Study of Safety and Efficacy of RGT-61159 in Adults With Relapsed/Refractory Adenoid Cystic Carcinoma (ACC) or Colorectal Carcinoma (CRC)

Inclusion Criteria: * Histologically confirmed ACC or CRC * Radiographically measurable disease as assessed per RECIST 1.1, with at least 1 site of disease that is measurable and that has not been previously irradiated; or, if the patient has had previous radiation to the target lesion(s), there must be evidence of progression since the radiation * Patients with locally relapsed/refractory (R/R) advanced or metastatic ACC not amenable to potentially curative surgery or radiotherapy and progression of disease within 12 months at study entry * Patients with CRC must have locally R/R advanced or metastatic disease not amenable to potentially curative surgery or radiotherapy; must have been previously treated with, or are not considered candidates for, available therapies including fluoropyrimidines-, oxaliplatin-, and irinotecan-based chemotherapies, anti-VEGF agents, and if RAS wild-type, an anti-EGFR therapy. * Adequate hematologic status, organ function, renal function, liver function and prothrombin time (PT) or INR ≤ 1.5 × ULN and partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT) ≤ 1.5 × ULN * Resolved acute effects of any prior therapy to baseline * Patients with ACC must have documented evidence of intact MYB pseudoexon positive criteria or be MYB wild type and patients with CRC must have amplification of MYB as determined by designated assay Exclusion Criteria: * Major surgery or significant traumatic injury within 28 days prior to Cycle 1 Day 1 * Chemotherapy within 14 days prior to Cycle 1 Day 1 * Use of nitrosoureas or mitomycin C within 6 weeks prior to Cycle 1 Day 1 * Radiation therapy within 21 days prior to Cycle 1 Day 1 * Investigational drug use, targeted therapy, or biologic therapy within 28 days or 5 half-lives, whichever is shorter, prior to Cycle 1 Day 1 * Ongoing systemic infection requiring treatment with antibiotic, antiviral, or antifungal treatment * Active known second malignancy * Clinically significant cardiac disease * Infection with human immunodeficiency virus (HIV)-1 or HIV-2 unless it's well-controlled HIV (eg, cluster of differentiation 4 \[CD4\] \> 350/mm3 and undetectable viral load) * Current active liver disease including hepatitis A (hepatitis A \[HepA\] virus immunoglobulin M \[IgM\] positive), hepatitis B (hepatitis B virus \[HBV\] surface antigen positive), or hepatitis C (hepatitis C virus \[HCV\] antibody positive, confirmed by HCV RNA) * Refractory nausea and vomiting, malabsorption, external biliary shunt, or significant small bowel resection that would preclude adequate absorption * Uncontrolled diabetes * Treatment with a long-acting hematopoietic growth factor within 14 days before Cycle 1 Day 1 or a short-acting hematopoietic growth factor within 7 days before Cycle 1 Day 1 * Treatment with high-dose chemotherapy and stem-cell rescue (autologous stem cell transplant) or allogeneic stem cell transplant within 90 days before Cycle 1 Day 1 * Patients with central nervous system (CNS) metastases are not eligible, unless they have completed local therapy and have discontinued the use of corticosteroid throughout this indication for at least 4 weeks before starting treatment in this study * History of solid organ transplantation * Coronavirus disease 2019 (COVID-19) vaccination within 14 days prior to first dose of study drug * Prior treatment with a MYB inhibitor