Safety Parameters - Dose tolerance and treatment toxicity, especially cardiotoxicity, of GPX-100 will be evaluated. A baseline medical history including Karnofsky Performance Status and a physical examination, hematology profile (CBC, differential, platelet count), chemistry profile including electrolytes, serum calcium, liver and renal function tests, urinalysis, chest and abdominal CT scans, and a bone scan will be done. Interval history with adverse event (AE) assessment and performance status, physical examination, and hematology and clinical chemistry profile will be repeated every 3 weeks during treatment. In addition, hematology and chemistry profiles will be repeated weekly between treatment visits. Chest and abdominal CTs and bone scans will be repeated at 6-week intervals as appropriate for tumor assessment. An MRI of the brain will be performed at the baseline visit if clinically indicated. Urinalysis will be repeated at six-week intervals during treatment. Cardiotoxicity will be assessed with ECG and MUGA scans at baseline, every 6 weeks during treatment, and 6-8 weeks after the last dose of GPX-100. There will be continued follow-up at 6-8 week intervals if indicated by changing cardiac function until normal or stable. Treatment will be discontinued if there is objective disease progression or unacceptable treatment toxicity. A follow-up visit will occur 6-8 weeks after the last treatment visit for each patient, whether the study was completed per protocol or the patient discontinues study treatment early for any reason. The following evaluations will be performed at the follow-up visit: physical examination, adverse event assessment, ECG, MUGA scan, hematology and clinical chemistry profiles, and urinalysis. Serum pregnancy tests will be performed at baseline and at the follow-up visit, if necessary.