Clinical Pharmacology for Erleada
Mechanism Of Action
Apalutamide is an Androgen Receptor (AR) inhibitor that binds directly to the ligand-binding domain of the AR. Apalutamide inhibits AR nuclear translocation, inhibits DNA binding, and impedes AR-mediated transcription. A major metabolite, N-desmethyl apalutamide, is a less potent inhibitor of AR, and exhibited one-third the activity of apalutamide in an in vitro transcriptional reporter assay. Apalutamide administration caused decreased tumor cell proliferation and increased apoptosis leading to decreased tumor volume in mouse xenograft models of prostate cancer.
Pharmacodynamics
Apalutamide 240 mg daily in addition to ADT in patients with mCSPC (TITAN) reduced PSA to undetectable levels (<0.2 ng/mL) in 68% of patients compared to 32% of patients taking ADT alone.
Apalutamide 240 mg daily in addition to ADT in patients with nmCRPC (SPARTAN) reduced PSA to undetectable levels (<0.2 ng/mL) in 38% of patients compared to no patients (0%) taking ADT alone.
The exposure-response relationship and time course of pharmacodynamic response for the safety and effectiveness of apalutamide have not been fully characterized.
Cardiac Electrophysiology
The effect of apalutamide 240 mg once daily on the QTc interval was assessed in an open-label, uncontrolled, multi-center, single-arm dedicated QT study in 45 patients with CRPC. The maximum mean QTcF change from baseline was 12.4 ms (2-sided 90% upper CI: 16.0 ms). An exposure-QT analysis suggested a concentrationdependent increase in QTcF for apalutamide and its active metabolite.
Pharmacokinetics
Apalutamide pharmacokinetic parameters are presented as the mean [standard deviation (SD)] unless otherwise specified. Apalutamide Cmax and area under the concentration curve (AUC) increased proportionally following repeated once-daily dosing of 30 to 480 mg (0.125 to 2 times the recommended dosage). Following administration of the recommended dosage, apalutamide steady-state was achieved after 4 weeks and the mean accumulation ratio was approximately 5-fold. Apalutamide Cmax was 6.0 mcg/mL (1.7) and AUC was 100 mcg•h/mL (32) at steady-state. Daily fluctuations in apalutamide plasma concentrations were low, with mean peak-to-trough ratio of 1.63. An increase in apparent clearance ERLEADA® (apalutamide) tablets ERLEADA® (apalutamide) tablets (CL/F) was observed with repeat dosing, likely due to induction of apalutamide’s own metabolism. The auto-induction effect likely reached its maximum at the recommended dosage because exposure of apalutamide across the dose range of 30 to 480 mg is dose-proportional.
The major active metabolite N-desmethyl apalutamide Cmax was 5.9 mcg/mL (1.0) and AUC was 124 mcg•h/mL (23) at steady-state after the recommended dosage. N-desmethyl apalutamide was characterized by a flat concentration-time profile at steady-state with a mean peak-to-trough ratio of 1.27. Mean AUC metabolite/parent drug ratio for N-desmethyl apalutamide following repeat-dose administration was 1.3. Based on systemic exposure, relative potency, and pharmacokinetic properties, N-desmethyl apalutamide likely contributed to the clinical activity of apalutamide.
Absorption
Mean absolute oral bioavailability was approximately 100%. Median time to achieve peak plasma concentration (tmax) was 2 hours (range: 1 to 5 hours).
Oral administration of four 60 mg apalutamide tablets dispersed in applesauce resulted in no clinically relevant changes in Cmax and AUC when compared to administration of four intact 60 mg tablets under fasting condition.
Effect Of Food
Administration of apalutamide to healthy subjects under fasting conditions and with a high-fat meal (approximately 500 to 600 fat calories, 250 carbohydrate calories, and 150 protein calories) resulted in no clinically relevant changes in Cmax and AUC. Median time to reach tmax was delayed approximately 2 hours with food.
