Phase 2 Study of IDH305 in Low Grade Gliomas

Inclusion Criteria: 1. Written informed consent prior to any screening procedures that are not part of standard of care. 2. Age greater than or equal to 18 years. 3. Male or female of any racial or ethnic origin. 4. Measurable 2HG by MR Spectroscopy (above threshold of 1mM, established at UTSW). 5. Karnofsky Performance Status \> 70%. 6. Measurable disease per RANO criteria. 7. Female subjects with reproductive potential must have a negative serum pregnancy test within 7 days prior to start of therapy. Subjects with reproductive potential are defined as one who is biologically capable of becoming pregnant. Women of childbearing potential as well as fertile men and their partners must agree to abstain from sexual intercourse or to use two effective forms of contraception during the study and for 30 days (females and males) following the last dose of IDH305. Exclusion Criteria: 1. 2HG by MR Spectroscopy below 1 mM. 2. Patients who are currently receiving treatment with a prohibited medication or herbal remedy that cannot be discontinued at least one week prior to the start of treatment. 3. Narrow therapeutic index substrates of CYP3A, CYP2C9, CYP2C19, and CYP2C8. 4. Medications, herbs and supplements that are strong inhibitors and strong inducers of CYP3A. 5. Other herbal preparations and supplements. 6. Inhibitors of UGT1A1. 7. Patients who have out of range laboratory values defined as: * Absolute neutrophil count (ANC) \<1.0 x 109/L * Hemoglobin (Hgb) \<8 g/dL * Platelets \<75 x 109/L * Total bilirubin \> ULN * AST or ALT \>3 x ULN * Serum creatinine \>1.5 x ULN 8. Karnofsky Performance Status \< 70%. 9. Malignant disease other than that being treated in this study. Exceptions to this exclusion include the following: malignancies that were treated curatively and have not recurred within the prior 2 years; completely resected basal cell and squamous cell skin cancers; any malignancy considered to be indolent and that has never required therapy; and completely resected carcinoma in situ of any type. 10. Patients with corrected QT using the Fridericia correction (QTcF) \> 470 msec, or other clinically significant, uncontrolled heart disease, including acute myocardial infarction or unstable angina \< 3 months prior to the first dose of IDH305. 11. Any other medical condition that would, in the investigator's judgment, prevent the patient's participation in the clinical study due to safety concerns or compliance with clinical study procedures such as the presence of other clinically significant cardiac, respiratory, gastrointestinal, renal, hepatic or neurological disease. 12. Patients with Gilbert's syndrome or other heritable diseases of bile processing. 13. Patients who are claustrophobic or who have other contraindications to MRI, such as an implanted pacemaker device, vascular clips, prosthetic valves, or otologic implants. 14. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. 15. Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception during dosing and for 30 days after the use of the investigational medication. Highly effective contraception methods include: * Total abstinence (when this is in line with the preferred and usual lifestyle of the patient). Periodic abstinence (e.g., calendar, ovulation, symptothermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception. * Female sterilization (have had surgical bilateral oophorectomy with or without hysterectomy), total hysterectomy, or tubal ligation at least six weeks before taking study treatment. In case of oophorectomy alone, only when the reproductive status of the woman has been confirmed by follow up hormone level assessment Male sterilization (at least 6 months prior to screening). The vasectomized male partner should be the sole partner for that patient. * Combination of any two of the following (a+b, a+c, or b+c): a. Use of oral, injected or implanted hormonal methods of contraception or other forms of hormonal, for example hormone vaginal ring or transdermal hormone contraception. * In case of use of oral contraception women should have been stable on the same pill for a minimum of 3 months before taking study treatment. b. Placement of an intrauterine device (IUD) or intrauterine system (IUS). c. Barrier methods of contraception: condom or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/vaginal suppository 16. Women are considered post-menopausal and not of child bearing potential if they have had 12 months of natural (spontaneous) amenorrhea with an appropriate clinical profile (e.g. age appropriate, history of vasomotor symptoms) or have had surgical bilateral oophorectomy (with or without hysterectomy), total hysterectomy or tubal ligation at least six weeks ago. In the case of oophorectomy alone, only when the reproductive status of the woman has been confirmed by follow up hormone level assessment is she considered not of child bearing potential. 17. Sexually active males must use a condom during intercourse while taking the drug and for 30 days after stopping treatment and should not father a child in this period. A condom is required to be used also by vasectomized men as well as during intercourse with a male partner in order to prevent delivery of the drug via semen.