Abstract: The invention relates to compositions and methods for treating cancer in a patient comprising subcutaneously administering a PD-1 antagonist, e.g., an anti-PD-1 antibody (e.g. pembrolizumab), or antigen binding fragment thereof, with or without hyaluronidase every six weeks, in specific amounts to the patient. In specific embodiments, the amount of anti-PD-1 antibody, or antigen binding fragment thereof, is about 600 mg to about 1000 mg. In specific embodiments, the administration occurs about every three weeks, and the amount of anti-PD-1 antibody, or antigen binding fragment thereof, is about 300 mg to about 500 mg. In certain embodiments, the PD-1 antagonist is pembrolizumab, or an antigen binding fragment thereof. Also provided are compositions and kits formulated for subcutaneous administration comprising a particular dosage of an anti-PD-1 antibody, or antigen-binding fragment thereof, and uses thereof for treating cancer.