Key Inclusion Criteria:  1.0. Part 1 - Subjects with advanced and/or metastatic solid tumors. Histologic or cytologic confirmation of malignancy must have been obtained at diagnosis. The tumor types include:  i. CRPC - Subjects with progressive disease in the setting of medical or surgical castration (i.e., castration-resistant prostate cancer).  ii. NSCLC (adenocarcinoma subtype) - Subjects with no targetable mutations must have received a platinum-containing doublet chemotherapy regimen and a checkpoint inhibitor (either in combination or monotherapy, if indicated) and have progressed. Subjects with targetable mutations/alterations such as EGFR, ALK, or NTRK must have received prior targeted therapy and have progressed.  iii. CRC - Subjects must have received one prior line of standard chemotherapy such as FOLFOX +/- a VEGF-inhibitor and have progressed or are intolerant of oxaliplatin based regimens.  1.1. Part 2 - Subjects with advanced and/or metastatic solid tumors. Histologic or cytologic confirmation of malignancy must have been obtained at diagnosis. The tumor types include:  i. CRPC - Subjects with progressive disease in the setting of medical or surgical castration (i.e., castration- resistant prostate cancer).  ii. NSCLC (adenocarcinoma subtype) - Subjects with no targetable mutations must have received a platinum-containing doublet chemotherapy regimen and a checkpoint inhibitor (either in combination or monotherapy, if indicated) and have progressed. Subjects with targetable mutations/alterations such as EGFR, ALK, NTRK must have received prior targeted therapy and have progressed.  iii. CRC - Subjects must have received one prior line of standard chemotherapy such as FOLFOX +/- either a VEGF-inhibitor or EGFR inhibitor (if indicated) and have progressed or are intolerant of oxaliplatin based regimens.  2.0. Male or female subjects ≥ 18 years of age.  3.0 Measurable or evaluable disease per RECIST 1.1 (Part 1). For Part 2, at least one measurable lesion per RECIST 1.1 that has not been previously irradiated. In CRPC subjects (Parts 1 and 2) without measurable disease per RECIST 1.1, a PSA that is concordant with clinical disease progression (rising) is eligible. A PSA value of 2 ng/ml or greater is required for study entry for those without measurable disease.  4.0. Subjects must have archived tumor specimens available for analysis Otherwise, a fresh tumor biopsy will be required at study entry.  5.0.. Subjects must have recovered (i.e., Grade 1 [or better] based on CTCAE v5.0) from all toxicity associated with previous chemotherapy, targeted therapy, experimental therapy, biological therapy, immuno-oncology therapy, surgery, radiotherapy, or other locoregional therapy.  The following intervals must elapse between end of last treatment and receiving the first dose of SM08502:  Chemotherapy: 3 weeks. Mitomycin C or a nitrosourea: 6 weeks. Radiotherapy: 3 weeks. Major surgery: 6 weeks. Targeted therapy, including monoclonal antibodies and immuno-oncology therapies: 4 weeks or 5 half-lives, whichever is shortest.  6.0. Subjects must meet the following laboratory criteria at Screening for study entry:  Hepatic function: serum total bilirubin ≤ 1.5x upper limit of normal (ULN), AST/ALT ≤ 2.5x ULN. For subjects with Gilbert's syndrome, serum total bilirubin ≤ 3x ULN. Renal function: measured or calculated creatinine clearance via Cockcroft-Gault formula >35 mL/min. Hematology: absolute neutrophil counts ≥ 1500/mm3, platelet counts ≥ 100,000/mm3, hemoglobin ≥ 9.0 g/dL. Coagulation: prothrombin time (PT) and partial thromboplastin time (PTT) ≤ 1.5x ULN.  7.0. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1.  8.0. Life expectancy > 3 months.  9.0. Subjects must have no uncontrolled intercurrent illness.  10.0 Subjects must have the ability to swallow and retain oral medication.  11.0 Subjects must be willing to sign and provide informed consent and be capable of giving informed consent in accordance with the Institutional Review Board (IRB) / Ethics Committee (EC) policy.  Key Exclusion Criteria:  Women who are pregnant or lactating. Women of childbearing potential (WOCBP) must agree to follow the contraceptive guidelines as outlined in protocol. Men of reproductive potential must agree to follow the contraceptive guidelines as outlined in protocol. Subjects with a QTc (Fridericia's) prolongation > CTCAE v5.0 Grade 1 (>480 msec) at Screening. Subjects with clinically significant ventricular tachycardia (VT), atrial fibrillation (AF), ventricular fibrillation (VF), second- or third-degree heart block. Subjects with myocardial infarction (MI) within 1 year, Class II-IV congestive heart failure (CHF) per New York Heart Association (NYHA) classification, or clinically significant coronary artery disease (CAD).. Subjects with active infection (e.g., requiring antibiotic therapy). Organ transplant recipients. Subjects with untreated, progressing, or known symptomatic brain metastasis. Subjects with a second malignancy unless adequately treated with no recurrence for 3 years. Subjects with a history of previous or recent adequately treated basal cell or squamous cell carcinoma of the skin, or carcinoma in situ of any source are eligible. Subjects with known hypersensitivity to any excipients in the study drug formulation. Subjects with active gastrointestinal (GI) disease or other condition that will interfere significantly with the absorption, distribution, metabolism, or excretion of SM08502 per Investigator's opinion. Subjects with known active human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV) infection. Subjects considered by the Investigator to be unsuitable for the study for any other reason. Subjects with chronic liver disease or dysfunction and a Child-Pugh score of B or C.