MC# 19-15 - An Extended/Phase II, Multi-Center, Randomized, Open-Label, Study to Evaluate the Safety and Tolerability of Proxalutamide (GT0918) in Subjects with Metastatic Castrate Resistant Prostate Cancer (mCRPC) who Failed Either Abiraterone or Enzalutamide

  • Agent(s): Proxalutamide
  • Disease Type(s): Prostate
  • Phase(s): II
  • Drug Classification(s): Targeted Therapy, Small Molecule
  • Molecular Target(s): AR

Mechanism of Action

Proxalutamide is a novel dual MOA androgen receptor (AR) blocker with potent AR antagonist activity and capability to down-regulate AR level.


In this study, the sponsor and investigators want to learn:

  • How much of proxalutamide can be given with an acceptable level of side effects
  • About the safety and tolerability of proxalutamide 
  • How proteins that indicate the status of your disease are affected with use of proxalutamide 
Inclusion Criteria
  1. Written informed consent obtained prior to any study-related procedure being performed
  2. Subjects at least 18 years of age or older at the time of consent
  3. Subjects with histologically confirmed metastatic castrate resistant prostate cancer (mCRPC) who progressed after abiraterone or enzalutamide
  4. Ongoing androgen deprivation therapy with a luteinizing hormone-releasing hormone (LHRH) “super-agonist” or antagonist, or bilateral orchiectomy and serum testosterone level < 50 ng/dL (< 0.5 ng/mL, < 1.7 nmol/L) at screening
  5. Metastatic disease documented by computed tomography (CT)/magnetic resonance imaging (MRI) or bone scan
  6. Progressive disease despite hormonal treatment with abiraterone or enzalutamide, but not both. One line of chemotherapy is eligible. Progressive disease is defined by 1 or more of the following criteria:
    • Subjects with a rising prostate specific antigen (PSA) value > 2 ng/mL in at least 2 measurements, at least 1 week apart. If the confirmatory PSA value is less than the screening PSA value, then an additional test for the rising PSA is required to document progression
    • Subjects with measurable disease, progression defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria
    • Subjects with metastatic bone disease, progression defined by 2 or more new lesions in a radionuclide bone scan
  7. ECOG performance status of 0-1
  8. Screening blood counts of the following:
    • Absolute neutrophil count ≥ 1500/μL
    • Platelets ≥ 100,000/μL
    • Hemoglobin > 9 g/dL (if asymptomatic)
  9. Screening chemistry values of the following:
    • Alanine aminotransferase (ALT) and aspartate transaminase (AST) ≤ 2.5 × upper limit of the normal reference range (ULN)
    • Total bilirubin ≤ 2 × ULN
    • Creatinine ≤ 1.5 × ULN
    • Albumin > 2.8 g/dL
  10. At screening, life expectancy of at least 6 months
  11. Subjects whose partners are women of childbearing potential (WOCBP) must use an adequate method of birth control while on study drug and for at least 3 months after discontinuation of study drug
  12. Subject is willing and able to comply with all protocol required visits and assessments
Exclusion Criteria
  1. Discontinuation of enzalutamide or abiraterone less than 3 weeks, prior to the start of study medication
  2. Prior chemotherapy, radiation, sipuleucel-T or other experimental immunotherapy less than 3 weeks prior to the start of study medication
  3. Prior chemotherapies more than 1 line
  4. Ongoing acute treatment-related toxicity associated with a previous therapy greater than grade 1 except for grade 2 alopecia or neuropathy
  5. History of impaired adrenal gland function (e.g., Addison’s disease, Cushing’s syndrome)
  6. Known gastrointestinal disease or condition that affects the absorption of proxalutamide
  7. History of congestive heart failure New York Heart Association (NYHA) class III or IV or uncontrolled hypertension at screening
  8. History or family history of long QT syndrome
  9. History of other malignancy within the previous 3 years, except basal cell or squamous cell carcinoma, or non-muscle invasive bladder cancer
  10. Use of systemic glucocorticoid (e.g., prednisone, dexamethasone) within 14 days prior to the start of study medication. Inhaled or topical steroids are allowed
  11. Co-administration of CYP3A4 ligands that serve as substrates or induce or inhibit the enzyme
  12. Prior use of any herbal products known to decrease PSA levels (e.g., PC-SPES or saw palmetto) within 30 days prior to the start of study medication
  13. Major surgery within 30 days prior to the start of study medication
  14. Blood transfusion (including blood products) within 1 week of screening
  15. Serious persistent infection within 14 days prior to the start of study medication
  16. Serious concurrent medical condition including CNS disorders
  17. Previous history of difficulty swallowing capsules
  18. Known hypersensitivity to GT0918 or its excipients
  19. Any condition that, in the opinion of the investigator, would impair the subject’s ability to comply with study procedures


  • Dallas, TX - Mary Crowley Cancer Research - Medical City
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Re: MC# 19-15