Immune Checkpoint Inhibitors and Glioblastoma: A Review on Current State and Future Directions.

Glioblastoma (GBM) is the most prevalent malignant tumor of the central nervous system. The prognosis of GBM is grim, with a median overall survival of 14.6 months and only 6.9% of patients surviving 5 years after the initial diagnosis. Despite poor outcomes, standard therapy of surgical resection, radiotherapy, chemotherapy, and tumor-treating fields has remained largely unchanged. The introduction of immune checkpoint inhibitors (ICI) has been a paradigm shift in oncology, with efficacy across a broad spectrum of cancer types. Nonetheless, investigations of ICIs in both newly diagnosed and recurrent GBM have thus far been disappointing. This lack of clinical benefit has been largely attributed to the highly immunosuppressive nature of GBM. However, immunotherapy still holds promise for the treatment of GBM, with combinatorial strategies offering hope for potentially overcoming these current limitations. In this review, we discuss the outcomes of clinical trials employing ICIs in patients with GBM. Afterward, we review ICI combination strategies and how these combinations may overcome the immunosuppressive microenvironment of GBM in the context of preclinical/clinical evidence and ongoing clinical trials.

Cerebrospinal Fluid Liquid Biopsies in the Evaluation of Adult Gliomas.

PURPOSE OF REVIEW: This review aims to discuss recent research regarding the biomolecules explored in liquid biopsies and their potential clinical uses for adult-type diffuse gliomas. RECENT FINDINGS: Evaluation of tumor biomolecules via cerebrospinal fluid (CSF) is an emerging technology in neuro-oncology. Studies to date have already identified various circulating tumor DNA, extracellular vesicle, micro-messenger RNA and protein biomarkers of interest. These biomarkers show potential to assist in multiple avenues of central nervous system (CNS) tumor evaluation, including tumor differentiation and diagnosis, treatment selection, response assessment, detection of tumor progression, and prognosis. In addition, CSF liquid biopsies have the potential to better characterize tumor heterogeneity compared to conventional tissue collection and CNS imaging. Current imaging modalities are not sufficient to establish a definitive glioma diagnosis and repeated tissue sampling via conventional biopsy is risky, therefore, there is a great need to improve non-invasive and minimally invasive sampling methods. CSF liquid biopsies represent a promising, minimally invasive adjunct to current approaches which can provide diagnostic and prognostic information as well as aid in response assessment.

Proton craniospinal irradiation with bevacizumab and pembrolizumab for leptomeningeal disease: a case report.

Leptomeningeal disease (LMD) remains a challenging condition with a dismal prognosis. In this case study, we report partial response of LMD in a patient with metastatic large cell neuroendocrine carcinoma following treatment with proton craniospinal irradiation (CSI), bevacizumab, and pembrolizumab. Two years after the initial diagnosis, he presented with LMD. He underwent proton CSI with bevacizumab followed by combination therapy with pembrolizumab and bevacizumab. He had a partial disease response with progression-free survival after LMD diagnosis of 4.6 months. He unfortunately developed pembrolizumab induced hypophysitis, after which he experienced rapid neurologic clinical progression. Overall, this novel combination led to a durable partial response which warrants prospective evaluation.

Patients with leptomeningeal disease have few therapeutic options and poor treatment outcomes. Single-agent therapies have not yet been as successful in improving patient survival. In this paper, we discuss how combination therapy with proton craniospinal irradiation, bevacizumab, and pembrolizumab led to neurological improvement and disease regression. These results show that this novel combination may lead to a significant benefit not seen previously with these individual drugs given alone. We hope to lay a foundation for a novel therapeutic approach in a critically high need disease which has previously been thought to be resistant to radiotherapy or immunotherapy.

Belzutifan in adults with VHL-associated central nervous system hemangioblastoma: a single-center experience.

