Purpose The presence of an ALK aberration correlates with inferior survival for patients with high-risk neuroblastoma. The emergence of ALK inhibitors such as crizotinib has provided novel treatment opportunities. However, certain ALK mutations result in de novo crizotinib resistance, and a phase I trial of crizotinib showed a lack of response in patients harboring those ALK mutations. Thus, understanding mechanisms of resistance and defining circumvention strategies for the clinic is critical. Experimental Design The sensitivity of human neuroblastoma-derived cell lines, cell line-derived and patient-derived xenograft (PDX) models with varying ALK statuses to crizotinib combined with topotecan and cyclophosphamide (topo/cyclo) was examined. Cultured cells and xenografts were evaluated for effects of these drugs on proliferation, signaling, and cell death, and assessment of synergy. Results In neuroblastoma murine xenografts harboring the most common ALK mutations, including those mutations associated with resistance to crizotinib (but not in those with wild-type ALK), crizotinib combined with topo/cyclo enhanced tumor responses and mouse event-free-survival. Crizotinib + topo/cyclo showed synergistic cytotoxicity and higher caspase-dependent apoptosis than crizotinib or topo/cyclo alone in neuroblastoma cell lines with ALK aberrations (mutation or amplification). Conclusions Combining crizotinib with chemotherapeutic agents commonly used in treating newly diagnosed patients with high-risk neuroblastoma restores sensitivity in preclinical models harboring both sensitive ALK aberrations and de novo resistant ALK mutations. These data support clinical testing of crizotinib and conventional chemotherapy with the goal of integrating ALK inhibition into multi-agent therapy for ALK-aberrant neuroblastoma patients.

Purpose Anaplastic Lymphoma Kinase (ALK) is the most frequently mutated oncogene in the pediatric cancer neuroblastoma. We performed an in vitro screen for synergistic drug combinations that target neuroblastomas with mutations in ALK to determine if drug combinations could enhance anti-tumor efficacy. Experimental Design We screened combinations of eight molecularly targeted agents against seventeen comprehensively characterized human neuroblastoma-derived cell lines. We investigated the combination of Ceritinib and Ribociclib on in vitro proliferation, cell cycle, viability, caspase activation, and the Cyclin D/CDK4/CDK6/RB and pALK signaling networks in cell lines with representative ALK status. We performed in vivo trials in CB17 SCID mice bearing conventional and patient-derived xenograft models comparing Ceritinib alone, Ribociclib alone, and the combination, with plasma pharmacokinetics to evaluate for drug-drug interactions. Results The combination of Ribociclib, a dual inhibitor of cyclin-dependent kinase (CDK) 4 and 6, and the ALK inhibitor Ceritinib demonstrated higher cytotoxicity (p=0.008) and synergy scores (p=0.006) in cell lines with ALK mutations as compared to cell lines lacking mutations or alterations in ALK. Compared to either drug alone, combination therapy enhanced growth inhibition, cell cycle arrest, and caspase-independent cell death. Combination therapy achieved complete regressions in neuroblastoma xenografts with ALK-F1174L and F1245C de novo resistance mutations, and prevented the emergence of resistance. Murine Ribociclib and Ceritinib plasma concentrations were unaltered by combination therapy. Conclusions This preclinical combination drug screen with in vivo validation has provided the rationale for a first in children trial of combination Ceritinib and Ribociclib in a molecularly selected pediatric population.

<p>Body weight of mice as a percentage of their initial weight as a measure of systemic toxicity.</p>

<p>Complete dataset for synergy screen.</p>

<p>Overview of compound activity by cell line.</p>