CNS Derived Stem Cells for the Treatment of Thoracic and Cervical Spinal Cord Injury

Funding Type: 
Disease Team Research I
Grant Number: 
DR1-01421
ICOC Funds Committed: 
$0
Disease Focus: 
Brain Cancer
Cancer
Stem Cell Use: 
Adult Stem Cell
Cell Line Generation: 
Adult Stem Cell
Public Abstract: 
Spinal cord injury is a particularly debilitating form of trauma, in part because there is no current curative treatment. The unmet medical need in patients who have suffered paraplegia or quadriplegia has long been recognized as one that is in need of novel therapeutic approaches. Stem cell-based strategies may offer a broad regenerative platform that may address many aspects of the injury to the spinal cord and create opportunities to intervene long after the initial trauma. Spinal cord injury (SCI) affects a variety of neural cells, such as neurons and oligodendrocytes. The latter produce myelin, an insulating sheath that ensures normal conductivity. Therefore, an approach that offers the replacement and/or restoration of function to damaged cells holds much promise. Research has now shown that cell therapy may be capable of producing more than one effect in the injured spinal cord. The spectrum of benefits derived from this approach explains why this area is now a major research focus not only for SCI, but other neurological diseases as well. Research with central nervous system stem cells derived from the human brain have demonstrated that these cells survive after transplantation, differentiate into neurons and oligodendrocytes, and most importantly improve neurological function in animal models of SCI. One of the first steps prior to testing a potential therapy in humans is to conduct animal experiments in models that reflect the human trauma as closely as possible. Therefore the primary goal of this research is to establish further evidence that the human central nervous system stem cell (HuCNS-SC) is safe when transplanted into the spinal cord, and that it also leads to a better recovery when compared to animals that did not receive transplantation. The research proposed will study the effects of HuCNS-SC cells in the setting of lower SCI (thoracic cord trauma that results in paraplegia) and upper SCI (cervical cord trauma that leads to quadriplegia) in animal models that will allow survival of the human cells. Effectiveness will be tested by measuring neurological function and determining the degree of improvement after transplantation of the human cells. Safety will be tested by closely examining the animals to show that there are no adverse reactions to the transplanted cells. Investigating the effects of human central nervous system stem cells in these animal experiments will enable collection of data necessary to begin human clinical trials. The regenerative therapy potential represented by stem cells for patients with spinal cord injury has captured the imagination of scientists and patients alike. The opportunity to embark on this exciting field of research shows that new approaches are on the horizon and the field of cell therapy for spinal cord injury will be significantly advanced by the results obtained in this research program.
Statement of Benefit to California: 
Spinal cord injury (SCI) causes a devastating condition; its effects vary depending on the level and degree of damage to the spinal cord. The trauma usually occurs at younger ages and results in a lifetime of paralysis which becomes associated with other medical complications and creates significant demands on the health care system. SCI is the second leading cause of paralysis in the US and it is currently estimated that there are approximately 1.3 million affected individuals. Although there are no official estimates, it is projected that there are more than 140,000 Californians living with SCI. In addition to the considerable personal burden placed on the individual and family, the economic impact of SCI is highly significant. The estimated costs related to loss of wages and health care for affected patients may be higher than 1.5 billion dollars annually for patients living in California. A therapy that can restore at least some spinal cord function has the potential for a significant improvement not only in the patient’s quality-of-life, but also the shared costs of health care and loss of productive employment. The use of stem cells, and in particular human central nervous system stem cells (HuCNS-SC) , as therapeutics for SCI holds much promise for ailing patients. Most clinical investigations for SCI have focused on developing treatments that are aimed at very early time points after injury and have not been associated with major changes in outcome. This research will focus on developing an approach that will have broader applicability in terms of larger window of treatment after injury and include both upper and lower levels of spinal cord trauma. The development of a novel treatment that can address time points beyond the acute phase of trauma, and include thoracic as well as cervical levels, will more fully address the unmet medical need of the entire spectrum of patients with SCI. The range of potential benefit to patients includes improved sensory, motor, bowel/bladder, and even important reflex, or autonomic, function. A change in any one or combination of these deficits, if only for one or two spinal cord functional levels, could translate into improved quality-of-life for a patient. The results of the research proposed will enable the regulatory approval and execution of clinical trials using hCNS-SCns to treat spinal cord injured patients. This research program will capitalize on the combination of a team of world-class scientists and clinicians in California that together can advance this field of endeavor. The outcome of the proposed studies will help not only those Californians with SCI, but will more globally pave the way for the use of stem cells in a variety of diseases. Additionally, our California-based effort will not only help individuals ailed by this state, but will also ensure that California ranks very highly in terms of SCI therapeutic advances and benefits from jobs created and retained.