Distribution
The mean apparent volume of distribution at steady-state of apalutamide was approximately 276 L.
Apalutamide was 96% and N-desmethyl apalutamide was 95% bound to plasma proteins with no concentration dependency.
Elimination
he CL/F of apalutamide was 1.3 L/h after single dosing and increased to 2.0 L/h at steady-state after once-daily dosing likely due to CYP3A4 auto-induction. The mean effective half-life for apalutamide in patients was approximately 3 days at steady-state.
Metabolism
Metabolism is the main route of elimination of apalutamide. Apalutamide is primarily metabolized by CYP2C8 and CYP3A4 to form active metabolite, N-desmethyl apalutamide. The contribution of CYP2C8 and CYP3A4 in the metabolism of apalutamide is estimated to be 58% and 13% following single dose but changes to 40% and 37%, respectively at steady-state.
Apalutamide represented 45% and N-desmethyl apalutamide represented 44% of the total AUC following a single oral administration of radiolabeled apalutamide 240 mg.
Excretion
Up to 70 days following a single oral administration of radiolabeled apalutamide, 65% of the dose was recovered in urine (1.2% of dose as unchanged apalutamide and 2.7% as N-desmethyl apalutamide) and 24% was recovered in feces (1.5% of dose as unchanged apalutamide and 2% as N-desmethyl apalutamide).
Specific Populations
No clinically significant differences in the pharmacokinetics of apalutamide or N-desmethyl apalutamide were observed based on age (18-94 years), race (Black, non-Japanese Asian, Japanese), mild to moderate (eGFR 30-89 mL/min/1.73 m2, estimated by the modification of diet in renal disease [MDRD] equation) renal impairment, or mild (Child-Pugh A) to moderate (Child-Pugh B) hepatic impairment.
The effect of severe renal impairment or end stage renal disease (eGFR ≤29 mL/min/1.73 m2, MDRD) or severe hepatic impairment (Child-Pugh C) on apalutamide pharmacokinetics is unknown.
Drug Interactions
Effect Of Other Drugs On ERLEADA
Strong CYP2C8 inhibitors
Apalutamide Cmax decreased by 21% while AUC increased by 68% following co-administration of ERLEADA as a 240 mg single dose with gemfibrozil (a strong CYP2C8 inhibitor). Gemfibrozil is predicted to increase the steady-state apalutamide Cmax by 32% and AUC by 44%. For the active moieties (sum of unbound apalutamide plus the potency-adjusted unbound N-desmethyl apalutamide), the predicted steady-state Cmax increased by 19% and AUC by 23%. Strong CYP3A4 inhibitors Apalutamide Cmax decreased by 22% while AUC was similar following co-administration of ERLEADA as a 240 mg single dose with itraconazole (a strong CYP3A4 inhibitor). Ketoconazole (a strong CYP3A4 inhibitor) is predicted to increase the single-dose apalutamide AUC by 24% but have no impact on Cmax. Ketoconazole is predicted to increase the steady-state apalutamide Cmax by 38% and AUC by 51%. For the active moieties, the predicted steady-state Cmax increased by 23% and AUC by 28%.
CYP3A4/CYP2C8 inducers
Rifampin (a strong CYP3A4 and moderate CYP2C8 inducer) is predicted to decrease the steady-state apalutamide Cmax by 25% and AUC by 34%. For the active moieties, the predicted steady-state Cmax decreased by 15% and AUC by 19%.
Acid lowering agents
Apalutamide is not ionizable under relevant physiological pH condition, therefore acid lowering agents (e.g., proton pump inhibitor, H2-receptor antagonist, antacid) are not expected to affect the solubility and bioavailability of apalutamide.
Drugs affecting transporters
In vitro, apalutamide and N-desmethyl apalutamide are substrates for P-gp but not BCRP, OATP1B1, and OATP1B3. Because apalutamide is completely absorbed after oral administration, P-gp does not limit the absorption of apalutamide and therefore, inhibition or induction of P-gp is not expected to affect the bioavailability of apalutamide.
