin Efficacy Results from Study 5
| Efficacy Parameter |
Avastin +
Paclitaxel
(n=368) |
Paclitaxel
Alone
(n=354) |
p-value |
HR
(95% CI) |
| Progression-free Survival |
11.3 |
5.8 |
|
0.48 |
| [median, months (95% CI)] |
(10.5, 13.3) |
(5.4, 8.2) |
< 0.0001 |
(0.39, 0.61) |
| Overall Survival |
26.5 |
24.8 |
|
0.87 |
| [median, months (95% CI)] |
(23.7, 29.2) |
(21.4, 27.4) |
0.14 |
(0.72, 1.05) |
| Partial Response Rate1 (PR) |
48.9%2 |
22.2% |
< 0.001 |
- |
1 Includes only patients with measurable disease.
2 The difference in partial response rates is 26.7% with a
95% CI (18.4%, 35.0%). |
The addition of Avastin to paclitaxel resulted in an improvement in PFS with
no significant improvement in OS. Partial response rates in patients with measurable
disease were higher with Avastin plus paclitaxel. No complete responses were
observed.
Thirty-four percent of the patients had incomplete follow-up
for disease progression; therefore an exploratory analysis using similar
imputation between arms was performed, which yielded a hazard ratio of 0.57.
Study 6
The efficacy and safety of Avastin as second- and third-line
treatment of patients with MBC was studied in a single open-label randomized
study. Patients who had received prior anthracycline and taxane therapy in the
adjuvant setting or for their MBC were randomized (1:1) to receive capecitabine
alone or in combination with Avastin. Of the 462 enrolled patients, the median
age was 51 years, 81% were white, and 50% were ER positive. Patient
characteristics were similar across the treatment arms.
The study failed to demonstrate a statistically significant
effect on PFS or OS. The median PFS was 4.2 months in the capecitabine arm and
4.9 months in the capecitabine plus Avastin arm (log-rank p-value = 0.86,
hazard ratio 0.98). The median OS was 14.5 months in the capecitabine arm and
15.1 months in the capecitabine plus Avastin arm (hazard ratio of 1.08).
Glioblastoma
Study 7
The efficacy and safety of Avastin was evaluated in Study 7,
an open-label, multicenter, randomized, non-comparative study of patients with
previously treated glioblastoma. Patients received Avastin (10 mg/kg IV) alone
or Avastin plus irinotecan every 2 weeks until disease progression or until
unacceptable toxicity. All patients received prior radiotherapy (completed at
least 8 weeks prior to receiving Avastin) and temozolomide. Patients with
active brain hemorrhage were excluded.
Of the 85 patients randomized to the Avastin arm, the median
age was 54 years, 32% were female, 81% were in first relapse, Karnofsky
performance status was 90-100 for 45% and 70-80 for 55%.
The efficacy of Avastin was demonstrated using response
assessment based on both WHO radiographic criteria and by stable or decreasing
corticosteroid use, which occurred in 25.9% (95% CI 17.0%, 36.1%) of the patients.
Median duration of response was 4.2 months (95% CI 3.0, 5.7). Radiologic
assessment was based on MRI imaging (using T1 and T2/FLAIR). MRI does not
necessarily distinguish between tumor, edema, and radiation necrosis.
Study 8
Study 8, was a single-arm, single institution trial with 56
patients with glioblastoma. All patients had documented disease progression
after receiving temozolomide and radiation therapy. Patients received Avastin
10 mg/kg IV every 2 weeks until disease progression or unacceptable toxicity.
The median age was 54, 54% were male, 98% Caucasian, and 68%
had a Karnofsky Performance Status of 90-100.
The efficacy of Avastin was supported by an objective
response rate of 19.6% (95% CI 10.9%, 31.3%) using the same response criteria
as in Study 7. Median duration of response was 3.9 months 95% CI 2.4, 17.4).
Metastatic Renal Cell Carcinoma (mRCC)
Study 9
Patients with treatment-naïve mRCC were evaluated in a
multicenter, randomized, double-blind, international study comparing Avastin plus
interferon alfa 2a (IFN- α2a) versus placebo plus IFN-α2a. A total of
649 patients who had undergone a nephrectomy were randomized (1:1) to receive
either Avastin (10 mg/kg IV infusion every 2 weeks; n = 327) or placebo (IV
every 2 weeks; n = 322) in combination with IFN-α2a (9 MIU subcutaneously
three times weekly, for a maximum of 52 weeks). Patients were treated until
disease progression or unacceptable toxicity. The main outcome measure of the
study was investigator-assessed PFS. Secondary outcome measures were ORR and
OS.
The median age was 60 years (range 18-82), 96% were
white, and 70% were male. The study population was characterized by Motzer
scores as follows: 28% favorable (0), 56% intermediate (1-2), 8% poor (3-5),
and 7% missing.
The results are presented in Figure 3. PFS was statistically
significantly prolonged among patients receiving Avastin plus IFN-α2a
compared to those receiving IFN-α2a alone; median PFS was 10.2 months vs.
5.4 months [HR 0.60 (95% CI 0.49, 0.72), p-value < 0.0001, stratified
log-rank test]. Among the 595 patients with measureable disease, ORR was also
significantly higher (30% vs. 12%, p < 0.0001, stratified CMH test). There
was no improvement in OS based on the final analysis conducted after 444
deaths, with a median OS of 23 months in the Avastin plus IFN-α2a arm and
21 months in the IFN-α2a plus placebo arm [HR 0.86, (95% CI 0.72, 1.04)].
Figure 3 : Progression-Free Survival in Study 9
Last updated on RxList: 8/12/2009