A Phase 1/2a study to assess the safety, tolerability, PK and biological activity of CCS1477 in patients with metastatic castration resistant prostate cancer, metastatic breast cancer, non-small cell lung cancer or advanced solid tumours.

Inclusion Criteria:

• Provision of consent
• ECOG performance status 0-1
• Assessable disease (by CT, MRI, bone scan or X-ray)
• Adequate organ function
• Highly effective contraception measures for duration of study

Additional inclusion criteria for mCRPC patients only:

• Previously received abiraterone and/or enzalutamide (or equivalent anti-androgen), and docetaxel (unless ineligible or refused)

• Progressive disease documented by one or more of the following:

  • Biochemical progression defined as at least 2 stepwise increases in a series of any 3 PSA values
  • Progression as defined by RECIST v1.1 guideline for assessment of malignant soft tissue disease.
  • Progression defined as two or more new metastatic bone lesions confirmed on bone scan from a previous assessment

• PSA at screening ≥2 μg/L

• Serum testosterone concentration ≤50 ng/dL

• Serum albumin >2.5 g/dL

Additional inclusion criteria for patients in CCS1477 plus abiraterone combination arm:

• Patients must have previously progressed on abiraterone treatment
• Patients whose last dose of abiraterone is greater than 6 months prior to start of study treatment will receive a 4-week run-in treatment with abiraterone to confirm refractoriness to abiraterone treatment

Additional inclusion criteria for patients in CCS1477 plus enzalutamide combination arm:

• Patients must have previously progressed on enzalutamide treatment
• Patients whose last dose of enzalutamide is greater than 6 months prior to start of study treatment will receive a 4-week run-in treatment with enzalutamide to confirm refractoriness to enzalutamide treatment

Additional inclusion criteria for patients in mutation arm:

• Advanced solid tumour with identification of markers which may indicate potential for response to p300/CBP inhibition. Markers include loss of function mutations in CREBBP, EP300 or ARID1A, MYC gene amplifications or rearrangements and androgen receptor (AR) gene amplifications or over-expression.

Exclusion Criteria:

• Intervention with any chemotherapy, investigational agents or other anti-cancer drugs within 14 days or 5 half-lives of the first dose
• Radiotherapy with a wide field of radiation or to more than 30% of the bone marrow within 4 weeks of the first dose of study treatment
• Major surgical procedure or significant traumatic injury within 4 weeks of the first dose of study treatment
• Strong inhibitors of CYP3A4 or CYP3A4 substrates with a narrow therapeutic range taken within 2 weeks of the first dose of study treatment
• Strong inducers of CYP3A4 within 4 weeks of the first dose of study treatment
• Statins; patients should discontinue statins prior to starting study treatment
• Any unresolved reversible toxicities from prior therapy >CTCAE grade 1 at the time of starting study treatment
• Any evidence of severe or uncontrolled systemic diseases
• Any known uncontrolled inter-current illness
• QTcF prolongation (> 480 msec).
• Primary brain tumours or known or suspected brain metastases.

Additional exclusion criteria for patients in CCS1477 plus abiraterone combination arm:

• Clinically significant cardiac abnormalities

Additional exclusion criteria for patients in CCS1477 plus enzalutamide combination arm:

• History of seizures or other predisposing factors
• Use of substrates with a narrow therapeutic index metabolised by CYP2C9 or CYP2C19 within 2 weeks of the first dose of study treatment
• Clinically significant cardiac abnormalities