Lay Summary

Diffuse intrinsic pontine glioma (DIPG) is one of the most formidable challenges faced by pediatric oncologists. For the last 30 years, all treatment approaches for these type of tumors have failed, leaving a terrible prospect of survival at 5 years for these children virtually of zero. Thus, it is clear that new therapeutic strategies are required that allow not only for more effective treatments of these tumors but also that defer the severe side effects derived from the current therapeutic choices. Oncolytic adenoviruses designed to replicate in and destroy tumor cells selectively represent a promising new therapeutic strategy that could improve the outcome of this malignancy. Delta-24-RGD (DNX-2401 in the clinic) is a tumor selective oncolytic virus that has been being tested in a phase I clinical trial in adults with brain tumors with very promising results. Of importance, DNX-2401 is currently being evaluated in a phase I trial for naïve DIPGs. Even though the trial is still on-going (8 patients have been treated) the virus has already showed lack of toxicity and some degree of efficacy due to the trigger of an immune response against the tumor. Nevertheless, it is clear that there is room to improve the efficacy of the strategy. Therefore, strategies directed to boost the immune response would be amenable to use in combination with the virus. In this project, we propose to combine Delta-24-RGD with an anti-C5aR1 drug. This inhibitor has the ability to reverse the non-inflammatory microenvironment that contributes to maintain the aggressive phenotype of DIPGs. We hypothesize, based in our preliminary data, that this combination will be able to awaken the patient´s own immune system, resulting in a synergistic antitumor immune response. Altogether, we hope this strategy will demonstrate safety and efficacy for these terrible tumors. If successful, at the end of this project, we will be in the position to propel a clinical trial phase I/II for children with DIPGs with the innovative therapeutic strategy developed and tested during the course of this project.

Executive Summary

It is clear that the management of DIPGs is suboptimal and novel strategies are required that allow not only for more effective treatments but also to defer the severe side effects derived from the current therapeutic choices. Oncolytic adenoviruses therapies have proven to be safe and clinically efficacious and provide a radically different approach for the treatment of DIPGs. Delta-24-RGD is a replication-competent adenovirus that has already shown efficacy in animal models of gliomas and which is more relevant for this application, in animal models of pediatric High Grade Glioma and DIPGs. Of clinical significance, compelling results from Phase I/II clinical studies conducted at MDACC (Houston, TX) and in our institution (CUN, Spain) in adult GBM and in DIPGs indicate that Delta-24-RGD can cause ongoing tumor destruction and achieve a complete response to therapy in a subset of patients. Equally important is the Delta-24-RGD superior clinical safety profile, with no significant side effects observed at any dose. Preliminary results from the first trials revealed that the intratumoral injection of the virus instigated an initial phase of oncolysis with consequent release of tumor antigens followed by a delayed inflammatory response that ultimately resulted in tumor shrinkage with complete regression in a subset of the patients, emphasizing the urgent need to further develop this approach and the suitability to translate it to DIPGs. It has been shown that the DIPGs display a non-inflammatory phenotype of microglia/macrophages. Therefore, identifying molecular cues that guide immune responses in the tumor microenvironment (TME) is of utmost importance for DIPGs. The complement system has emerged as a master regulator of cancer immunity. Dr. Pío´s group (coPI in this grant) and others have provided evidences to support the idea that complement inhibition blocks many of the effector routes associated with the cancer-immunity cycle, providing the rationale for novel therapeutic combinations aimed to enhance the antitumor efficacy of the immune response

The intrinsic ability for multiple target recognition of the host immune system makes its utilization an ideal approach to target tumors with a heterogeneous pool of aberrantly expressed proteins. Based on our preliminary data, we believe that oncolytic adenovirus in combination with a complement antagonist could enhance the immune response and in turn the antitumor effect and therefore the outcome for these patients. The objective of this application is to evaluate the safety and effectiveness of the oncolytic virus Delta-24-RGD in combination with the modulation of the complement response to reverse the non-inflammatory microenvironment for DIPGs In addition; we want to decipher the molecular and immune underpinnings driving the efficacy of this strategy. We plan to test our central hypothesis and accomplish the objective of this application by pursuing the following three aims:

Aim 1. To evaluate the antitumor activity and safety of Delta-24-RGD in combination with PMX-53 DIPG in vitro and in vivo.  Based in our preclinical and clinical data our premise here is that oncolytic adenoviruses engineered to replicate in and destroy tumor cells selectively represent a promising therapeutic strategy for DIPGs. However due to the immunosuppress-non-inflammatory nature of the tumor the virus will not work to its full potential. Therefore, in order to improve the virus efficacy we will combine it with PMX-53, a CaR1 agonist, with the capacity to change TME. To address this question, we will evaluate the cytotoxic effect and safety of the virus through in vitro and in vivo preclinical experiments using relevant cell lines and immunodeficient and immunocompetent DIPGs models.

