This study is for adults with advanced or metastatic solid tumors. It examines the safety and effects of a new drug, WTX-124, which is a special version of a treatment that activates the immune system, called a prodrug. The study has two parts: dose escalation (testing different amounts of the drug) and dose expansion (testing the drug on more people). WTX-124 is tested alone and with another drug, pembrolizumab (also called Pembro), used for certain cancers.

• Participants must be at least 18 years old and have a specific type of cancer.
• The study involves receiving WTX-124 alone or with Pembro, and requires regular check-ups.
• Participants cannot join if they have certain health conditions or have received specific treatments recently.

Those participating may need to follow certain rules, like using reliable birth control. The study ensures regular monitoring and requires pre-treatment and on-treatment biopsies (a small tissue sample from the tumor). Compensation details are not specified. Participants should consider their health and treatment history before joining.