Treatment response
No patients on either stratum had an objective response to palbociclib. A patient with anaplastic ependymoma in Stratum I was treated on a dose of 75 mg/m2 for 18 courses before coming off therapy. This patient was a 21 year-old male with neurofibromatosis type I and a multiply recurrent WHO grade III anaplastic ependymoma first diagnosed when he was 14 years-old. Prior treatment included multiple surgeries and 2 rounds of radiation therapy. He had 7 courses of 5-fluorouracil followed by a 1.5 year off-therapy period before starting palbociclib. Subsequent to his progression on palbociclib, he was maintained on additional chemotherapy regimens for 2.5 years before dying of his tumor. A mutation profile of his tumor confirmed a C11orf95-RELA fusion (pathognomonic of ependymoma), alterations in NF1 , and homozygous deletion of CDKN2A and CDKN2B . He additionally had multiple segmental chromosomal gains and losses across the genome. Another patient with a GBM treated at 75 mg/m2 stayed on treatment for 6 courses. In Stratum II, 3 subjects (2 at 50 mg/m2 and 1 at 75 mg/m2) remained on treatment for 4 courses. In Stratum I and II, 16/21 (76%) and 12/13 (92%) of patients, respectively, who initiated protocol therapy experienced disease progression while on treatment. The majority of patients received 2 or fewer cycles of therapy (Table 5 )