Xtandi 40 mg soft capsules
Each soft capsule contains 40 mg of enzalutamide.
Excipient with known effect:
Each soft capsule contains 52.4 mg of sorbitol.
For the full list of excipients, see section 6.1.
Soft capsule.
White to off-white oblong soft capsules (approximately 20 mm x 9 mm) imprinted with “ENZ” in black ink on one side.
Xtandi is indicated for:
• the treatment of adult men with metastatic castration-resistant prostate cancer who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated (see section 5.1)
• the treatment of adult men with metastatic castration-resistant prostate cancer whose disease has progressed on or after docetaxel therapy.
Posology
The recommended dose is 160 mg enzalutamide (four 40 mg capsules) as a single oral daily dose.
Medical castration with an LHRH analogue should be continued during treatment of patients not surgically castrated.
If a patient misses taking Xtandi at the usual time, the prescribed dose should be taken as close as possible to the usual time. If a patient misses a dose for a whole day, treatment should be resumed the following day with the usual daily dose.
If a patient experiences a ≥ Grade 3 toxicity or an intolerable adverse reaction, dosing should be withheld for one week or until symptoms improve to ≤ Grade 2, then resumed at the same or a reduced dose (120 mg or 80 mg) if warranted.
Concomitant use with strong CYP2C8 inhibitors
The concomitant use of strong CYP2C8 inhibitors should be avoided if possible. If patients must be co-administered a strong CYP2C8 inhibitor, the dose of enzalutamide should be reduced to 80 mg once daily. If co-administration of the strong CYP2C8 inhibitor is discontinued, the enzalutamide dose should be returned to the dose used prior to initiation of the strong CYP2C8 inhibitor (see section 4.5).
Older people
No dose adjustment is necessary for older people (see section 5.1 and 5.2).
Hepatic impairment
No dose adjustment is necessary for patients with mild, moderate or severe hepatic impairment (Child-Pugh Class A, B or C, respectively). An increased drug half-life has however been observed in patients with severe hepatic impairment (see section 4.4 and 5.2).
Renal impairment
No dose adjustment is necessary for patients with mild or moderate renal impairment (see section 5.2). Caution is advised in patients with severe renal impairment or end-stage renal disease (see section 4.4).
Paediatric population
There is no relevant use of enzalutamide in the paediatric population in the indication of treatment of adult men with metastatic castration-resistant prostate cancer.
Method of administration
Xtandi is for oral use. The capsules should be swallowed whole with water, and can be taken with or without food.
Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
Women who are or may become pregnant (see section 4.6).
Risk of seizure
Caution should be used in administering Xtandi to patients with a history of seizures or other predisposing factors including, but not limited to, underlying brain injury, stroke, primary brain tumours or brain metastases, or alcoholism. In addition, the risk of seizure may be increased in patients receiving concomitant medicinal products that lower the seizure threshold.
Posterior reversible encephalopathy syndrome
There have been rare reports of posterior reversible encephalopathy syndrome (PRES) in patients receiving Xtandi (see section 4.8). PRES is a rare, reversible, neurological disorder which can present with rapidly evolving symptoms including seizure, headache, confusion, blindness, and other visual and neurological disturbances, with or without associated hypertension. A diagnosis of PRES requires confirmation by brain imaging, preferably magnetic resonance imaging (MRI). Discontinuation of Xtandi in patients who develop PRES is recommended.
Concomitant use with other medicinal products
Enzalutamide is a potent enzyme inducer and may lead to loss of efficacy of many commonly used medicinal products (see examples in section 4.5). A review of concomitant medicinal products should therefore be conducted when initiating enzalutamide treatment. Concomitant use of enzalutamide with medicinal products that are sensitive substrates of many metabolising enzymes or transporters (see section 4.5) should generally be avoided if their therapeutic effect is of large importance to the patient, and if dose adjustments cannot easily be performed based on monitoring of efficacy or plasma concentrations.
Co-administration with warfarin and coumarin-like anticoagulants should be avoided. If Xtandi is co-administered with an anticoagulant metabolised by CYP2C9 (such as warfarin or acenocoumarol), additional International Normalised Ratio (INR) monitoring should be conducted (see section 4.5).
Renal impairment
Caution is required in patients with severe renal impairment as enzalutamide has not been studied in this patient population.
Severe hepatic impairment
An increased drug half-life has been observed in patients with severe hepatic impairment, possibly related to increased tissue distribution. The clinical relevance of this observation remains unknown. A prolonged time to reach steady state concentrations is however anticipated, and the time to maximum pharmacological effect as well as time for onset and decline of enzyme induction (see section 4.5) may be increased.
Recent cardiovascular disease
The phase 3 studies excluded patients with recent myocardial infarction (in the past 6 months) or unstable angina (in the past 3 months), New York Heart Association Class (NYHA) III or IV heart failure except if Left Ventricular Ejection Fraction (LVEF) ≥ 45%, bradycardia or uncontrolled hypertension. This should be taken into account if Xtandi is prescribed in these patients.
Androgen deprivation therapy may prolong the QT interval
In patients with a history of or risk factors for QT prolongation and in patients receiving concomitant medicinal products that might prolong the QT interval (see section 4.5) physicians should assess the benefit risk ratio including the potential for Torsade de pointes prior to initiating Xtandi.
