CLINICAL PHARMACOLOGY
Mechanism Of Action
Gaucher disease is caused by a deficiency of the
lysosomal enzyme acid β-glucosidase. Acid β-glucosidase catalyzes the
conversion of the sphingolipid glucocerebroside into glucose and ceramide. The
enzymatic deficiency causes an accumulation of glucosylceramide (GL-1)
primarily in the lysosomal compartment of macrophages, giving rise to foam
cells or “Gaucher cells”. CERDELGA is a specific inhibitor of
glucosylceramide synthase (IC50 = 10 ng/mL), and acts as a substrate reduction
therapy for GD1. In clinical trials CERDELGA 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, spleen, and bone marrow leads to organomegaly and skeletal disease.
Presence of Gaucher cells in the bone marrow and spleen lead to clinically
significant anemia and thrombocytopenia.
Pharmacodynamics
Electrocardiographic Evaluation
QTc interval prolongation was studied in a double-blind,
single dose, placebo- and positive-controlled crossover study in 42 healthy
subjects. Concentration-related increases were observed for the
placebo-corrected change from baseline in the PR, QRS, and QTc intervals. Based
on PK/PD modeling, eliglustat plasma concentrations of 500 ng/mL are predicted
to cause mean (upper bound of the 95% one-sided confidence interval) increases
in the PR, QRS, and QTcF intervals of 22 (26), 7 (10), and 13 (19) msec,
respectively. At the highest geometric mean concentrations of 237 ng/mL
following a single supratherapeutic dose tested in the thorough QT study,
CERDELGA did not prolong the QT/QTc interval to any clinically relevant extent.
Pharmacokinetics
At a given dose, the systemic exposure (Cmax and AUC)
depends on the CYP2D6 phenotype. In CYP2D6 EMs and IMs, the eliglustat
pharmacokinetics is time-dependent and the systemic exposure increases in a
more than dose proportional manner. After multiple oral doses of 84 mg twice
daily in EMs, eliglustat systemic exposure (AUC0-12) increased up to about
2-fold at steady state compared to after the first dose (AUC0-∞). The pharmacokinetics
of eliglustat in CYP2D6 PMs is expected to be linear and timeindependent.
Compared to EMs, the systemic exposure following 84 mg twice daily at steady
state is 7- to 9-fold higher in PMs.
Absorption
In CYP2D6 EMs, median time to reach maximum plasma
concentrations (tmax) occurs at 1.5 to 2 hours following multiple doses of
CERDELGA 84 mg twice daily. The corresponding mean Cmax values range from 12.1
to 25.0 ng/mL in EMs. The mean AUCtau values range from 76.3 to 143 hr*ng/mL in
EMs. The Cmax and AUCtau in one IM subject receiving multiple doses of CERDELGA
84 mg twice daily was 44.6 ng/mL and 306 hr*ng/mL, respectively. The oral
bioavailability is low in EMs ( < 5%) following single dose of CERDELGA 84 mg
due to significant first-pass metabolism.
In PMs, median tmax occurs at 3 hours following multiple
doses of CERDELGA 84 mg twice daily. The corresponding mean Cmax and AUCtau
values range from 113 to 137 ng/mL and 922 to 1057 hr*ng/mL, respectively.
Oral dosing of CERDELGA 84 mg once daily has not been
studied in PMs. The predicted Cmax and AUC0-24hr in PMs using
physiologically-based pharmacokinetic (PBPK) model with 84 mg once daily are 75
ng/mL and 956 hr*ng/mL, respectively.
Administration of CERDELGA with a high fat meal resulted in
a 15% decrease in Cmax but no change in AUC. Food does not have a clinically
relevant effect on eliglustat pharmacokinetics.
Distribution
Eliglustat is moderately bound to human plasma proteins
(76 to 83%). In the blood, it is mainly distributed in plasma and not red blood
cells. After intravenous (IV) administration, the volume of distribution of
eliglustat was 835 L in CYP2D6 EMs, suggesting wide distribution to tissues
(CERDELGA is only for oral use).
