Inclusion Criteria:

Phase Ib:

1. Advanced or metastatic solid tumor malignancy that is refractory to standard therapy, or that has relapsed after standard therapy, or for which conventional therapy is not reliably effective, or no effective therapy is available.
2. Measurable disease as defined by RECIST. If recurrence is documented following radiation therapy, the recurrence must have occurred outside the radiation field. Lesions which are located within a previously irradiated field are not considered measurable.
3. Age 18 years or older.
4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. (See Appendix I.)

5. Adequate organ and system function defined by the following parameters:

   • Bone marrow: Absolute neutrophil count (ANC) of >=1500/mm3, platelet count >=100,000/mm3, and hemoglobin >=9 g/dL;
   • Coagulation: PT <1.3 x ULN, PTT >LLN, <1.1 x ULN
   • Renal: Serum creatinine of <=1.5 x the institution's upper limit of normal (ULN) or calculated creatinine clearance >=60 mL/min/1.73m2;
   • Hepatic: Total bilirubin <=1.5 mg/dL, alanine aminotransferase (ALT) and aspartate transaminase (AST) <=2.5 x ULN (or 5 x ULN in the case of liver metastases), and alkaline phosphatase <=2.5 x ULN (or 5 x ULN in the case of liver metastases).
6. Recovered to <=Grade 1 from all acute toxicities caused by prior cancer therapies except for residual toxicities, such as alopecia, which do not pose an ongoing medical risk.
7. If of childbearing potential, agree to use an effective method of contraception prior to study entry, for the duration of the study, and for 30 days after the last dose of MBP-426 (in combination with FA/5-FU). A negative serum or urine pregnancy test must be documented at baseline for women of childbearing potential. Patients may not breastfeed while in this study.
8. Have the ability to maintain a central IV access (e.g., PICC, Groshong, or Hickman line).
9. Able to comply with the protocol treatments and procedures.
10. Provide written informed consent indicating that they are aware of the investigational nature of this study and in keeping with the policies of the institution.

Phase II:

1. Inoperable, histologically, or cytologically confirmed, locally advanced or metastatic gastric, gastro-esophageal junction, or esophageal adenocarcinoma that has recurred or progressed following 1 prior chemotherapy.
2. Measurable disease as defined by RECIST. If recurrence is documented following radiation therapy, the recurrence must have occurred outside the radiation field. Lesions which are located within a previously irradiated field are not considered measurable.
3. Identical to criteria numbers 3-10 for Phase Ib portion of the study.

Exclusion Criteria:

1. Radiotherapy or major surgery within 14 days prior to study enrollment.
2. Anticancer therapy (chemotherapy, radiotherapy, hormonal therapy, immunotherapy, or investigational agents) within 30 days of enrollment (6 weeks for mitomycin C). Concurrent use of bisphosphonates is permitted.
3. Have had a past or have a current second primary malignancy (except in situ carcinoma of the cervix or adequately treated nonmelanomatous carcinoma of the skin, or other malignancy treated at least 3 years previously with surgery and/or radiotherapy and no evidence of recurrence since that time).
4. Known or clinical evidence of central nervous system (CNS) metastases.
5. Receiving high-dose steroids (more than a dexamethasone-equivalent dose of 4 mg per day).
6. Current active infections requiring anti-infectious treatment (e.g., antibiotics, antivirals, or antifungals).
7. Significant intercurrent illnesses that, in the opinion of the Investigator, would compromise the safety of the patient or compromise the ability of the patient to complete the study.
8. Documented or known hematologic malignancy and/or bleeding disorder.
9. Peripheral neuropathy >= grade 2 (NCI-CTCAE, Version 3.0).
10. Any requirement(s) for therapeutic anticoagulation that increases international normalized ratio (INR) or activated partial thromboplastin time (aPTT) above the normal range (low dose deep vein thrombosis [DVT] or line prophylaxis is allowed).
11. Have New York Heart Association (NYHA) Class 3 or 4 heart disease, active ischemia, or any uncontrolled, unstable cardiac condition for which treatment for the condition is indicated but is not controlled despite adequate therapy including angina pectoris, cardiac arrhythmia, hypertension, or congestive heart failure. (See Appendix II).
12. History of allergy to any of the treatment components (oxaliplatin, 5-FU, folinic acid, liposome, ferritin).