A Study of AC176 for the Treatment of Metastatic Castration Resistant Prostate Cancer

Inclusion Criteria: 1. Males who are at least 18 years-of-age at the time of signature of the informed consent form (ICF) 2. Patients with histological, pathological, or cytological confirmed diagnosis of advanced or mCRPC who have had disease progression per Prostate Cancer Working Group 3(PCWG3) guidance following standard treatment, including approved taxane-based chemotherapy, or who are not amenable (intolerability, patient choice) to standard therapies, or for whom no therapy of proven efficacy exists. 3. Advanced or metastatic disease per PCWG3 guidance documented by either: • Positive bone scan (2 lesions) or metastatic lesions on computed tomography (CT)/magnetic resonance imaging (MRI) that can be followed for response. Or • Prostate-specific antigen (PSA) values with a starting value of ≥1.0 ng/mL that have increased on 3 occasions obtained a minimum of 1 week apart. 4. Patients must have progressed on at least 2 prior approved systemic therapies (in any setting), with at least 1 being abiraterone, or enzalutamide, or apalutamide or darolutamide 5. Patients who have had surgical or medical castration. 6. Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 to 1 7. Life expectancy ≥3 months after the start of the treatment according to the Investigator's judgment Exclusion Criteria: Patients who meet any of the following criteria will be excluded from study entry: 1. Treatment with any of the following: * More than 2 lines of chemotherapy * Any systemic anti-cancer therapy, chemotherapy, biologic, or hormonal agent from a previous treatment regimen or clinical study within 4 weeks prior to the first dose of study drug. Any systemic small molecules from a previous treatment regimen or clinical study within 2 weeks or 5 half-lives (whichever is longer, not to exceed 4 weeks) prior to the first dose of study drug, except ADT for medical castration purpose. * Any investigational agents from a previous clinical study within 4 weeks prior to the first dose of study treatment * Radiation therapy (including therapeutic radioisotopes) within 4 weeks prior to first dose of study drug. Radiation for palliation within 2 weeks of study drug. Palliative radiation for the alleviation of pain due to bone metastasis will be allowed during the study 2. With the exception of alopecia and ≤ Grade 2 peripheral neuropathy, any unresolved toxicities from prior therapy greater than the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Grade 1 at the time of starting study treatment. Note: subjects with chronic Grade 2 toxicities that are asymptomatic or adequately managed with stable medication may be eligible with Sponsor approval 3. Major surgery (excluding placement of vascular access) within 4 weeks of first dose of study drug. 4. Known symptomatic brain metastases requiring steroids (above physiologic replacement doses) 5. Men who plan to father a child while in the study or within 90 days after the last administration of study treatment 6. Any condition that impairs a patient's ability to swallow whole pills. Presence of active gastrointestinal disease or other condition that will interfere significantly with the absorption, distribution, metabolism, or excretion of AC176 (e.g., ulcerative disease, uncontrolled nausea, vomiting, diarrhea Grade ≥2, malabsorption syndrome) 7. Any of the following cardiac criteria experienced currently or within the last 6 months: * Mean resting corrected QT interval (QTc) \>470 msec * Any clinically important abnormalities (as assessed by the Investigator) in rhythm, conduction, or morphology of resting electrocardiograms (ECGs), e.g., complete left bundle branch block, third-degree heart block * Congestive heart failure (New York Heart Association ≥ Grade 2) * Any factors that increase the risk of QTc prolongation or risk of arrhythmic events such as heart failure, hypokalemia, congenital long QT syndrome, family history of long QT syndrome or unexplained sudden death under 40 years-of-age, or any concomitant medication known to prolong the QT interval * Left ventricular ejection fraction (LVEF) \<50% or the lower limit of normal of the institutional standard. 8. As judged by the Investigator, any evidence of severe or uncontrolled systemic diseases, including uncontrolled hypertension, uncontrolled diabetes mellitus, active bleeding diatheses, or active infection. Screening for chronic conditions is not required. Psychological, familial, sociological, or geographical conditions that do not permit compliance with the protocol and/or follow-up procedures outlined in the protocol.