• To determine the safety, tolerability and maximum tolerated dose (MTD) of AP23573 when administered orally as an enteric or film coated tablet to patients with progressive or recurrent malignancies. Several dosage regimens will be examined in this trial [ Time Frame: Complete duration of study ] [ Designated as safety issue: Yes ]
  

• Examine pharmacokinetic and pharmacodynamic characteristics of AP23573 (e.g., AP23573 blood levels, phospho-4E-BP1 levels, plasma partitioning) [ Time Frame: Complete duration of study ] [ Designated as safety issue: No ]
  
• Describe the antitumor activity of the study drug regimens [ Time Frame: Complete duration of the study ] [ Designated as safety issue: No ]
  

Drug: AP23573
10 mg tablet of AP23573 administered orally according to one of six different dosing regimens for a four-week treatment cycle.

The advent of oral anticancer therapy has created a means to reduce dependency on a system for treating cancer that relies on hospital-based services to administer treatment. While known disadvantages of oral therapies such as potential variable absorption, unpredictable bioavailability and sometimes poor patient compliance pose challenges, the use of orally administered compounds permits investigation of alternative or varied dose regimens, which may ultimately enhance overall patient care.

AP23573 is currently being studied in phase 1 and phase II clinical trials in patients with advanced cancers. Thus far, these trials have demonstrated that AP23573 has a favorable safety profile and possesses anticancer activity when administered as a 30-minute intravenous (IV) infusion daily x 5 every-two-weeks or on a weekly schedule. The primary objective of this current phase I trial is to study the safety and tolerability of an orally administered dosage form of AP23573. This will be accomplished by an ascending dose study of several dosage regimens in patients with advanced malignancies.

Inclusion Criteria:

• Male or female patients ≥18 years of age.
• Patients with a histological/cytological diagnosis of unresectable or metastatic cancer that is refractory to standard therapies or for which no standard therapy exists.
• Patients must must have measurable or nonmeasurable lesions assessable using an appropriate radiographical procedure (e.g., CT or MRI scans).
• Fertile male or female patients who agree to use approved barrier methods of contraception (non hormonal methods).
• ECOG performance status ≤ 2.
• Adequate renal and hepatic function, defined as: *Total serum bilirubin ≤ 2 x upper limit of normal (ULN) for the institution; *AST and/or ALT ≤ 2.5 x ULN for the institution (≤ 5 x if due to hepatic metastases); *Serum albumin ≥ 2 g/dL; Serum creatinine ≤ 2 x ULN for the institution
• Adequate bone marrow function, defined as: * ANC ≥ 1.5 x 10^9/L; *Platelet count ≥ 100 x 10^9/L
• Serum cholesterol < 350 mg/dL and triglycerides < 400 mg/dL.
• Anticipated life expectancy of ≥ 3 months.
• Able to give and understand a written informed consent.

Exclusion Criteria:

• Patients with active central nervous system (CNS) metastases or leptomeningeal disease, not controlled by prior surgery or radiotherapy.
• Prior therapy with rapamycin, rapamycin analogs or tacrolimus, or known sensitivity to these agents.
• Prior anticancer treatment, standard or experimental, within 4 weeks prior to the first dose of AP23573 (except LH-RH agonists); the interval is ≥ 2 weeks for signal transduction inhibitors with a half-life known to be < 24 hours, and is ≥ 6 weeks for nitrosourea or mitomycin.
• Concomitant treatment with medications that induce, inhibit, or are metabolized by cytochrome P450 (CYP3A). Patients should be off these medications 2 weeks prior to the first dose of AP23573.
• Ongoing toxicity associated with prior anticancer therapy (except peripheral neuropathy of ≤ grade 1 by National Cancer Institute (NCI) Terminology Criteria and alopecia).
• Another primary malignancy within the past three years (except in situ carcinoma).
• Known or suspected hypersensitivity to any excipient contained in the study drug.
• Known Grade 3 or 4 hypersensitivity to macrolide antibiotics (e.g., clarithromycin, erythromycin, azithromycin).
• Significant uncontrolled cardiovascular disease.
• Active infection requiring systemic therapy.
• Women who are pregnant or lactating.
• Known HIV infection .
• Other life-threatening illness, any medical condition, or organ system dysfunction, which, in the opinion of the Investigator and Sponsor, would either compromise the patient's safety or interfere with evaluation of the safety of AP23573, or could interfere with the absorption of the oral study drug.
• Concurrent treatment with immunosuppressive agents other than prescribed corticosteroids at stable doses for ≥ 2 weeks prior to first planned dose of study drug.
• Inadequate recovery from any prior surgical procedure or having undergone any major surgical procedure within the last 3 to 4 weeks prior to the first dose of AP23573.