RX108 is a novel, potent, small-molecule inhibitor of Na+/K+-ATPase. The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics (PK) and efficacy of RX108 in patients with locally advanced or metastatic solid tumors.

This is a open-label, two-part study comprised of a dose escalation part and a dose expansion part. In the dose escalation part, RX108 will be administered in ascending doses to evaluate the safety and tolerability of RX108 and determine the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D). The dose expansion part will assess the safety, pharmacokinetics, and efficacy of RX108 at the RP2D.

Inclusion Criteria:

• Histologically confirmed locally advanced or metastatic cancer that has failed all systemic therapies known to confer clinical benefit
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Minimum age of 18 years
• Adequate hematologic, hepatic and renal function
• Written Informed Consent
• Must agree to use adequate contraception (females and males)

Exclusion Criteria:

• History of certain cardiac abnormalities
• History of inadequate pulmonary function
• Symptomatic brain metastasis
• Treatment with prohibited medications
• Known contra-indication to digoxin
• Treatment with any unapproved therapies for cancer, or any other anti-cancer therapy within 3 weeks
• Any toxicity related to prior treatment must have resolved to Grade 1 or less, with the exception of alopecia
• Clinically significant active infection requiring systemic antibiotic treatment
• Females who are pregnant or breastfeeding

To be determined.