Effective treatment of pediatric solid tumors has been hampered by the predominance of currently "undruggable" driver transcription factors. Improving outcomes while decreasing the toxicity of treatment necessitates the development of novel agents that can directly inhibit or degrade these elusive targets. MYCN in pediatric neural-derived tumors, including neuroblastoma and medulloblastoma, is a paradigmatic example of this problem. Attempts to directly and specifically target MYCN have failed due to its similarity to MYC, the unstructured nature of MYC family proteins in their monomeric form, the lack of an understanding of MYCN-interacting proteins and ability to test their relevance in vivo, the inability to obtain structural information on MYCN protein complexes, and the challenges of using traditional small molecules to inhibit protein-protein or protein-DNA interactions. However, there is now promise for directly targeting MYCN based on scientific and technological advances on all of these fronts. Here, we discuss prior challenges and the reasons for renewed optimism in directly targeting this "undruggable" transcription factor, which we hope will lead to improved outcomes for patients with pediatric cancer and create a framework for targeting driver oncoproteins regulating gene transcription.

Purpose

Alisertib is an oral Aurora A kinase inhibitor with preclinical activity in neuroblastoma. Irinotecan and temozolomide have activity in patients with advanced neuroblastoma. The goal of this phase I study was to determine the maximum tolerated dose (MTD) of alisertib with irinotecan and temozolomide in this population.

Patients and methods

Patients age 1 to 30 years with relapsed or refractory neuroblastoma were eligible. Patients received alisertib tablets at dose levels of 45, 60, and 80 mg/m(2) per day on days 1 to 7 along with irinotecan 50 mg/m(2) intravenously and temozolomide 100 mg/m(2) orally on days 1 to 5. Dose escalation of alisertib followed the rolling six design. Samples for pharmacokinetic and pharmacogenomic testing were obtained.

Results

Twenty-three patients enrolled, and 22 were eligible and evaluable for dose escalation. A total of 244 courses were administered. The MTD for alisertib was 60 mg/m(2), with mandatory myeloid growth factor support and cephalosporin prophylaxis for diarrhea. Thrombocytopenia and neutropenia of any grade were seen in the majority of courses (84% and 69%, respectively). Diarrhea in 55% of courses and nausea in 54% of courses were the most common nonhematologic toxicities. The overall response rate was 31.8%, with a 50% response rate observed at the MTD. The median number of courses per patient was eight (range, two to 32). Progression-free survival rate at 2 years was 52.4%. Pharmacokinetic testing did not show evidence of drug-drug interaction between irinotecan and alisertib.

Conclusion

Alisertib 60 mg/m(2) per dose for 7 days is tolerable with a standard irinotecan and temozolomide backbone and has promising response and progression-free survival rates. A phase II trial of this regimen is ongoing.

Purpose

In phase I testing, alisertib tablets with irinotecan and temozolomide showed significant antitumor activity in patients with neuroblastoma. This study sought to confirm activity of this regimen; evaluate an alisertib oral solution; and evaluate biomarkers of clinical outcomes.

Patients and methods

We conducted a two-stage phase II trial of alisertib tablets (60 mg/m²/dose × 7 days), irinotecan (50 mg/m²/dose i.v. × 5 days), and temozolomide (100 mg/m²/dose orally × 5 days) in patients with relapsed or refractory neuroblastoma. The primary endpoint was best objective response. A separate cohort was treated with alisertib at 45 mg/m² using oral solution instead of tablets. Exploratory analyses sought to identify predictors of toxicity, response, and progression-free survival (PFS) using pooled data from phase I, phase II, and oral solution cohorts.

Results

Twenty and 12 eligible patients were treated in the phase II and oral solution cohorts, respectively. Hematologic toxicities were the most common adverse events. In phase II, partial responses were observed in 19 evaluable patients (21%). The estimated PFS at 1 year was 34%. In the oral solution cohort, 3 patients (25%) had first cycle dose-limiting toxicity (DLT). Alisertib oral solution at 45 mg/m² had significantly higher median C _max and exposure compared with tablets at 60 mg/m². Higher alisertib trough concentration was associated with first cycle DLT, whereas MYCN amplification was associated with inferior PFS.

Conclusions

This combination shows antitumor activity, particularly in patients with MYCN nonamplified tumors. Data on an alisertib oral solution expand the population able to be treated with this agent.

Accelerating cures for children with cancer remains an immediate challenge as a result of extensive oncogenic heterogeneity between and within histologies, distinct molecular mechanisms evolving between diagnosis and relapsed disease, and limited therapeutic options. To systematically prioritize and rationally test novel agents in preclinical murine models, researchers within the Pediatric Preclinical Testing Consortium are continuously developing patient-derived xenografts (PDXs)-many of which are refractory to current standard-of-care treatments-from high-risk childhood cancers. Here, we genomically characterize 261 PDX models from 37 unique pediatric cancers; demonstrate faithful recapitulation of histologies and subtypes; and refine our understanding of relapsed disease. In addition, we use expression signatures to classify tumors for TP53 and NF1 pathway inactivation. We anticipate that these data will serve as a resource for pediatric oncology drug development and will guide rational clinical trial design for children with cancer.