Current strategies to circumvent the antiviral immunity to optimize cancer virotherapy

Tutorial: design, production and testing of oncolytic viruses for cancer immunotherapy

Oncolytic viruses (OVs) represent a novel class of cancer immunotherapy agents that preferentially infect and kill cancer cells and promote protective antitumor immunity. Furthermore, OVs can be used in combination with established or upcoming immunotherapeutic agents, especially immune checkpoint inhibitors, to efficiently target a wide range of malignancies. The development of OV-based therapy involves three major steps before clinical evaluation: design, production and preclinical testing. OVs can be designed as natural or engineered strains and subsequently selected for their ability to kill a broad spectrum of cancer cells rather than normal, healthy cells. OV selection is further influenced by multiple factors, such as the availability of a specific viral platform, cancer cell permissivity, the need for genetic engineering to render the virus non-pathogenic and/or more effective and logistical considerations around the use of OVs within the laboratory or clinical setting. Selected OVs are then produced and tested for their anticancer potential by using syngeneic, xenograft or humanized preclinical models wherein immunocompromised and immunocompetent setups are used to elucidate their direct oncolytic ability as well as indirect immunotherapeutic potential in vivo. Finally, OVs demonstrating the desired anticancer potential progress toward translation in patients with cancer. This tutorial provides guidelines for the design, production and preclinical testing of OVs, emphasizing considerations specific to OV technology that determine their clinical utility as cancer immunotherapy agents.

Targeted Suicide Gene Therapy with Retroviral Replicating Vectors for Experimental Canine Cancers

Cancer in dogs has increased in recent years and is a leading cause of death. We have developed a retroviral replicating vector (RRV) that specifically targets cancer cells for infection and replication. RRV carrying a suicide gene induced synchronized killing of cancer cells when administered with a prodrug after infection. In this study, we evaluated two distinct RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV) in canine tumor models both in vitro and in vivo. Despite low infection rates in normal canine cells, both RRVs efficiently infected and replicated within all the canine tumor cells tested. The efficient intratumoral spread of the RRVs after their intratumoral injection was also demonstrated in nude mouse models of subcutaneous canine tumor xenografts. When both RRVs encoded a yeast cytosine deaminase suicide gene, which converts the prodrug 5-fluorocytosine (5-FC) to the active drug 5-fluorouracil, they caused tumor-cell-specific 5-FC-induced killing of the canine tumor cells in vitro. Furthermore, in the AZACF- and AZACH-cell subcutaneous tumor xenograft models, both RRVs exerted significant antitumor effects. These results suggest that RRV-mediated suicide gene therapy is a novel therapeutic approach to canine cancers.

Optimal strategies of oncolytic virus-bortezomib therapy via the apoptotic, necroptotic, and oncolysis signaling network

Bortezomib and oncolytic virotherapy are two emerging targeted cancer therapies. Bortezomib, a proteasome inhibitor, disrupts protein degradation in cells, leading to the accumulation of unfolded proteins that induce apoptosis. On the other hand, virotherapy uses genetically modified oncolytic viruses (OVs) to infect cancer cells, trigger cell lysis, and activate anti-tumor response. Despite progress in cancer treatment, identifying administration protocols for therapeutic agents remains a significant concern, aiming to strike a balance between efficacy, minimizing toxicity, and administrative costs. In this work, optimal control theory was employed to design a cost-effective and efficient co-administration protocols for bortezomib and OVs that could significantly diminish the population of cancer cells via the cell death program with the NF$ \kappa $B-BAX-RIP1 signaling network. Both linear and quadratic control strategies were explored to obtain practical treatment approaches by adapting necroptosis protocols to efficient cell death programs. Our findings demonstrated that a combination therapy commencing with the administration of OVs followed by bortezomib infusions yields an effective tumor-killing outcome. These results could provide valuable guidance for the development of clinical administration protocols in cancer treatment.

