Phase 1/2A Study of TRC253, an Androgen Receptor Antagonist, in Metastatic Castration-resistant Prostate Cancer Patients

Inclusion Criteria:

   1. Must have received at least 2 prior therapies approved for CRPC; including a prior AR
   inhibitor (e.g., enzalutamide or apalutamide). (Part 1 only)

   2. Must have received enzalutamide or apalutamide. (Note: additional therapies approved
   for CRPC prior to enzalutamide or apalutamide are allowed.) (Part 2 only)

   3. Must have shown clinical characteristics of acquired resistance to enzalutamide or
   apalutamide defined as: decline in serum PSA ≥50% compared to baseline serum levels by
   week 12 (±4 weeks) of enzalutamide or apalutamide treatment and before disease
   progression by PCWG3 PSA criteria, OR disease progression by PCWG3 radiographic
   criteria. (Part 2 only)

   Parts 1 and 2:

   4. Histologically confirmed adenocarcinoma of the prostate with metastatic disease.

   5. Male ≥18 years of age.

   6. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

   7. Prior orchiectomy or serum testosterone levels <50 ng/dL determined within 4 weeks
   prior to start of study drug.

   8. Adequate baseline organ function.

   9. Ongoing androgen depletion therapy with a gonadotropin-releasing hormone (GnRH) analog
   or inhibitor, or orchiectomy (i.e., surgical or medical castration). Note: patients
   who have not undergone orchiectomy must continue GnRH analog therapy for the duration
   of this protocol.

10. For patients previously treated with first generation anti-androgens (i.e., flutamide,
   nilutamide, or bicalutamide), discontinuation of flutamide or nilutamide therapy must
   occur >4 weeks (>6 weeks for bicalutamide) prior to start of study drug with no
   evidence of an anti-androgen withdrawal response (i.e., no decline in serum PSA).

11. For patients previously treated with chemotherapy, targeted therapy, immunotherapy, or
   treatment with an investigational anticancer agent, discontinuation must have occurred
   ≥2 weeks, or after at least 4 half-lives, whichever is longer, prior to study drug
   administration. For enzalutamide and apalutamide, the washout period will be at least
   3 weeks prior to start of study drug with no evidence of an anti-androgen withdrawal
   response (i.e., no decline in serum PSA).

12. For patients previously treated with other agents approved for the treatment of
   prostate cancer (5-α reductase inhibitors, estrogens, others), discontinuation of
   therapy must have occurred ≥4 weeks prior to start of study drug.

13. Palliative radiotherapy (to bone or soft tissue lesions) must be completed >2 weeks
   prior to start of study drug.

14. For patients receiving bone-loss prevention treatment (e.g., bisphosphonates or
   denosumab), the patient must be on stable dose ≥4 weeks prior to start of study drug.

15. A man who is sexually active with a woman of childbearing potential must agree to use
   a barrier method of birth control during the study and for 4 weeks after receiving the
   last dose of study drug. All men must also not donate sperm during the study and for
   90 days after receiving the last dose of study drug.

16. Patient must be willing and able to adhere to the prohibitions and restrictions
   specified in this protocol.

17. Each patient must sign an informed consent form (ICF) indicating that he understands
   the purpose of and procedures required for the study and is willing to participate in
   the study. Consent is to be obtained prior to the initiation of any study-related
   tests or procedures that are not part of standard-of-care for the patient's disease.

Exclusion Criteria:

   1. History of seizures.

   2. Previously documented or current brain metastases.

   3. Untreated spinal cord compression.

   4. Positive test result for human immunodeficiency virus.

   5. History of clinically significant cardiovascular disease including.

   6. Active or chronic hepatitis B or hepatitis C as demonstrated by hepatitis B surface
   antigen positivity and/or anti- hepatitis C virus positivity, respectively. Patients
   with clinically active or chronic liver disease, including liver cirrhosis of
   Child-Pugh class C, are also excluded.

   7. Second primary malignancy that has not been in remission for greater than 3 years.
   Exceptions that do not require a 3 year remission include: related non-melanoma skin
   cancer or resected melanoma in situ.

   8. Any serious underlying medical or psychiatric condition (e.g., alcohol or drug abuse),
   dementia or altered mental status or any issue that would impair the ability of the
   patient to receive or tolerate the planned treatment, to understand informed consent
   or that in the opinion of the investigator would contraindicate the patient's
   participation in the study or that would confound the results of the study.

   9. Evidence of active viral, bacterial, or systemic fungal infection requiring systemic
   treatment within 7 days prior to the first dose of study drug. Patients requiring any
   systemic antiviral, antifungal, or antibacterial therapy for active infection must
   have completed treatment no less than 7 days prior to the first dose of study drug.

10. Known allergies, hypersensitivity, or intolerance to TRC253 or its excipients.

11. Enrollment in another interventional study.

12. Major surgery (e.g., requiring general anesthesia) within 3 weeks before screening, or
   has not fully recovered from prior surgery (i.e., unhealed wound), or surgery planned
   during the time the patient is expected to participate in the study. Note: patients
   with planned surgical procedures to be conducted under local anesthesia may
   participate.

13. Plan to father a child while enrolled in this study or within 90 days after the last
   dose of study drug.