Free Energy Profile and Kinetics Studies of Paclitaxel Internalization from the Outer to the Inner Wall of Microtubules

Several pieces of experimental evidence led us to hypothesize that the mechanism of action of paclitaxel (Taxol) could involve a two-steps binding process, with paclitaxel first binding within the outer wall of microtubules and then moving into the inner binding site. In this work, we first used multiply targeted molecular dynamics (MTMD) for steering paclitaxel from the outer toward the inner binding site. This rough trajectory was then submitted to a refinement procedure in the path collective variables space. Paclitaxel binding energy was monitored along the refined pathway, highlighting the relevance of residues belonging to the H6–H7 and the M- loops. Computational results were supported by kinetics studies performed on fluorescent paclitaxel derivatives

The effect of Lx2-32c liposome on WBC, RBC, PLT counts, HGB concentration and CK-MB in C57BL/6J mice.

<p>Data are expressed as means ± SD (n = 10).</p><p>*<i>p<0.05,</i> compared with that in control group;</p>#<p><i>p<0.05</i>, compared with that in Cremophor-based Lx2-32c group.</p><p>The effect of Lx2-32c liposome on WBC, RBC, PLT counts, HGB concentration and CK-MB in C57BL/6J mice.</p

Preparation, Pharmacokinetics, Biodistribution, Antitumor Efficacy and Safety of Lx2-32c-Containing Liposome

<div><p>Lx2-32c is a novel taxane that has been demonstrated to have robust antitumor activity against different types of tumors including several paclitaxel-resistant neoplasms. Since the delivery vehicles for taxane, which include cremophor EL, are all associated with severe toxic effects, liposome-based Lx2-32c has been developed. In the present study, the pharmacokinetics, biodistribution, antitumor efficacy and safety characteristics of liposome-based Lx2-32c were explored and compared with those of cremophor-based Lx2-32c. The results showed that liposome-based Lx2-32c displayed similar antitumor effects to cremophor-based Lx2-32c, but with significantly lower bone marrow toxicity and cardiotoxicity, especially with regard to the low ratio of hypersensitivity reaction. In comparing these two delivery modalities, targeting was superior using the Lx2-32c liposome formulation; it achieved significantly higher uptake in tumor than in bone marrow and heart. Our data thus suggested that the Lx2-32c liposome was a novel alternative formulation with comparable antitumor efficacy and a superior safety profiles to cremophor-based Lx2-32c, which might be related to the improved pharmacokinetic and biodistribution characteristics. In conclusion, the Lx2-32c liposome could be a promising alternative formulation for further development.</p></div

Inhibitory effects of Lx2-32c liposome on the xenograft tumor growth of B16 in C57BL/6J mice.

<p>Data are expressed as means ± SD (n = 10).</p><p>*: <i>p<0.05,</i> compared with that in control group;^#: <i>p<0.05</i>, compared with that in Cremophor-based Lx2-32c group.</p><p>Inhibitory effects of Lx2-32c liposome on the xenograft tumor growth of B16 in C57BL/6J mice.</p

Mean pharmacokinetic parameters of Lx2-32c liposome and cremophor-based Lx2-32c in SD rats.

<p>Data are expressed as mean ± SD (n = 4).</p><p>AUC: Area Under Curve; MRT: Mean Retention Time; CLz/F: Clearance; Vz/F: Apparent Volume of Distribution.</p><p>Mean pharmacokinetic parameters of Lx2-32c liposome and cremophor-based Lx2-32c in SD rats.</p

Hypersensitivity grade of Lx2-32c liposome and cremophor-based Lx2-32c in mice.

<p>Hypersensitivity grade of Lx2-32c liposome and cremophor-based Lx2-32c in mice.</p

Lx2-32c Plasma concentration–time profile in SD rats following a single i.p. dose of Lx2-32c liposome and cremophor-based Lx2-32c at 30 mg/kg.

<p>Data are expressed as mean ± SD (n = 4).</p

Characterization of the Lx2-32c liposome.

<p>A, Scanning electron microscope photograph of Lx2-32c liposome; B, The mean diameter and polydispersity index (PDI) of freshly prepared Lx2-32c liposome; C, The average zeta potential of Lx2-32c liposome.</p

Hypersensitivity reactions grading standard.

<p>Hypersensitivity reactions grading standard.</p

Lx2-32c tissue distribution–time after a single i.p. dose of Lx2-32c liposome and cremophor-based Lx2-32c at 30 mg/kg.

<p>(a) tumor; (b) heart; (c) bone marrow. Data are expressed as mean ± SD (n = 4).</p