Abstract 7173: Animal pharmacokinetics of an anti-Her2+ immunoliposome of docetaxel

Abstract Despite the success of docetaxel in combination with trastuzumab in HER2+ breast cancer, docetaxel still has serious limitations, including poor water solubility and the canonical systemic toxicity of taxanes. These side effects of taxanes need to be overcome to improve patient management. In this context, we have developed a nanoparticle drug delivery system. We have developed an immunoliposome loaded with docetaxel and grafted with trastuzumab using a microfluidic method by mixing an aqueous phase (KH2PO4 buffer) and an organic phase composed of phosphatidylcholine, cholesterol and PEGmal in a molar ratio of 50:31:1, to which docetaxel is added at a rate of 1.8% of the total lipid. We perform a thiolation reaction to graft the trastuzumab onto the polyethylene glycol chain. Resulting immunoliposomes were characterized by a mean diameter of 140 nm, a docetaxel encapsulation rate of 73% and a trastuzumab uptake rate of 400 units of trastuzumab by nanoparticle. C57BL/6 mice were administered with docetaxel 1.9 mg/kg and trastuzumab 160 ng/kg or a mixture of free drugs or as liposomes at the same dose by intraperitoneal injection. Blood was collected 1h, 2h, 3h, 6h, 8h and 24h after injection and plasma was analyzed by HPLC-UV with Paclitaxel as internal standard. For each treatment group, pharmacokinetic parameters and exposure metrics were calculated using PKanalix®: half-life T1/2, elimination rate constant Kel and area under the curve AUC at the end points (AUCtlast) and infinity (AUCinfinity). Statistical tests were performed with Sigmastats®. The results showed a marked change in pharmacokinetics with increased plasma exposure with liposomal docetaxel. Preliminary results show a longer half-life for liposomal docetaxel (40.76 h VS. 4.33 h, i.e., a 9.4-fold increase). The concentration of docetaxel appeared to decrease more rapidly between T1h and T6h with free docetaxel (Kel 0.16h-1) than with liposomal docetaxel (Kel 0.017h-1). The concentration of docetaxel reached a plateau over time, up to 24 hours (52.72± 9.45 ng/ml) in mice treated with immunoliposomes whereas Docetaxel was undetectable at T24h when treated with free drugs. There was a statistical difference in PK at T6h between liposomal docetaxel and free docetaxel, 69.86 ± 15.25 ng/ml and 53.67 ± 4.92 ng/ml, respectively (p < 0.001, non-paired t-test). Liposomal docetaxel showed higher AUC0-t (x3.75) and AUC0-∞ values (x5.9) compared to non-liposomal docetaxel. In conclusion, these preliminary results suggest that we have developed a promising immunoliposome for the systemic delivery of docetaxel in HER2+ breast cancer with sustained exposure. Citation Format: Mathilde Dacos, Erwan Diroff, Sarah Giacometti, Joseph Ciccolini, Raphaelle Fanciullino. Animal pharmacokinetics of an anti-Her2+ immunoliposome of docetaxel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7173.