Integrating innate and adaptive immunity in oncolytic virus therapy

Oncolytic viruses (OVs), viruses engineered to lyse tumor cells, work hand in hand with the immune response. While for decades the field isolated lytic capability and viral spread to increase response to virotherapy, there is now a wealth of research that demonstrates the importance of immunity in the OV mechanism of action. In this review, we will cover how OVs interact with the innate immune system to fully activate the adaptive immune system and yield exceptional tumor clearances as well as look forward at combination therapies which can improve clinical responses.

An Engineered Influenza a Virus Expressing the Co-Stimulator OX40L as an Oncolytic Agent Against Hepatocellular Carcinoma

Background

Oncolytic virus (OV) therapy has emerged as a promising novel form of immunotherapy. Moreover, an increasing number of studies have shown that the therapeutic efficacy of OV can be further improved by arming OVs with immune-stimulating molecules.

Methods

In this study, we used reverse genetics to produce a novel influenza A virus, termed IAV-OX40L, which contained the immune-stimulating molecule OX40L gene in the influenza virus nonstructural (NS1) protein gene. The oncolytic effect of IAV-OX40L was explored on hepatocellular carcinoma (HCC)HCC cells in vitro and in vivo.

Results

Hemagglutination titers of the IAV-OX40L virus were stably 27-28 in specific-pathogen-free chicken embryos. The morphology and size distribution of IAV-OX40L are similar to those of the wild-type influenza. Expression of OX40L protein was confirmed by Western blot and immunofluorescence. MTS assays showed that the cytotoxicity of IAV-OX40L was higher in HCC cells (HepG2 and Huh7) than in normal liver cells (MIHA) in a time- and dose-dependent manner in vitro. We found that intratumoral injection of IAV-OX40L reduced tumor growth and increased the survival rate of mice compared with PR8-treated controls in vivo. In addition, the pathological results showed that IAV-OX40L selectively destroyed tumor tissues without harming liver and lung tissues. CD4+ and CD8+ T cells of the IAV-OX40L group were significantly increased in the splenic lymphocytes of mice. Further validation confirmed that IAV-OX40L enhanced the immune response mainly by activating Th1-dominant immune cells, releasing interferon-γ and interleukin-2.

Conclusion

Taken together, our findings demonstrate the novel chimeric influenza OV could provide a potential therapeutic strategy for combating HCC and improve the effectiveness of virotherapy for cancer therapy.

Promises of oncolytic viral therapy for adult and children with brain glioma

PURPOSE OF REVIEW

The purpose of this review is to give an overview of early clinical studies addressing the safety and efficacy of oncolytic immunovirotherapy in adults and children with brain gliomas, and to highlight the extensive potential for the development of this therapeutic alternative.

RECENT FINDINGS

The lack of curative treatments and poor prognosis of high-grade glioma patients warrants research on innovative therapeutic alternatives such as oncolytic immunovirotherapy. Engineered modified oncolytic viruses exert both a direct lytic effect on tumor cells and a specific antitumor immune response. Early clinical trials of different DNA and RNA oncolytic viruses, mainly Herpes Simplex Virus Type-1 and adenovirus based platforms, have consistently demonstrated an acceptable safety profile, hints of efficacy and the potential of this therapy to reshape the tumor microenvironment in both adult and pediatric patients with glioma, thus constituting the basis for the development of more advanced clinical trials.

SUMMARY

The future landscape of oncolytic immunovirotherapy is still plenty of challenges and opportunities to enable its full therapeutic potential in both adult and children with brain gliomas.

Oncolytic viruses in hematological malignancies: hijacking disease biology and fostering new promises for immune and cell-based therapies

The increased tropism for malignant cells of some viruses has been highlighted in recent studies, prompting their use as a strategy to modify the transcriptional profile of those cells, while sparing the healthy ones. Likewise, they have been recognized as players modulating microenvironmental immunity, namely through an increase in antigen-presenting, natural-killer, and T CD8+ cytotoxic cells by a cross-priming mechanism elicited by tumor-associated antigens. The immunomodulatory role of the oncolytic virus seems relevant in hematological malignancies, which may relapse as a result of a proliferative burst elicited by an external stimulus in progenitor or neoplastic stem cells. By reprogramming the host cells and the surrounding environment, the potential of virotherapy ranges from the promise to eradicate the minimal measurable disease (in acute leukemia, for example), to the ex vivo purging of malignant progenitor cells in the setting of autologous bone marrow transplantation. In this review, we analyze the recent advances in virotherapy in hematological malignancies, either when administered alone or together with chemotherapeutic agents or other immunomodulators.