Metabolism and Elimination
CERDELGA is extensively metabolized with high clearance,
mainly by CYP2D6 and to a lesser extent CYP3A4. Primary metabolic pathways of
eliglustat involve sequential oxidation of the octanoyl moiety followed by
oxidation of the 2,3-dihydro-1,4- benzodioxane moiety, or a combination of the
two pathways, resulting in multiple oxidative metabolites. No active
metabolites have been identified.
After oral administration of 84 mg [14C]-eliglustat, the
majority of the administered dose is excreted in urine (41.8%) and feces
(51.4%), mainly as metabolites. After 42 mg IV administration in healthy
volunteers, mean (CV%) of eliglustat total body clearance was 88 L/h (8.8%) in
CYP2D6 EMs (CERDELGA is only for oral use). Following multiple oral doses of
CERDELGA 84 mg twice daily, eliglustat terminal elimination half-life(T½) was
approximately 6.5 hours in EMs and 8.9 hours in PMs.
Specific Populations
Based on population PK analysis, there was no effect of
mild renal impairment on eliglustat PK. Furthermore, gender, body weight, age,
and race had no clinically relevant impact on the pharmacokinetics of
eliglustat.
Drug Interactions - Effect of Other Drugs on CERDELGA
In vitro, eliglustat is metabolized primarily by CYP2D6
and to a lesser extent by CYP3A4. Eliglustat is also a substrate of P-glycoprotein
(P-gp).
Co-administration of CERDELGA with CYP2D6 Inhibitors
Systemic exposure (Cmax and AUCtau) of eliglustat
increased 7.0-fold and 8.4-fold, respectively, following co-administration of
CERDELGA 84 mg twice daily with paroxetine (a strong CYP2D6 inhibitor) 30 mg
once daily in EMs (N=30), respectively.
Simulations using PBPK models suggested that paroxetine
may increase the Cmax and AUCtau of eliglustat 2.1- and 2.3-fold in IMs,
respectively.
Compared to paroxetine, the effects of terbinafine (a
moderate inhibitor of CYP2D6) on the exposure of eliglustat in EMs or IMs were
predicted to be smaller. Simulations using PBPK models suggested that
terbinafine may increase the Cmax and AUCtau of eliglustat 3.8- and 4.5-fold in
EMs, respectively. Both Cmax and AUCtau increased 1.6-fold in IMs.
Co-administration of CERDELGA with CYP3A Inhibitors
CYP2D6 EMs and IMS
Following co-administration of CERDELGA 84 mg twice daily
with ketoconazole (a strong CYP3A inhibitor) 400 mg once daily, the systemic
exposure (Cmax and AUCtau) of eliglustat increased 4.0-fold and 4.4-fold in EMs
(N=31).
Simulations using PBPK models suggested that ketoconazole
may increase the Cmax and AUCtau of eliglustat 4.4- and 5.4-fold in IMs,
respectively.
Compared to ketoconazole, the effects of fluconazole (a
moderate inhibitor of CYP3A) on the exposure of eliglustat in EMs or IMs were
predicted to be smaller. Simulations using PBPK models suggested that
fluconazole may increase the Cmax and AUCtau of eliglustat 2.8- and 3.2-fold in
EMs, respectively, and 2.5- to 2.9-fold in IMs, respectively.
CYP2D6 PMS
The effect of CYP3A inhibitors on the systemic exposure
of eliglustat in PMs has not been evaluated in clinical studies. Simulations
using PBPK models suggest that ketoconazole may increase the Cmax and AUC0-24h
of eliglustat 4.3- and 6.2-fold when coadministered with CERDELGA 84 mg once
daily in PMs. Simulations using PBPK models suggested that fluconazole may
increase the Cmax and AUC0-24h of eliglustat 2.4- and 3.0-fold, respectively,
when co-administered with CERDELGA 84 mg once daily.
