Inclusion Criteria:

• Confirmed solid malignancy; metastatic or unresectable; for which standard effective anti-neoplastic therapy does not exist or is no longer effective
• Eligibility is regardless of types of previous therapies administered. Should have recovered from acute toxicities associated with most recent regimen and have been off treatment with investigational agents for 4 weeks (6 weeks min. for nitrosoureas or mitomycin C).
• ECOG performance status < 2
• Life expectancy > 4 months.
• Normal organ and marrow function: 1eukocytes >3,000/mcL; absolute neutrophil count >1,500/mcL; platelets >100,000/mcL; total bilirubin <1.5 X institutional ULN; AST(SGOT)/ALT(SGPT) <2.5 X institutional ULN; creatinine within normal institutional ULN; OR, creatinine clearance >60 mL/min/1.73 m2 for patients with creatinine levels above ULN.
• Patients with known brain metastases will only be eligible after tumors have been treated with definitive resection and/or radiotherapy and they are neurologically stable for at least 1 month off steroids.
• No history of gastrointestinal disease causing malabsorption or obstruction.
• Women of child-bearing potential must agree to use two forms of acceptable contraception prior to study entry, for duration of participation, and for a minimum of 1 month after completion of the study. Women who know or suspect that they have become pregnant during the study, should discontinue the study drug and inform treating physician immediately. Pregnancy test is required prior to study enrollment and monthly while on treatment with 1-MT. Men should be discouraged from fathering children while on treatment.
• Signed written consent document.

Exclusion Criteria:

• Chemotherapy or radiotherapy treatment within 2 weeks (6 weeks for nitrosoureas or mitomycin C) prior to entering study or those who have not recovered from adverse events due to agents administered more than 4 weeks earlier.
• May not be receiving any other investigational agents.
• Known untreated brain metastases, because of their poor prognosis and they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events. Patients with previously treated lesions as specified in protocol will not be excluded.

• History of allergic reactions attributed to compounds of similar chemical or biologic composition to

  1-Methyl-D-tryptophan.

• 1-MT is not metabolized through the p450 cytochrome, so there are no specific exclusions for such medications that are metabolized through this pathway. No supplements containing L-tryptophan or derivatives thereof are allowed to be taken while on study. Antacid compounds should be timed a minimum of 2 hours before or after ingestion of 1-MT.
• Active autoimmune disease, chronic inflammatory condition, conditions requiring concurrent use of any systemic immunosuppressants or steroids. Patients with an allo-transplant of any kind. Mild-intermittent asthma requiring only occasional beta-agonist inhaler use or mild localized eczema will not be excluded.
• Uncontrolled concurrent illness or social situations that would limit compliance with study requirements as judged by primary investigator. Those with well controlled, chronic medical conditions under the supervision of patient's primary physician (hypertension, hyperlipidemia, coronary heart disease, diabetes mellitus...) would not be excluded.
• Women pregnant or breastfeeding.
• HIV-positive patients and those with other acquired/inherited immunodeficiencies are ineligible.
• Having more than 1 active malignancy at time of enrollment.