To evaluate the short-term and longer-term safety, tolerability, and effectiveness of neoadjuvant and adjuvant Pembrolizumab on top of standard therapy (Stupp protocol) in patients with Glioblastoma Multiforme (GBM).

Randomized comparison of safety, tolerability, and clinical efficacy of (1) neoadjuvant and adjuvant Pembrolizumab (on top of Stupp protocol, n=12 patients), (2) neoadjuvant Pembrolizumab (on top of Stupp protocol, n=12 patients), and (3) standard of care (Stupp protocol only, n=12 patients). Immuno-PET examination will be performed before and after surgery in all patients.

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.

After EOT patient's follow up period will continue for up to 3 years from initial resection with MRI assessment every 3 months.

If progression/relapse is identified, patients will undergo a tumor resection or biopsy within 48 hours thereafter.

All patients will then stay in follow up until the end of three years follow up period or death from any cause.

The evaluation of safety, tolerability, and quality-of-life (QoL) will be based on adverse event reporting criteria (Common Terminology Criteria for Adverse Events - CTCAE/WHO Classification of Diseases - ICD10), ECOG status assessment, KPS assessment, EORTC - QLQ-C30 and EORTC-QLQ-BN20 scale.

Clinical assessment will be based on Response Assessment in Neuro-Oncology (RANO). For patients treated with immunotherapy beyond onset of objective disease progression, the iRANO scale will be used within first 6 months of immunotherapy.

Due to a significant risk of identifying other pathology than GBM (i.e. metastasic tumor) in post-surgery histopathology it is anticipated that up to additional 6 patients may be recruited in order to achieve planned number of evaluable patients.

1. Signed Informed Consent Form

2. Age ≥ 18 years

3. Age ≤70 years

4. Able to comply with the study protocol in the investigator's judgment

5. Clinically and radiologically (contrast CT, full profile MRI - T1-weighted with or without contrast, T2-weighted, FLAIR, DWI, PWI, MR-spectroscopy) confirmed diagnosis of GBM, localized outside eloquent brain areas

6. Resectable tumor

7. Fully physically active ≥80 points in Karnofsky performance scale

8. Life expectancy of at least 3 months

9. Adequate organ function (confirmed within 1 weeks before enrollment):

   1. Hemoglobin ≥ 9g/dL
   2. Absolute Neutrophils Count (ANC) ≥1.5×109/L
   3. White Blood Cells (WBC) count ≥3×109/L
   4. Platelets (PTL) ≥ 100×109/L
   5. AST/ALT ≤2.5×ULN
   6. Serum creatinine (S-Cr) ≤ ULN
   7. Glomerular Filtration Rate (GFR) ≥50mL/min
   8. Albumin ≥ LLN
   9. Bilirubin ≤ 1.5 ULN (except patients with documented Gilbert's Syndrome, who must present adequate level of direct bilirubin)
   10. International normalized ratio (INR) and activated partial thromboplastin time (aPTT) ≤ 1.5×ULN. (Elevation of INR and aPTT due to administration of anticoagulation drugs is not a contraindication for the enrollment. However, it must return to normal range prior to surgery).

10. For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use double barrier contraceptive methods that result in a failure rate of < 1% per year during the treatment period and for at least 120 days after the last immuno-PET imaging.

11. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use double barrier contraceptive methods that result in a failure rate of < 1% per year during the treatment period and for at least 120 days after the last immuno-PET imaging.

Exclusion criteria:

Patients who meet any of the following criteria will be excluded from study entry:

1. Any active concomitant malignancy, except:

   1. Locally treated basal or squamous cell carcinoma
   2. Cervical carcinoma in situ
   3. Breast cancer in situ
   4. Bladder cancer in situ
   5. Low grade prostate cancer (under observation with PSA level in normal range)

2. Any previous systemic cancer treatment, including, but not limited to:

   1. Radiotherapy
   2. Brachytherapy for brain tumor
   3. Chemotherapy
   4. Carmustine wafer treatment (Gliadel®)
   5. Any immune checkpoint inhibitor therapy or any anticancer vaccination

3. Hypersensitivity or allergy to any substance with similar action mechanism to Pembrolizumab, Atezolizumab, Temozolomide, other monoclonal antibodies or contrast agents

4. Any active immunosuppressive systemic therapy (except corticosteroids under 12mg)

5. Any active autoimmune disease or systemic therapy for autoimmune disease within 2 years before enrollment

6. History of any immunodeficiency

7. Active infection

8. Significant cardiovascular disease, such as New York Heart Association cardiac disease ≥ Class III, myocardial infarction within 3 months, coronary artery disease, unstable arrhythmias or unstable angina

9. Active liver disease, hepatitis, HBV or HCV infection

10. History of tuberculosis

11. Any mental disorder that may affect patient's participation

12. Any drug or psychoactive substance dependence

13. Evidence of significant uncontrolled concomitant disease that could affect compliance with the protocol

14. Treatment with any other investigational agent or participation in another clinical trial with therapeutic intent within 28 days prior to study treatment initiation

15. Major surgical procedure within 4 weeks prior to study enrollment or anticipation of need for a major surgical procedure during the course of the study other than for diagnosis

16. Any live vaccination within 30 days before enrollment

17. Any active immunosuppressive systemic infection including history of human immunodeficiency virus (HIV) infection

18. Body mass index (BMI) ≥ 35 kg/m2

19. Pregnant or lactating or intending to become pregnant during the study - women who are not postmenopausal (postmenopausal defined as ≥ 12 months of non-drug-induced amenorrhea) or surgically sterile must have a negative serum pregnancy test result within 2 weeks prior to initiation of study treatment

20. Any condition that the patient's physician determines to be detrimental to the patient participating in this study; including any clinically important deviations from normal clinical laboratory values or concurrent medical events.

21. Inability to understand the local language for use of the patient QoL instruments.

22. Tumor other than glioblastoma grade 4 IDH-wildtype, astrocytoma grade 3 or 4 IDH-mutant identified in post-surgery histopathology.

23. Presence of 1p19q codeletion.

Open Label