Oncolytic Virus-Driven Biotherapies from Bench to Bedside

With advances in cancer biology and an ever-deepening understanding of molecular virology, oncolytic virus (OV)-driven therapies have developed rapidly and become a promising alternative to traditional cancer therapies. In recent years, satisfactory results for oncolytic virus therapy (OVT) are achieved at both the cellular and organismal levels, and efforts are being increasingly directed toward clinical trials. Unfortunately, OVT remains ineffective in these trials, especially when performed using only a single OV reagent. In contrast, integrated approaches, such as using immunotherapy, chemotherapy, or radiotherapy, alongside OVT have demonstrated considerable efficacy. The challenges of OVT in clinical efficacy include the restricted scope of intratumoral injections and poor targeting of intravenous administration. Further optimization of OVT delivery is needed before OVs become a viable therapy for tumor treatment. In this review, the development process and antitumor mechanisms of OVs are introduced. The advances in OVT delivery routes to provide perspectives and directions for the improvement of OVT delivery are highlighted. This review also discusses the advantages and limitations of OVT monotherapy and combination therapy through the lens of recent clinical trials and aims to chart a course toward safer and more effective OVT strategies.

Defects in intratumoral arginine metabolism attenuate the replication and therapeutic efficacy of oncolytic myxoma virus

BACKGROUND

Arginine (Arg) is a semiessential amino acid whose bioavailability is required for the in vitro replication of several oncolytic viruses. In vivo, Arg bioavailability is regulated by a combination of dietary intake, protein catabolism, and limited biosynthesis through portions of the urea cycle. Interestingly, despite the importance of bioavailable Arg to support cellular proliferation, many forms of cancer are functionally auxotrophic for this amino acid due to the epigenetic silencing of argininosuccinate synthetase 1 (ASS1), an enzyme responsible for the conversion of citrulline and aspartate into the Arg precursor argininosuccinate. The impact of this silencing on oncolytic virotherapy (OV), however, has never been examined.

METHODS

To address this gap in knowledge, we generated tumor cells lacking ASS1 and examined how loss of this enzyme impacted the in vivo replication and therapeutic efficacy of oncolytic myxoma virus (MYXV). We also generated a series of recombinant MYXV constructs expressing exogenous ASS1 to evaluate the therapeutic benefit of virally reconstituting Arg biosynthesis in ASS1^-/- tumors.

RESULTS

Our results show that the in vitro replication of oncolytic MYXV is dependent on the presence of bioavailable Arg. This dependence can be overcome by the addition of the metabolic precursor citrulline, however, this rescue requires expression of ASS1. Because of this, tumors formed from functionally ASS1^-/- cells display significantly reduced MYXV replication as well as poorer therapeutic responses. Critically, both defects could be partially rescued by expressing exogenous ASS1 from recombinant oncolytic MYXVs.

CONCLUSIONS

These results demonstrate that intratumoral defects to Arg metabolism can serve as a novel barrier to virally induced immunotherapy and that the exogenous expression of ASS1 can improve the efficacy of OV in Arg-auxotrophic tumors.

