Clinical Pharmacology for Cerdelga
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." The clinical features of this lysosomal storage disorder (LSD) are reflective of the accumulation of Gaucher cells in the reticuloendothelial system (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 leads to clinically significant anemia and thrombocytopenia.
CERDELGA is a specific inhibitor of glucosylceramide synthase (IC50=10 ng/mL) and acts as a substrate reduction therapy for GD1 by reducing the production of GL-1. By reducing GL-1 production, CERDELGA alleviates the accumulation of GL-1 in the target organs.
Pharmacodynamics
Effects on spleen and liver volume, hemoglobin, and platelets increased with increasing steady-state average trough concentrations of eliglustat ranging up to 14 ng/mL in treatment naive patients in Trial 1. In patients previously treated with enzyme-replacement therapy in Trial 2 [see Clinical Studies], no clinically relevant exposure-response relationship was observed.
Cardiac Electrophysiology
Concentration-related increases were observed for the placebo-corrected change from baseline in the PR, QRS, and QTc intervals. At the mean peak concentration of 237 ng/mL at a dose of 800 mg eliglustat tartrate (8 times the recommended dose), CERDELGA did not prolong the QT/QTc interval to any clinically relevant extent. However, pharmacokinetic/ pharmacodynamic modeling predicts 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 eliglustat plasma concentration of 500 ng/mL [see WARNINGS AND PRECAUTIONS].
Pharmacokinetics
Absorption
The oral bioavailability of eliglustat was less than 5% in CYP2D6 EMs following a single 84 mg dose of CERDELGA.
In CYP2D6 EMs, the eliglustat pharmacokinetics is time-dependent and the systemic exposure increases in a more than dose-proportional manner over the dose range of 42 to 294 mg (0.5 to 3.5 times the recommended dosage). In addition, 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 time-independent. Compared to EMs, the systemic exposure following 84 mg twice daily at steady state is 7-fold to 9-fold higher in PMs.
Dosing of CERDELGA 84 mg once daily has not been studied in PMs. The predicted Cmax and AUC0–24hr in PMs using a physiologically based pharmacokinetic (PBPK) model with 84 mg once daily were 75 ng/mL and 956 hr·ng/mL, respectively.
Table 7 describes the pharmacokinetic parameters for eliglustat in healthy subjects following multiple doses of 84 mg CERDELGA twice daily.
Table 7: Pharmacokinetic Parameters for Eliglustat following Multiple Doses of 84 mg CERDELGA Twice Daily
| Parameter |
CYP2D6 Metabolizer Status |
EMs
(n=96) |
IMs
(n=1) |
PMs*
(n=9) |
| Cmax (ng/mL)† |
12.1 (42%)
to
25.0 (141%) |
44.6 |
113 (32%)
to
137 (40%) |
| AUCtau (ng·hr/mL)† |
76.3 (37%)
to
143 (160%) |
306 |
922 (33%)
to
1057 (38%) |
| Median Tmax (hr) [min to max]‡ |
1.5 [0.5 to 3.0]
to
2 [1.5 to 2.1] |
2 |
3 [2 to 4] |
*84 mg twice daily is not the recommended dosage in PMs [see DOSAGE AND ADMINISTRATION].
†Range of the mean (CV%) values from multiple studies.
‡Range of the median time to reach maximum plasma concentration (Tmax) from multiple studies. |
Administration of CERDELGA with a high fat meal (approximately 1000 calories with 50% calories from fat) resulted in a 15% decrease in Cmax (not clinically significant) but no change in AUC.
Distribution
Following intravenous administration, the volume of distribution of eliglustat was 835 L in EMs. Plasma protein binding of eliglustat ranges from 76% to 83%.
Elimination
Eliglustat terminal elimination half-life was approximately 6.5 hours in CYP2D6 EMs, and 8.9 hours in PMs. Following intravenous administration of 42 mg (0.5 times the recommended oral dose) in healthy subjects, the mean (range) of eliglustat total body clearance was 88 L/h (80 to 105 L/h) in EMs.
Metabolism
CERDELGA is primarily metabolized by CYP2D6 and to a lesser extent by CYP3A4.
Excretion
After oral administration of radiolabeled eliglustat, the majority of the administered dose is excreted in urine (42%) and feces (51%), mainly as metabolites.
Specific Populations
No clinically significant differences in the pharmacokinetics of eliglustat were observed based on age (18 to 71 years), sex, race (mostly were Caucasian, including those of Ashkenazi Jewish descent; however, it included the following populations: African American, American Indians, Hispanics, and Asians), or body weight (41 to 136 kg).
Patients With Renal Impairment
Eliglustat pharmacokinetics was similar in CYP2D6 EMs with severe renal impairment and healthy CYP2D6 EMs. Eliglustat pharmacokinetics in EMs with ESRD and in IMs or PMs with any degree of renal impairment is unknown [see Use In Specific Populations].
Patients With Hepatic Impairment
Table 8 describes the effect of mild and moderate hepatic impairment on the pharmacokinetics of eliglustat in CYP2D6 EMs compared to EMs with normal hepatic function following a single 84 mg dose. The effect of hepatic impairment is highly variable with the coefficients of variation (CVs%) of 135% and 110% for Cmax and 171% and 121% for AUC in CYP2D6 EMs with mild and moderate hepatic impairment, respectively.
Table 8: Effect of Hepatic Impairment on Eliglustat Pharmacokinetics following a Single Dose of 84 mg CERDELGA in CYP2D6 EMs
|
Mild Hepatic Impairment
(n=6) |
Moderate Hepatic Impairment
(n=7) |
| Cmax |
↑ 1.2-fold |
↑ 2.8-fold |
| AUC |
↑ 1.2-fold |
↑ 5.2-fold |
Steady-state pharmacokinetics of eliglustat in CYP2D6 IMs and PMs with mild and moderate hepatic impairment is unknown. The effect of severe hepatic impairment in subjects with any CYP2D6 phenotype is unknown [see Use In Specific Populations].
