Inclusion Criteria:

* Relapse or refractory castration-resistant prostate cancer (CRPC) following at least one anti-androgen regimen and a docetaxel-containing regimen OR
* metastatic or unresectable NUT midline carcinoma for which standard curative or palliative measures do not exist; OR
* patients who have other types of relapsed or refractory solid tumors with pathological and/or biological features suggesting a potential benefit from dual BET and CBP/p300 inhibition may be enrolled after discussion with and approval from medical monitor and sponsor
* Eastern Cooperative Oncology Group (ECOG) performance status 0-1
* Life expectancy ≥ 3 months
* Evaluable disease
* Adequate bone marrow function:

Hemoglobin ≥ 9.0 g/dL Absolute neutrophil count (ANC) ≥ 1,500/dL Platelet count ≥100,000/?L

* Adequate renal function:

Creatinine clearance (CLcr) estimated by Cockcroft-Gault Equation to be ≥ 60 mL/min. Estimated glomeruli filtration rate (eGRF) ≥ 60 mL/min may be used if provided by the testing laboratory

* Adequate liver function

* Total bilirubin ≤ 1.5 x ULN except in patients diagnosed with Gilbert's disease for which direct bilirubin must be ≤ 1.5 x ULN
* Alanine aminotransferase (ALT) or aspartate Aminotransferase (AST) ≤ 2.5 x ULN or ≤ 5 x ULN in patients with liver metastases
* Internal normalized ratio for prothrombin time (INR) ≤ 1.2 in patients not receiving chronic anticoagulation
* Four weeks from prior anti-cancer therapy including chemotherapy, immunotherapy, investigational anti-cancer therapy or 5 half-lives from targeted agents, radiation and have recovered from prior treatment toxicities to grade 1 or less. Prostate cancer patients may continue androgen-deprivation therapy by luteinizing hormone-releasing hormone (LHRH) agonists.
* Four weeks from major surgery.
* For fertile men and women, agreement to use effective contraceptive methods duration of study participation and 4 weeks after the last dose of study drug.
* Ability to understand and willingness to sign the informed consent form.

Exclusion Criteria:

* New and progressive central nervous system (CNS) metastasis; patients with treated brain metastases are eligible if follow-up brain imaging at least 4 weeks after CNS-directed therapy shows no evidence of progression and the patient is neurologically stable
* Corrected QT interval ≥470 msec
* Uncontrolled concurrent illnesses including, but not limited to, ongoing active infection requiring intravenous antibiotics or antifungal agents, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia or psychiatric illness/social situations that would affect compliance with study requirements; patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of EP31670 are eligible for this trial
* Pregnant or lactating women
* Known history of hepatitis B, hepatitis C requiring antiviral treatment
* Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 7/18/2024. Questions regarding updates should be directed to the study team contact.