- Symptomatic or untreated leptomeningeal or brain metastases or spinal cord compression. Subjects previously treated for these conditions that have had stable central nervous system (CNS) disease (verified with consecutive imaging studies) for >1 month , are asymptomatic and off corticosteroids, or are on stable dose of corticosteroids for at least 1 month prior to study Day 1 are permitted. Stability of brain metastases must be confirmed with imaging. Subject treated with gamma knife therapy can be enrolled 2 weeks post-procedure as long as there are no post-procedure complications/they are stable. This criterion does not apply to subjects with GBM cohort. In Part 1, subjects with GBM may enroll provided that they are on a stable to decreasing dose of corticosteroids for at least 14 days prior to the first dose of GSK3326595. In Part 2, subjects with GBM may enroll irrespective of steroid dose.