Encapsulation of temozolomide in a calixarene nanocapsule improves its stability and enhances its therapeutic efficacy against glioblastoma

Abstract

The alkylating agent temozolomide (TMZ) is the first-line chemotherapeutic for glioblastoma (GBM), a common and aggressive primary brain tumour in adults. However, its poor stability and unfavourable pharmacokinetic profile limit its clinical efficacy. There is an unmet need to tailor the therapeutic window of TMZ, either through complex derivatization or by utilizing pharmaceutical excipients. To enhance stability and aqueous solubility, we encapsulated TMZ in a p-sulphonatocalix[4]arene (Calix) nanocapsule and employed 1H-NMR, LC-MS and UV-Vis spectroscopy to chart the stability of this novel TMZ@Calix complex according to FDA and EMA guidelines. LC-MS/MS plasma stability assays were conducted in mice to further explore the stability profile of TMZ@Calix in vivo. The therapeutic efficacy of TMZ@Calix was compared to that of unbound TMZ in GBM cell lines and patient derived primary cells with known O6-methylguanine-DNA methyltransferase (MGMT) expression status and in vivo in an intracranial U87 xenograft mouse model. Encapsulation significantly enhanced the stability of TMZ in all conditions tested. TMZ@Calix was more potent than native TMZ at inhibiting the growth of established GBM cell lines and patient derived primary lines expressing MGMT and highly resistant to TMZ. In vivo, native TMZ was rapidly degraded in mouse plasma, whereas the stability of TMZ@Calix was enhanced 3-fold with increased therapeutic efficacy in an orthotopic model. In the absence of new effective therapies, this novel formulation is of clinical importance serving as an inexpensive and highly efficient treatment that could be made readily available to GBM patients and warrants further pre-clinical and clinical evaluation.