Use with chemotherapy
The safety and efficacy of concomitant use of Xtandi with cytotoxic chemotherapy has not been established. Co-administration of enzalutamide has no clinically relevant effect on the pharmacokinetics of intravenous docetaxel (see section 4.5); however, an increase in the occurrence of docetaxel-induced neutropenia cannot be excluded.
Excipients
Xtandi contains sorbitol (E420). Patients with rare hereditary problems of fructose intolerance should not take this medicinal product.
Hypersensitivity reactions
Hypersensitivity reactions manifested by symptoms including, but not limited to, tongue oedema, lip oedema and pharyngeal oedema have been observed with enzalutamide (see section 4.8).
Potential for other medicinal products to affect enzalutamide exposures
CYP2C8 inhibitors and inducers
CYP2C8 plays an important role in the elimination of enzalutamide and in the formation of its active metabolite. Following oral administration of the strong CYP2C8 inhibitor gemfibrozil (600 mg twice daily) to healthy male subjects, the AUC of enzalutamide increased by 326% while Cmax of enzalutamide decreased by 18%. For the sum of unbound enzalutamide plus the unbound active metabolite, the AUC increased by 77% while Cmax decreased by 19%. Strong inhibitors (e.g. gemfibrozil) or inducers (e.g. rifampicin) of CYP2C8 are to be avoided or used with caution during enzalutamide treatment. If patients must be co-administered a strong CYP2C8 inhibitor, the dose of enzalutamide should be reduced to 80 mg once daily (see section 4.2).
CYP3A4 inhibitors and inducers
CYP3A4 plays a minor role in the metabolism of enzalutamide. Following oral administration of the strong CYP3A4 inhibitor itraconazole (200 mg once daily) to healthy male subjects, the AUC of enzalutamide increased by 41% while Cmax was unchanged. For the sum of unbound enzalutamide plus the unbound active metabolite, the AUC increased by 27% while Cmax was again unchanged. No dose adjustment is necessary when Xtandi is co-administered with inhibitors or inducers of CYP3A4.
Potential for enzalutamide to affect exposures to other medicinal products
Enzyme induction
Enzalutamide is a potent enzyme inducer and increases the synthesis of many enzymes and transporters; therefore, interaction with many common medicinal products that are substrates of enzymes or transporters is expected. The reduction in plasma concentrations can be substantial, and lead to lost or reduced clinical effect. There is also a risk of increased formation of active metabolites. Enzymes that may be induced include CYP3A in the liver and gut, CYP2B6, CYP2C9, CYP2C19, and uridine 5'-diphospho-glucuronosyltransferase (UGTs - glucuronide conjugating enzymes). The transport protein P-gp may also be induced, and probably other transporters as well, e.g. multidrug resistance-associated protein 2 (MRP2), breast cancer resistance protein (BCRP) and the organic anion transporting polypeptide 1B1 (OATP1B1).
In vivo studies have shown that enzalutamide is a strong inducer of CYP3A4 and a moderate inducer of CYP2C9 and CYP2C19. Co-administration of enzalutamide (160 mg once daily) with single oral doses of sensitive CYP substrates in prostate cancer patients resulted in an 86% decrease in the AUC of midazolam (CYP3A4 substrate), a 56% decrease in the AUC of S-warfarin (CYP2C9 substrate), and a 70% decrease in the AUC of omeprazole (CYP2C19 substrate). UGT1A1 may have been induced as well. In a clinical study in patients with metastatic CRPC, Xtandi (160 mg once daily) had no clinically relevant effect on the pharmacokinetics of intravenously administered docetaxel (75 mg/m2 by infusion every 3 weeks). The AUC of docetaxel decreased by 12% [geometric mean ratio (GMR) = 0.882 (90% CI: 0.767, 1.02)] while Cmax decreased by 4% [GMR = 0.963 (90% CI: 0.834, 1.11)].
Interactions with certain medicinal products that are eliminated through metabolism or active transport are expected. If their therapeutic effect is of large importance to the patient, and dose adjustments are not easily performed based on monitoring of efficacy or plasma concentrations, these medicinal products are to be avoided or used with caution. The risk for liver injury after paracetamol administration is suspected to be higher in patients concomitantly treated with enzyme inducers.
Groups of medicinal products that can be affected include, but are not limited to:
• Analgesics (e.g. fentanyl, tramadol)
• Antibiotics (e.g. clarithromycin, doxycycline)
• Anticancer agents (e.g. cabazitaxel)
• Anticoagulants (e.g. acenocoumarol, warfarin)
• Antiepileptics (e.g. carbamazepine, clonazepam, phenytoin, primidone, valproic acid)
• Antipsychotics (e.g. haloperidol)
• Betablockers (e.g. bisoprolol, propranolol)
• Calcium channel blockers (e.g. diltiazem, felodipine, nicardipine, nifedipine, verapamil)
• Cardiac glycosides (e.g. digoxin)
• Corticosteroids (e.g. dexamethasone, prednisolone)
• HIV antivirals (e.g. indinavir, ritonavir)
• Hypnotics (e.g. diazepam, midazolam, zolpidem)
• Statins metabolized by CYP3A4 (e.g. atorvastatin, simvastatin)
• Thyroid agents (e.g. levothyroxine)
The full induction potential of enzalutamide may not occur until approximately 1 month after the start of treatment, when steady-state plasma concentrations of enzalutamide are reached, although some induction effects may be apparent earlier. Patients taking medicinal products that are substrates of CYP2B6, CYP3A4, CYP2C9, CYP2C19, or UGT1A1 should be eva luated for possible loss of pharmacological effects (or increase in effects in cases where active metabolites are formed) during the first month of enzalutamide treatment, and dose adjustment should be considered as appropriate. In consideration of the long half-life of enzalutamide (5.8 days, see section 5.2), effects on enzymes may persist for one month or longer after stopping enzalutamide. A gradual dose reduction of the concomitant medicinal product may be necessary when stopping enzalutamide treatment.
