Binding affinities of paclitaxel and docetaxel for generic and nanoparticle albumin-bound paclitaxel-derived albumin from human serum

Nanoparticle albumin-bound (nab)-paclitaxel is a 130-nm formulation containing human serum albumin (HSA). The clinical efficacy of this formulation is considered to depend on its affinity for HSA. The high pressure employed during the manufacture of nab-paclitaxel HSA (nab HSA) may influence its conformation and/or oligomerization, and ultimately its affinity for HSA. Therefore, studies are required to evaluate whether the affinity of paclitaxel for nab HSA is similar to that of generic HSA (control HSA). In the present study, nab HSA was isolated from nab-paclitaxel by gel filtration, and the binding affinities (K(D)s) were determined by surface plasmon resonance. Furthermore, the affinity of docetaxel for nab HSA and control HSA was measured, as their binding sites are similar. Paclitaxel showed K(D)s of 8.93 +/- 8.60 and 7.39 +/- 5.81 mu M for nab HSA and control HSA, respectively, whereas the corresponding K(D)s for docetaxel were 44.3 +/- 9.50 and 55.9 +/- 2.28 mu M, respectively. This suggests that the paclitaxel binding site was not modified during the nab-paclitaxel manufacturing process. Additionally, nab HSA likely does not affect paclitaxel and blood HSA binding, as evidenced by the similar affinities of paclitaxel and docetaxel for nab HSA and control HSA. In conclusion, the binding affinities of paclitaxel and docetaxel for nab HSA and control HSA were found to be comparable. Additionally, the manufacturing process did not influence the paclitaxel binding affinity for nab HSA. These results also suggest that nab HSA may not affect the clinical effectiveness of nab-paclitaxel.