Protocol Amendment 2: - Description of the use of new dosing and the tablet formulation planned for use in this study was added. Identified the initial starting dose for all subjects at 50 mg/m2 (35 mg/m2 as per original protocol) based on clinical experience. - Revised the dose modification criteria for thrombocytopenia (to hold the drug for ≥Grade 3 thrombocytopenia until resolved to ≤ Grade 1 and then resume at a lower dose; specified when to further dose reduce and when to discontinue for recurrent toxicity) and for renal toxicity based on NCI-CTCAE (Version 4.03) criteria for serum creatinine levels. - Expanded the inclusion criteria to allow enrollment of subjects with AST levels less than twice the upper limit of normal (< 2 x ULN). - Clarified that the 7 surgical subjects planned to be enrolled in Arm A will receive 3 doses instead of 2 to 3 doses prior to surgery. - Revised the selinexor administration time after brain surgery for subjects in Arm A based on data regarding previously observed thrombocytopenia in Phase I human experience. The initial protocol stated that selinexor would be administered post-operatively 1 to 5 weeks from the date of surgery.

Protocol Amendment 3: - Expanded the number of subjects in Arm A from 7 to 20 subjects based on initial PK data from 5 subjects dosed 2 hours prior to surgery suggest that selinexor consistently reaches therapeutic concentrations (50-300 nM) within brain tumor lesions. Thus, further exploration was warranted. Enrollment method was updated as sequential enrollment into Groups 1-4 with 5 subjects per group. Following enrollment completion of Group 1 selinexor tumor exposure was to be evaluated and enrollment of each subsequent group to be initiated if selinexor tumor levels exceeds 25 nM levels. Subjects were to receive 3 doses of selinexor (BIW on Day 1 and 3, and between 2 and 48 hours prior to surgery on Day 8-10). - Expanded the overall number of subjects enrolled in the study from approximately 37 to approximately 50 subjects due to increase in number of subjects in Arm A. - Updated information related to the MTD to specify that escalating beyond 70 mg/m2 BIW was prohibited in any study.

Protocol Amendment 4: - Changed to flat dosing: 60 mg BIW during Weeks 1-3 of each 4-week cycle (Arms A, B, C, E, and F) and 80 mg QIW (Arm D) based on the analysis of prolonged dosing results in KCP-330-002: a dose of 35 mg/m2 (~60 mg) BIW had acceptable efficacy and improved long-term tolerability and a dose of 50 mg/m2 (~85 mg) BIW was tolerated and cleared DLT evaluation. - Added Arms C and D (1:1 randomization) to compare the efficacy, tolerability and safety of selinexor (60 mg) administered BIW during Weeks 1-3 of each 4 week cycle (Arm C) with selinexor (80 mg) administered QIW (Arm D). - Added Arm E for subjects with malignant gliomas other than GBM and Arm F for subjects with GBM or anaplastic gliomas (AG) with bevacizumab-refractory recurrent disease with approximately 10 subjects in each new arm to evaluate preliminary evidence of efficacy of selinexor in these exploratory populations. - Updated the planned number of subjects from 50 to 115. - Revised inclusion criteria to include diagnoses for the new exploratory arms (Arms E and F): Arm E “Pathologically confirmed malignant gliomas other than GBM (WHO Grade 3 anaplastic astrocytomas, oligodendrogliomas, or oligo-astrocytomas), with radiographic evidence of recurrent disease after treatment with temozolomide and radiotherapy”, Arm F “Pathologically confirmed GBM (including all histologic variants) or AG with bevacizumab-refractory disease (defined as recurrence or progression of disease per RANO criteria during prior therapy with bevacizumab or other direct VEGF/VEGFR inhibitors) with radiographic evidence of recurrent disease after treatment with temozolomide and radiotherapy”. - Revised the dose adjustment guidelines for selinexor-related toxicities to include supportive treatment based on the event and the severity of the event. - Deleted PK blood draws for Arm B because enrollment in Arm B had been stopped and additional PK data were not needed.

Protocol Amendment 5: - Expanded Arm E by 10 subjects (for a total of 20 subjects) due to the limited availability of treatment options for this subject population and updated total sample size from 115 to 125. - Revised the end of study definition to clarify that the study will continue after collection of data for the primary analysis (6mPFS). - Revised the mITT population (primary efficacy population) to include subjects who discontinued treatment prior to the first post-baseline assessment due to death, toxicity, or disease progression, to adopt a more conservative approach by including subjects who do not have at least 1 post-dosing efficacy evaluation due to death, toxicity, or disease progression. -Changed dosing frequency of selinexor from BIW during Weeks 1-3 of each 4-week cycle to BIW during Weeks 1-4 of each cycle for arms with BIW dosing. This was based on discussions with Investigators who indicated that some subjects could benefit from dosing during Week 4, especially if they were tolerating the drug well and did not require a dosing break to mitigate side effects.

Protocol Amendment 6: - To eliminate Arms E and F (which were introduced in the last protocol amendment but did not yet contain enrolled subjects) as these arms are not going forward due to budgetary limitations. - To add an exclusion criterion requiring subjects not to have undergone major surgery within 4 weeks prior to Cycle 1 Day 1. - Revised the end of study definition (text in bold was added and strikethrough was deleted): The study will continue until the last subject in the study has died, has been off study treatment for 12 months has been lost to follow-up, or has withdrawn consent, whichever occurs first.