Optimization of a Neural Stem-Cell-Mediated Carboxylesterase/Irinotecan Gene Therapy for Metastatic Neuroblastoma

Abstract

Despite improved survival for children with newly diagnosed neuroblastoma (NB), recurrent disease is a significant problem, with treatment options limited by anti-tumor efficacy, patient drug tolerance, and cumulative toxicity. We previously demonstrated that neural stem cells (NSCs) expressing a modified rabbit carboxylesterase (rCE) can distribute to metastatic NB tumor foci in multiple organs in mice and convert the prodrug irinotecan (CPT-11) to the 1,000-fold more toxic topoisomerase-1 inhibitor SN-38, resulting in significant therapeutic efficacy. We sought to extend these studies by using a clinically relevant NSC line expressing a modified human CE (hCE1m6-NSCs) to establish proof of concept and identify an intravenous dose and treatment schedule that gave maximal efficacy. Human-derived NB cell lines were significantly more sensitive to treatment with hCE1m6-NSCs and irinotecan as compared with drug alone. This was supported by pharmacokinetic studies in subcutaneous NB mouse models demonstrating tumor-specific conversion of irinotecan to SN-38. Furthermore, NB-bearing mice that received repeat treatment with intravenous hCE1m6-NSCs and irinotecan showed significantly lower tumor burden (1.4-fold, p = 0.0093) and increased long-term survival compared with mice treated with drug alone. These studies support the continued development of NSC-mediated gene therapy for improved clinical outcome in NB patients.

GMP Production and Scale-Up of Adherent Neural Stem Cells with a Quantum Cell Expansion System

“…Finally, having now developed SOPs to adenovirally transduce our HB1.F3.CD NSCs to express a modified human CE (hCE1m6), the GMP clinical lot of hCE1m6-adenovirally transduced NSCs is currently being release tested and reviewed by the FDA for use in an upcoming NSC gene therapy trial for the treatment of metastatic neuroblastoma. 14 In conclusion, the QCE system offers a novel, advanced alternative to conventional methods for the production of scaled-up clinical cell banks for patient use.…”

“…Due to their inherent pathotropism to sites of damage in the CNS, NSCs are currently being evaluated in clinical trials for the repair of damage associated with stroke, multiple sclerosis, Parkinson’s disease, and other neurodegenerative diseases. 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 We are using an adherent, genetically modified allogeneic NSC line that has demonstrated tumor-tropic properties as a delivery vehicle to target enzyme/prodrug gene therapies selectively to glioma foci throughout the brain. To evaluate this approach, we are conducting two first-in-human NSC-mediated gene therapy clinical trials for recurrent glioma patients (ClinicalTrials.gov: NCT02015819 and NCT02192359 ).…”

Recent Progress of Stem Cell Therapy in Cancer Treatment: Molecular Mechanisms and Potential Applications

“…In the neuroblastoma mice model, the tumor grafts were found more sensitive to co-administration of CE-expressing NSCs and irinotecan, in comparison to single-drug treatment [63,64]. Till now, several phase I/II clinical trials on the GDEPT system have been tested (Table 2).…”

Development of a Split Esterase 1 for Protein-Protein 2 Interaction Dependent Small Molecule Activation

“…We then tested the utility of the split esterase to uncage a pharmacological agent in a proximitydependent manner. The prodrug irinotecan (CPT-11) is converted to the cytotoxic active metabolite SN-38, a 1,000-fold more potent topoisomerase-1 inhibitor, by carboxylesterases 31,48,49 . Irinotecan is currently in clinical trials for neuroblastoma 50 , colon cancer 51 , and other solid malignancies [52][53][54][55][56] .…”

“…New strategies to more effectively activate irinotecan by modified rabbit and human carboxylesterases are also in development. 31,48 We reasoned our new split esterase system could potentially be used to activate irinotecan analogues in an orthogonal and programmable manner. We therefore synthesized a new methyl-cyclopropyl caged version irinotecan to generate SN-38-CM2 (Figure 5a).…”