Clioquinol (CQ) is an FDA-approved topical
antifungal agent known to kill
cancer cells. This facilitated the initiation of clinical trials in patients with refractory
hematologic malignancies. These repurposing efforts were not successful; this was likely due to low intracellular levels of the drug owing to poor absorption and rapid metabolism upon
oral administration. CQ forms a sparingly soluble
copper complex (Cu(CQ)2) that exhibits enhanced anticancer activity in some cell lines. We have utilized a novel method to synthesize Cu(CQ)2 inside
liposomes, an approach that maintains the complex suspended in
solution and in a format suitable for
intravenous administration. The complex was prepared inside 100-nm
liposomes composed of 1,2-distearoyl-sn-glycero-3-
phosphocholine/
cholesterol (55:45). The therapeutic activity of the resultant formulation was evaluated in two subcutaneous
tumor models (
glioblastoma and
ovarian cancers) but was not active. We also assessed the ability of the Cu(CQ)2 formulation to increase
copper delivery to
cancer cells in vitro and its potential to be used in combination with
disulfiram (DSF). The results suggested that addition of Cu(CQ)2 enhanced cellular
copper levels and the activity of DSF in vitro; however, this combination did not result in a statistically significant reduction in
tumor growth in vivo. These studies demonstrate that a Cu(CQ)2 formulation suitable for intravenous use can be prepared, but this formulation used alone or in combination with DSF was not efficacious. The methods described are suitable for development formulations of other analogues of
8-hydroxyquinoline which could prove to be more potent.