The goal of this research is to develop a ligand product and facile method to use it to target FDA approved liposomal anticancer drugs to cancer stem cells that overexpress CD44. We have devised a highly efficient chemo-enzymatic synthesis of a hyaluronan-lipid (HA-lipid) ligand and have teamed with ZoneOne Pharma to develop a simple and robust micelle transfer method to insert the HA-lipid into the FDA approved liposome cytotoxic drugs (Doxil(R), LipoDox(R) and Daunoxome(R)). This will target the approved liposomal drugs to CD44, a cell surface marker that is over-expressed on many human cancers such as: breast, prostate, colon, glioblastoma, head/neck, ovarian and pancreatic cancers. Recently, CD44 was found to be expressed at high levels on cancer stem cells, which are considered essential for rapid tumor proliferation and tumor metastases. CD44 is a cell surface receptor that is part of a complex biochemical/physiological system involved in the synthesis, degradation and signaling of hyaluronan. The principle ligand for CD44 is hyaluronan itself, a high molecular weight carbohydrate polymer that consists of a two-sugar repeat. We will pursue three aims.
Aim 1 : At UCSF we will synthesize and characterize large quantities of the lipid-modified HA ligand of a low molecular weight and narrow polydispersity and a fluorescent-modified HA ligand.
Aim 2 : Scientists at ZoneOne Pharma Inc will devise and validate a micelle transfer method to introduce the ligand into commercial available FDA approved Doxil(R), LipoDox(R) and Daunoxome(R) with retention of the drug content and particle size of the starting liposomes. They will verify the ligand density required to effectivel target the liposomes to CD44 expressing cells in culture.
Aim 3 : At the UC cancer center the therapeutic activity of Doxil(R) will be compared to HA-modified Doxil(R) in the primary tumor and tumor metastases in the orthotopic 4T1 breast tumor model. The company will prepare the HA-targeted Doxil(R) and transfer it to the UCSF cancer center to determine the antitumor activity of the HA-modified liposomes in the 4T1 tumor in BALB/c mice. Completion of the first two aims will enable a test of the hypothesis that the insertion of a HA-lipid ligand into approved liposomal anticancer drugs can target the liposomal drug to CD44 over expressing cancer cells. Completion of aim 3 will provide a test of the hypothesis that administration of the HA-lipid modified Doxil(R) to CD44 results in a better antitumor effect in the 4T1 breast cancer in BALB/c mice both in the primary tumor and in metastatic lesions than does administration of the non-targeted Doxil(R). Successful completion of the research plan would validate the potential of targeting FDA approved liposomes to treat human cancers that express CD44. We think the evaluation of a targeting lipid HA ligand added in the pharmacy to available liposomal drugs, would experience a rapid entry into clinical trials. This is because the comparator population would be patients who receive the unmodified liposomal drug and in the targeted arm of the study, there could be a lesser risk of treatment failures hence patients would be less likely to be placed at risk than if a completely new drug was being evaluated. Finally, the path to commercialization could be shortened since ZoneOne Pharma would manufacture the ligand product not the entire formulation and provide a robust, validated protocol for inserting the lipid HA into the currently approved liquid FDA liposome formulations.
A critical barrier to developing new cancer treatments is the time it takes for a new treatment to prove it is efficacious in clinical trials. We propose to re-target currently approved liposomal anticancer drugs such as Doxil, LipoDox and Daunoxome by adding to the liposome at the bedside, a ligand that binds to the cancer stem cell marker, CD44. CD44 is over expressed in cancer stem cells and also in breast, prostate, colon, glioblastoma, head/neck, ovarian and pancreatic tumors. Successful completion of the plan could lead a vial of lyophilized sterile lipid carbohydrate ligand to which the approved liposomes can be added. This would enable the rapid introduction into clinical trials, novel targeted liposomal drugs that could dramatically slow the progression of aggressive CD44-expressing human cancers.
