The therapeutic potential of polymersomes loaded with 225 Ac evaluated in 2D and 3D in vitro glioma models

• Published in: European journal of pharmaceutics and biopharmaceutics 2018-02
• Main Authors: de Kruijff, R M, van der Meer, A J G M, Windmeijer, C A A, Kouwenberg, J J M, Morgenstern, A, Bruchertseifer, F, Sminia, P, Denkova, A G
• Format: Article
• Language: English
• ISSN: 1873-3441

Alpha emitters have great potential in targeted tumour therapy, especially in destroying micrometastases, due to their high linear energy transfer (LET). To prevent toxicity caused by recoiled daughter atoms in healthy tissue, alpha emitters like Ac can be encapsulated in polymeric nanocarriers (polymersomes), which are capable of retaining the daughter atoms to a large degree. In the translation to a (pre-)clinical setting, it is essential to evaluate their therapeutic potential. As multicellular tumour spheroids mimic a tumour microenvironment more closely than a two-dimensional cellular monolayer, this study has focussed on the interaction of the polymersomes with U87 human glioma spheroids. We have found that polymersomes distribute themselves throughout the spheroid after 4 days which, considering the long half-life of Ac (9.9 d) [1], allows for irradiation of the entire spheroid. A decrease in spheroidal growth has been observed upon the addition of only 0.1 kBq Ac, an effect which was more pronounced for the Ac in polymersomes than when only coupled to DTPA. At higher activities (5 kBq), the spheroids have been found to be destroyed completely after two days. We have thus demonstrated that Ac containing polymersomes effectively inhibit tumour spheroid growth, making them very promising candidates for future in vivo testing.