Co-administration of CERDELGA with CYP2D6 and CYP3A
inhibitors
Simulations using PBPK models suggested that concomitant
use of CERDELGA 84 mg twice daily with paroxetine and ketoconazole may increase
the Cmax and AUCtau of eliglustat 16.7- and 24.2-fold in EMs, respectively. The
predicted Cmax and AUCtau of eliglustat increased 7.5- to 9.8-fold in IMs,
respectively.
Simulations using PBPK models suggested that concomitant
use of CERDELGA 84 mg twice daily with terbinafine and fluconazole may increase
the Cmax and AUCtau of eliglustat 10.2- and 13.6-fold in EMs. The predicted
Cmax and AUCtau of eliglustat increased 4.2- to 5.0-fold in IMs, respectively.
Effect of CYP3A inducers on Eliglustat PK
Systemic exposures (Cmax and AUCtau) of eliglustat
decreased by approximately 90% in EMs and IMs, following co-administration of
CERDELGA 127 mg twice daily with rifampin (a strong CYP3A inducer) 600 mg PO
once daily. The only approved dose of CERDELGA is 84 mg. Systemic exposures of
eliglustat decreased by approximately 95% following co-administration of
CERDELGA 84 mg twice daily with rifampin 600 mg PO once daily in PMs.
Effect of OATP (organic anion transporting polypeptide)
Inhibitors on Eliglustat PK
Systemic exposures of eliglustat were similar with or
without co-administration of single 600 mg IV dose of rifampin (a potent OATP
inhibitor) regardless of subjects' CYP2D6 phenotypes.
Effect of P-gp Inhibitors on Eliglustat PK
The effect of P-gp inhibitors on the systemic exposure of
eliglustat has not been studied clinically.
Effect of Gastric pH-Modifying Agents on Eliglustat PK
Gastric pH-modifying agents (Maalox®, Tums®, Protonix®)
did not have a clinically relevant effect on eliglustat exposure.
Drug Interactions - Effect of CERDELGA on the PK of Other
Drugs
Eliglustat is an inhibitor of P-gp and CYP2D6.
Following multiple doses of CERDELGA 127 mg twice daily,
systemic exposures (Cmax and AUC) to metoprolol (a CYP2D6 substrate) increased
compared to metoprolol administration alone. Mean Cmax and AUC increased by
1.7- and 2.3-fold, respectively, in EMs and by 1.2- and 1.6-fold, respectively
in IMs. The only approved dose of CERDELGA is 84 mg.
Following multiple doses of CERDELGA 127 mg twice daily
in EMs and IMs or 84 mg twice daily in PMs, systemic exposures (Cmax and AUC)
to digoxin (a P-gp substrate, with narrow therapeutic index) increased compared
to digoxin administration alone. Â Mean Cmax and AUC increased by 1.7- and
1.5-fold, respectively. The only approved dose of CERDELGA is 84 mg.
In vitro, eliglustat is a weak inhibitor of CYP3A.
Repeated doses of CERDELGA 84 mg twice daily did not change the exposures to
norethindrone (1.0 mg) and ethinyl estradiol (0.035 mg). Therefore, CERDELGA is
not expected to impact the efficacy or safety of oral contraceptives containing
norethindrone and ethinyl estradiol.
Clinical Studies
The efficacy of CERDELGA was evaluated in three clinical
trials in patients with Gaucher disease type 1.
CERDELGA In Treatment-Naïve GD1 Patients – Trial 1
Trial 1 was a randomized, double-blind,
placebo-controlled, multicenter clinical study evaluating the efficacy and
safety of CERDELGA in 40 treatment-naïve GD1 patients 16 years of age or older
(median age 30.4 years) with pre-existing splenomegaly and hematological
abnormalities. Patients were required to have received no treatment with substrate
reduction therapy within 6 months or ERT within 9 months prior to randomization;
all but 5 patients in the study had no prior therapy. Patients were stratified
according to baseline spleen volume ( ≤ 20 or > 20 multiples of normal
[MN]) and randomized in a 1:1 ratio to receive CERDELGA or placebo for the
duration of the 9-month blinded primary analysis period. The CERDELGA treatment
group was comprised of IM (5%), EM (90%) and URM (5%) patients. Patients
randomized to CERDELGA treatment received a starting dose of 42 mg twice daily,
with a dose increase to 84 mg twice daily possible at Week 4 based on the
plasma trough concentration at Week 2. The majority of patients (17 [85%])
received a dose escalation to 84 mg twice daily at Week 4, and 3 (15%)
continued to receive 42 mg twice daily for the duration of the 9-month blinded
primary analysis period.