Progress Report: 
  • Primary brain tumors are among the most difficult cancers to treat. High-grade gliomas, the most common primary brain tumors in adults, remain incurable with current therapies. These devastating tumors present significant treatment challenges for several reasons: 1) surgical removal runs the risk of causing permanent neurologic damage and does not eliminate cancer cells that have migrated throughout the brain; 2) most anti-cancer drugs are prevented from entering the brain because of the presence of the blood-brain barrier, which often does not allow enough chemotherapy into the brain to kill the cancer cells; and 3) typically, the amount of chemotherapy that can be given to cancer patients is limited by intolerable or harmful side effects from these agents. If concentrated cancer therapies could be specifically localized to sites of tumor, damage to healthy tissues would be avoided.
  • The long-range goal of this research project is to develop a neural stem cell (NSC)-based treatment strategy that produces a potent, localized anti-tumor effect while minimizing toxic side effects. NSCs hold the promise of improved treatment for brain cancers because they have the natural ability to distribute themselves within a tumor, as well as seek out other sites of tumor in the brain. Because they can home to the tumor cells, NSCs may offer a new way to bring more chemotherapy selectively to brain tumor sites. After modifying the NSCs by transferring a therapeutic gene into them, NSCs can serve as vehicles to deliver anti-cancer treatment directly to the primary tumor, as well as potentially to malignant cells that have spread away from the original tumor site. With funding from CIRM, we are studying the ability of NSCs, that carry an activating protein called carboxylesterase (CE) to convert the chemotherapy agent CPT-11 (irinotecan) to its more potent form, SN-38, at sites of tumor in the brain.
  • During the first year of funding we have determined that 1) when administered directly into the brain or into a peripheral vein (intravenous injection) of mice with brain tumors, NSCs will travel to several different subtypes of gliomas; 2) we can engineer the NSCs to consistently produce high levels of more powerful forms of CE: rCE and hCE1m6; 3) glioma cells die when they are exposed to very low (nanomolar) concentrations of SN-38, and 4) although glioma cells survive when exposed to a relatively high concentration of CPT-11 alone, they do die when the same concentration of CPT-11 is administered in combination with either rCE or hCE1m6. These results suggest that the engineered NSCs are expressing relatively high levels of CE enzymes and that the CE enzymes are converting CPT-11 into SN-38. We have also been able to label our NSCs with iron particles, so that we can track their movement in real-time by magnetic resonance imaging (MRI), and follow their location and distribution in relation to the tumor.
  • All of our data thus far support the original hypothesis that effective, tumor-specific therapy for glioma patients can be developed using NSCs that express rCE or hCE1 and the prodrug CPT-11. During the second year of CIRM funding, we will further analyze our data to make a final determination regarding the best form of CE to develop towards clinical trials, and the best dose range and route of delivery of NSCs to achieve maximal tumor coverage. We will then begin our therapeutic studies and start discussions with the Food and Drug Administration, to define the safety studies necessary to obtain approval for testing this new treatment strategy in patients with brain tumors.
