pH-responsive artemisinin dimer in lipid nanoparticles are effective against human breast cancer in a xenograft model.

Artemisinin (ART), a well-known antimalaria drug, also exhibits anticancer activities. We previously reported a group of novel dimeric artemisinin piperazine conjugates (ADPs) possessing pH-dependent aqueous solubility and a proof-of-concept lipid nanoparticle formulation based on natural egg phosphatidylcholine (EPC). EPC may induce allergic reactions in individuals sensitive to egg products. Therefore, the goal of this report is to develop ADP-synthetic lipid particles suitable for in vivo evaluation. We found that ADP binds to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) with greater than 90% efficiency and forms drug-lipid particles (d ∼ 80 nm). Cryo-electron microscopy of the ADP drug-lipid particles revealed unilamellar vesicle-like structures. Detailed characterization studies show insertion of the ADP lead compound, ADP109, into the DPPC membrane and the presence of an aqueous core. Over 50% of the ADP109 was released in 48 hours at pH4 compared with less than 20% at neutral. ADP109-lipid particles exhibited high potency against human breast cancer, but was tolerated well by nontumorigenic cells. In MDA-MB-231 mouse xenograft model, lipid-bound ADP109 particles were more effective than paclitaxel in controlling tumor growth. Cellular uptake studies showed endocytosis of the nanoparticles and release of core-trapped marker throughout the cytosol at 37°C. These results demonstrate, for the first time, the in vivo feasibility of lipid-bound ART dimer for cancer chemotherapy.