Abiraterone Acetate Tablets

Name: Abiraterone Acetate Tablets

Description

Abiraterone acetate, the active ingredient of YONSA tablet is the acetyl ester of abiraterone. Abiraterone is an inhibitor of CYP17 (17α-hydroxylase/C17,20-lyase). Each YONSA Tablet contains 125 mg of abiraterone acetate. Abiraterone acetate is designated chemically as (3β)17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate and its structure is:

Abiraterone acetate is micronized (smaller particle size) white to off-white, non-hygroscopic, crystalline powder. Its molecular formula is C26H33NO2 and it has a molecular weight of 391.55. Abiraterone acetate is a lipophilic compound with an octanol-water partition coefficient of 5.12 (Log P) and is practically insoluble in water. The pKa of the aromatic nitrogen is 5.19.

Inactive ingredients in the tablets are lactose monohydrate, microcrystalline cellulose, croscarmellose sodium, sodium lauryl sulfate, sodium stearyl fumarate, butylated hydroxyanisole, butylated hydroxytoluene.

Indications

YONSA is indicated in combination with methylprednisolone for the treatment of patients with metastatic castration-resistant prostate cancer.

Side effects

The following are discussed in more detail in other sections of the labeling:

  • Hypertension, Hypokalemia, and Fluid Retention due to Mineralocorticoid Excess [see WARNINGS AND PRECAUTIONS].
  • Adrenocortical Insufficiency [see WARNINGS AND PRECAUTIONS].
  • Hepatotoxicity [see WARNINGS AND PRECAUTIONS].

Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

Two randomized placebo-controlled, multicenter clinical trials enrolled patients who had metastatic castration-resistant prostate cancer who were using a gonadotropin-releasing hormone (GnRH) agonist or were previously treated with orchiectomy. In both Study 1 and Study 2 abiraterone acetate was administered at a dose equivalent to 500 mg of YONSA daily in combination with a different corticosteroid twice daily in the active treatment arms. Placebo plus corticosteroid was given to control patients.

The most common adverse drug reactions (≥10%) reported in the two randomized clinical trials that occurred more commonly (>2%) in the abiraterone acetate arm were fatigue, joint swelling or discomfort, edema, hot flush, diarrhea, vomiting, cough, hypertension, dyspnea, urinary tract infection and contusion.

The most common laboratory abnormalities (>20%) reported in the two randomized clinical trials that occurred more commonly (≥2%) in the abiraterone acetate arm were anemia, elevated alkaline phosphatase, hypertriglyceridemia, lymphopenia, hypercholesterolemia, hyperglycemia, elevated AST, hypophosphatemia, elevated ALT and hypokalemia.

Study 1

Metastatic CRPC Following Chemotherapy

Study 1 enrolled 1195 patients with metastatic CRPC who had received prior docetaxel chemotherapy. Patients were not eligible if AST and/or ALT ≥ 2.5 XULN in the absence of liver metastases. Patients with liver metastases were excluded if AST and/or ALT > 5X ULN.

Table 1 shows adverse reactions on the abiraterone acetate arm in Study 1 that occurred with a ≥2% absolute increase in frequency compared to placebo or were events of special interest. The median duration of treatment with abiraterone acetate was 8 months.

Table 1: Adverse Reactions due to Abiraterone Acetate in Study 1

System Organ Class
   Adverse Reaction
Abiraterone Acetate with Corticosteroid
(N=791)
Placebo with Corticosteroid
(N=394)
All Grades1
%
Grade 3-4
%
All Grades
%
Grade 3-4
%
Musculoskeletal and connective tissue disorders
  Joint swelling/ discomfort2 30 4.2 23 4.1
  Muscle discomfort3 26 3.0 23 2.3
General Disorders
  Edema4 27 1.9 18 0.8
Vascular Disorders
  Hot Flush 19 0.3 17 0.3
  Hypertension 8.5 1.3 6.9 0.3
Gastrointestinal Disorders
  Diarrhea 18 0.6 14 1.3
  Dyspepsia 6.1 0 3.3 0
Infections and infestations
  Urinary tract infection 12 2.1 7.1 0.5
  Upper respiratory tract infection 5.4 0 2.5 0
Respiratory, thoracic and mediastinal disorders
  Cough 11 0 7.6 0
Renal and urinary disorders
  Urinary frequency 7.2 0.3 5.1 0.3
  Nocturia 6.2 0 4.1 0
Injury, poisoning and procedural complications
  Fractures5 5.9 1.4 2.3 0
Cardiac disorders
  Arrhythmia6 7.2 1.1 4.6 1.0
  Chest pain or chest discomfort7 3.8 0.5 2.8 0
  Cardiac failure8 2.3 1.9 1.0 0.3
1 Adverse events graded according to CTCAE version 3.0
2 Includes terms Arthritis, Arthralgia, Joint swelling, and Joint stiffness
3 Includes terms Muscle spasms, Musculoskeletal pain, Myalgia, Musculoskeletal discomfort, and Musculoskeletal stiffness
4 Includes terms Edema, Edema peripheral, Pitting edema, and Generalized edema
5 Includes all fractures with the exception of pathological fracture
6 Includes terms Arrhythmia, Tachycardia, Atrial fibrillation, Supraventricular tachycardia, Atrial tachycardia, Ventricular tachycardia, Atrial flutter, Bradycardia, Atrioventricular block complete, Conduction disorder, and Bradyarrhythmia
7 Includes terms Angina pectoris, Chest pain, and Angina unstable. Myocardial infarction or ischemia occurred more commonly in the placebo arm than in the abiraterone acetate arm (1.3% vs. 1.1% respectively).
8 Includes terms Cardiac failure, Cardiac failure congestive, Left ventricular dysfunction, Cardiogenic shock, Cardiomegaly, Cardiomyopathy, and Ejection fraction decreased

Table 2 shows laboratory abnormalities of interest from Study 1. Grade 3-4 low serum phosphorus (7%) and low potassium (5%) occurred at a greater than or equal to 5% rate in the abiraterone acetate arm.