  • High-grade gliomas, the most common primary brain tumors in adults, have a poor prognosis and remain incurable with current therapies. These devastating tumors present significant treatment challenges: 1) surgery may cause permanent neurologic damage; 2) surgery misses cancer cells that have invaded beyond the edge of the tumor or to other sites in the brain; 3) many, if not most, chemotherapy drugs cannot enter the brain because of the blood-brain barrier; and 4) due to the highly toxic nature of chemotherapy agents the therapeutic window (the difference between the dose that kills the tumor and the dose that causes toxic side effects) is very small, resulting in undesirable side-effects. Therefore, if therapeutic agents could be localized and concentrated selectively to the tumor sites, treatment efficacy may be improved while toxic side effects are minimized.
  • The overarching goal of this project is to develop a human Neural Stem Cell (NSC)-based treatment strategy that produces potent localized anti-tumor effects while minimizing toxic side effects. NSCs hold the promise of improved treatment for brain cancers because they have an innate ability to distribute within and around a tumor mass and to seek out tumor cells that have invaded further into surrounding brain tissue. By homing to cancer cells, NSCs offer a way to selectively deliver concentrated chemotherapy to brain tumor sites. We are modifying NSCs to make the protein carboxylesterase (CE), which will convert a systemically administered prodrug, CPT-11 (irinotecan) to an active, potent anti-cancer drug, SN38 at the tumor sites.
  • Our second year of funding was highly productive and informative. We validated key elements of our system, successfully negotiating Go/No Go milestones, yielding substantial progress:
  • (1) We have selected the optimal genetically modified human CE to efficiently convert CPT-11 to SN-38. This CE is being developed for clinical grade use.
  • (2) We have determined the volume of tumor coverage by NSCs injected directly into the brain versus injecting them intravenously. We found that we achieve more tumor coverage with direct injection of the NSCs into the brain, and will focus on developing this approach for initial NSC.CE/CPT-11 clinical trials. However, following intravenous injections we found the NSCs localize prominently at the invasive tumor edges, which may prove therapeutically efficacious as well. Due to the significant clinical and commercial advantages that intravenous administration presents, this approach will also be developed toward patient trials. We have determined the starting NSC dose range for both approaches.
  • (3) We have shown that CPT-11 + CE is1,000 fold more toxic to glioma cells than CPT-11 alone. Importantly, microdialysis studies in our preclinical models have confirmed the conversion of CPT-11 to SN-38 by our CE-secreting NSCs in the brain.
  • (4) We have completed studies labeling our NSCs with iron (Feraheme) nanoparticles, which allows for non-invasive cell tracking by Magnetic Resonance Imaging (MRI). Safety studies for clinical use of this iron-labeling method were completed and submitted to the FDA, for consideration of use in brain tumor patients enrolled in our current NSC.CD/5-FC recurrent glioma clinical trial. This would be the first-in-human use of Feraheme-labeled stem cells for MRI tracking.
  • Our results to date robustly support the original hypothesis that an effective, glioma-specific therapy can be developed using NSCs that home to tumors and express CE to convert CPT-11 to the potent anti-cancer agent SN-38. Pre-clinical therapeutic efficacy studies to optimize CPT-11 regimens are now in progress.
  • High-grade gliomas, the most common primary brain tumors in adults, have a poor prognosis and remain incurable with current therapies. These devastating tumors present significant treatment challenges; 1) surgery may cause permanent neurologic damage; 2) surgery misses cancer cells that have invaded beyond the edge of the tumor or disseminated to other sites in the brain; 3) many, if not most, chemotherapy drugs cannot enter the brain because of the blood-brain barrier; and 4) due to the highly toxic nature of chemotherapy agents the therapeutic window (the difference between the dose that kills the tumor and the dose that causes toxic side effects) is very small. Therefore, if therapeutic agents could be concentrated and localized to the tumor sites, treatment efficacy may be improved while toxic side effects are minimized.
  • The overarching goal of this project is to develop a human Neural Stem Cell (NSC)-based treatment strategy that produces potent localized anti-tumor effects while minimizing toxic side effects. NSCs hold the promise of improved treatment for brain cancers because they have an innate ability to distribute within and around a tumor mass and to seek out other, secondary and smaller tumor nodules in the brain. By homing to cancer cells, NSCs offer a way to selectively deliver concentrated chemotherapy to brain tumor sites. After modifying NSCs by adding the gene to make the protein carboxylesterase (CE), NSCs deliver CE to convert the drug CPT-11 (irinotecan) to its more potent form, SN-38 at primary and secondary brain tumor sites.