Oncolytic virotherapy for the treatment of pediatric brainstem gliomas

Diffuse intrinsic pontine glioma (DIPG) is the most frequent brainstem glioma and the most lethal brain tumor in childhood. Despite transient benefit with radiotherapy, the prognosis of children with this disease remains dismal with severe neurological morbidity and median survival less than 12months. Oncolytic immunovirotherapy is emerging as a potential therapeutic approach in neuro-oncology. The oncolytic adenovirus Delta-24-RGD has shown efficacy in adult patients with recurrent GBM. Our group has demonstrated that Delta-24-RGD has oncolytic activity and triggers immune response in preclinical models of DIPG, and has a synergistic effect with radiotherapy in animal models of this disease. In this scenario, we conducted a first-in-human phase 1 clinical trial to evaluate the safety and efficacy of intratumoral injection of Delta-24-RGD in pediatric patients with newly diagnosed DIPG prior to standard radiotherapy. The study confirmed the feasibility of this treatment with an acceptable safety profile and encouraging efficacy results. Correlative analyses showed a biological activity from Delta-24-RGD in DIPG. Further advanced trials are needed to validate these results. Meanwhile, plenty of opportunities to increase the potential contribution of oncolytic viruses in the management of devastating tumors with no current effective treatment such as DIPG need to be explored and exploited.

Phase I/II study of PexaVec in combination with immune checkpoint inhibition in refractory metastatic colorectal cancer

BACKGROUND

Oncolytic immunotherapy represents a unique therapeutic platform for the treatment of cancer. Here, we evaluated the safety and efficacy of the combination of pexastimogene devacirepvec (PexaVec) plus durvalumab (anti-programmed death ligand 1) with and without tremelimumab (anti-cytotoxic T-lymphocyte associated protein 4) in patients with standard chemotherapy refractory mismatch repair proficient (pMMR) metastatic colorectal cancer (mCRC) in a phase I/II trial.

METHODS

Adult patients with histologically confirmed advanced pMMR mCRC, who had progressed on at least two prior lines of systemic chemotherapy were studied in four cohorts. Patients received four doses of PexaVec IV at a dose of 3×10⁸ plaque forming units (pfu) (dose level 1) or 1×10⁹ pfu (dose level 2) every 2 weeks. Twelve days after the first PexaVec administration, patients received either 1500 mg of durvalumab every 28 days alone or an additional single dose of 300 mg tremelimumab on day 1. Responses were assessed every 8 weeks by CT or MRI. AEs were recorded. The primary endpoints were safety and feasibility. Secondary endpoints included progression-free survival (PFS) and overall survival. Paired tumor samples and peripheral blood were collected to perform immune monitoring.

RESULTS

Thirty-four patients with mCRC enrolled on to the study: 16 patients in the PexaVec/durvalumab cohorts and 18 patients in the PexaVec/durvalumab/tremelimumab cohorts. Overall, the combination of PexaVec plus immune checkpoint inhibitors did not result in any unexpected toxicities. Most common toxicities observed were fever and chills after PexaVec infusion. Two cases of grade 3 colitis, one case of a grade 2 myositis and one case of grade 3 hypotension resulted in discontinuation of immune checkpoint inhibitor and PexaVec treatment, respectively. The median PFS in the PexaVec/durvalumab/tremelimumab cohorts was 2.3 months (95% CI: 2.2 to 3.2 months) vs 2.1 months (95% CI: 1.7 to 2.8 months; p=0.57) in the PexaVec/durvalumab cohorts. Flow cytometry analysis of peripheral blood mononuclear cells revealed an increase in Ki67⁺CD8⁺ T cells on treatment.

CONCLUSION

PexaVec in combination with durvalumab and tremelimumab is safe and tolerable. No unexpected toxicities were observed. The combination of PexaVec/durvalumab/tremelimumab demonstrated potential clinical activity in patients with pMMR mCRC, but further studies are needed to identify the predictive biomarkers.

TRIAL REGISTRATION NUMBER

NCT03206073.

Preexisting immunity: Barrier or bridge to effective oncolytic virus therapy?

