A polymer-drug conjugate, which can be used in medical applications such as stents, has at least one active agent conjugated through a carboxylic acid moiety to a copolymer derived from at least one isoolefin monomer and at least one copolymerizable monomer, where the copolymerizable monomer is at least one multiolefin monomer, a β-pinene monomer or a mixture thereof. Such conjugates show improved adhesion to stainless steel and a substantial decrease in burst release of paclitaxel form a drug eluting stent (DES).