Table 2: Laboratory Abnormalities of Interest in Study 1

Laboratory Abnormality Abiraterone Acetate with Corticosteroid
(N=791)
Placebo with Corticosteroid
(N=394)
All Grades
%
Grade 3-4
%
All Grades
%
Grade 3-4
%
Hypertriglyceridemia 63 0.4 53 0
High AST 31 2.1 36 1.5
Hypokalemia 28 5.3 20 1.0
Hypophosphatemia 24 7.2 16 5.8
High ALT 11 1.4 10 0.8
High Total Bilirubin 6.6 0.1 4.6 0

Study 2

Metastatic CRPC Prior to Chemotherapy

Study 2 enrolled 1088 patients with metastatic CRPC who had not received prior cytotoxic chemotherapy. Patients were ineligible if AST and/or ALT ≥ 2.5X ULN and patients were excluded if they had liver metastases.

Table 3 shows adverse reactions on the abiraterone acetate arm in Study 2 that occurred with a ≥ 2% absolute increase in frequency compared to placebo. The median duration of treatment with abiraterone acetate was 13.8 months.

Table 3: Adverse Reactions in ≥5% of Patients on the Abiraterone Acetate Arm in Study 2

System Organ Class
  Adverse Reaction
Abiraterone Acetate with Corticosteroid
(N=542)
Placebo with Corticosteroid
(N=540)
All Grades1
%
Grade 3-4
%
All Grades
%
Grade 3-4
%
General Disorders
  Fatigue 39 2.2 34 1.7
  Edema2 25 0.4 21 1.1
  Pyrexia 8.7 0.6 5.9 0.2
Musculoskeletal and connective tissue disorders
  Joint swelling/ discomfort3 30 2.0 25 2.0
  Groin Pain 6.6 0.4 4.1 0.7
Gastrointestinal Disorders
  Constipation 23 0.4 19 0.6
  Diarrhea 22 0.9 18 0.9
  Dyspepsia 11 0.0 5.0 0.2
Vascular Disorders
  Hot Flush 22 0.2 18 0.0
  Hypertension 22 3.9 13 3.0
Respiratory, thoracic and mediastinal disorders
  Cough 17 0.0 14 0.2
  Dyspnea 12 2.4 9.6 0.9
Psychiatric Disorders
  Insomnia 14 0.2 11 0.0
Injury, poisoning and procedural complications
  Contusion 13 0.0 9.1 0.0
  Falls 5.9 0.0 3.3 0.0
Infections and infestations
  Upper respiratory tract infection 13 0.0 8.0 0.0
  Nasopharyngitis 11 0.0 8.1 0.0
Renal and urinary disorders
  Hematuria 10 1.3 5.6 0.6
Skin and subcutaneous tissue disorders
  Rash 8.1 0.0 3.7 0.0
1 Adverse events graded according to CTCAE version 3.0
2 Includes terms Edema peripheral, Pitting edema, and Generalized edema
3 Includes terms Arthritis, Arthralgia, Joint swelling, and Joint stiffness

Table 4 shows laboratory abnormalities that occurred in greater than 15% of patients, and more frequently (>5%) in the abiraterone acetate arm compared to placebo in Study 2.

Table 4: Laboratory Abnormalities in > 15% of Patients in the Abiraterone Acetate Arm of Study 2

Laboratory Abnormality Abiraterone Acetate with Corticosteroid
(N=542)
Placebo with Corticosteroid
(N=540)
Grade 1-4
%
Grade 3-4
%
Grade 1-4
%
Grade 3-4
%
Hematology        
  Lymphopenia 38 8.7 32 7.4
Chemistry        
  Hyperglycemia1 57 6.5 51 5.2
  High ALT 42 6.1 29 0.7
  High AST 37 3.1 29 1.1
  Hypernatremia 33 0.4 25 0.2
  Hypokalemia 17 2.8 10 1.7
1 Based on non-fasting blood draws

Cardiovascular Adverse Reactions

In the combined data for studies 1 and 2, cardiac failure occurred more commonly in patients treated with abiraterone acetate compared to patients on the placebo arm (2.1% versus 0.7%). Grade 3-4 cardiac failure occurred in 1.6% of patients taking abiraterone acetate and led to 5 treatment discontinuations and 2 deaths. Grade 3-4 cardiac failure occurred in 0.2% of patients taking placebo. There were no treatment discontinuations and one death due to cardiac failure in the placebo group.

In Study 1 and 2, the majority of arrhythmias were grade 1 or 2. There was one death associated with arrhythmia and one patient with sudden death in the abiraterone acetate arms and no deaths in the placebo arms. There were 7 (0.5 %) deaths due to cardiorespiratory arrest in the abiraterone acetate arms and 3 (0.3 %) deaths in the placebo arms. Myocardial ischemia or myocardial infarction led to death in 3 patients in the placebo arms and 2 deaths in the abiraterone acetate arms.

Post Marketing Experience

The following additional adverse reactions have been identified during post approval use of abiraterone acetate with a different corticosteroid. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Respiratory, Thoracic and Mediastinal Disorders: non-infectious pneumonitis.
Musculoskeletal and Connective Tissue Disorders: myopathy, including rhabdomyolysis.
Hepatobiliary Disorders: fulminant hepatitis, including acute hepatic failure and death.

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