Advancing clinical response against glioblastoma: Evaluating SHP1705 CRY2 activator efficacy in preclinical models and safety in phase I trials

Abstract Background It has been reported that circadian clock components, Brain and Muscle ARNT-Like 1 (BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK), are essential for glioblastoma (GBM) stem cell (GSC) biology and survival. Consequently, we developed a novel Cryptochrome (CRY) activator SHP1705, which inhibits BMAL1-CLOCK transcriptional activity. Methods We utilized GlioVis to determine which circadian genes are differentially expressed in non-tumor versus GBM tissues. We employed in vitro and in vivo methods to test the efficacy of SHP1705 against patient-derived GSCs and xenografts in comparison to earlier CRY activator scaffolds. We applied a novel REV-ERB agonist SR29065, which inhibits BMAL1 transcription, to determine whether targeting both negative limbs of the circadian transcription-translation feedback loop (TTFL) would yield synergistic effects against various GBM cells. Results SHP1705 is the first circadian clock-modulating compound to be found safe and well-tolerated in Phase I clinical trials. SHP1705 has increased selectivity for the CRY2 isoform and potency against GSC viability compared to previously published CRY activators, making it promising for applications in GBM where CRY2 levels are found to be low. SHP1705 prolonged survival in mice bearing GBM tumors established with GSCs. When combined with novel REV-ERB agonist SR29065, SHP1705 displayed synergy against multiple GSC lines and differentiated GSCs (DGCs). Conclusions We demonstrate the efficacy of SHP1705 against GSCs, which pose as a major source of chemoradiation resistance leading to poor GBM patient prognosis. Novel circadian clock compounds have high potential for targeting GBM as single agents or in combination with each other or current standard-of-care.