This study is for people with a type of kidney cancer called clear cell renal cell carcinoma (ccRCC) that has returned or hasn't responded to standard treatments. It looks at a new drug, **XmAb®819**, given either into the vein (_intravenous, IV_) or under the skin (_subcutaneous, SC_). The study checks if the drug is safe and how well it works. It's a **Phase 1 study**, meaning it's the first time this drug is being tested in humans for these purposes. The study is split into two parts: the first figures out the right dose, and the second sees how well that dose works. Participants need to have specific criteria, like showing cancer growth despite previous treatments and being healthy enough to participate. They should not have certain conditions, such as severe allergic reactions to similar treatments or active brain cancer. The study is designed to help others in the future by finding new ways to treat this cancer.

• The study involves multiple visits and doses.
• Eligibility requires cancer to have returned or not responded to treatment.
• Participants should not have certain health issues like recent infections.