Re-defining response and treatment effects for neuro-oncology immunotherapy clinical trials

Analysis of Histomorphologic/Molecular Association and Immune Checkpoint Regulators in Epithelioid Glioblastoma and Pleomorphic Xanthoastrocytoma: Are These Tumors Potential Candidates for Immune Checkpoint Blockade?

Accurate diagnosis of Epithelioid glioblastoma (eGB) and pleomorphic xanthoastrocytoma (PXA) is sometimes challenging owing to overlapping histologic and genetic features. There are limited reports on the immune profile of these tumors. In this study, we assessed 21 PXA [15 PXA Grade 2 (PXAG2); 6 PXA Grade 3 (PXAG3)] and 14 eGB for their histopathological and molecular association. Further, their immune profile was compared with GB, IDH1 wild-type (wt) (n-18). Morphologically, PXAG2 mostly differed from eGB; however, it was occasionally difficult to differentiate PXAG3 from eGB due to their epithelioid pattern and less obvious degenerative features. PXAG2 showed predominantly diffuse, whereas variable positivity for epithelial and glial markers was seen in PXAG3 and eGB. All cases showed retained nuclear ATRX and INI-1 . H3K27M or IDH1 mutation was seen in none. P53 mutation was more common in eGB, followed by PXAG3, and least common in PXAG2. BRAF V600E mutation was observed in 66.67% PXAG2, 33.33% PXAG3, and 50% eGB, with 100% concordance between immunohistochemistry (IHC) and sequencing. Thirty-six percent eGB, 33% PXAG3, and 61% PXAG2 harbored CDKN2A homozygous deletion. EGFR amplification was observed in 14% eGB and 66% of GB, IDH wt. PDL1 and CTLA-4 expression was higher in eGB (71.4% and 57.1%), PXAG3 (66.6% and100%), and PXAG2 (60% & 66.7%) as compared with GB, IDH wt (38.8% and 16.7%). Tumor-infiltrating lymphocytes were also observed in a majority of eGB and PXA (90% to 100%) in contrast to GB, IDH wt (66%). This analysis highlights the homogenous molecular and immune profile of eGB and PXA, suggesting the possibility that histologically and molecularly, these two entities represent 2 ends of a continuous spectrum with PXAG3 lying in between. Higher upregulation of PDL1, CTLA-4, and increased tumor infiltrating lymphocytes in these tumors as compared with GB, IDH wt suggests potential candidature for immunotherapy.

A single dose of peripherally infused EGFRvIII-directed CAR T cells mediates antigen loss and induces adaptive resistance in patients with recurrent glioblastoma

We conducted a first-in-human study of intravenous delivery of a single dose of autologous T cells redirected to the epidermal growth factor receptor variant III (EGFRvIII) mutation by a chimeric antigen receptor (CAR). We report our findings on the first 10 recurrent glioblastoma (GBM) patients treated. We found that manufacturing and infusion of CAR-modified T cell (CART)-EGFRvIII cells are feasible and safe, without evidence of off-tumor toxicity or cytokine release syndrome. One patient has had residual stable disease for over 18 months of follow-up. All patients demonstrated detectable transient expansion of CART-EGFRvIII cells in peripheral blood. Seven patients had post-CART-EGFRvIII surgical intervention, which allowed for tissue-specific analysis of CART-EGFRvIII trafficking to the tumor, phenotyping of tumor-infiltrating T cells and the tumor microenvironment in situ, and analysis of post-therapy EGFRvIII target antigen expression. Imaging findings after CART immunotherapy were complex to interpret, further reinforcing the need for pathologic sampling in infused patients. We found trafficking of CART-EGFRvIII cells to regions of active GBM, with antigen decrease in five of these seven patients. In situ evaluation of the tumor environment demonstrated increased and robust expression of inhibitory molecules and infiltration by regulatory T cells after CART-EGFRvIII infusion, compared to pre-CART-EGFRvIII infusion tumor specimens. Our initial experience with CAR T cells in recurrent GBM suggests that although intravenous infusion results in on-target activity in the brain, overcoming the adaptive changes in the local tumor microenvironment and addressing the antigen heterogeneity may improve the efficacy of EGFRvIII-directed strategies in GBM.

