A novel 64Cu-liposomal PET agent (MM-DX-929) predicts response to liposomal chemotherapeutics in preclinical breast cancer models.

Background: Liposomal anthracyclines (such as pegylated liposomal doxorubicin (PLD) or HER2-targeted liposomal doxorubicin (MM-302)) are being used and/or evaluated for the clinical management of breast cancer, but responses vary from patient to patient. It is hypothesized that variability in the deposition of liposomal therapeutics within tumors leads to differences in drug exposure, thereby directly influencing tumor response. We have developed MM-DX-929, a novel 64Cu-liposomal PET imaging agent, as a clinically-implementable tool to investigate whether image-based quantification of liposome deposition in tumors can predict treatment response to liposomal chemotherapeutics, including PLD, MM-302 and/or liposomal irinotecan (MM-398). Objectives: Our primary objective is to demonstrate that the extent of tumor uptake of MM-DX-929 is predictive of tumor response to MM-302 in preclinical breast cancer xenograft models. A secondary objective is to enable clinical translation of MM-DX-929 to enable incorporation into existing therapeutic trials. Methods: Mice bearing BT474-M3 mammary and subcutaneous tumors were injected intravenously with MM-DX-929 prior to dosing with MM-302. PET/CT imaging was performed at 16h post MM-DX-929 injection, and tumor uptake was determined. Response to treatment was quantified as tumor volume changes measured over a 2-month period by MRI. Results: Tumor deposition of MM-DX-929 administration correlated well with treatment response to MM-302 (Spearman correlation coefficient of -0.891 and a p-value of 0.0004). MM-DX-929 accumulation in tumors prior to the start of the MM-302 treatment successfully predicted improved tumor growth inhibition following MM-302 treatment. Conclusion: These findings support trials of MM-DX-929 as a predictive imaging agent to select patients who are most likely to respond to liposomal therapies. The clinical development of MM-DX-929 for identification of breast cancer patients likely to respond to liposomal therapeutics is currently being pursued. [ABSTRACT FROM AUTHOR]