the invention provides amphiphilic biocompatible copolymers which have a hydrophilic backbone and pendant hydrophobic groups . the polymers form nanoscale molecular aggregates in aqueous environments , which have hydrophobic interiors within which anticancer drugs may be solubilized . the polymers optionally feature attached antibodies , receptor ligands , and other targeting moieties which mediate adherence of the drug - carrying aggregates to targeted cancer cells .