An Open-Label Study of GV20-0251 in Patients with Advanced and/or Refractory Solid Tumor Malignancies

• Participants ≥18 years of age
• Previously treated, histologically-confirmed advanced solid malignancy with progressive disease requiring therapy
• Refractory or intolerant to standard therapy(ies)
• Must have received, be not eligible or decline standard of care therapy
• Participants must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST version 1.1)
• For participants who have received prior treatment with a checkpoint inhibitor there must be documented disease progression
• ECOG performance status of 0 or 1
• Life expectancy of ≥ 12 weeks in Parts A and C and ≥ 24 weeks in Parts B and D
• Participants must be willing to provide fresh tumor biopsy (core biopsy) both pre-treatment (Parts A, B, C and D) and on-treatment (Parts A and B), if clinically feasible
• Disease-free of active second/secondary or prior malignancies for ≥ 2 years
• Laboratory test results within the required parameters
• Women of child bearing potential (WOCBP) and men must agree to use adequate contraception
• Parts B, C and D may include the following tumor types:
• Endometrial carcinoma
• Squamous head and neck carcinoma
• Cutaneous melanoma
• Non-small cell lung cancer
• Proficient MMR (pMMR)/MSS adenocarcinoma of the colon or rectum (Parts C and D only)

Parts A, B, C and D Exclusion Criteria:

• Participant with acute leukemia or CLL (Parts A and B only)
• Participant with heart disease or unstable arrhythmia
• Active, uncontrolled bacterial, viral, or fungal infections requiring systemic therapy
• Participant has active autoimmune disease or other medical conditions requiring chronic systemic steroid or immunosuppressive therapy
• History of major organ transplant
• History of a bone marrow transplant
• Symptomatic central nervous system (CNS) malignancy or metastasis
• Serious nonmalignant disease
• Pregnant or nursing women
• Treatment with PD-1 and equivalent immune modulators or major surgery prior to the first dose of study medication
• Participants who are currently receiving any other investigational agent or have received an investigational agent within 4 weeks prior to the first dose of study medication
• Treatment with any anticancer treatments with 2-weeks prior to the first dose of study medication
• Radiation for symptomatic lesions must have been completed prior to the first dose of study medication
• Participants with liver metastases unless approved by the Sponsor
• Any history of an immune related ≥ Grade 3 AE attributed to prior cancer immunotherapy
• Has a known additional malignancy that is progressing or has required active treatment within the past 2 years from C1D1
• Has received radiation therapy to the lung that is higher than 30 Gy within 6 months prior to C1D1 for NSCLC (Parts C and D only)
• Has a known additional malignancy that is progressing or has required active treatment within the past 2 years from C1D1 (Parts C and D only)
• Has severe hypersensitivity ( ≥ Grade 3) to Pembrolizumab and/or any of its excipients (Parts C and D only)
• Has a history of (non-infectious) pneumonitis / interstitial lung disease that required steroids or has current pneumonitis / interstitial lung disease (Parts C and D only)
• Has a condition, therapy, laboratory abnormality, or circumstance that could confound study results or interfere with full participation, making it unsuitable for the participant, as determined by the treating Investigator (Parts C and D only)