Disclosed herein are an N-terminal modified PEG-TRAIL conjugates and methods of making and using thereof. The PEG-TAIL conjugates have bioactivity that is substantially similar to that of native TRAIL coupled with an extended in vivo half-life and enhanced stability. The disclosed PEG-TRAIL conjugates exhibit significantly reduced hepatotoxicity when compared to that of non-PEGylated trimeric TRAIL. The disclosed methods of making the PEG-TRAIL conjugates provide a homogeneous, highly pure, form of N-terminal modified PEG-TRAIL. Compared to native TRAIL, the PEG-TRAIL conjugates exhibits high solubility and solution stability. The PEG-TRAIL conjugates are useful in preventing and treating proliferative or autoimmune diseases.
