A Single Center, Open-Label, Randomized Study to Evaluate the Safety and Efficacy of Neoadjuvant and Adjuvant Pembrolizumab on Top of Standard Chemo-Radiotherapy (Stupp Protocol) in Treatment of Patients With Newly Diagnosed Glioblastoma Multiforme (GBM).

This is an open-label, Phase IV study of Pembrolizumab employed in neoadjuvant and adjuvant setting on top of standard therapy to evaluate the short-term and long-term safety, tolerability and efficacy in disease control in Glioblastoma Multiforme (GBM) patients. The control arm will be a group of patients treated in accordance with Standard of Care (SoC).

The study will include 3 treatment arms (up to n=12 evaluable patients per arm) and will be conducted at single site in Poland.

Patients with GBM will be randomly assigned in 1:1:1 ratio into one of 3 treatment arms:

• Treatment arm 1 - n=12 evaluable patients - neoadjuvant Pembrolizumab (2 doses, 200mg each) plus adjuvant Pembrolizumab (16 cycles q3w, 200mg each) on top of standard chemo-radiotherapy (Stupp protocol: radiotherapy 60Gy over 6 weeks, 2 Gy per daily fraction Mo-Fri setting plus Temozolomide 75mg/m2 BSA daily during radiotherapy and six cycles post-radiotherapy of 150-200mg/m2 BSA for 5 days in each 28-day cycle)
• Treatment arm 2 - n=12 evaluable patients - neoadjuvant Pembrolizumab (2 doses, 200mg each) on top of standard chemo-radiotherapy (Stupp protocol: radiotherapy 60Gy over 6 weeks, 2 Gy per daily fraction Mo-Fri setting plus Temozolomide 75mg/m2 BSA daily during radiotherapy and six cycles post-radiotherapy of 150-200mg/m2 BSA for 5 days in each 28-day cycle)
• Treatment arm 3 - n=12 evaluable patients - standard chemo-radiotherapy (Stupp protocol: radiotherapy 60Gy over 6 weeks, 2 Gy per daily fraction Mo-Fri setting plus Temozolomide 75mg/m2 BSA daily during radiotherapy and six cycles post-radiotherapy of 150-200mg/m2 BSA for 5 days in each 28-day cycle) A pre-screening period will identify potential candidates for enrollment. Once qualified to the study patients will be randomized to one of the treatment arms. Then patients randomized to treatment arm 1 and 2 will receive first dose of neoadjuvant Pembrolizumab on day 4 and day 18 (200mg each). An immuno-PET scan for these arm 1 and 2 patients will be performed on day 29 and 30. Up to 72 hours after last immuno-PET scan all patients will undergo tumor resection. After surgery all patients will be treated in accordance with standard of care (Stupp protocol) with combined radio- and chemotherapy. Radiotherapy will consist of 60Gy over 6 weeks in daily fraction of 2Gy in Mo-Fri setting and parallel chemotherapy with Temozolomide of 75mg/m2 of BSA on a daily basis. After completion of radiotherapy the chemotherapy will continue for six cycles of 28 days with 150-200mg/m2 Temozolomide on days 1-5 of each cycle. In addition, patients randomized to arm 1 will receive 16 cycles of 21 days with Pembrolizumab treatment in adjuvant setting of 200mg/cycle.

During treatment period all patients will be assessed every three months and MRI will be performed in order to evaluate disease status/response.