CYP2C8 substrates
Enzalutamide (160 mg once daily) did not cause a clinically relevant change in the AUC or Cmax of pioglitazone (CYP2C8 substrate). The AUC of pioglitazone increased by 20% while Cmax decreased by 18%. No dose adjustment is indicated when a CYP2C8 substrate is co-administered with Xtandi.
P-gp substrates
In vitro data indicate that enzalutamide may be an inhibitor of the efflux transporter P-gp. The effect of enzalutamide on P-gp substrates has not been eva luated in vivo; however, under conditions of clinical use, enzalutamide may be an inducer of P-gp via activation of the nuclear pregnane receptor (PXR). Medicinal products with a narrow therapeutic range that are substrates for P-gp (e.g. colchicine, dabigatran etexilate, digoxin) should be used with caution when administered concomitantly with Xtandi and may require dose adjustment to maintain optimal plasma concentrations.
BCRP, MRP2, OAT3 and OCT1 substrates
Based on in vitro data, inhibition of BCRP and MRP2 (in the intestine), as well as organic anion transporter 3 (OAT3) and organic cation transporter 1 (OCT1) (systemically) cannot be excluded. Theoretically, induction of these transporters is also possible, and the net effect is presently unknown.
Medicinal products which prolong the QT interval
Since androgen deprivation treatment may prolong the QT interval, the concomitant use of Xtandi with medicinal products known to prolong the QT interval or medicinal products able to induce Torsade de pointes such as class IA (e.g. quinidine, disopyramide) or class III (e.g. amiodarone, sotalol, dofetilide, ibutilide) antiarrhythmic medicinal products, methadone, moxifloxacin, antipsychotics, etc. should be carefully eva luated (see section 4.4).
Effect of food on enzalutamide exposures
Food has no clinically significant effect on the extent of exposure to enzalutamide. In clinical trials, Xtandi was administered without regard to food.
Women of childbearing potential
There are no human data on the use of Xtandi in pregnancy and this medicinal product is not for use in women of childbearing potential.
Contraception in males and females
It is not known whether enzalutamide or its metabolites are present in semen. A condom is required during and for 3 months after treatment with enzalutamide if the patient is engaged in sexual activity with a pregnant woman. If the patient engages in sexual intercourse with a woman of childbearing potential, a condom and another form of birth control must be used during and for 3 months after treatment. Studies in animals have shown reproductive toxicity (see section 5.3).
Pregnancy
Enzalutamide is not for use in women. Enzalutamide is contraindicated in women who are or may become pregnant (see sections 4.3 and 5.3).
Breast-feeding
Enzalutamide is not for use in women.
Fertility
Animal studies showed that enzalutamide affected the reproductive system in male rats and dogs (see section 5.3).
Enzalutamide may have a moderate influence on the ability to drive and use machines as psychiatric and neurologic events including seizure have been reported (see section 4.8). Patients with a history of seizures or other predisposing factors (see section 4.4) should be advised of the risk of driving or operating machines. No studies to establish the effects of enzalutamide on the ability to drive and use machines have been conducted.
Summary of the safety profile
The most common adverse reactions are asthenia/fatigue, hot flush, headache, and hypertension. Other important adverse reactions include falls, nonpathologic fractures, cognitive disorder, and neutropenia.
Seizure occurred in 0.4% of enzalutamide-treated patients and in 0.1% of placebo-treated patients. Rare cases of posterior reversible encephalopathy syndrome have been reported in enzalutamide-treated patients (see section 4.4).
Tabulated summary of adverse reactions
Adverse reactions observed during clinical studies are listed below by frequency category. Frequency categories are defined as follows: very common (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1,000 to < 1/100); rare (≥ 1/10,000 to < 1/1,000); very rare (< 1/10,000); not known (cannot be estimated from the available data). Within each frequency grouping, adverse reactions are presented in order of decreasing seriousness.