Melanoma brain metastases treated with stereotactic radiosurgery and concurrent pembrolizumab display marked regression; efficacy and safety of combined treatment

Background

Brain metastases are common in patients with metastatic melanoma. With increasing numbers of melanoma patients on anti-PD-1 therapy, we sought to evaluate the safety and initial response of brain metastases treated with concurrent pembrolizumab and radiation therapy.

Methods

From an institutional database, we retrospectively identified patients with melanoma brain metastases treated with radiation therapy (RT) who received concurrent pembrolizumab. Concurrent treatment was defined as RT during pembrolizumab administration period and up to 4 months after most recent pembrolizumab treatment. Response was categorized by change in maximum diameter on first scheduled follow-up MRI. Lesion and patient specific outcomes including response, lesion control, brain control and overall survival were recorded and descriptively compared to contemporary treatments with RT and concurrent ipilimumab or RT without immunotherapy.

Results

From January 2014 through December 2015, we identified 21 patients who received concurrent radiation therapy and pembrolizumab for brain metastases or resection cavities that had at least one scheduled follow-up MRI. Eleven underwent stereotactic radiosurgery (SRS), 7 received hypofractionated radiation and 3 had whole brain treatment (WBRT). All treatments were well tolerated with no observed Grade 4 or 5 toxicities; Grade 3 edema and confusion occurred in 1 patient treated with WBRT after prior SRS. For metastases treated with SRS, at first scheduled follow-up MRI (median 57 days post SRS), 70% (16/23) exhibited complete (CR, n = 8) or partial response (PR, n = 8). The intracranial response rates (CR/PR) for patients treated with SRS and concurrent ipilimumab and SRS without concurrent immunotherapy was 32% and 22%, respectively.

Conclusions

Concurrent pembrolizumab with brain RT appears safe in patients with metastatic melanoma, and SRS in particular is effective in markedly reducing the size of brain metastases at the time of first follow-up MRI. These results compare favorably to SRS in combination with ipilimumab and SRS without concurrent immunotherapy.

Immune Checkpoint Inhibitors in Gliomas

PURPOSE OF REVIEW

Malignant gliomas result in disproportionately high morbidity and mortality compared with other primary tumors, and progression of disease is inevitable. Novel therapies to improve outcomes are needed and immune checkpoint inhibitors hold significant promise.

RECENT FINDINGS

A limited body of preclinical evidence suggests that checkpoint inhibitors may be effective treatment for gliomas. Biomarkers to identify characteristics of gliomas responsive to these therapies will be essential. These may include mismatch repair deficiency and high mutational load that might be germline, somatic, or acquired after therapy. Evidence on the use of immune checkpoint inhibitors in gliomas is evolving. Clinical trials are underway and results are eagerly awaited. Understanding the role of immune checkpoint inhibitors in combination with other treatment modalities for gliomas is crucial to the improvement of outcomes. The design and conduct of future clinical trials need to account for increasingly complex treatment options.

Chimeric antigen receptor T-cell therapy for glioblastoma

Chimeric antigen receptor (CAR) T-cell therapy has shown great promise in the treatment of hematological disease, and its utility for treatment of solid tumors is beginning to unfold. Glioblastoma continues to portend a grim prognosis and immunotherapeutic approaches are being explored as a potential treatment strategy. Identification of appropriate glioma-associated antigens, barriers to cell delivery, and presence of an immunosuppressive microenvironment are factors that make CAR T-cell therapy for glioblastoma particularly challenging. However, insights gained from preclinical studies and ongoing clinical trials indicate that CAR T-cell therapy will continue to evolve and likely become integrated with current therapeutic strategies for malignant glioma.

