Delivery of Monomethyl Auristatin E Using Ionizable Lipid Nanoparticles for B‑Cell Acute Lymphoblastic Leukemia Treatment.

Ionizable lipid nanoparticles (LNPs) are the leading method for clinically delivering nucleic acid cargoes such as messenger or small interfering RNAs. The capacity of LNPs to encapsulate and deliver small molecule therapeutics alongside traditional nucleic acid cargo remains largely unexplored. Beginning the development of a dual delivery approach using LNPs holds significant potential for treating malignancies prone to therapeutic resistance. B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic malignancy with a poor prognosis in patients who experience relapse or are refractory to standard-of-care treatments. Here, we encapsulated the antimitotic agent, monomethyl auristatin E (MMAE), within prefabricated LNPs containing nonfunctional negative control small interfering RNA (siRNA) and evaluated the resulting antileukemic activity in B-ALL preclinical models. We optimized a postfabrication loading technique to encapsulate MMAE within LNPs while maintaining their superior siRNA retention and favorable physicochemical characteristics. Flow cytometry and confocal microscopy studies confirmed that the LNP uptake by B-ALL cells occurred through clathrin-mediated endocytosis and macropinocytosis. MMAE loaded within LNPs demonstrated potent antileukemic efficacy against B-ALL cells in vitro compared to the standard-of-care chemotherapeutic vincristine. Furthermore, within a B-ALL human xenograft murine model, MMAE-loaded LNPs exhibited over a 2-fold reduction of leukemic burden in the spleen and the peripheral blood as compared to LNPs without MMAE. Taken together, this study provides the groundwork for developing LNPs as a clinically translatable codelivery platform for chemotherapy and siRNA to improve the treatment of challenging malignancies, such as B-ALL.