Table 1: Adverse reactions identified in the phase 3 clinical trials and post-marketing
|
MedDRA System organ class
|
Frequency
|
|
Blood and lymphatic system disorders
|
uncommon: leucopenia, neutropenia
|
|
Immune system disorders
|
not known*: tongue oedema, lip oedema, pharyngeal oedema
|
|
General disorders
|
very common: asthenia/fatigue
|
|
Psychiatric disorders
|
common: anxiety
uncommon: visual hallucinations
|
|
Nervous system disorders
|
very common: headache
common: memory impairment, amnesia, disturbance in attention, restless legs syndrome
uncommon: cognitive disorder, seizure
not known*: posterior reversible encephalopathy syndrome
|
|
Cardiac disorders
|
not known*: QT-prolongation (see sections 4.4 and 4.5)
|
|
Reproductive system and breast disorder
|
common: gynaecomastia
|
|
Vascular disorders
|
very common: hot flush, hypertension
|
|
Gastrointestinal disorders
|
not known*: nausea, vomiting
|
|
Skin and subcutaneous tissue disorders
|
common: dry skin, pruritus
not known*: rash
|
|
Musculoskeletal and connective tissue disorders
|
common: fractures**
not known*: myalgia, muscle spasms, muscular weakness, back pain
|
|
Injury, poisoning and procedural complications
|
common: falls
|
* Spontaneous reports from post-marketing experience
** Includes all fractures with the exception of pathological fractures
Description of selected adverse reactions
Seizure
In the phase 3 clinical studies, 7 patients (0.4%) experienced a seizure out of 1671 patients treated with a daily dose of 160 mg enzalutamide, whereas one patient (<0.1%) receiving placebo experienced a seizure. Dose appears to be an important predictor of the risk of seizure, as reflected by preclinical data, and data from a dose-escalation study. In both phase 3 studies, patients with prior seizure or risk factors for seizure were excluded.
In the AFFIRM trial, six patients (0.8%) experienced a seizure out of 800 post-chemotherapy patients treated with a daily dose of 160 mg enzalutamide, whereas no seizures occurred in patients receiving placebo. Potentially contributing factors were present in several of these patients that may have independently increased their risk of seizure. In the PREVAIL trial, one patient (0.1%) out of 871 chemotherapy-naive patients treated with a daily dose of 160 mg enzalutamide, and one patient (0.1%) receiving placebo experienced a seizure.
The mechanism by which enzalutamide may lower the seizure threshold is not known, but could be related to data from in vitro studies showing that enzalutamide and its active metabolite bind to and can inhibit the activity of the GABA-gated chloride channel.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
There is no antidote for enzalutamide. In the event of an overdose, treatment with enzalutamide should be stopped and general supportive measures initiated taking into consideration the half-life of 5.8 days. Patients may be at increased risk of seizures following an overdose.
Pharmacotherapeutic group: not yet assigned, ATC code: not yet assigned
Mechanism of action
Prostate cancer is known to be androgen sensitive and responds to inhibition of androgen receptor signalling. Despite low or even undetectable levels of serum androgen, androgen receptor signalling continues to promote disease progression. Stimulation of tumour cell growth via the androgen receptor requires nuclear localization and DNA binding. Enzalutamide is a potent androgen receptor signalling inhibitor that blocks several steps in the androgen receptor signalling pathway. Enzalutamide competitively inhibits binding of androgens to androgen receptors, inhibits nuclear translocation of activated receptors and inhibits the association of the activated androgen receptor with DNA even in the setting of androgen receptor overexpression and in prostate cancer cells resistant to anti-androgens. Enzalutamide treatment decreases the growth of prostate cancer cells and can induce cancer cell death and tumour regression. In preclinical studies enzalutamide lacks androgen receptor agonist activity.
Pharmacodynamic effects
In a phase 3 clinical trial of patients who failed prior chemotherapy with docetaxel, 54% of patients treated with enzalutamide, versus 1.5% of patients who received placebo, had at least a 50% decline from baseline in PSA levels.
Clinical efficacy and safety
Efficacy of enzalutamide was established in two randomized placebo-controlled multicentre phase 3 clinical studies [CRPC2 (AFFIRM), MDV3100-03 (PREVAIL)] of patients with progressive metastatic prostate cancer who had failed androgen deprivation therapy [luteinising hormone-releasing hormone (LHRH) analogue or after bilateral orchiectomy]. The PREVAIL study enrolled chemotherapy-naive patients; whereas the AFFIRM study enrolled patients who had received prior docetaxel. All patients continued on a LHRH analogue or had prior bilateral orchiectomy. In the active treatment arm, Xtandi was administered orally at a dose of 160 mg daily. In both clinical trials, patients received placebo in the control arm and patients were allowed, but not required, to take prednisone (maximum daily dose allowed was 10 mg prednisone or equivalent).
Changes in PSA serum concentration independently do not always predict clinical benefit. Therefore, in both studies it was recommended that patients be maintained on their study treatments until discontinuation criteria were met as specified below for each study.
MDV3100-03 (PREVAIL) study (chemotherapy-naive patients)
A total of 1717 asymptomatic or mildly symptomatic chemotherapy-naive patients were randomized 1:1 to receive either enzalutamide orally at a dose of 160 mg once daily (N = 872) or placebo orally once daily (N = 845). Patients with visceral disease, patients with a history of mild to moderate heart failure (NYHA Class 1 or 2), and patients taking medications associated with lowering the seizure threshold were allowed. Patients with a previous history of seizure or a condition that might predispose to seizure and patients with moderate or severe pain from prostate cancer were excluded. Study treatment continued until disease progression (evidence of radiographic progression, a skeletal-related event, or clinical progression) and the initiation of either a cytotoxic chemotherapy or an investigational agent, or until unacceptable toxicity.
