The invention relates to nanoparticles having an average hydrodynamic diameter smaller than or equal to 150 nm, comprising: at least one cytotoxic agent representing a total amount higher than or equal to 1 wt. % in relation to the total weight of the nanoparticles； and at least one diblock copolymer comprising a hyaluronic acid block and a polylactic acid block, said blocks being covalently bonded, optionally by means of a spacer, the total amount of diblock copolymer being higher than or equal to 40 wt. % in relation to the total weight of the nanoparticles. The invention also relates to a method for producing said nanoparticles, and to pharmaceutical compositions comprising same. Said compositions can be used especially in cancer treatment.
