The present invention provides polymeric pegylated carfilzomib compounds, and pharmaceutically acceptable salts thereof, of Formula 1 wherein R<;sup>;1<;/sup>;, R<;sup>;2<;/sup>; , linker, PEG, n and o are as defined herein. The invention also provides methods of making and using these compounds to treat cancer, and particularly to treat hematological malignancies including multiple myeloma.