Sara Claire Horton

The purpose of this study is to evaluate the investigational drug, silmitasertib (a pill taken by mouth), in combination with FDA approved drugs for solid tumors. An investigational drug is one that has not been approved by the U.S. Food \& Drug Administration (FDA), or any other regulatory authorities around the world for use alone or in combination with any drug, for the condition or illness it is being used to treat.

The goals of this part of the study are:

* Establish a recommended dose of silmitasertib in combination with chemotherapy
* Test the safety and tolerability of silmitasertib in combination with chemotherapy in subjects with cancer
* To determine the activity of study treatments chosen based on:
* How each subject responds to the study treatment
* How long a subject lives without their disease returning/progressing

Difluoromethylornithine (DFMO) will be used in an open label, single agent, multicenter, study for patients with neuroblastoma in remission. In this study subjects will receive 730 Days of oral difluoromethylornithine (DFMO) at a dose of 750 mg/m2 ± 250 mg/m2 BID (strata 1, 2, 3, and 4) OR 2500 mg/m2 BID (stratum 1B) on each day of study. This study will focus on the use of DFMO in high risk neuroblastoma patients that are in remission as a strategy to prevent recurrence.

Difluoromethylornithine (DFMO) will be used in an open label, multicenter, study in combination with etoposide for subjects with relapsed/refractory neuroblastoma.