Drug Interaction Studies
Effect Of Other Drugs On CERDELGA
Table 9 describes the effect of drug interactions on the pharmacokinetics of eliglustat [see DRUG INTERACTIONS].
Table 9: Drug Interactions Affecting Eliglustat Concentrations
| Concomitant Drug(s) |
CYP2D6 Metabolizer Status |
| EMs |
IMs |
PMs |
| Cmax |
AUCtau |
Cmax |
AUCtau |
Cmax |
AUCtau |
| CYP2D6 Inhibitor |
| Paroxetine (strong) |
↑ 7.0-
fold |
↑ 8.4-
fold |
↑ 2.1-
fold* |
↑ 2.3-
fold* |
No increase expected† |
| Terbinafine (moderate) |
↑ 3.8-
fold |
↑ 4.5-
fold |
↑ 1.6-fold* |
| CYP3A Inhibitor |
| Ketoconazole (strong) |
↑ 4.0-
fold |
↑ 4.4-
fold |
↑ 4.4-
fold* |
↑ 5.4-
fold* |
↑ 4.3-
fold*,‡ |
↑ 6.2-
fold*,‡ |
| Fluconazole (moderate) |
↑ 2.8-
fold* |
↑ 3.2-
fold* |
↑ 2.5-
fold* |
↑ 2.9-
fold* |
↑ 2.4-
fold*,‡ |
↑ 3.0-
fold*,‡ |
| CYP2D6 Inhibitors Concomitantly with CYP3A Inhibitors |
| Paroxetine with ketoconazole |
↑ 16.7-
fold* |
↑ 24.2-
fold* |
↑ 7.5-
fold* |
↑ 9.8-
fold* |
Expected similar
increase as with CYP3A inhibitors alone† |
| Terbinafine with fluconazole |
↑ 10.2-
fold* |
↑ 13.6-
fold* |
↑ 4.2-
fold* |
↑ 5.0-
fold* |
| CYP3A Inducers |
Rifampin
(strong) |
↓ 90%§ |
↓ 95% |
↑ = Increased; ↓ = Decreased
*Predicted pharmacokinetic parameters based on PBPK models.
†Due to little or no CYP2D6 activity in CYP2D6 PMs.
‡Following coadministration with CERDELGA 84 mg once daily.
§Following coadministration with CERDELGA 127 mg twice daily (1.5 times the recommended dosage). |
No clinically significant pharmacokinetic changes were observed for eliglustat when coadministered with intravenous rifampin (an OATP inhibitor), or gastric pH modifying drugs (e.g., aluminum hydroxide, magnesium hydroxide, calcium carbonate, pantoprazole).
In vitro, eliglustat is a substrate of P-glycoprotein (P-gp). The effect of P-gp inhibitors on eliglustat pharmacokinetics is unknown.
Effect Of CERDELGA On Other Drugs
CYP2D6 substrates
Following multiple doses of CERDELGA 127 mg twice daily (1.5 times the recommended dosage), metoprolol (a CYP2D6 substrate) mean Cmax and AUC increased by 1.7-fold and 2.3-fold in CYP2D6 EMs, respectively, and by 1.2-fold and 1.6-fold in IMs, respectively [see DRUG INTERACTIONS].
P-gp substrates
Following multiple doses of CERDELGA 127 mg twice daily (1.5 times the recommended dosage) in CYP2D6 EMs and IMs, or 84 mg twice daily in PMs, digoxin (a P-gp substrate) mean Cmax increased by 1.7-fold and AUC increased by 1.5-fold [see DRUG INTERACTIONS].
Oral contraceptives
Repeated doses of CERDELGA 84 mg twice daily did not change the exposures to norethindrone (1.0 mg) and ethinyl estradiol (0.035 mg).
Clinical Studies
CERDELGA In Treatment-Naive GD1 Patients – Trial 1
Trial 1 (NCT00891202) was a randomized, double-blind, placebo-controlled, multicenter clinical study evaluating the efficacy and safety of CERDELGA in 40 treatment-naive 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 × 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 10.
Table 10: Change from Baseline to Month 9 in Treatment-Naive 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 (× 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 (≤20 MN, >20 MN) and baseline parameter value. |
In the open-label extension phase of Trial 1 in naive GD1 patients, 38 of 40 patients who continued treatment with CERDELGA for 2 years demonstrated the following changes in clinical parameters from baseline to 2 years: mean (SD) percent change in spleen volume (MN) -51.1% (10.7); mean (SD) percent change in liver volume (MN) -16.1% (11.3); mean (SD) absolute change in hemoglobin level (g/dL) 1.3 (1.2), and mean (SD) percent change in platelet count (mm3) 65.3% (40.9).
In a separate uncontrolled study (NCT00358150) of treatment-naive 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
Trial 2 (NCT00943111) 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 × 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 11. There were no clinically meaningful differences between groups for any of the four parameters.
Table 11: 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 (× 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 |
In the open-label extension phase of Trial 2, 141 of 146 patients (42 patients previously treated with enzyme treatment therapy and 99 who continued treatment with CERDELGA) were evaluated for stability, as defined in the initial 12 months of the trial, in clinical parameters (composite of spleen and liver volume, hemoglobin level, and platelet count).
Stability was shown in 120/141 (85%) patients at one year and 111/129 (86%) patients at 2 years of CERDELGA exposure.