provided are methods and compositions for reducing the toxicity of certain hydrophobic therapeutic agents , especially polyene antibiotics , in particular , amphotericin b , and therapeutics such as paclitaxel , tamoxifen , an acylated prodrug or an acylated cis - platin , by incorporating these agents within micelles comprising an amphiphilic block - forming copolymer . where the polyene is amphotericin b , desirably the spacer is an alkyl molecule of aabout 2 to about 8 carbon atoms , desirably 6 carbon atoms , and the core is an n - alkyl molecule of about 8 to about 28 carbon atoms , desirably 12 to 22 carbon atoms , advantageously , 12 to 18 carbon atoms , and as specifically embodied , 18 carbon atoms . for the formulation of a larger polyene , the spacer and core are proportionately larger than those for amphotericin b . as specifically exemplified herein , the polymer backbone is a peo of about 270 units with about 10 - 30 core - forming plaa subunits , and advantageously about 14 - 24 . desirably the stearate moiety has a substitution level on the copolymer from about 35 percent to about 70 percent .