Inclusion Criteria:

          -  Male or female and ≥12 years-of-age at the time of informed consent.

          -  Lansky performance status ≥50% for patients ≤16 years of age, or ECOG score of 0, 1,
             or 2 for patients >16 years of age.

          -  Locally advanced or metastatic resistant or refractory solid tumors.

          -  Patients <18 years of age must weigh at least 40 kg.

          -  Submission of available tumor tissue at screening or willingness to have a biopsy
             performed if safe and feasible

          -  Next generation sequencing (NGS) report obtained in a CLIA-certified or equivalent
             laboratory demonstrating eligible tumor biomarker.

          -  Measurable disease as per RECIST v1.1.

          -  Ability to swallow and retain oral medications.

          -  Acceptable hematologic and organ function at screening.

          -  Negative pregnancy test (serum) for women of childbearing potential (WOCBP) at
             Screening.

          -  Resolution of all toxicities of prior therapy or surgical procedures.

          -  Any prior radiation must have been completed at least 7 days prior to the start of
             study drugs, and patients must have recovered from any acute adverse effects prior to
             the start of study treatment.

        Exclusion Criteria:

          -  Chemotherapy or small molecule antineoplastic agent given within 21 days or <5
             half-lives, whichever is shorter, prior to first dose of study drug.

          -  History or current condition, therapy, or laboratory abnormality that might confound
             the study results or interfere with the patient's participation for the full duration
             of the study treatment.

          -  Patients who are pregnant or breastfeeding.

          -  Life-threatening illness, medical condition, active uncontrolled infection, or organ
             system dysfunction or other reasons which, in the investigator's opinion, could
             compromise the participating patient's safety.

          -  Major surgery within 4 weeks prior to first dose of RP-6306.

          -  Uncontrolled, symptomatic brain metastases.

          -  Uncontrolled hypertension.

          -  Psychological, familial, sociological, or geographical conditions that do not permit
             compliance with the protocol and/or follow-up procedures outlined in the protocol.