A water-soluble gel polymer matrix comprising hyaluronic acid and an antitumor agent is described herein. The antitumor agent is crosslinked with the hyaluronic acid by at least one of covalent and/or non-covalent bonding resulting in improved water solubility of the antitumor agent. Pharmacokinetic studies illustrated that the antitumor agent exhibits enhanced Cmax (maximum drug plasma concentration) and Tmax (time required to reach Cmax) values.