We propose a phase I study to assess a vaccination regime [intradermal (i.d.)] injections of lysate derived from cultured brain tumor-initiating cells (BTICs) with concurrent topical application of an immunoadjuvant (imiquimod) in adults with World Health Organization (WHO) grade II low-grade gliomas (LGGs). Our objective is to collect immunological and safety data to determine whether a larger study of clinical efficacy is warranted. We selected the well-characterized BTICs as the antigen source since they persist in tumors as a distinct population and cause relapse by giving rise to new tumors. Both LGG and high-grade glioma (HGG) tissues appear to contain tumor cells expressing CD133+, a marker of BITCs. We have established a glioblastoma (GBM) patient-derived BTIC line, GBM6, grown under Good Manufacturing Practice (GMP) conditions. Flow cytometry data demonstrate that GBM6 expresses many important GAAs, including interleukin-13 receptor (IL- 13R)?2, EphA2, and Her-2. Moreover, GBM6 also expresses key BTIC antigens, including CD133, nestin, and Sox-2. These data suggest vaccinating with GBM6 lysate could offer both immunotherapeutic and immunoprophylactic potential to reduce the risk of tumor recurrence in LGG. We will combine i.d. administration of GBM6 lysate and Imiquimod, an FDA-approved immunoadjuvant that enhances the efficacy of vaccines and anti-glioma immunity. We hypothesize that this whole tumor antigen-based vaccine combined with Imiquimod will safely induce potent anti-glioma immune response. Because prior radiation therapy (RT) may influence the immunological activity of vaccines, we will stratify newly diagnosed high-risk LGG patients into two cohorts, depending on whether patients received RT. We will treat a total of 18 patients (9 patients/cohort) to evaluate the following specific aims in each cohort:
Aim 1 : Induction of GBM6-specific T-cell response: We will determine the response rate and magnitude of immune response in peripheral blood mononuclear cells (PBMC) against the GBM6-lysate, using interferon (IFN)-g-enzyme-linked immuno-spot (ELISPOT). We will compare the rate and magnitude of GAA-specific immune responses in the 2 cohorts (high-risk LGG with and without post-operative RT). We will consider a cohort worthy of further investigation if there are at least 4 responses in the 9 subjects.
Aim 2 : Safety: The incidence and severity of adverse events (AEs) associated with the vaccine regime will be assessed, with an early stopping rule based on the frequency of dose-limiting toxicity (DLT). We will closely monitor the potential induction of autoimmune encephalitis. If this pilot phase I trial confirms the vaccine strategy is safe and demonstrates immunological activity as defined above (Aim 1), we will design a larger multi-site phase II clinical trial in which progression-free survival will be evaluated as the primary endpoint.
We plan to conduct a pilot phase I clinical study to assess safety and immunological activity of a novel vaccination regimen using lysate derived from cultured brain tumor initiating cells (BTICs) in adult patients with World Health Organization (WHO) grade II low-grade gliomas (LGGs). We hypothesize that this form of vaccine will safely induce potent anti-glioma immune response, which may eventually translate to prevention of progression and malignant transformation of their LGGs. If our hypothesis is proven in the current study, we will design a larger multi-site Phase II clinical trial, in which progression-fre survival will be evaluated as the primary endpoint.