Present management of metastatic prostate cancer, which includes hormonal 
therapy, chemotherapy, and radiotherapy, are frequently palliative. Taxanes, and 
specifically docetaxel, are being extensively investigated to improve the 
survival of metastatic prostate cancer patients. Although paclitaxel exhibits a 
wide spectrum of antitumor activity, its therapeutic application is limited, in 
part, due to its low water solubility that necessitates the use of Cremophor EL, 
which is known to induce hypersensitivity reactions. Therefore, the objective of 
this present study was to assess the efficiency of paclitaxel palmitate-loaded 
anti-HER2 immunoemulsions, a targeted drug delivery system based on cationic 
emulsion covalently linked to anti-HER2 monoclonal antibody (Herceptin), in a 
well-established in vivo pharmacologic model of metastatic prostate cancer that 
overexpresses the HER2 receptor. It was clearly noted that the cationic emulsion 
and immunoemulsion did not activate the complement compared with the commercial 
and paclitaxel palmitate hydroalcoholic formulations. In addition, 10 mg/kg of 
paclitaxel palmitate-loaded immunoemulsion once weekly over 3 weeks inhibits the 
tumor growth in severe combined immunodeficient mice much more than the cationic 
emulsion (P < 0.05) and the paclitaxel palmitate formulation (P < 0.01). The 
histopathologic analysis suggested a therapeutic improvement trend in favor of 
the immunoemulsion. However, there was no significant difference in 
antimetastatic activity between the emulsion and the immunoemulsion despite the 
affinity of the immunoemulsion towards the HER2 receptor. Although the tumor 
growth was not fully inhibited, the actual results are encouraging and may lead 
to an improved therapeutic strategy of metastatic prostate cancer treatment.