Inclusion Criteria:

• Male or female and ≥ 18 years-of-age at the time of informed consent.
• ECOG Performance status 0 or 1.
• Locally advanced or metastatic resistant or refractory solid tumors.
• Submission of available tumor tissue at screening or willingness to have a biopsy performed if safe and feasible.
• 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.
• Life expectancy ≥ 12 weeks after the start of the 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.
• Known sensitivity to any of the ingredients of RP-6306 or gemcitabine.
• 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 and gemcitabine.
• Uncontrolled, symptomatic brain metastases.
• Uncontrolled hypertension.
• Moderate or severe hepatic impairment.
• Psychological, familial, sociological, or geographical conditions that do not permit compliance with the protocol and/or follow-up procedures outlined in the protocol.

Eligibility last updated 2/14/22. Questions regarding updates should be directed to the study team contact.