PET Imaging of PARP Activity in Cancer

Summary

Participation Requirements

Description

Poly(ADP-ribose) polymerase 1 (PARP1) is a deoxyribonucleic acid (DNA) repair enzyme that enables normal cell survival as well as certain cancers. Pharmaceutical companies have invested heavily in PARP1 inhibitor development because these agents can effectively treat certain cancers as single agents...

Poly(ADP-ribose) polymerase 1 (PARP1) is a deoxyribonucleic acid (DNA) repair enzyme that enables normal cell survival as well as certain cancers. Pharmaceutical companies have invested heavily in PARP1 inhibitor development because these agents can effectively treat certain cancers as single agents, thus sparing those patients from chemotherapy toxicities. However, clinical trials testing PARP1 inhibitors have demonstrated mixed results due to the inability to measure the degree of PARP1 inhibition in tumors reliably. Accurately measuring tumoral PARP1 activity levels before and after PARP1 inhibitor treatment will: (1) enable identification of patients whose tumors exhibit PARP activity and are therefore good candidates for PARP inhibitor therapy, and (2) confirm that adequate doses of PARP1 inhibitors are being administered to patients, thus improving dose selection for further study in clinical trials. Thus, noninvasive approaches for measuring tumoral PARP1 activity would have commercialization potential in not only supporting development of PARP1 inhibitors but also after Food and Drug Administration (FDA) approval to assess clinical PARP1 inhibitor treatment responses. Inflammation also contributes to a number of diseases involving the lungs and other organs. Increasing evidence suggests that PARP1 may also play a central role in modulating immune inflammatory responses. Thus, the data from this trial will also be used to develop this approach for studying lung inflammatory responses. A new radiolabeled compound, [18F]FluorThanatrace ([18F]FTT), has been generated which can be used to measure PARP1 activity noninvasively and quantitatively using positron emission tomography (PET). Our data in cancer models show that the uptake of our compound is specific for PARP1 activity and correlates with biochemically determined PARP1 activity. Additional preliminary data also suggests that decreased [18F]FTT uptake predicts tumor response to PARP inhibition with olaparib, a PARP1 inhibitor currently being evaluated in clinical trials. Therefore, the investigators are conducting this Phase 0 trial to develop [18F]FTT for clinical use in cancer patients. To date, no biomarkers have been developed beyond genetic testing for breast cancer 1 and 2 (BRCA1/2) mutations that can aid in patient selection for treatment with PARP inhibition. Moreover, no technologies are available to monitor the efficacy of PARP inhibition. Our technology provides both a biomarker for patient selection as well as a means of monitoring PARP activity during treatment.

Tracking Information