This is a single-centre, open label, dose finding, phase I study to determine the recommended phase II dose (RP2D) for the combination of doxorubicin and pantoprazole in patients with advanced tumours and no standard treatment options. A minimum of 3 patients will be enrolled per dose level and intra-patient dose escalation is not permitted. Once the RP2D has been identified, six additional patients with metastatic solid tumours will be treated at the RP2D to confirm its tolerability.

Inclusion Criteria:

1. Patients must have histologically or cytologically proven advanced solid tumours for whom no standard anticancer therapy exists

2. Measureable and non-measureable disease are both eligible, but disease must be evaluable as defined by RECIST 1.1.

3. Patients >18 years old

4. At least 21 days since last chemotherapy regimen and/or radiotherapy

5. Recovery from all reversible adverse events of previous anticancer therapies to baseline or to grade < or =1, except for alopecia.

6. Patients must have documented evidence of disease progression on prior systemic therapy.

7. ECOG Performance Status of 0 or 1

8. Adequate cardiovascular function and no history of serious cardiac diseases (see Exclusion criteria for definition) Left ventricular ejection fraction > 50% by multi-gated nuclear angiogram

9. Patient consent must be obtained according to Institutional REB requirements. The patient must sign the consent form prior to registration.

10. Patients must be accessible for treatment and follow-up.

11. Previous Therapy

    1. Chemotherapy: Patients can have had limited exposure to prior anthracyclines defined as no more than a total dose of 240 mg/m2 of doxorubicin or 300 mg/m2 of epirubicin (e.g. as received in the AC x 4 or FEC x 3 adjuvant regimens). Patients with prior exposure to other cardiotoxic anticancer drugs (e.g. mitoxantrone) are not eligible.
    2. Radiation: Patients may have had prior radiation therapy (including that to the breast or chest wall) provided that has not exceeded 25% of the bone marrow reserve.
    3. Previous Surgery: Previous surgery is permitted provided that wound healing has occurred.
    4. Hormonal Therapy: Patients may have had prior hormonal therapy. All hormonal agents must be discontinued at least 3 weeks prior to study entry.

12. Laboratory Requirements (must be done within 7 days prior to registration)

    1. Neutrophil count (ANC) > or = 1.5 x 10^9/L
    2. Hemoglobin > or = 90 g/L
    3. Platelet count > or = 100 x 10^9/L
    4. Bilirubin <1.5 x UNL
    5. AST or ALT < or = 2 x UNL
    6. Creatinine < or = 1.5 x UNL or creatinine clearance > or = 50mL/min

Exclusion Criteria:

1. Patients who have previously received more than 240 mg/m2 doxorubicin or 300 mg/m2 epirubicin.

2. Patients receiving concurrent treatment with experimental drugs or anti-cancer therapy.

3. Patients who are receiving drugs that are known to interact with pantoprazole, including:

   1. The anti-fungal agents fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole;
   2. The antiviral agents: atazanavir, delavirdine, indinavir, nelfinavir, raltegravir, saquinavir, tipranavir;
   3. The anticoagulant agents: clopidogrel, dabigatran;
   4. The immunosuppressive agent: mycophenolate
   5. The anti-inflammatory agent: mesalamine

4. Patients who are receiving oral pantoprazole or other PPI inhibitors may participate if these agents are discontinued at least 7 days before trial entry.

5. Patients with untreated brain or meningeal metastases. (MR or CT scans are not required to rule this out unless there is a clinical suspicion of CNS disease). Patients with treated and stable brain metastases are eligible providing that they have radiological evidence of disease stabilization of at least 3 months duration and are asymptomatic.

6. Patients who have a history of clinically significant cardiac disease, including:

   1. Unstable angina/ acute coronary syndrome
   2. Congestive heart failure
   3. Myocardial infarction within the past year
   4. Clinically significant arrhythmia
   5. Pericarditis or myocarditis
   6. Symptomatic valvular disease Patients with well-controlled hypertension, uncomplicated mitral valve prolapsed or other stable cardiac conditions are eligible.

7. Patients with active or uncontrolled infections or with serious illnesses or medical conditions that would not permit the patient to be managed according to the protocol.

8. Patients with a known bleeding disorder. Patients who are on stable anticoagulation with warfarin or s.c. heparin products are eligible. Patients receiving clopidogrel are excluded.

9. Patients unable or unwilling to give written, informed consent prior to study participation.

10. Women who are pregnant or nursing.