The primary endpoint was the percentage change in spleen
volume (in MN) from baseline to 9 months as compared to placebo. Secondary
endpoints were absolute change in hemoglobin level, percentage change in liver
volume (in MN), and percentage change in platelet count from baseline to 9
months compared to placebo.
At baseline, mean spleen volumes were 12.5 and 13.9 MN in
the placebo and CERDELGA groups, respectively, and mean liver volumes were 1.4
MN for both groups. Mean hemoglobin levels were 12.8 and 12.1 g/dL, and
platelet counts were 78.5 and 75.1 x 109/L, respectively.
During the 9-month primary analysis period, CERDELGA
demonstrated statistically significant improvements in all primary and
secondary endpoints compared to placebo, as shown in Table 6.
Table 6: Change from Baseline to Month 9 in
Treatment-Naïve Patients with GD1 Receiving Treatment with CERDELGA in Trial 1
|
Placebo
(n=20) |
CERDELGA
(n=20) |
Difference (CERDELGA -Placebo) [95% CI] |
p value* |
Percentage Change in Spleen Volume MN (%) |
2.3 |
-27.8 |
-30.0
[-36.8, -23.2] |
< 0.0001 |
Absolute Change in Spleen Volume (MN) |
0.3 |
-3.7 |
-4.1
[-5.3, -2.9] |
NA |
Absolute Change in Hemoglobin Level (g/dL) |
-0.5 |
0.7 |
1.2
[0.6, 1.9] |
0.0006 |
Percentage Change in Liver Volume MN (%) |
1.4 |
-5.2 |
-6.6
[-11.4, -1.9] |
0.0072 |
Absolute Change in Liver Volume (MN) |
0.0 |
-0.1 |
-0.1
[-0.2, 0.0] |
NA |
Percentage Change in Platelet Count (%) |
-9.1 |
32.0 |
41.1
[24.0, 58.2] |
< 0.0001 |
Absolute Change in Platelet Count (x 109/L) |
-7.2 |
24.1 |
31.3
[18.8, 43.8] |
NA |
MN = Multiples of Normal, CI = confidence interval, NA =
Not applicable
*Estimates and p-value are based on ANCOVA model that includes treatment group,
baseline spleen severity group ( ≤ 20MN, > 20MN) and baseline parameter
value. |
In an uncontrolled study of treatment naïve GD1 patients,
improvements in spleen and liver volume, hemoglobin level, and platelet count
continued through the 4 year treatment period.
Patients Switching From Enzyme Replacement Therapy To CERDELGA
–Trial 2
Trial 2 was a randomized, open-label, active-controlled,
non-inferiority, multicenter clinical study evaluating the efficacy and safety
of CERDELGA compared with imiglucerase in 159 treated GD1 patients (median age
37.4 years) previously treated with enzyme replacement therapy ( ≥ 3 years
of enzyme replacement therapy, dosed at 30-130 U/kg/month in at least 6 of the
prior 9 months) who met pre-specified therapeutic goals at baseline.
Pre-specified baseline therapeutic goals included: no bone crisis and free of symptomatic
bone disease within the last year; mean hemoglobin level of ≥ 11 g/dL in females
and ≥ 12 g/dL in males; mean platelet count ≥ 100,000/mm³ ; spleen
volume < 10 times normal and liver volume < 1.5 times normal.
Patients were randomized 2:1 to receive CERDELGA or
imiglucerase for the duration of the 12-month primary analysis period.