Effect Of ERLEADA On Other Drugs
CYP substrates
In vitro studies showed that apalutamide and N-desmethyl apalutamide are moderate to strong CYP3A4 and CYP2B6 inducers, are moderate inhibitors of CYP2B6 and CYP2C8, and weak inhibitors of CYP2C9, CYP2C19, and CYP3A4. Apalutamide and N-desmethyl apalutamide do not affect CYP1A2 and CYP2D6 at therapeutically relevant concentrations.
Co-administration of ERLEADA with single oral doses of sensitive CYP substrates resulted in a 92% decrease in the AUC of midazolam (a CYP3A4 substrate), 85% decrease in the AUC of omeprazole (a CYP2C19 substrate), and 46% decrease in the AUC of S-warfarin (a CYP2C9 substrate). ERLEADA did not cause clinically significant changes in exposure to a CYP2C8 substrate.
P-gp, BCRP and OATP1B1 substrates
Co-administration of ERLEADA with single oral doses of transporter substrates resulted in a 30% decrease in the AUC of fexofenadine (a P-gp substrate) and 41% decrease in the AUC of rosuvastatin (a BCRP/OATP1B1 substrate) but had no impact on Cmax.
UGT substrates
Apalutamide may induce UGT. Concomitant administration of ERLEADA with medications that are substrates of UGT may result in lower exposure to these medications.
OCT2, OAT1, OAT3 and MATEs substrates
In vitro, apalutamide and N-desmethyl apalutamide inhibit organic cation transporter 2 (OCT2), organic anion transporter 3 (OAT3) and multidrug and toxin extrusions (MATEs), and do not inhibit organic anion transporter 1. Apalutamide is not predicted to cause clinically significant changes in exposure to an OAT3 substrate.
GnRH analog
In mCSPC subjects receiving leuprolide acetate (a GnRH analog) co-administered with apalutamide, PK data indicated that apalutamide had no apparent effect on the steady-state exposure of leuprolide.
Clinical Studies
The efficacy and safety of ERLEADA was established in two randomized placebocontrolled clinical trials.
TITAN (NCT02489318)
Metastatic Castration-sensitive Prostate Cancer (mCSPC)
TITAN was a randomized, double-blind, placebo-controlled, multinational, clinical trial in which 1052 patients with mCSPC were randomized (1:1) to receive either ERLEADA orally at a dose of 240 mg once daily (N=525) or placebo once daily (N=527). All patients in the TITAN trial received concomitant GnRH analog or had prior bilateral orchiectomy. Patients were stratified by Gleason score at diagnosis, prior docetaxel use, and region of the world. Patients with both high- and lowvolume mCSPC were eligible for the study. High volume of disease was defined as metastases involving the viscera with 1 bone lesion or the presence of 4 or more bone lesions, at least 1 of which must be in a bony structure beyond the vertebral column and pelvic bones.
The following patient demographics and baseline disease characteristics were balanced between the treatment arms. The median age was 68 years (range 43-94) and 23% of patients were 75 years of age or older. The racial distribution was 68% Caucasian, 22% Asian, and 2% Black. Sixty-three percent (63%) of patients had highvolume disease and 37% had low-volume disease. Sixteen percent (16%) of patients had prior surgery, radiotherapy of the prostate or both. A majority of patients had a Gleason score of 8 or higher (67%). Sixty-eight percent (68%) of patients received prior treatment with an anti-androgen (bicalutamide, flutamide, or nilutamide). All patients except one in the placebo group, had an Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 or 1 at study entry.
The major efficacy outcome measures of the study were overall survival (OS) and radiographic progression-free survival (rPFS). Radiographic progressionfree survival was based on investigator assessment and was defined as time from randomization to radiographic disease progression or death. Radiographic disease progression was defined by identification of 2 or more new bone lesions on a bone scan with confirmation (Prostate Cancer Working Group 2 criteria) and/or progression in soft tissue disease.