Patient demographics and baseline disease characteristics were balanced between the treatment arms. The median age was 71 years (range 42-93) and the racial distribution was 77% Caucasian, 10% Asian, 2% Black and 11% other or unknown races. Sixty-eight percent (68%) of patients had an ECOG performance status score of 0 and 32% patients had ECOG performance status 1. Baseline pain assessment was 0-1 (asymptomatic) in 67% of patients and 2-3 (mildly symptomatic) in 32% of patients as defined by the Brief Pain Inventory Short Form (worst pain over past 24 hours on a scale of 0 to 10). Approximately 45% of patients had measurable soft tissue disease at study entry, and 12% of patients had visceral (lung and/or liver) metastases.
Co-primary efficacy endpoints were overall survival and radiographic progression-free survival (rPFS). In addition to the co-primary endpoints, benefit was also assessed using time to initiation of cytotoxic chemotherapy, best overall soft tissue response, time to first skeletal-related event, PSA response (≥50% decrease from baseline), time to PSA progression, and time to FACT-P total score degradation.
Radiographic progression was assessed with the use of sequential imaging studies as defined by Prostate Cancer Clinical Trials Working Group 2 (PCWG2) criteria (for bone lesions) and/or Response eva luation Criteria in Solid Tumors (RECIST v 1.1) criteria (for soft tissue lesions). Analysis of rPFS utilized centrally-reviewed radiographic assessment of progression.
At the pre-specified interim analysis for overall survival when 540 deaths were observed, treatment with enzalutamide demonstrated a statistically significant improvement in overall survival compared to treatment with placebo with a 29.4% reduction in risk of death [HR=0.706, (95% CI: 0.596; 0.837), p < 0.0001]. An updated survival analysis was conducted when 784 deaths were observed. Results from this analysis were consistent with those from the interim analysis (Table 2, Figure 1). At the updated analysis 52% of enzalutamide-treated and 81% of placebo-treated patients had received subsequent therapies for metastatic CRPC that may prolong overall survival.
Table 2: Overall Survival of Patients Treated with Either Enzalutamide or Placebo in the PREVAIL Study (Intent-to-Treat Analysis)
|
|
Enzalutamide
(N = 872)
|
Placebo
(N = 845)
|
|
Pre-specified interim analysis
|
|
Number of deaths (%)
|
241 (27.6%)
|
299 (35.4%)
|
|
Median survival, months (95% CI)
|
32.4 (30.1, NR)
|
30.2 (28.0, NR)
|
|
P-valuea
|
< 0.0001
|
|
Hazard ratio (95% CI)b
|
0.71 (0.60, 0.84)
|
|
Updated survival analysis
|
|
Number of deaths (%)
|
368 (42.2%)
|
416 (49.2%)
|
|
Median survival, months (95% CI)
|
35.3 (32.2, NR)
|
31.3 (28.8, 34.2)
|
|
P-valuea
|
0.0002
|
|
Hazard ratio (95% CI)b
|
0.77 (0.67, 0.88)
|
a P-value is derived from an unstratified log-rank test
b Hazard Ratio is derived from an unstratified proportional hazards model. Hazard ratio <1 favours enzalutamide
NR, not reached..
Figure 1: Kaplan-Meier Overall Survival Curves Based on Updated Survival Analysis in the PREVAIL Study (Intent-to-Treat Analysis)
Figure 2: Updated Overall Survival Analysis by Subgroup: Hazard Ratio and 95% Confidence Interval in the PREVAIL Study (Intent-to-Treat Analysis)
At the pre-specified rPFS analysis, a statistically significant improvement was demonstrated between the treatment groups with an 81.4% reduction in risk of radiographic progression or death [HR = 0.186 (95% CI: 0.149, 0.231), p < 0.0001]. One hundred and eighteen (14%) enzalutamide-treated patients and 321 (40%) of placebo-treated patients had an event. The median rPFS was not reached (95% CI: 13.8, not reached) in the enzalutamide-treated group and was 3.9 months (95% CI: 3.7, 5.4) in the placebo-treated group (Figure 3). Consistent rPFS benefit was observed across all pre-specified patient subgroups (e.g., age, baseline ECOG performance, baseline PSA and LDH, Gleason score at diagnosis, and visceral disease at screening). A pre-specified follow-up rPFS analysis based on the investigator assessment of radiographic progression demonstrated a statistically significant improvement between the treatment groups with a 69.3% reduction in risk of radiographic progression or death [HR = 0.307 (95% CI: 0.267, 0.353), p < 0.0001]. The median rPFS was 19.7 months in the enzalutamide group and 5.4 months in the placebo group.
Figure 3: Kaplan-Meier Curves of Radiographic Progression-Free Survival in the PREVAIL Study (Intent-to-Treat Analysis)
In addition to the co-primary efficacy endpoints, statistically significant improvements were also demonstrated in the following prospectively defined endpoints.
The median time to initiation of cytotoxic chemotherapy was 28.0 months for patients receiving enzalutamide and 10.8 months for patients receiving placebo (HR=0.350, 95% CI: [0.303, 0.403], p<0.0001).
The proportion of enzalutamide-treated patients with measurable disease at baseline who had an objective soft tissue response was 58.8% (95% CI: 53.8, 63.7) compared with 5.0% (95% CI: 3.0, 7.7) of patients receiving placebo. The absolute difference in objective soft tissue response between enzalutamide and placebo arms was 53.9% (95% CI: 48.5%, 59.1%, p<0.0001). Complete responses were reported in 19.7% of enzalutamide-treated patients compared with 1.0% of placebo-treated patients, and partial responses were reported in 39.1% of enzalutamide-treated patients versus 3.9% of placebo-treated patients.