PURPOSE: Belzutifan is a selective inhibitor of hypoxia-inducible factor 2 alpha (HIF-2a) that has emerged as a targeted therapy option for Von Hippel-Lindau (VHL) syndrome-associated tumors with recent FDA approval. There is limited real-world evidence regarding safety and efficacy in CNS hemangioblastoma. Our objective was to report on our clinical experience with belzutifan in adult patients with VHL-associated CNS hemangioblastoma. METHODS: We retrospectively reviewed our institutional experience of belzutifan in adult patients (> 18 years of age at time of therapy) with VHL and craniospinal CNS hemangioblastomas not amenable to surgical resection. The period for study review was October 2021 to March 2023. RESULTS: 4 patients (all female) with a median age of 36 years at time of belzutifan initiation were included. Median duration of therapy at last follow-up was 11 months (6-17 months). All patients had radiographic response to therapy after a median of 3 months (2-5 months), with maximal response to therapy after a median of 8 months (3-17 months). Therapy was well tolerated, with the most common adverse effect being anemia. No patients had treatment pauses or dose adjustments due to belzutifan-related toxicity. No patients experienced hypoxia. CONCLUSION: We showed that belzutifan is safe and well-tolerated with strong disease response for CNS hemangioblastoma in adults with VHL, supporting continued use of belzutifan in this patient population. Future studies should assess duration of treatment, effects of cessation after long-term use, and markers of therapeutic response.

Current Status and Challenges of Oncolytic Virotherapy for the Treatment of Glioblastoma.

Despite decades of research and numerous clinical trials, the prognosis of patients diagnosed with glioblastoma (GBM) remains dire with median observed survival at 8 months. There is a critical need for novel treatments for GBM, which is the most common malignant primary brain tumor. Major advances in cancer therapeutics such as immune checkpoint inhibitors and chimeric antigen receptor (CAR) T-cell therapy have not yet led to improved outcomes for GBM. Conventional therapy of surgery followed by chemoradiation with or without tumor treating fields remains the standard of care. One of the many approaches to GBM therapy currently being explored is viral therapies. These typically work by selectively lysing target neoplastic cells, called oncolysis, or by the targeted delivery of a therapeutic transgene via a viral vector. In this review, we discuss the underlying mechanisms of action and describe both recent and current human clinical trials using these viruses with an emphasis on promising viral therapeutics that may ultimately break the field's current stagnant paradigm.

Trap and ambush therapy using sequential primary and tumor escape-selective oncolytic viruses.

In multiple models of oncolytic virotherapy, it is common to see an early anti-tumor response followed by recurrence. We have previously shown that frontline treatment with oncolytic VSV-IFN-ß induces APOBEC proteins, promoting the selection of specific mutations that allow tumor escape. Of these mutations in B16 melanoma escape (ESC) cells, a C-T point mutation in the cold shock domain-containing E1 (CSDE1) gene was present at the highest frequency, which could be used to ambush ESC cells by vaccination with the mutant CSDE1 expressed within the virus. Here, we show that the evolution of viral ESC tumor cells harboring the escape-promoting CSDE1C-T mutation can also be exploited by a virological ambush. By sequential delivery of two oncolytic VSVs in vivo, tumors which would otherwise escape VSV-IFN-ß oncolytic virotherapy could be cured. This also facilitated the priming of anti-tumor T cell responses, which could be further exploited using immune checkpoint blockade with the CD200 activation receptor ligand (CD200AR-L) peptide. Our findings here are significant in that they offer the possibility to develop oncolytic viruses as highly specific, escape-targeting viro-immunotherapeutic agents to be used in conjunction with recurrence of tumors following multiple different types of frontline cancer therapies.

The Current Status, Challenges, and Future Potential of Therapeutic Vaccination in Glioblastoma.

Glioblastoma (GBM) is the most common malignant primary brain tumor and confers a dismal prognosis. With only two FDA-approved therapeutics showing modest survival gains since 2005, there is a great need for the development of other disease-targeted therapies. Due, in part, to the profound immunosuppressive microenvironment seen in GBMs, there has been a broad interest in immunotherapy. In both GBMs and other cancers, therapeutic vaccines have generally yielded limited efficacy, despite their theoretical basis. However, recent results from the DCVax-L trial provide some promise for vaccine therapy in GBMs. There is also the potential that future combination therapies with vaccines and adjuvant immunomodulating agents may greatly enhance antitumor immune responses. Clinicians must remain open to novel therapeutic strategies, such as vaccinations, and carefully await the results of ongoing and future trials. In this review of GBM management, the promise and challenges of immunotherapy with a focus on therapeutic vaccinations are discussed. Additionally, adjuvant therapies, logistical considerations, and future directions are discussed.