A statistically significant improvement in OS and rPFS was demonstrated in patients randomized to receive ERLEADA compared with patients randomized to receive placebo. The results for OS are based upon a prespecified interim efficacy analysis. An updated OS analysis was conducted at the time of final study analysis when 405 deaths were observed. The median follow-up time was 44 months. Thirtynine percent of patients in the placebo arm crossed over to receive ERLEADA. Efficacy results of TITAN are summarized in Table 5 and Figures 1 and 2.
Table 5: Efficacy Results from the TITAN Study
| Endpoint |
ERLEADA
(N=525) |
Placebo
(N=527) |
| Primary Overall Survivala |
| Deaths (%) |
83 (16%) |
117 (22%) |
| Median, months (95% CI)b |
NE (NE, NE) |
NE (NE, NE) |
| Hazard Ratio (95% CI)c |
0.67 (0.51, 0.89) |
| p-valued |
0.0053 |
| Updated Overall Survival |
| Deaths (%) |
170 (32%) |
235 (45%) |
| Median, months (95% CI)b |
NE (NE, NE) |
52 (42, NE) |
| Hazard Ratio (95% CI)c |
0.65 (0.53, 0.79) |
| Radiographic Progression-free Survival |
| Disease progression or death (%) |
134 (26%) |
231 (44%) |
| Median, months (95% CI)b |
NE (NE, NE) |
22.1 (18, 33) |
| Hazard Ratio (95% CI)c |
0.48 (0.39, 0.60) |
| p-valued |
<0.0001 |
a Interim analysis is based on 50% of the number of events planned for the finalanalysis. Allocated alpha = 0.01.
b NE=Not Estimable
c Hazard ratio is from stratified proportional hazards model. Hazard ratio <1 favorsERLEADA.
d p-value is from the log-rank test stratified by Gleason score at diagnosis
(≤7 vs. >7), Region (NA/EU vs. Other Countries) and Prior docetaxel use (Yes vs. No). |
Consistent improvement in rPFS was observed across the following patient subgroups: disease volume (high vs low), prior docetaxel use (yes or no), and Gleason score at diagnosis (≤7 vs. >7).
Consistent improvement in OS was observed across the following patient subgroups: disease volume (high vs low) and Gleason score at diagnosis (≤7 vs. >7). Treatment with ERLEADA resulted in a statistically significant delay in the initiation of cytotoxic chemotherapy (HR = 0.39, 95% CI = 0.27, 0.56; p < 0.0001).
Figure 1: Kaplan-Meier Plot of Updated Overall Survival (OS); Intent-to-treat mCSPC Population (TITAN)
Figure 2: Kaplan-Meier Plot of Radiographic Progression-Free Survival (rPFS); Intent-to-treat mCSPC Population (TITAN)
SPARTAN (NCT01946204)
Non-metastatic, Castration-resistant Prostate Cancer (nmCRPC)
SPARTAN was a multicenter, double-blind, randomized (2:1), placebo-controlled clinical trial in which 1207 patients with nmCRPC were randomized (2:1) to receive either ERLEADA orally at a dose of 240 mg once daily (N=806) or placebo once daily (N=401). All patients in the SPARTAN trial received a concomitant GnRH analog or had a bilateral orchiectomy. Patients were stratified by Prostate Specific Antigen (PSA) Doubling Time (PSADT), the use of bone-sparing agents, and locoregional disease. Patients were required to have a PSADT ≤ 10 months and confirmation of non-metastatic disease by blinded independent central review (BICR). PSA results were blinded and were not used for treatment discontinuation. Patients randomized to either arm discontinued treatment for radiographic disease progression confirmed by BICR, locoregional-only progression, initiation of new treatment, unacceptable toxicity, or withdrawal.