Oncolytic viruses (OVs) represent a highly promising treatment strategy for a wide range of cancers, by mediating both the direct killing of tumor cells as well as mobilization of antitumor immune responses. As many OVs circulate in the human population, preexisting OV-specific immune responses are prevalent. Indeed, neutralizing antibodies (NAbs) are abundantly present in the human population for commonly used OVs, such as Adenovirus type 5 (Ad5), Herpes Simplex Virus-1 (HSV-1), Vaccinia virus, Measles virus, and Reovirus. This review discusses (pre)clinical evidence regarding the effect of preexisting immunity against OVs on two distinct aspects of OV therapy; OV infection and spread, as well as the immune response induced upon OV therapy. Combined, this review provides evidence that consideration of preexisting immunity is crucial in realizing the full potential of the highly promising therapeutic implementation of OVs. Future investigation of current gaps in knowledge highlighted in this review should yield a more complete understanding of this topic, ultimately allowing for better and more personalized OV therapies.

Dynamic impact of virome on colitis and colorectal cancer: Immunity, inflammation, prevention and treatment

The gut microbiome includes a series of microorganism genomes, such as bacteriome, virome, mycobiome, etc. The gut microbiota is critically involved in intestine immunity and diseases, including inflammatory bowel disease (IBD) and colorectal cancer (CRC); however, the underlying mechanism remains incompletely understood. Clarifying the relationship between microbiota and inflammation may profoundly improve our understanding of etiology, disease progression, patient management, and the development of prevention and treatment. In this review, we discuss the latest studies of the influence of enteric viruses (i.e., commensal viruses, pathogenic viruses, and bacteriophages) in the initiation, progression, and complication of colitis and colorectal cancer, and their potential for novel preventative approaches and therapeutic application. We explore the interplay between gut viruses and host immune systems for its effects on the severity of inflammatory diseases and cancer, including both direct and indirect interactions between enteric viruses with other microbes and microbial products. Furthermore, the underlying mechanisms of the virome's roles in gut inflammatory response have been explained to infer potential therapeutic targets with examples in specific clinical trials. Given that very limited literature has thus far discussed these various topics with the gut virome, we believe these extensive analyses may provide insight into the understanding of the molecular pathogenesis of IBD and CRC, which could help add the design of improved therapies for these important human diseases.

Pre-Existing HSV-1 Immunity Enhances Anticancer Efficacy of a Novel Immune-Stimulating Oncolytic Virus

Oncolytic viruses (OVs) can specifically replicate in the host and cause cancer cell lysis while inducing an antitumor immune response. The aim of this study is to investigate the impact of either pre-existing immunity against herpes simplex virus type-1 (HSV-1) or multicycle treatment with OVs on anticancer efficacy of VG161, an HSV-1 OV in phase 2 clinical trial. VG161 efficacy was tested in CT26 mouse models by comparing the efficacy and immune response in naïve mice or in mice that were immunized with VG161. Moreover, VG161 efficacy in HLA-matched CD34+ humanized intrahepatic cholangiocarcinoma (ICC) patient-derived xenograft (PDX) models was also tested in multicycle treatment and was compared to standard chemotherapy for this type of cancer (gemcitabine). The HSV-1-immunized mice significantly inhibited tumor growth in VG161-treated mice compared to control naïve treated mice. RNA expression profiling and ELISPOT analyses indicated changes in the tumor's immune profile in the immunized and treated group compared to naïve and treated mice, as well as enhanced T cell function depicted by higher numbers of tumor specific lymphocytes, which was enhanced by immunization. In the ICC PDX model, repeated treatment of VG161 with 2 or 3 cycles seemed to increase the anticancer efficacy of VG161. In conclusion, the anticancer efficacy of VG161 can be enhanced by pre-immunization with HSV-1 and multicycle administration when the virus is given intratumorally, indicating that pre-existing antiviral immunity might enhance OV-induced antitumor immunity. Our results suggest potential clinical benefits of HSV-1-based OV therapy in HSV-1-seropositive patients and multicycle administration of VG161 for long-term maintenance treatment.

