CLINICAL PHARMACOLOGY
Mechanism Of Action
Gaucher disease is an autosomal recessive disorder caused by mutations in the GBA gene, which
results in a deficiency of the lysosomal enzyme beta-glucocerebrosidase. Glucocerebrosidase
catalyzes the conversion of the sphingolipid glucocerebroside into glucose and ceramide. The
enzymatic deficiency causes an accumulation of glucocerebroside primarily in the lysosomal
compartment of macrophages, giving rise to foam cells or "Gaucher cells". Velaglucerase alfa
catalyzes the hydrolysis of glucocerebroside, reducing the amount of accumulated glucocerebroside.
In clinical trials VPRIV reduced spleen and liver size, and improved anemia and thrombocytopenia.
In this lysosomal storage disorder (LSD), clinical features are reflective of the accumulation of
Gaucher cells in the liver, spleen, bone marrow, and other organs. The accumulation of Gaucher cells
in the liver and spleen leads to organomegaly. Presence of Gaucher cells in the bone marrow and spleen
lead to clinically significant anemia and thrombocytopenia.
Pharmacokinetics
In a multicenter study conducted in pediatric (N=7, 4 to 17 years old) and adult (N=15, 19 to 62 years
old) patients with type 1 Gaucher disease, pharmacokinetic evaluations were performed at Weeks 1 and
37 following 60-minute intravenous infusions of VPRIV 60 Units/kg every other week. Serum
velaglucerase alfa concentrations declined rapidly with a mean half life of 11 to 12 minutes. The mean
velaglucerase alfa clearance ranged from 6.72 to 7.56 mL/min/kg. The mean volume of distribution at
steady state ranged from 82 to 108 mL/kg (8.2% to 10.8% of body weight).
No accumulation or change in velaglucerase alfa pharmacokinetics over time from Weeks 1 to 37 was
observed upon multiple-dosing 60 Units/kg every other week.
Based on the limited data, there were no notable pharmacokinetic differences between male and female
patients in this study. The effect of age on pharmacokinetics of velaglucerase alfa was inconclusive.
The effect of anti-drug antibody formation on the pharmacokinetic parameters of velaglucerase alfa is
unknown.
Clinical Studies
Overview Of Clinical Studies Of VPRIV For Gaucher Disease
The efficacy of VPRIV was assessed in three clinical trials in a total of 99 patients with type 1 Gaucher
disease: 82 patients age 4 years and older received VPRIV and 17 patients age 3 years and older
received imiglucerase. Studies I and II were conducted in patients who were not currently receiving
Gaucher disease-specific therapy. Study III was conducted in patients who were receiving imiglucerase
treatment immediately before starting VPRIV. The long-term safety of VPRIV was assessed in Study
IV, an open-label extension trial in a total of 93 patients with type 1 Gaucher disease ages 3 years and
older. Patients who had completed Studies I to III were eligible to participate in Study IV. In Studies I
through IV, VPRIV was administered intravenously over 60 minutes at a maximum dose of 60 Units/kg
every other week. Doses above 60 Units/kg were not studied in these trials.
Clinical Trials Of VPRIV As Initial Therapy
Study I was a 12-month, randomized, double-blind, parallel-dose-group, multinational trial in 25 patients
age 4 years and older with Gaucher disease-related anemia and either thrombocytopenia or
organomegaly. Patients were not allowed to have had disease-specific therapy for at least the previous
30 months; all but one had no prior therapy. The mean age was 26 years and 60% were male. Patients
were randomized to receive VPRIV at a dose of either 45 Units/kg (N=13) or 60 Units/kg (N=12) every
other week. The recommended starting dose in naïve patients is 60 Units/kg. The 45 Units/kg dosage is
not recommended as a starting dose in naïve patients [see DOSAGE AND ADMINISTRATION].
At baseline, mean hemoglobin concentration was 10.6 g/dL, mean platelet count was 97 × 109/L, mean
liver volume was 3.6 % of body weight (% BW), and mean spleen volume was 2.9 % BW.
For all studies, liver and spleen volumes were measured by MRI. The changes in clinical parameters
after 12 months of treatment are shown in Table 3. The observed change from baseline in the primary
endpoint, hemoglobin concentration, was considered to be clinically meaningful in the 60 Units/kg dose,
in light of the natural history of untreated Gaucher disease.