Enzalutamide significantly decreased the risk of the first skeletal-related event by 28% [HR = 0.718 (95% CI: 0.610, 0.844) p-value < 0.0001]. A skeletal-related event was defined as radiation therapy or surgery to bone for prostate cancer, pathologic bone fracture, spinal cord compression, or change of antineoplastic therapy to treat bone pain. The analysis included 587 skeletal-related events, of which 389 events (66.3%) were radiation to bone, 79 events (13.5%) were spinal cord compression, 70 events (11.9%) were pathologic bone fracture, 45 events (7.6%) were change in antineoplastic therapy to treat bone pain, and 22 events (3.7%) were surgery to bone.
Patients receiving enzalutamide demonstrated a significantly higher total PSA response rate (defined as a ≥ 50% reduction from baseline), compared with patients receiving placebo, 78.0% versus 3.5% (difference = 74.5%, p < 0.0001).
The median time to PSA progression per PCWG2 criteria was 11.2 months for patients treated with enzalutamide and 2.8 months for patients who received placebo [HR=0.169, (95% CI: 0.147, 0.195), p<0.0001].
Treatment with enzalutamide decreased the risk of FACT-P degradation by 37.5% compared with placebo (p<0.001). The median time to degradation in FACT-P was 11.3 months in the enzalutamide group and 5.6 months in the placebo group.
CRPC2 (AFFIRM) study (patients who previously received chemotherapy)
The efficacy and safety of enzalutamide in patients with metastatic castration-resistant prostate cancer who had received docetaxel and were using a LHRH analogue or had undergone orchiectomy were assessed in a randomised, placebo-controlled, multicentre phase 3 clinical trial. A total of 1199 patients were randomised 2:1 to receive either enzalutamide orally at a dose of 160 mg once daily (N = 800) or placebo once daily (N = 399). Patients were allowed but not required to take prednisone (maximum daily dose allowed was 10 mg prednisone or equivalent). Patients randomised to either arm were to continue treatment until disease progression (defined as confirmed radiographic progression or the occurrence of a skeletal-related event) and initiation of new systemic antineoplastic treatment, unacceptable toxicity, or withdrawal.
The following patient demographics and baseline disease characteristics were balanced between the treatment arms. The median age was 69 years (range 41-92) and the racial distribution was 93% Caucasian, 4% Black, 1% Asian, and 2% Other. The ECOG performance score was 0-1 in 91.5% of patients and 2 in 8.5% of patients; 28% had a mean Brief Pain Inventory score of ≥4 (mean of patient's reported worst pain over the previous 24 hours calculated for seven days prior to randomization). Most (91%) patients had metastases in bone and 23% had visceral lung and/or liver involvement. At study entry, 41% of randomized patients had PSA progression only, whereas 59% of patients had radiographic progression. Fifty-one percent (51%) of patients were on bisphosphonates at baseline.
The AFFIRM study excluded patients with medical conditions that may predispose them to seizures (see section 4.8) and medicinal products known to decrease the seizure threshold, as well as clinically significant cardiovascular disease such as uncontrolled hypertension, recent history of myocardial infarction or unstable angina, New York Heart Association class III or IV heart failure (unless ejection fraction was ≥ 45%), clinically significant ventricular arrhythmias or AV block (without permanent pacemaker).
The protocol pre-specified interim analysis after 520 deaths showed a statistically significant superiority in overall survival in patients treated with enzalutamide compared to placebo (Table 3 and Figures 4 and 5).
Table 3: Overall Survival of Patients Treated with Either Enzalutamide or Placebo in the AFFIRM Study (Intent-to-Treat Analysis)
|
|
Enzalutamide (N = 800)
|
Placebo (N = 399)
|
|
Deaths (%)
|
308 (38.5%)
|
212 (53.1%)
|
|
Median survival (months) (95% CI)
|
18.4 (17.3, NR)
|
13.6 (11.3, 15.8)
|
|
p valuea
|
< 0.0001
|
|
Hazard ratio (95% CI)b
|
0.631 (0.529, 0.752)
|
a P-value is derived from a log-rank test stratified by ECOG performance status score (0-1 vs. 2) and mean pain score (< 4 vs. ≥ 4)
b Hazard Ratio is derived from a stratified proportional hazards model. Hazard ratio < 1 favours enzalutamide
NR, not reached.
Figure 4: Kaplan-Meier Overall Survival Curves in the AFFIRM Study (Intent-to-Treat Analysis)
Figure 5: Overall Survival by Subgroup in the AFFIRM Study – Hazard Ratio and 95% Confidence Interval
ECOG: Eastern Cooperative Oncology Group; BPI-SF: Brief Pain Inventory-Short Form; PSA: Prostate Specific Antigen
In addition to the observed improvement in overall survival, key secondary endpoints (PSA progression, radiographic progression-free survival, and time to first skeletal-related event) favoured enzalutamide and were statistically significant after adjusting for multiple testing.
Radiographic progression-free survival as assessed by the investigator using RECIST v 1.1 for soft tissue and appearance of 2 or more bone lesions in bone scan was 8.3 months for patients treated with enzalutamide and 2.9 months for patients who received placebo (HR = 0.404, 95% CI: [0.350, 0.466]; p < 0.0001). The analysis involved 216 deaths without documented progression and 645 documented progression events, of which 303 (47%) were due to soft tissue progression, 268 (42%) were due to bone lesion progression and 74 (11%) were due to both soft tissue and bone lesions.