The following patient demographics and baseline disease characteristics were balanced between the treatment arms. The median age was 74 years (range 48-97) and 26% of patients were 80 years of age or older. The racial distribution was 66% Caucasian, 12% Asian, and 6% Black. Seventy-seven percent (77%) of patients in both treatment arms had prior surgery or radiotherapy of the prostate. A majority of patients had a Gleason score of 7 or higher (78%). Fifteen percent (15%) of patients had <2 cm pelvic lymph nodes at study entry. Seventy-three percent (73%) of patients received prior treatment with an anti-androgen; 69% of patients received bicalutamide and 10% of patients received flutamide. All patients had an Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 or 1 at study entry.
The major efficacy outcome measure of the study was metastasis-free survival (MFS), defined as the time from randomization to the time of first evidence of BICR-confirmed distant metastasis, defined as new bone or soft tissue lesions or enlarged lymph nodes above the iliac bifurcation, or death due to any cause, whichever occurred first. Additional efficacy endpoints were time to metastasis (TTM), progression-free survival (PFS) which also includes locoregional progression, time to symptomatic progression, overall survival (OS), and time to initiation of cytotoxic chemotherapy.
A statistically significant improvement in MFS and OS was demonstrated in patients randomized to receive ERLEADA compared with patients randomized to receive placebo. The major efficacy outcome (MFS) was supported by improvements in TTM and PFS. The final analysis of OS and time to initiation of cytotoxic chemotherapy was conducted 32 months after the analysis of MFS, TTM and PFS. The efficacy results from SPARTAN are summarized in Table 6 and Figures 3 and 4.
Table 6: Efficacy Results from the SPARTAN Study
| Endpoint |
ERLEADA
(N=806) |
Placebo
(N=401) |
| Metastasis Free Survivala,b,c |
| Number of Events (%) |
184 (23%) |
194 (48%) |
| Median, months (95% CI)d |
40.5 (NE, NE) |
16.2 (15, 18) |
| Hazard Ratio (95% CI) |
0.28 (0.23, 0.35) |
| p-valuea |
<0.0001 |
| Time to Metastasisa,b |
| Number of Events (%) |
175 (22%) |
191 (48%) |
| Median, months (95% CI)d |
40.5 (NE, NE) |
16.6 (15, 18) |
| Hazard Ratio (95% CI) |
0.27 (0.22, 0.34) |
| p-valuea |
<0.0001 |
| Progression-Free Survivala,b |
| Number of Events (%) |
200 (25%) |
204 (51%) |
| Median, months (95% CI)d |
40.5 (NE, NE) |
14.7 (14, 18) |
| Hazard Ratio (95% CI) |
0.29 (0.24, 0.36) |
| p-valuea |
<0.0001 |
| Overall Survival |
| Number of Events (%) |
274 (34%) |
154 (38%) |
| Median, months (95% CI)d |
73.9 (61, NE) |
59.9 (53, NE) |
| Hazard Ratio (95% CI) |
0.78 (0.64, 0.96) |
| p-valuea |
0.0161 |
a All analyses stratified by PSA doubling time, bone-sparing agent use, and locoregional disease status.
b Confirmed responses assessed by BICR.
c Locoregional-only progression is observed in 2.4% of patients overall.
d NE=Not Estimable |
Consistent results for MFS were observed across patient subgroups including PSADT (≤ 6 months or > 6 months), use of a prior bone-sparing agent (yes or no), and locoregional disease (N0 or N1).
Treatment with ERLEADA resulted in a statistically significant delay in the initiation of cytotoxic chemotherapy [HR = 0.63 (95% CI:0.49, 0.81), p=0.0002].
Figure 3: Kaplan-Meier Metastasis-Free Survival (MFS) Curve in SPARTAN (nmCRPC)
Figure 4: Kaplan-Meier Overall Survival (OS) Curve in SPARTAN (nmCRPC)