Early Translational III
Glioblastoma multiforme is the most prevalent and aggressive type of brain tumor. Our proposed research focuses on a new theory that brain tumor cells are initiated and maintained by a small fraction of cells with stem cell properties and if this small subset of cancer stem cells could be inactivated, the tumor would cease to grow. We reasoned that cancer-specific genetic alterations in a glioblastoma tumor could be a potential marker for cancer stem cells and zeroing in on these cells could result in targeted therapeutics. CD133 is a marker for normal neural and hematopoietic stem cells and EGFRvlll is a receptor that is genetically altered in glioblastoma tumors. We found that CD133 and the EGFRvIII are both tightly associated in glioblastoma tumors and tumor cells that express both CD133 and EGFRvIII grow more quickly. We have already developed a “bispecific” antibody that recognizes both of these markers and we have shown that this antibody selectively kills the cancer cells in glioblastoma tumors that express both CD133 and EGFRvIII, but not normal stem cells. When we injected glioblastoma cells pre-treated with BsAb into mice, tumor formation was severely inhibited. Our goal is to ready this antibody for the investigational new drug phase and to ultimately generate a human therapeutic effective against glioblastoma.
Statement of Benefit to California:
As the most populous state in the U.S., more Californians are diagnosed with glioblastoma each year than any other state, with a consequent significant economic toll to the state. We have shown that two markers of cancer stem cells, CD133 and EGFRvIII, are tightly associated in glioblastoma tumors. We created a recombinant bispecific antibody (BsAb) selectively targeting CD133 and EGFRvIII. This antibody selectively kills glioblastoma tumor cells but not normal cells. Our goal is to ready the BsAb for investigational new drug-related development. Californians will benefit from this research project in several significant ways. 1. Most importantly, this research has the promise to dramatically extend the long-term survival rates for Californians with glioblastomas, with potential applications to multiple other human cancers. 2. The research will take place in California with direct benefit to the California economy through the hiring of employees and purchase of supplies and reagents. 3. An investigational new drug application will be the direct next step, requiring employing a local contract research organization to generate clinical grade antibody, requiring additional employees along with associated expenditures. 4. If the therapeutic BsAb generated is commercialized, profits derived from the production of the BsAbs by CIRM policy will result in improved treatments to insured patients and lower cost treatments to the uninsured, thus ultimately benefiting all Californians.
The ultimate goal of this project is to develop an antibody targeting cancer stem cells for the treatment of glioblastoma. Toward that end, the current Development Candidate (DC) proposal aims to carry out preclinical studies to evaluate the efficacy, pharmacology and mechanism of action of an existing bi-specific antibody targeting EGFRvIII and CD133. A second antibody targeting only EGFRvIII will be characterized in parallel. Six milestones are proposed: 1) to develop methods to express high levels of clinically compatible antibodies; 2) to develop scalable antibody purification methods; 3) to carry out mechanism-of-action studies on these two antibodies (effects on cell growth and cell signaling); 4) to evaluate efficacy and pharmacokinetics in animal models and determine route of delivery; 5) to carry out safety studies, examining ability to bind to normal human tissues and stimulate antibody-dependent cell-mediated cytotoxicity (ADCC); 6) to select a development candidate for further development and carry out a pre-IND meeting with the FDA. Objective and Milestones - Targeting cancer stem cells with a bivalent antibody directed against a stem cell antigen and a tumor specific antigen is a clinically reasonable approach. The desired clinical activity of the development candidate to produce at least a two-month increase in survival is sound based on other agents with demonstrated impact on GBM. - The objective of proposed work is a very good fit for a DC award. However, the proposed GMP production and GLP toxicology are considered to be IND-enabling and thus out of scope. Rationale and Significance - The significance is that current therapy for GBM is minimally effective, thus alternative approaches need to be developed. However, it should be recognized that the total number of treatable patients is very small. - The investigators claim that a bi-specific reagent will reduce potential toxicity of CD133 targeting, but very little data on this critical point has been shown. - The objective to provide a passive immune reagent for immediate post-surgical treatment as a component of combined passive and active immune approaches to treatment is a strength. Research Project Feasibility and Design - Specific Aim 2 addresses the potential for direct antibody-mediated modulation of EGFRvIII function to induce an anti-CSC effect. It is an extensive series of experiments for which no clear rationale is provided. The potential for non-ADCC effects should be provided before embarking on this series of experiments. - The toxicity evaluation in Specific Aim 4 does not address an important issue: this mAb may not cross react with mouse (CD133 ~60% similarity mu-hu, EGFRvIII antigen not present) so only limited information will be obtained regarding toxicity in their murine studies. - The blood/brain barrier is essentially dismissed as issue for an IV delivery approach. They will rely on ADCC for killing of CSC; it is unclear how effective this mechanism is in within the brain environment - Specific Aim 3 will perform a preclinical trial but lacks a power calculation to support the use of a small number of mice (six) per dose group to distinguish dose-dependent effects. - The order of the proposed aims is non-optimal: Efficacy and safety testing should occur before large scale-up of FDA-compliant reagent or signaling studies. Efficacy assessments could result in the need to redesign the current bi-specific reagent and necessitate repeating scale-up and signaling studies. Qualification of the PI (Co-PI and Partner PI, if applicable) and Research Team - Generally this is a good team with academic experience in drug development and clinical IND testing. - The PI has assembled a very strong team of academic and industry collaborators with extensive experience in the development of antibody reagents, including bivalent antibodies for clinical application. - The PI and team have appropriate training, experience and track record. Missing competencies are supplemented with very skilled experts. The plan and team structure are well organized. Collaborations, Assets, Resources and Environment - The collaborations are strengths of this proposal and key to its success. - There should be no IP issues that present an obstacle to clinical application of this reagent in the proposed timeframe. - Plan for meetings and communication is adequate. Consultants have good experience with antibody development, but exact role in this project is not clear. Responsiveness to the RFA - Human GBM-derived GBM stem or tumor-initiating cells are necessary for these studies.
- This application scored below the initial scientific merit funding line, no programmatic reason to fund the application was proposed, and the GWG voted to place the application in Tier 3, Not Recommended for Funding.