The seller of the brain-cancer drug Gleostine has pulled out of a federal discount program for Medicare patients, leaving some struggling to pay for a therapy that can cost as much as $1,000 per capsule. NextSource Biotechnology LLC’s decision to leave the program, rendering its drug ineligible for the Medicare Part D drug benefit, comes after the Miami company raised the drug’s price exponentially since acquiring rights in 2013. Gleostine, which treats a tumor known as glioblastoma and other brain cancers, is off-patent but has no generic alternative.