Imaging PARP with [18F]rucaparib in pancreatic cancer models

PURPOSE: Rucaparib, an FDA-approved PARP inhibitor, is used as a single agent in maintenance therapy to provide promising treatment efficacy with an acceptable safety profile in various types of BRCA-mutated cancers. However, not all patients receive the same benefit from rucaparib-maintenance therapy. A predictive biomarker to help with patient selection for rucaparib treatment and predict clinical benefit is therefore warranted. With this aim, we developed [18F]rucaparib, an 18F-labelled isotopologue of rucaparib, and employed it as a PARP-targeting agent for cancer imaging with PET. Here, we report the in vitro and in vivo evaluation of [18F]rucaparib in human pancreatic cancer models. METHOD: We incorporated the positron-emitting 18F isotope into rucaparib, enabling its use as a PET imaging agent. [18F]rucaparib binds to the DNA damage repair enzyme, PARP, allowing direct visualisation and measurement of PARP in cancerous models before and after PARP inhibition or other genotoxic cancer therapies, providing critical information for cancer diagnosis and therapy. Proof-of-concept evaluations were determined in pancreatic cancer models. RESULTS: Uptake of [18F]rucaparib was found to be mainly dependent on PARP1 expression. Induction of DNA damage increased PARP expression, thereby increasing uptake of [18F]rucaparib. In vivo studies revealed relatively fast blood clearance of [18F]rucaparib in PSN1 tumour-bearing mice, with a tumour uptake of 5.5 ± 0.5%ID/g (1 h after i.v. administration). In vitro and in vivo studies showed significant reduction of [18F]rucaparib uptake by addition of different PARP inhibitors, indicating PARP-selective binding. CONCLUSION: Taken together, we demonstrate the potential of [18F]rucaparib as a non-invasive PARP-targeting imaging agent for pancreatic cancers

[123I]CC1:A PARP-Targeting, Auger Electron-Emitting Radiopharmaceutical for Radionuclide Therapy of Cancer

Poly(adenosine diphosphate ribose) polymerase (PARP) has emerged as an effective therapeutic strategy against cancer that targets the DNA damage repair enzyme. PARP-targeting compounds radiolabeled with an Auger electron-emitting radionuclide can be trapped close to damaged DNA in tumor tissue, where high ionizing potential and short range lead Auger electrons to kill cancer cells through the creation of complex DNA damage, with minimal damage to surrounding normal tissue. Here, we report on [ 123I]CC1, an 123I-labeled PARP inhibitor for radioligand therapy of cancer.Methods: Copper-mediated 123I iododeboronation of a boronic pinacol ester precursor afforded [ 123I]CC1. The level and specificity of cell uptake and the therapeutic efficacy of [ 123I]CC1 were determined in human breast carcinoma, pancreatic adenocarcinoma, and glioblastoma cells. Tumor uptake and tumor growth inhibition of [ 123I]CC1 were assessed in mice bearing human cancer xenografts (MDA-MB-231, PSN1, and U87MG).Results: In vitro and in vivo studies showed selective uptake of [ 123I]CC1 in all models. Significantly reduced clonogenicity, a proxy for tumor growth inhibition by ionizing radiation in vivo, was observed in vitro after treatment with as little as 10 Bq [ 123I]CC1. Biodistribution at 1 h after intravenous administration showed PSN1 tumor xenograft uptake of 0.9 ± 0.06 percentage injected dose per gram of tissue. Intravenous administration of a relatively low amount of [ 123I]CC1 (3 MBq) was able to significantly inhibit PSN1 xenograft tumor growth but was less effective in xenografts that expressed less PARP. [ 123I]CC1 did not cause significant toxicity to normal tissues.Conclusion: Taken together, these results show the potential of [ 123I]CC1 as a radioligand therapy for PARP-expressing cancers. </p

Radiofluorination of a highly potent ATM inhibitor as a potential PET imaging agent