Blocking the PD-1/PD-L1 pathway in glioma: a potential new treatment strategy

Gliomas are the most common type of primary brain tumor in adults. High-grade neoplasms are associated with poor prognoses, whereas low-grade neoplasms are associated with 5-year overall survival rates of approximately 85%. Despite considerable progress in treatment modalities, the outcomes remain dismal. As is the case with many other tumors, gliomas express or secrete several immunosuppressive molecules that regulate immune cell function. Programmed death-ligand 1 (PD-L1) is a coinhibitory ligand that is predominantly expressed by tumor cells. The binding of PD-L1 to its receptor PD-1 has been demonstrated to induce an immune escape mechanism and to play a critical role in tumor initiation and development. Encouraging results following the blockade of the PD-1/PD-L1 pathway have validated PD-L1 or PD-1 as a target for cancer immunotherapy. Studies have reported that the PD-1/PD-L1 pathway plays a key role in glioma progression and in the efficacy of immunotherapies. Thus, progress in research into PD-L1 will enable us to develop a more effective and individualized immunotherapeutic strategy for gliomas. In this paper, we review PD-L1 expression, PD-L1-mediated immunosuppressive mechanisms, and the clinical applications of PD-1/PD-L1 inhibitors in gliomas. Potential treatment strategies and the challenges that may occur during the clinical development of these agents for gliomas are also reviewed.

Advances in the treatment of newly diagnosed glioblastoma

Glioblastoma is a refractory malignancy with limited treatment options at tumor recurrence. Only a small proportion of patients survive 2 years or longer with the current standard of care. Gene expression profiling can segregate newly diagnosed patients into groups with different prognoses, and these biomarkers are being incorporated into a new generation of personalized clinical trials. Using the experience from recently completed large scale, multi-faceted, randomized glioblastoma clinical trials, a new clinical trial paradigm is being established to move promising therapies forward into the newly diagnosed treatment setting. Upcoming trials using the immune check-point inhibitors are an example of this changing paradigm and these and other immunotherapies have potential as promising new treatment modalities for newly diagnosed GB patients.

Updates from the Neuro-Oncology Section of the 2015 American Neurological Association Annual Meeting

American Neurological Association Annual Meeting, Chicago, IL, USA, 27-29 September 2015 The American Neurological Association (ANA) held its annual meeting in Chicago, IL, USA on 27-29 September 2015. The Scientific Programming Advisory Committee was chaired by Dr. S Pleasure from the University of California-San Francisco (CA, USA). The Neuro-Oncology session, chaired by Dr. A Pruitt from the University of Pennsylvania (PA, USA) and cochaired by Dr. J Laterra from Johns Hopkins University (MD, USA), was held on 27 September 2015. Speakers included Dr. D Wainwright (Northwestern University, IL, USA), Dr. N Kolb (University of Utah, UT, USA), Dr. A Nath (NINDS/NIH, MD, USA), Dr. D Franz (Cincinnati Children's Hospital, OH, USA) and Dr. R Lukas (University of Chicago, IL, USA). A summary of key presentations from the Neuro-Oncology section of the 2015 American Neurological Association annual meeting is reported. Preclinical and clinical advances in the use of immunotherapies for the treatment of primary and metastatic CNS tumors are covered. Particular attention is paid to the enzyme indoleamine dioxygenase and the immune checkpoints CTLA4 and PD1 and their ligands. Specific nervous system toxicities associated with novel immunotherapies are also discussed. The recent success of targeting the mTOR pathway in the neurocutaneous syndrome tuberous sclerosis is detailed. Finally, important early steps in our understanding of the common toxicity of chemotherapy induced neuropathy are reviewed.

Overview of current immunotherapeutic strategies for glioma

In the last decade, numerous studies of immunotherapy for malignant glioma (glioblastoma multiforme) have brought new knowledge and new hope for improving the prognosis of this incurable disease. Some clinical trials have reached Phase III, following positive outcomes in Phase I and II, with respect to safety and immunological end points. Results are encouraging especially when considering the promise of sustained efficacy by inducing antitumor immunological memory. Progress in understanding the mechanisms of tumor-induced immune suppression led to the development of drugs targeting immunosuppressive checkpoints, which are used in active clinical trials for glioblastoma multiforme. Insights related to the heterogeneity of the disease bring new challenges for the management of glioma and underscore a likely cause of therapeutic failure. An emerging therapeutic strategy is represented by a combinatorial, personalized approach, including the standard of care: surgery, radiation, chemotherapy with added active immunotherapy and multiagent targeting of immunosuppressive checkpoints.