Drug activation by PCI has several clear advantages: 1) There are no restrictions on the size of the molecules that can be effectively delivered, making PCI highly suitable for a wide variety of drug conjugates, 2) PCI limits the toxic effect of drugs to the sufficiently illuminated regions, sparing normal tissue, 3) PCI is a method that increases the therapeutic efficacy of a wide range of macromolecules allowing for the possibility of using lower drug doses to minimize morbidity, and 4) PCI can be combined with other therapeutic modalities in a synergistic manner. Therefore, the combination of local, intra-cavity hydrogels, sustained-release drug delivery, and PCI, as illustrated in Figure 2d, has the potential of bypassing the BBB, increasing drug concentration in the resection cavity walls, and promoting increased chemotherapeutic efficacy.
Two potent, hydrophilic anti-cancer drugs, bleomycin (BLM) and doxorubicin (DOX), have had limited use for the treatment of GBM. Due to their hydrophilic nature and relatively large size, BLM and DOX have very limited ability to penetrate through the BBB and plasma cell membrane [ 39 , 40 ]. Although this is a clear disadvantage in terms of treatment efficacy, these drugs would not re-enter the systemic blood stream, thereby limiting their toxic effects on normal areas of the brain. On the other hand, drugs like BCNU or TMZ, due to their lipophilic character, can re-enter the systemic circulation. PCI has been demonstrated to significantly enhance the efficacy of BLM and DOX [ 41 , 42 , 43 ]. Thus, PCI-mediated BLM or DOX could be highly effective drugs for treatment of GBM employing local hydrogel delivery strategies.
Bleomycin som gav otroligt bra effekt i Head & Beck studien.
6.2 Clinical Translation
The combination of intra-cavity hydrogel sustained-release drug delivery with light activation has the potential of spatial-temporal specific treatment in a limited targeted confined area. Increasing the drug dose allows it to reach the remaining infiltrative tumor cells in the brain parenchyma while avoiding systemic side effects. Localized drug delivery also opens to the use of a variety of complex anti-cancer drugs as well as targeted toxins, consisting of a tumor cell binding antibody/ligand moiety and a protein toxin moiety, that kills the cell. Since these types of macro-molecules are too large to cross the BBB they are in turn, when applied locally, prevented from entering the systemic blood stream, thereby limiting their toxic effects on normal areas of the brain. Additionally, local application protects these agents from degradation and clearance until released.
Stora molekyler som ges lokalt och sedan inte passerar blod-hjärnbarriären minskar systemiska sidoeffekterna.
Verkar inte som de helt släppt ultraljudsspåret även om de nämner att de behövs MYCKET PREKLINISKA försök.
Kanske med en annan photosensitizer eller sonosentizizer som reagerar bättre på fokuserat ultraljud.
The possibility of using focused ultrasound (FUS) energy, in place of light, to activate sonosensitizers for sonochemical internalization (SCI) would, for the most part, overcome this problem [ 55 ]. FUS has a much greater depth penetration compared to light. Furthermore, since FUS can be applied externally through the skull, in a non-invasive manner, it lends itself to effective, repetitive treatment protocols. Clearly, there is considerable preclinical animal model research remaining to be explored before these strategies can be translated to efficient clinical treatment protocols for patients harboring GBM.
Acknowledgments
The authors are grateful for the support from the Norwegian Radium Hospital Research Foundation.