PURPOSE: Ataxia telangiectasia mutated (ATM) is a key mediator of the DNA damage response, and several ATM inhibitors (ATMi) are currently undergoing early phase clinical trials for the treatment of cancer. A radiolabelled ATMi to determine drug pharmacokinetics could assist patient selection in a move towards more personalised medicine. The aim of this study was to synthesise and investigate the first 18F-labelled ATM inhibitor [18F]1 for non-invasive imaging of ATM protein and ATMi pharmacokinetics. METHODS: Radiofluorination of a confirmed selective ATM inhibitor (1) was achieved through substitution of a nitro-precursor with [18F]fluoride. Uptake of [18F]1 was assessed in vitro in H1299 lung cancer cells stably transfected with shRNA to reduce expression of ATM. Blocking studies using several non-radioactive ATM inhibitors assessed binding specificity to ATM. In vivo biodistribution studies were performed in wild-type and ATM-knockout C57BL/6 mice using PET/CT and ex vivo analysis. Uptake of [18F]1 in H1299 tumour xenografts was assessed in BALB/c nu/nu mice. RESULTS: Nitro-precursor 2 was synthesised with an overall yield of 12%. Radiofluorination of 2 achieved radiochemically pure [18F]1 in 80 ± 13 min with a radiochemical yield of 20 ± 13% (decay-corrected) and molar activities up to 79.5 GBq/μmol (n = 11). In vitro, cell-associated activity of [18F]1 increased over 1 h, and retention of [18F]1 dropped to 50% over 2 h. [18F]1 uptake did not correlate with ATM expression, but could be reduced significantly with an excess of known ATM inhibitors, demonstrating specific binding of [18F]1 to ATM. In vivo, fast hepatobiliary clearance was observed with tumour uptake ranging 0.13-0.90%ID/g after 1 h. CONCLUSION: Here, we report the first radiofluorination of an ATM inhibitor and its in vitro and in vivo biological evaluations, revealing the benefits but also some limitations of 18F-labelled ATM inhibitors

Correlation between molar activity, injection mass and uptake of the PARP targeting radiotracer [F-18]olaparib in mouse models of glioma

Purpose Radiopharmaceuticals targeting poly(ADP-ribose) polymerase (PARP) have emerged as promising agents for cancer diagnosis and therapy. PARP enzymes are expressed in both cancerous and normal tissue. Hence, the injected mass, molar activity and potential pharmacological effects are important considerations for the use of radiolabelled PARP inhibitors for diagnostic and radionuclide therapeutic applications. Here, we performed a systematic evaluation by varying the molar activity of [F-18]olaparib and the injected mass of [F-Total]olaparib to investigate the effects on tumour and normal tissue uptake in two subcutaneous human glioblastoma xenograft models. Methods [F-18]Olaparib uptake was evaluated in the human glioblastoma models: in vitro on U251MG and U87MG cell lines, and in vivo on tumour xenograft-bearing mice, after administration of [F-Total]olaparib (varying injected mass: 0.04-8.0 mu g, and molar activity: 1-320 GBq/mu mol). Results Selective uptake of [F-18]olaparib was demonstrated in both models. Tumour uptake was found to be dependent on the injected mass of [F-Total]olaparib (mu g) but not the molar activity. An injected mass of 1 mu g resulted in the highest tumour uptake (up to 6.9 +/- 1.3%ID/g), independent of the molar activity. In comparison, both the lower and higher injected masses of [F-Total]olaparib resulted in lower relative tumour uptake (%ID/g; P 0.5 mu g). Conclusion Our findings show that the injected mass of [F-Total]olaparib has significant effects on tumour uptake. Moderate injected masses of PARP inhibitor-derived radiopharmaceuticals may lead to improved relative tumour uptake and tumour-to-background ratio for cancer diagnosis and radionuclide therapy

A Longitudinal Integrative Course Series to Prepare Students for Advanced Pharmacy Practice Experiences

Background: This paper describes a series of integrative courses intentionally designed to prepare students for Advanced Pharmacy Practice Experiences (APPEs) in a block system curriculum.  Innovation:  Three integration blocks are interspersed throughout the didactic curriculum to serve as checkpoints to ensure competency as students progress in the curriculum, rather than waiting until the end to determine competency. Complex patient case discussions and a series of high-stakes assessments are used to reinforce and evaluate cumulative retention of knowledge, skills, and attitudes.  Findings:  Class of 2022 exam results showed that in the cohort of students who failed the high-stakes comprehensive knowledge assessment (CKA) and pharmacy calculations exams during the first integration block (IB), failure rates decreased in subsequent IBs, indicating early detection of knowledge deficiencies and either exam performance improvement in each IB or failure to progress to the next IB. A survey of the same cohort indicated that the final integration block prior to advanced pharmacy practice experiences (APPEs) helped improve confidence in applying key knowledge and skills into practice.  Conclusion:  The series of integration blocks designed and implemented at WesternU provides opportunities to reinforce knowledge and skills while requiring students to demonstrate maintenance of core competency as they progress through the curriculum