Aim 2. To elucidate the nature of the immune responses of the combination treatment.  Based on the preliminary results of the patients treated with Delta-24-RGD (DNX-2401) we know that the antitumor effect elicited by this virus is based on the trigger of an effective antitumor immune response and we will explore how the TME changes. To this end, we will characterize the immune response of the combination through preclinical experiments using immunocompetent DIPGs models (transgenic and humanized mice models).

Rationale: The lack of effective therapies represents a critical unmet need for DIPGs. Oncolytic viruses have proven to be safe and efficacious in clinical trials conducted at our institutions and others and provide a radically different approach for the treatment of this type of tumor. Cancer immunotherapy is an ideal alternative choice since the immune response is highly specific it would persist along time creating memory and will get rid of infiltrative cells even if they are far away. Preexisting lymphocytic infiltration of tumors has emerged as an important biomarker predictive of clinical benefit, suggesting that therapeutic effect could be enhanced through strategies that induce tumor inflammation. Here we plan to explore whether the inflammatory responses generated by oncolytic adenoviruses could be harnessed to improve therapeutic efficacy of agents targeting immunologic checkpoints by activating co-stimulatory pathways and inhibiting negative regulators. The clinical rationale behind the proposed project is the possibility of developing adenovirus-based immunotherapy for DIPGs. Oncolytic adenovirus in combination with a complement inhibitor could boost the immune response the antitumor effect and therefore the outcome for these patients. The objective of this application is to evaluate the safety and effectiveness of these combinations for DIPGs and we want to decipher the molecular and immune underpinnings driving the efficacy of these strategies.

Collaboration. This project stems from the preclinical and clinical experience of the researchers with oncolytic adenoviruses and specifically with Delta-24-RGD and complement antagonist development and implementation. The clinical samples, the viruses, the peptides and the murine immunocompetent DIPG model will be key in the proposal to evaluate feasibility, the antitumor effect and mechanism of action of the combination treatment. All four researches will contribute their expertise in oncolytic immune-boosting adenoviruses and complement antagonist. Together the team has the knowledge; the know-how and the complicity to successfully accomplished the project and bring it to the clinic.

Translation. This project emerged from the knowledge that Delta-24-RGD trials has generated in the treatment of recurrent glioma and pediatric brain tumors. As mentioned above the trials with this virus showed lack of toxicity and a degree of efficacy, in some patients, that is mediated by an immune response. Unfortunately, not all the patients responded and it seems that the ones that did are those, which were able to mount an efficacious cellular response against the tumor. With this project, we pretend to explore that concept and try to boost that immune response in all the patients. Of importance, upon the accomplishment of our project, we expect to provide enough preclinical rationale for a radically innovative clinical trial for DIPG patients, based on local delivery of oncolytic virus approach combined with immune boosting strategies. This project has gone from the bench to the bedside and back again.

Impact. To date DIPG is an incurable terrible disease that not only affects the children but it is devastating for a family. Clearly, there is a paucity of effective treatments for this disease if successful this proposal could impact the way this tumor is treated and bring hope to the children and families suffering from it. Any improvement in this area will result in a vertical advance in the field and will hopefully stop the string of poor results obtained after decades of clinical trials.

Innovation. The relevance of the current study resides in the fact that this approach bridges two immunotherapy approaches that are complementary and have the potential to be synergistic. In this project, it is proposed for the first time to combine the oncolytic capability of adenoviruses with an antagonist of the C5aR1 in order to regulate the immune synapsis. This approach has not been characterized by any other group. Results on this combination have not been published. Other innovative component of the project is the plan to examine the cellular and molecular mechanisms of tumor microenvironment anergy before the infection with viruses. The proposal is therefore innovative at conceptual level and aims to study new reagents that will be administered in untested therapy combinations for DIPGs. For all these reasons, we believe that our proposal may provide new insights that could be of great significance for the treatment of these type tumors.

Our research project will use novel and relevant immunocompetent DIPG in vitro and in vivo models to accomplish the experimental aims. We propose a new biological therapeutic tool that has the potential to drastically improve the prognosis of the children with brain tumors without resulting in unacceptable toxicity. Finally, if successful this strategy could be extensive to all kind of pediatric brain tumors and to other type of cancers.

Description of Research Proposal

Budget

Collaborations and Conflicts of Interest