Confirmed PSA decline of 50% or 90% were 54.0% and 24.8%, respectively, for patients treated with enzalutamide and 1.5% and 0.9%, respectively, for patients who received placebo (p < 0.0001). The median time to PSA progression was 8.3 months for patients treated with enzalutamide and 3.0 months for patients who received placebo (HR = 0.248, 95% CI: [0.204, 0.303]; p < 0.0001).
The median time to first skeletal-related event was 16.7 months for patients treated with enzalutamide and 13.3 months for patients who received placebo (HR = 0.688, 95% CI: [0.566, 0.835]; p < 0.0001). A skeletal-related event was defined as radiation therapy or surgery to bone, pathologic bone fracture, spinal cord compression, or change of antineoplastic therapy to treat bone pain. The analysis involved 448 skeletal-related events, of which 277 events (62%) were radiation to bone, 95 events (21%) were spinal cord compression, 47 events (10%) were pathologic bone fracture, 36 events (8%) were change in antineoplastic therapy to treat bone pain and 7 events (2%) were surgery to bone.
The efficacy of enzalutamide in patients who have previously received abiraterone acetate has not been studied.
Older people
Of the 1671 patients in the phase 3 trials who received enzalutamide, 1261 patients (75%) were 65 years and over and 516 patients (31%) were 75 years and over. No overall differences in safety or effectiveness were observed between these older patients and younger patients.
Paediatric population
The European Medicines Agency has waived the obligation to submit the results of studies with enzalutamide in all subsets of the paediatric population in prostate carcinoma (see section 4.2 for information on paediatric use).
Enzalutamide is poorly water soluble. In this product, the solubility of enzalutamide is increased by caprylocaproyl macrogolglycerides as emulsifier/surfactant. In preclinical studies, the absorption of enzalutamide was increased when dissolved in caprylocaproyl macrogolglycerides.
The pharmacokinetics of enzalutamide have been eva luated in prostate cancer patients and in healthy male subjects. The mean terminal half-life (t½) for enzalutamide in patients after a single oral dose is 5.8 days (range 2.8 to 10.2 days), and steady state is achieved in approximately one month. With daily oral administration, enzalutamide accumulates approximately 8.3-fold relative to a single dose. Daily fluctuations in plasma concentrations are low (peak-to-trough ratio of 1.25). Clearance of enzalutamide is primarily via hepatic metabolism, producing an active metabolite that is equally as active as enzalutamide and circulates at approximately the same plasma concentration as enzalutamide.
Absorption
Maximum plasma concentrations (Cmax) of enzalutamide in patients are observed 1 to 2 hours after administration. Based on a mass balance study in humans, oral absorption of enzalutamide is estimated to be at least 84.2%. Enzalutamide is not a substrate of the efflux transporters P-gp or BCRP. At steady state, the mean Cmax values for enzalutamide and its active metabolite are 16.6 μg/mL (23% coefficient of variation [CV]) and 12.7 μg/mL (30% CV), respectively.
Food has no clinically significant effect on the extent of absorption. In clinical trials, Xtandi was administered without regard to food.
Distribution
The mean apparent volume of distribution (V/F) of enzalutamide in patients after a single oral dose is 110 L (29% CV). The volume of distribution of enzalutamide is greater than the volume of total body water, indicative of extensive extravascular distribution. Studies in rodents indicate that enzalutamide and its active metabolite can cross the blood brain barrier.
Enzalutamide is 97% to 98% bound to plasma proteins, primarily albumin. The active metabolite is 95% bound to plasma proteins. There was no protein binding displacement between enzalutamide and other highly bound drugs (warfarin, ibuprofen and salicylic acid) in vitro.
Biotransformation
Enzalutamide is extensively metabolized. There are two major metabolites in human plasma: N-desmethyl enzalutamide (active) and a carboxylic acid derivative (inactive). Enzalutamide is metabolized by CYP2C8 and to a lesser extent by CYP3A4/5 (see section 4.5), both of which play a role in the formation of the active metabolite. In vitro, N-desmethyl enzalutamide is metabolized to the carboxylic acid metabolite by carboxylesterase 1, which also plays a minor role in the metabolism of enzalutamide to the carboxylic acid metabolite. N-desmethyl enzalutamide was not metabolized by CYPs in vitro.
Under conditions of clinical use, enzalutamide is a strong inducer of CYP3A4, a moderate inducer of CYP2C9 and CYP2C19, and has no clinically relevant effect on CYP2C8 (see section 4.5).
Elimination
The mean apparent clearance (CL/F) of enzalutamide in patients ranges from 0.520 and 0.564 L/h.
Following oral administration of 14C-enzalutamide, 84.6% of the radioactivity is recovered by 77 days post dose: 71.0% is recovered in urine (primarily as the inactive metabolite, with trace amounts of enzalutamide and the active metabolite), and 13.6% is recovered in faeces (0.39% of dose as unchanged enzalutamide).
In vitro data indicate that enzalutamide is not a substrate for OATP1B1, OATP1B3, or OCT1; and N-desmethyl enzalutamide is not a substrate for P-gp or BCRP.
