THP-SS-PEG1-t-butyl ester is a cleavable PEG linker with a THP protecting group, a disulfide bond and a t-butyl ester group. The THP protecting group is used to protect alcohol groups and can be removed under acidic conditions. The disulfide bonds can be cleaved via a reduction reaction using Dithiothreitol (DTT) reagent. The t-butyl ester group can also be removed under acidic conditions.