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.
Reporting Period:
Year 2
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.
Reporting Period:
Year 3
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.
Reporting Period:
Year 4
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.
Reporting Period:
Year 5/NCE
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 cannot remove the cancer cells that have invaded beyond the main tumor site; 3) 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 fifth (final) year include:
(1) completion of safety/tox and efficacy study data analysis reports
(2) completion of clinical protocol
(3) completion of clinical lot for initiation of patient trial
(4) Regulatory documents including IBC, IRB, SCRO, NIH-RAC Protocol #13071241 all approved
(5) submission of final IND package to the FDA
(6) phase I trial initiation pending
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 brain tumor metastases, as well as metastatic cancers.
Despite aggressive multimodal therapy and advances in imaging, surgical and radiation techniques, malignant brain tumors (high-grade gliomas) remain incurable, with survival often measured in months. Treatment failure is largely attributable to the diffuse and invasive nature of these brain tumor cells, ineffective delivery of chemotherapeutic agents to tumor sites, and toxic side-effects to the body, which limits the dose of drug that can be given. Therefore, new tumor-selective therapies are critically needed. Neural stem cells (NSCs) offer an unprecedented advantage over conventional treatment approaches because of their unique ability to target tumor cells throughout the brain. This ability allows NSCs to be used to deliver prodrug-activating enzymes to tumors, where these enzymes will generate high concentrations of powerful anti-cancer agents selectively at tumor sites.
We will use an established human NSC line to develop a novel NSC-based product to deliver the enzyme carboxylesterase (CE), which will activate a systemically administered prodrug, CPT-11, to a powerful chemotherapeutic agent, SN-38, selectively at tumor sites, destroying invasive glioma cells while sparing normal tissues. Based on our preliminary data, we hypothesize that CE-expressing NSCs will home to tumor sites in the brain, and, in combination with CPT-11, will generate high concentrations of SN-38 specifically at tumor sites. Thus, in addition to potentially improving lifespan by concentrating the powerful chemotherapeutic agent selectively at tumor sites, this NSC-mediated treatment strategy should significantly decrease toxic side-effects to normal tissues, thus preserving or improving the patient’s quality of life.
Our research, regulatory and clinical teams have the collective expertise and experience to conduct the preclinical studies necessary to optimize the efficacy of this innovative treatment approach. Specifically, we will determine the optimal dose and route of NSC administration; the optimal prodrug dosing regimen; and assess the safety of this treatment approach. We will perform these studies and analyses, generate clinical grade products, and file and obtain all appropriate regulatory documents and approvals. Completion of these activities will lead to the filing of a new Investigational New Drug (IND) proposal to the FDA, for a first-in-human Phase I clinical trial of this pioneering NSC-mediated treatment in patients with recurrent high-grade gliomas.
Importantly, our NSC line can be further modified for tumor-localized delivery of a variety of therapeutic agents, and can be given serially or in combination to maximize therapeutic benefit. Thus, the potential medical impact of this innovative NSC-mediated therapeutic approach may be very far-reaching, as it can be developed for application to other types of malignant brain tumors, as well as for metastatic cancers.
Statement of Benefit to California:
Despite aggressive multimodality therapy and advances in imaging, surgical and radiation techniques, high-grade gliomas remain incurable, with survival often measured in months. Approximately, 22,500 malignant brain tumors are diagnosed annually in the U.S., of which more than 2,600 cases are in California. New therapies are desperately needed to improve both the survival and quality of life of these brain tumor patients and to reduce the economic impact of billions of dollars in related healthcare costs.
We propose to develop a novel neural stem cell (NSC)-based treatment method that will selectively target glioma cells with a potent chemotherapy agent, locally activated by the NSCs at tumor sites to destroy neighboring tumor cells. Our tumor-selective approach also has the advantage of minimizing toxicity to normal tissues, thereby decreasing systemic side effects and damage to normal brain. This new therapeutic strategy, therefore, not only has the potential to improve survival, but, by preserving cognitive function and quality of life, it could also enable adult Californians diagnosed with brain tumors to continue making societal contributions that would benefit all Californians.
Important for clinical translation of this novel therapeutic approach, we have established the NSC line to be used in this study as a fully characterized cGMP Master Cell Bank. The NSC line is thus expandable, easily distributed to other medical centers, and cost-effective, which will allow this therapeutic approach to be quickly adopted. Importantly, this NSC line can be further modified for tumor-localized delivery of a variety of therapeutic agents, which may be given serially or in combination to maximize therapeutic benefit. There is tremendous potential for developing NSC-mediated treatment applications for other types of malignant brain tumors, as well as for metastatic solid tumors throughout the body. Therefore, the impact of these proposed studies to advance NSC-mediated treatment of glioma may be very far-reaching and may significantly contribute to reducing healthcare costs.
Finally, the combined strengths and experience of our research team will enable us to advance this NSC-meditated therapeutic approach in a timely, streamlined, and cost-effective manner to submit a new IND application for initiating first-in-human clinical trials in California, providing benefit to state taxpayers by efficient use of tax dollars and initial access to this novel therapy. In addition, our CIRM Disease Team NSC-mediated cancer treatment studies would stimulate and advance collaborative partnerships and alliances with other cancer centers and affiliates, pharmaceutical companies, academic institutions, and philanthropic societies within California, which would further enhance local and state economies.
