Synthesis of (Z)-2-((1H-indazol-3-yl)methylene)-6-[11C]methoxy-7-(piperazin-1-ylmethyl)benzofuran-3(2H)-one as a new potential PET probe for imaging of the enzyme PIM1

Design and synthesis of a novel mitochondria-targeted osteosarcoma theranostic agent based on a PIM1 kinase inhibitor

Osteosarcoma (OS) is the most common malignancy of the skeletal system, with a poor prognosis and high rate of recurrence. Adequate surgical margin and adjuvant chemotherapy improve the overall survival and limb salvage rate of osteosarcoma patients. Previous studies have showed that OS exhibits an increase in the expression of proviral integration site for Moloney murine leukemia virus 1 (PIM1) kinase, and high levels of PIM1 are also associated with poor OS prognosis and metastasis. We exploited the overexpression of proto-oncogenic PIM1 in OS towards the development of a novel near-infrared imaging and targeted therapeutic agent, namely QCAi-Cy7d by conjugating a PIM1 small molecule inhibitor and heptamethine cyanine dye, for simultaneous guiding surgery and chemotherapy. QCAi-Cy7d showed targeted imaging and anticancer activities against OS in vitro and vivo without any obvious toxicity, and its antitumoral activity was much greater than the parent PIMI inhibitor. These results demonstrated the potential of new conjugate of PIM1 inhibitor and near-infrared imaging, supporting structure-based design and development of theranostic agents for precise tumor imaging and targeted treatment.

Recent Advances in the Development and Application of Radiolabeled Kinase Inhibitors for PET Imaging

Over the last 20 years, intensive investigation and multiple clinical successes targeting protein kinases, mostly for cancer treatment, have identified small molecule kinase inhibitors as a prominent therapeutic class. In the course of those investigations, radiolabeled kinase inhibitors for positron emission tomography (PET) imaging have been synthesized and evaluated as diagnostic imaging probes for cancer characterization. Given that inhibitor coverage of the kinome is continuously expanding, in vivo PET imaging will likely find increasing applications for therapy monitoring and receptor density studies both in- and outside of oncological conditions. Early investigated radiolabeled inhibitors, which are mostly based on clinically approved tyrosine kinase inhibitor (TKI) isotopologues, have now entered clinical trials. Novel radioligands for cancer and PET neuroimaging originating from novel but relevant target kinases are currently being explored in preclinical studies. This article reviews the literature involving radiotracer design, radiochemistry approaches, biological tracer evaluation and nuclear imaging results of radiolabeled kinase inhibitors for PET reported between 2010 and mid-2015. Aspects regarding the usefulness of pursuing selective vs. promiscuous inhibitor scaffolds and the inherent challenges associated with intracellular enzyme imaging will be discussed.