Seventy-five percent of patients randomized to CERDELGA were previously treated
with imiglucerase; 21% with velaglucerase alfa and 4% were unreported. Patients
randomized to CERDELGA treatment received a starting dose of 42 mg twice daily,
with dose increases to 84 mg twice daily and 127 mg twice daily possible at
Weeks 4 and 8 based on plasma trough concentrations of CERDELGA at Weeks 2 and
6, respectively. The percentage of patients receiving the 3 possible CERDELGA
doses was: 42 mg twice daily (20%), 84 mg twice daily (32%) and 127 mg twice
daily (48%). The CERDELGA treatment group was comprised of PM (4%), IM (10%),
EM (80%) and URM (4%) patients.
At baseline, mean spleen volumes were 2.6 and 3.2 MN in
the imiglucerase and CERDELGA groups, respectively, and liver volumes were 0.9
MN in both groups. Mean hemoglobin levels were 13.8 and 13.6 g/dL, and platelet
counts were 192 and 207 x 109/L, respectively.
The primary composite endpoint required stability in all
four component domains (hemoglobin level, platelet count, liver volume, and
spleen volume) based on changes between baseline and 12 months. Stability was
defined by the following pre-specified thresholds of change: hemoglobin level
< 1.5 g/dL decrease, platelet count < 25% decrease, liver volume < 20%
increase and spleen volume < 25% increase. The percentages of patients
meeting the criteria for stability in the individual components of the
composite endpoint were assessed as secondary efficacy endpoints.
CERDELGA met the criteria to be declared non-inferior to
imiglucerase in maintaining patient stability. After 12 months of treatment,
the percentage of patients meeting the primary composite endpoint was 84.8% for
the CERDELGA group compared to 93.6% for the imiglucerase group. The lower
bound of the 95% CI of the 8.8% difference, -17.6%, was within the
pre-specified non-inferiority margin of -25%. At Month 12, the percentages of
CERDELGA and imiglucerase patients respectively, who met stability criteria for
the individual components of the composite endpoint were: hemoglobin level, 94.9%
and 100%; platelet count, 92.9% and 100%; spleen volume, 95.8% and 100%; and liver
volume, 96.0% and 93.6%. Of the patients who did not meet stability criteria
for the individual components, 12 of 15 CERDELGA patients and 3 of 3
imiglucerase patients remained within therapeutic goals for GD1.
Mean changes from baseline in the hematological and
visceral parameters through 12 months of treatment are shown in Table 7. There
were no clinically meaningful differences between groups for any of the four
parameters.
Table 7: Mean Changes from Baseline to Month 12 in
Patients with GD1 Switching to CERDELGA in Trial 2
|
Imiglucerase
(N=47) Mean [95% CI] |
CERDELGA
(N=99) Mean [95% CI] |
Percentage Change in Spleen Volume MN (%)* |
-3.0 [-6.4, 0.4] |
-6.2 [-9.5, -2.8] |
Absolute Change in Spleen Volume (MN)* |
-0.1 [-0.2, 0.0] |
-0.2 [-0.3, -0.1] |
Absolute Change in Hemoglobin Level (g/dL) |
0.0 [-0.2, 0.2] |
-0.2 [-0.4, -0.1] |
Percentage Change in Liver Volume MN (%) |
3.6 [0.6, 6.6] |
1.8 [-0.2, 3.7] |
Absolute Change in Liver Volume (MN) |
0.0 [0.0, 0.1] |
0.0 [0.0, 0.0] |
Percentage Change in Platelet Count (%) |
2.9 [-0.6, 6.4] |
3.8 [0.0, 7.6] |
Absolute Change in Platelet Count (x 109/L) |
6.0 [-0.9, 13.0] |
9.5 [1.4, 17.6] |
Patients Stable for 52 Weeks, n (%) (Composite Primary Endpoint) |
44 (93.6) |
84 (84.8) |
MN = Multiples of Normal, CI = confidence interval
* Excludes patients with a total splenectomy. |