ribociclib and Neuroendocrine-Tumors

The mammalian target of rapamycin inhibitor everolimus is an established therapy for well-differentiated (WD) foregut neuroendocrine tumors (NETs). Pre-clinical data demonstrates a potential synergistic role for cyclin dependent kinase 4/6 inhibition and everolimus to treat this disease. In this phase II multicenter study, patients with advanced foregut WDNETs received combination ribociclib and everolimus until confirmed disease progression or unacceptable toxicity. The first 12 patients received ribociclib 300 mg three weeks in a row with a 1 week break and everolimus 2.5 mg daily (recommended phase II dose). Due to unexpected hematologic and infectious toxicities, the trial was put on hold, modified, and an additional 9 patients received ribociclib 200 mg and everolimus 2.5 mg daily. The primary end point was progression-free survival. Archived pre-treatment tumor was profiled by next-generation sequencing to evaluate for genomic markers of drug response. Twenty-one patients were treated (median age, 56; range, 24 to 77). The study did not meet the pre-specified criteria to advance to stage two. No patients experienced an objective response. Thirteen patients (62%) experienced stable disease. Median progression-free survival was 7.7 months (95% CI, 2.8 months to not reached). Eleven of the first 12 patients (92%) developed grade 2 or more myelosuppression. Ten patients (84%) experienced treatment interruption and 8 patients (67%) required dose reduction. Genetic testing in archival tumor tissue samples failed to identify a predictive biomarker of disease stabilization. The combination of ribociclib and everolimus had insufficient activity to warrant further investigation in foregut WDNETs.

Topics: Aminopyridines; Everolimus; Humans; Middle Aged; Neuroendocrine Tumors; Purines

Cyclin-dependent kinases (CDKs) are crucial for cell cycle regulation, and alterations in the cell cycle are often observed in human cancer. CDK4/6 in particular orchestrates G1 phase progression and the G1/S transition. Here, we investigated the in vitro effects of the CDK4/6 inhibitor LEE011 in human neuroendocrine tumor cells.. The human neuroendocrine tumor cell lines BON1, QGP1, NCI-H727 and GOT1 were treated with different concentrations of LEE011 alone and in combination with 5-fluorouracil and everolimus.. Cell viability decreased in a time- and dose-dependent manner in BON1, QGP1, and NCI-H727 cells upon LEE011 treatment, whereas GOT1 cells were treatment resistant. Treatment sensitivity towards LEE011 was associated with the high expression of cyclin D1 and Rb. LEE011 caused the dephosphorylation of Rb and a subsequent G1 phase cell cycle arrest. Combined treatment with LEE011 and 5-fluorouracil or everolimus showed a significant enhancement in the inhibition of cell viability when compared to single-substance treatments due to PI3K-Akt-mTOR and Ras-Raf-MEK-ERK pathway downregulation and cooperative downregulation of cell cycle components. However, LEE011 also exhibited antagonizing effects with 5-fluorouracil, protecting NET cells from DNA-damaging chemotherapy by blocking PARP cleavage and caspase-3/7 activity.. Our data demonstrate that the CDK 4/6 inhibitor LEE011 exhibits promising anti-tumoral properties alone and in combination treatment approaches with 5-fluorouracil or everolimus in human neuroendocrine tumor cell lines.

Topics: Aminopyridines; Antineoplastic Agents; Cell Line, Tumor; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Therapy, Combination; Everolimus; Fluorouracil; Humans; Neuroendocrine Tumors; Protein Kinase Inhibitors; Purines; Time Factors