Overview

Part A: The purpose of this part is to assess the safety of GEH200520 and GEH200521 (18F) when administered to patients with solid cancer. Subjects will be requested to complete 3 study visits: 1 screening visit, 1 imaging visit (over 24 hours) and 1 follow-up visit (7 days later). The estimated duration of Part A is 21 days.

Part B: The purpose of this part of the study is to assess the imaging quality and findings as well as the safety and tolerability of GEH200520 and GEH200521 (18F) when administered to patients with cancer before and after immunotherapy treatment.

Subjects will be requested to complete 7 study visits: 1 screening visit, the first imaging visit, followed by 2 immunotherapy immune-checkpoint inhibitor (ICI) treatment visits and 2 additional imaging and 1 follow-up visit . The estimated duration of Part B is approximately 64 days.

Eligibility

Inclusion Criteria:

• The subject is able and willing to comply with all study procedures as described in the protocol, including the imaging day pre-visit requirements, and has read, signed, and dated an informed consent form prior to any study procedures being performed.
• The subject is male or female, ≥18 years of age.
• Subject has a life expectancy ≥12 weeks.
• Subject has Eastern Cooperative Oncology Group (ECOG) performance status 0-1.
• Subject has an irresectable or metastatic solid tumour or a local and resectable head and neck squamous cell carcinoma.
• Subject is eligible for ICI treatment.
• Subject is male, or a female who agrees to comply with the protocol contraception method.

Exclusion Criteria:

• Subject is unable to undergo all procedures in the study and/or is unable to remain still and tolerate the imaging procedure.
• Subject has 12-lead ECG significant findings during screening, per Investigator's assessment.
• Subject is not stable due to medical condition or therapy that, in the opinion of the Investigator, could compromise subject safety or protocol objectives.
• Subject has active autoimmune disease or a documented history of autoimmune disease or syndrome that requires systemic steroids or immunosuppressive agents.
• Subject has any safety laboratory test results (clinical chemistry, haematology, and urinalysis) that, in the opinion of the Investigator, could compromise subject safety or protocol objectives.
• Subject is pregnant or planning to become pregnant or is lactating.
• Subject has a history of alcohol or drug abuse within the last year.