  • The major milestone in our third year of funding was that we completed our pre-IND package and held our pre-IND meeting with the FDA. To this end, we validated the following:
  • (1) NSCs can potentiate the in vivo efficacy of irinotecan (CPT-11) using a low dose (7.5 mg/kg) daily x 5 schedule. Both real time Xenogen and integrated morphometric analysis of immunohistochemically stained sections of tumor were used to determine tumor volumes.
  • (2) In vivo pharmacokinetics demonstrated increased accumulation of SN-38 in tumor over that of tumor interstitium. The concentrations of tumor SN-38 were approximately 3-fold higher in tumor-bearing brain tissue than in corresponding normal tissue supporting the hypothesis that NSCs can direct toxic chemotherapy in a tumor localized manner.
  • (3) Following FDA approval of the incorporation of iron (Feraheme) into NSCs, three patients were treated with FeHe-labeled HB1.F3.CD, the first generation NSCs undergoing clinical trial. There were no adverse effects from the treatment demonstrating relative safety and lack of toxicity of this method.
  • Our results to date robustly support the original hypothesis that an effective, glioma-specific therapy can be developed using NSCs that home to tumors and express CE to convert CPT-11 to SN-38. During the fourth and coming year of CIRM funding, we will conduct experiments to determine the optimal schedule for NSC/CPT-11 therapy and demonstrate the safety and lack of toxicity of the treatment schema in rodents to fulfill requirements for IND submission and clinical trial in humans.
  • High-grade gliomas, the most common primary brain tumors in adults, have a poor prognosis and remain incurable with current therapies. These devastating tumors present significant treatment challenges; 1) surgery may cause permanent neurologic damage; 2) surgery misses cancer cells that have invaded beyond the tumor edge to other sites in the brain; 3) many, if not most, chemotherapy drugs cannot enter the brain because of the blood-brain barrier; and 4) chemotherapy drugs are toxic to normal tissues as well as tumor, causing undesirable side effects. Therefore, if therapeutic agents could be concentrated and localized to the tumor sites, treatment efficacy may improve while side effects are minimized.
  • Our goal is to bring to the clinic a human Neural Stem Cell (NSC)-based treatment strategy that produces potent localized anti-tumor effects while minimizing toxic side effects. NSCs have a natural ability to home to invasive brain tumor cells throughout the brain. NSCs, used as a delivery vehicle, offer a novel way to selectively target chemotherapy to brain tumor sites. NSCs are modified to express a certain enzyme (carboxylesterase; CE), that converts systemically administered prodrug (irinotecan) to a much more potent form (SN-38), that is up to 1000 times more effective at killing brain tumor cells.
  • Milestones reached in our fourth year include:
  • (1) receiving regulatory approval from the NIH/OBA following a public form in September, 2013.
  • (2) determining the dose and timing of NSC and irinotecan administration for optimal therapeutic efficacy in pre-clinical brain tumor models.
  • (3) demonstrating that the CE-expressing NSCs can increase concentrations of the toxic drug SN-38 by > 6-fold compared to giving irinotecan alone. Furthermore, SN-38 concentrations were dose proportional to administered irinotecan concentrations.
  • (4) Safety-toxicity studies required by the FDA for Investigational New Drug (IND) approval were completed. These studies demonstrated no significant toxicities and safety of our NSC treatment protocol in preclinical brain tumor models.
  • Our results to date support our hypothesis that a safe and effective NSC-mediated therapy can be developed for clinical use in patients with high-grade glioma, with potential application to other types of brain tumor and brain tumor metastases. We hope to initiate clinical trials with our CE-expressing NSCs and irinotecan by the end of 2014.

© 2013 California Institute for Regenerative Medicine