Table 3: Mean Change from Baseline to Month 12 for Clinical
Parameters in Patients with Type 1 Gaucher Disease Initiating Therapy
with VPRIV in Study I
Clinical Parameter |
Mean Changes from Baseline ± Std. Err. of the
Mean |
VPRIV Dose (given every other week) |
45 Units /kg*
N = 13 |
60 Units /kg
N = 12 |
Hemoglobin
concentration change
(g/dL) |
2.4 ± 0.4† |
2.4 ± 0.3‡ |
Platelet count change
(× 109/L) |
41 ± 14† |
51 ± 12† |
Liver volume change
(% BW) |
-0.30 ± 0.29 |
-0.84 ± 0.33 |
Spleen volume change
(% BW) |
-1.9 ± 0.6† |
-1.9 ± 0.5† |
*The recommended starting dose in naïve patients is 60 Units/kg. The 4 5 Units/kg
dosage is not recommended as a starting dose in naïve patients [see DOSAGE AND ADMINISTRATION].
†Statistically significant changes from baseline after adjusting for performing multiple
tests
‡Primary study endpoint was hemoglobin concentration change in the 60 Units/kg
group, p < 0.001 |
Study II was a 9-month, randomized, double-blind, active-controlled (imiglucerase), parallel-group,
multinational study in 34 patients age 4 years and older. Patients were required to have Gaucher
disease-related anemia and either thrombocytopenia or organomegaly. Patients were not allowed to
have had disease-specific therapy for at least the previous 12 months. The mean age was 30 years and
53% were female; the youngest patient who received VPRIV was age 4 years. Patients were
randomized to receive either 60 Units/kg of VPRIV (N=17) or 60 Units/kg of imiglucerase (N=17)
every other week.
At baseline, the mean hemoglobin concentration was 11.0 g/dL, mean platelet count was 171 × 109/L, and
mean liver volume was 4.3 % BW. For the patients who had not had splenectomy (7 in each group) the
mean spleen volume was 3.4 % BW. After 9 months of treatment, the mean absolute increase from
baseline in hemoglobin concentration was 1.6 g/dL ± 0.2 (SE) for patients treated with VPRIV. The
mean treatment difference in change from baseline to 9 months [VPRIV – imiglucerase] was 0.1 g/dL ±
0.4 (SE).
In both studies, examination of age and gender subgroups did not identify differences in response to
VPRIV among these subgroups. The number of non-Caucasian patients in these studies was too small to
adequately assess any difference in effects by race.
In Study IV, treatment naïve patients were administered VPRIV. Treatment-naïve patients continued to
show improvements in clinical parameters (hemoglobin concentration, platelet count, liver volume, and
spleen volume) compared with baseline for up to 60 months of treatment with ERT.
Clinical Trial In Patients Switching From Imiglucerase Treatment To VPRIV
Study III was a 12-month, open-label, single-arm, multinational study in 40 patients age 9 years and older
who had been receiving treatment with imiglucerase at doses ranging between 15 Units/kg to 60
Units/kg for a minimum of 30 consecutive months. Patients also were required to have a stable biweekly
dose of imiglucerase for at least 6 months prior to enrollment. The mean age was 36 years and 55%
were female. Imiglucerase therapy was stopped, and treatment with VPRIV was administered every
other week at the same number of units as the patient's previous imiglucerase dose. Adjustment of
dosage was allowed by study criteria if needed in order to maintain clinical parameters [see DOSAGE AND ADMINISTRATION].
Hemoglobin concentrations and platelet counts remained stable on average through 12 months of VPRIV
treatment. After 12 months of treatment with VPRIV the median hemoglobin concentration was 13.5 g/dL
(range: 10.8, 16.1) vs. the baseline value of 13.8 g/dL (range: 10.4, 16.5), and the median platelet count
after 12 months was 174 × 109/L (range: 24, 408) vs. the baseline value of 162 × 109/L (range: 29, 399).
No patient required dosage adjustment during the 12-month treatment period.
In Study IV, patients who had previously been receiving imiglucerase treatment were administered
VPRIV. Patients previously treated with imiglucerase maintained stability in clinical parameters
(hemoglobin concentration, platelet count, liver volume, and spleen volume) compared with baseline for
up to 60 months of treatment with ERT.