This study aims to test a new drug, **XmAb®819**, for people with a type of kidney cancer called clear cell renal cell carcinoma (ccRCC) that hasn't improved with other treatments. **XmAb®819** will be given to patients either through a vein (intravenous or IV) or under the skin (subcutaneous or SC) to find the safest and most effective dose. This Phase 1 study will check how the body handles the drug and if it helps fight cancer.

Participants must have ccRCC that has come back or not responded to regular treatments and must meet specific health criteria to join. They should not have had certain other cancer treatments recently or have specific health issues like active brain tumors or severe autoimmune diseases. The study will take place at multiple locations and involves various visits to the study center.

• The study involves multiple doses and may require regular hospital visits.
• Participants will receive compensation for their time and travel.
• Potential risks include side effects from the drug, such as reactions to the drug or other health impacts.