A major problem affecting the pharmaceutical industry is that 40-70% of new drug compounds belong to the biopharmaceutics classification system (BCS) class II with such poor aqueous solubility that they cannot be formulated on their own. Accordingly, the pharmaceutical industry devotes significant time and effort toward the formulation of BCS class II drugs. Although a number of methods for the formulation of BCS Class II drugs are available - including solubilization by cyclodextrin molecular containers - none is a general purpose solution. Accordingly, new tools to help address these solubility / bioavailability issues are highly prized. Our central hypothesis is that highly soluble acyclic cucurbit[n]uril-type (CB[n]) molecular containers will dramatically increase the aqueous solubility of BCS class II drugs and thereby improve their bioavailability. Dr. Isaacs'lab is a leading innovator in the creation of CB[n] type receptors and thus is uniquely positioned to develop acyclic CB[n] for drug delivery applications.
Specific Aim 1 presents the design and synthesis of new acyclic CB[n] molecules that differ in the nature of their aromatic walls, glycoluril oligomer backbone, and solubilizing arms. Subsequent evaluation of their capacity to increase the aqueous solubility of FDA approved poorly soluble drugs (e.g. paclitaxel, clopidogrel, fenofibrate, cinnarizine, itraconazole) as well as drugs in various stages of development by our academic and pharmaceutical collaborators and will be assessed by phase solubility diagrams and compared with that achievable with hydroxypropyl-beta-cyclodextrin. We will use 1H NMR to determine the self-association of each container, monitor container-drug complex release kinetics, and elucidate the geometry of the container-drug complexes. The influence of electrostatic and size/shape match as well as the presence of competitors on the association constants of the container-drug complexes will be determined.
In Specific Aim 2 the toxicity of the acyclic CB[n]-type containers and their capacity to increase the bioactivity of insoluble cancer drugs will be evaluated using in vitro and in vivo models. For example, in vitro toxicity in human kidney, liver, and erythrocytes as well as interference with the human Ether-a-go-go related gene ion channel, Ames tests, and chromosomal aberration assays will be performed. In vivo maximal tolerated dose studies including histopathology for the most promising containers will be performed. The pharmacokinetics for drugs (e.g. paclitaxel) solubilized with the acyclic CB[n]-type containers will be measured and compared with alternate solubilization methods (e.g. Cremophore). Lastly, in vivo bioactivity of the container-paclitaxel complexes will be studied using appropriate mouse xenograft models in comparison to established technology (e.g. Cremophore). The proposed work is significant because it promises to improve established drugs (e.g. improved bioavailability and reduced toxicity) and further advance drug candidates in the drug development pipeline. Therefore, the work is poised to have a major impact on the treatment of cancer and other disease states.

Public Health Relevance

Many promising drug candidates ultimately fail because of their poor solubility characteristics in water. In this project we develop a promising new class of molecular containers - acyclic cucurbit[n]uril type containers - that dramatically enhance the water solubility of established and candidate pharmaceutical agents. The project promises to impact human health by enabling the advancement or re-introduction of promising drugs in the drug development pipeline.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Synthetic and Biological Chemistry A Study Section (SBCA)
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Fu, Yali
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University of Maryland College Park
Schools of Earth Sciences/Natur
College Park
United States
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Oun, Rabbab; Floriano, Rafael S; Isaacs, Lyle et al. (2014) The ex vivo neurotoxic, myotoxic and cardiotoxic activity of cucurbituril-based macrocyclic drug delivery vehicles. Toxicol Res (Camb) 3:447-455
Isaacs, Lyle (2014) Stimuli responsive systems constructed using cucurbit[n]uril-type molecular containers. Acc Chem Res 47:2052-62
Ford Siltz, Lauren A; Viktorova, Ekaterina G; Zhang, Ben et al. (2014) New small-molecule inhibitors effectively blocking picornavirus replication. J Virol 88:11091-107
Zhang, Ben; Zavalij, Peter Y; Isaacs, Lyle (2014) Acyclic CB[n]-type molecular containers: effect of solubilizing group on their function as solubilizing excipients. Org Biomol Chem 12:2413-22