In vitro data indicate that enzalutamide and its major metabolites do not inhibit the following transporters at clinically relevant concentrations: OATP1B1, OATP1B3, OCT2, or OAT1.
Linearity
No major deviations from dose proportionality are observed over the dose range 40 to 160 mg. The steady-state Cmin values of enzalutamide and the active metabolite in individual patients remained constant during more than one year of chronic therapy, demonstrating time-linear pharmacokinetics once steady-state is achieved.
Renal impairment
No formal renal impairment study for enzalutamide has been completed. Patients with serum creatinine > 177 μmol/L (2 mg/dL) were excluded from clinical trials. Based on a population pharmacokinetic analysis, no dose adjustment is necessary for patients with calculated creatinine clearance (CrCL) values ≥ 30 mL/min (estimated by the Cockcroft and Gault formula). Enzalutamide has not been eva luated in patients with severe renal impairment (CrCL < 30 mL/min) or end-stage renal disease, and caution is advised when treating these patients. It is unlikely that enzalutamide will be significantly removed by intermittent haemodialysis or continuous ambulatory peritoneal dialysis.
Hepatic impairment
Hepatic impairment did not have a pronounced effect on the total exposure to enzalutamide or its active metabolite. Drug half-life was however doubled in patients with severe hepatic impairment compared with healthy controls (10.4 days compared to 4.7 days), possibly related to an increased tissue distribution.
The pharmacokinetics of enzalutamide were examined in subjects with baseline mild (N = 6), moderate (N = 8) or severe (N=8) hepatic impairment (Child-Pugh Class A, B or C, respectively) and in 22 matched control subjects with normal hepatic function. Following a single oral 160 mg dose of enzalutamide, the AUC and Cmax for enzalutamide in subjects with mild impairment increased by 5% and 24%, respectively, the AUC and Cmax of enzalutamide in subjects with moderate impairment increased by 29% and decreased by 11%, respectively, and the AUC and Cmax of enzalutamide in subjects with severe impairment increased by 5% and decreased by 41%, respectively, compared to healthy control subjects. For the sum of unbound enzalutamide plus the unbound active metabolite, the AUC and Cmax in subjects with mild impairment increased by 14% and 19%, respectively, the AUC and Cmax in subjects with moderate impairment increased by 14% and decreased by 17%, respectively, and the AUC and Cmax in subjects with severe hepatic impairment increased by 34% and decreased by 27%., respectively, compared to healthy control subjects.
Race
Most patients in the clinical trials (> 84%) were Caucasian. Based on pharmacokinetic data from a study in Japanese patients with prostate cancer, there were no clinically relevant differences in exposure between Japanese and Caucasians. There are insufficient data to eva luate potential differences in the pharmacokinetics of enzalutamide in other races.
Older people
No clinically relevant effect of age on enzalutamide pharmacokinetics was seen in the population pharmacokinetic analysis.
Enzalutamide treatment of pregnant mice resulted in an increased incidence of embryo-fetal deaths and external and skeletal changes. Reproductive toxicology studies were not conducted with enzalutamide, but in studies in rats (4 and 26 weeks) and dogs (4, 13, and 39 weeks), atrophy, aspermia/hypospermia, and hypertrophy/hyperplasia in the reproductive system were noted, consistent with the pharmacological activity of enzalutamide. In studies in mice (4 weeks), rats (4 and 26 weeks) and dogs (4, 13, and 39 weeks), changes in the reproductive organs associated with enzalutamide were decreases in organ weight with atrophy of the prostate and epididymis. Leydig cell hypertrophy and/or hyperplasia were observed in mice (4 weeks) and dogs (39 weeks). Additional changes to reproductive tissues included hypertrophy/hyperplasia of the pituitary gland and atrophy in seminal vesicles in rats and testicular hypospermia and seminiferous tubule degeneration in dogs. Gender differences were noted in rat mammary glands (male atrophy and female lobular hyperplasia). Changes in the reproductive organs in both species were consistent with the pharmacological activity of enzalutamide and reversed or partially resolved after an 8-week recovery period. There were no other important changes in clinical pathology or histopathology in any other organ system, including the liver, in either species.
Enzalutamide did not induce mutations in the microbial mutagenesis (Ames) assay and was not clastogenic in either the in vitro cytogenetic assay with mouse lymphoma cells or the in vivo mouse micronucleus assay. Long-term animal studies to eva luate the carcinogenic potential of enzalutamide have not been conducted. Enzalutamide was not phototoxic in vitro.
Capsule contents
Caprylocaproyl macrogol-8 glycerides
Butylhydroxyanisole (E320)
Butylhydroxytoluene (E321)
Capsule shell
Gelatin
Sorbitol sorbitan solution
Glycerol
Titanium dioxide (E171)
Purified water
Printing ink
Iron oxide black (E172)
Polyvinyl acetate phthalate
This medicinal product does not require any special storage conditions.
Cardboard wallet incorporating a PVC/PCTFE/aluminium blister of 28 soft capsules. Each carton contains 4 wallets (112 soft capsules).
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
Astellas Pharma Europe B.V.
Sylviusweg 62
2333 BE Leiden
The Netherlands
Date of first authorisation: 21 June 2013
22 June 2015
Detailed information on this medicinal product is available on the website of the European Medicines Agency http://www.ema.europa.eu.