Therapeutic Implementation of Oncolytic Viruses for Cancer Immunotherapy: Review of Challenges and Current Clinical Trials

The development of cancer therapeutics has evolved from general targets with radiation and chemotherapy and shifted toward treatments with a more specific mechanism of action such as small molecule kinase inhibitors, monoclonal antibodies against tumor antigens, or checkpoint inhibitors. Recently, oncolytic viruses (OVs) have come to the forefront as a viable option for cancer immunotherapy, especially for "cold" tumors, which are known to inhabit an immunologically suppressive tumor microenvironment. Desired characteristics of viruses are selected through genetic attenuation of uncontrolled virulence, and some genes are replaced with ones that enhance conditional viral replication within tumor cells. Treatment with OVs must overcome various hurdles such as premature viral suppression by the host's immune system and the dense stromal barrier. Currently, clinical studies investigate the efficacy of OVs in conjunction with various anti-cancer therapeutics, including radiotherapy, chemotherapy, immune checkpoint inhibitors, and monoclonal antibodies. Thus, future research should explore how cancer therapeutics work synergistically with certain OVs in order to create more effective combination therapies and improve patient outcomes.

Recombinant Viral Vectors for Therapeutic Programming of Tumour Microenvironment: Advantages and Limitations

Viral vectors have been widely investigated as tools for cancer immunotherapy. Although many preclinical studies demonstrate significant virus-mediated tumour inhibition in synergy with immune checkpoint molecules and other drugs, the clinical success of viral vector applications in cancer therapy currently is limited. A number of challenges have to be solved to translate promising vectors to clinics. One of the key elements of successful virus-based cancer immunotherapy is the understanding of the tumour immune state and the development of vectors to modify the immunosuppressive tumour microenvironment (TME). Tumour-associated immune cells, as the main component of TME, support tumour progression through multiple pathways inducing resistance to treatment and promoting cancer cell escape mechanisms. In this review, we consider DNA and RNA virus vectors delivering immunomodulatory genes (cytokines, chemokines, co-stimulatory molecules, antibodies, etc.) and discuss how these viruses break an immunosuppressive cell development and switch TME to an immune-responsive “hot” state. We highlight the advantages and limitations of virus vectors for targeted therapeutic programming of tumour immune cell populations and tumour stroma, and propose future steps to establish viral vectors as a standard, efficient, safe, and non-toxic cancer immunotherapy approach that can complement other promising treatment strategies, e.g., checkpoint inhibitors, CAR-T, and advanced chemotherapeutics.

Oncolytic viruses: challenges and considerations in an evolving clinical landscape

Despite advances in treatment, cancer remains a leading cause of death worldwide. Although treatment strategies are continually progressing, cancers have evolved many mechanisms for evading therapies and the host immune system. Oncolytic viruses (OVs) could provide a much-needed option for cancers that are resistant to existing treatments. OVs can be engineered to specifically target and kill cancer cells, while simultaneously triggering an immune response at the site of infection. This review will focus on the challenges of developing a successful OV and translation to clinical practice, discussing the innovative strategies that are being used to optimize the potential of OVs. Here, we will also explore the current clinical landscape and the prospects of OVs in early clinical development.

Agent-based computational modeling of glioblastoma predicts that stromal density is central to oncolytic virus efficacy

Oncolytic viruses (OVs) are emerging cancer immunotherapy. Despite notable successes in the treatment of some tumors, OV therapy for central nervous system cancers has failed to show efficacy. We used an ex vivo tumor model developed from human glioblastoma tissue to evaluate the infiltration of herpes simplex OV rQNestin (oHSV-1) into glioblastoma tumors. We next leveraged our data to develop a computational, model of glioblastoma dynamics that accounts for cellular interactions within the tumor. Using our computational model, we found that low stromal density was highly predictive of oHSV-1 therapeutic success, suggesting that the efficacy of oHSV-1 in glioblastoma may be determined by stromal-to-tumor cell regional density. We validated these findings in heterogenous patient samples from brain metastatic adenocarcinoma. Our integrated modeling strategy can be applied to suggest mechanisms of therapeutic responses for central nervous system cancers and to facilitate the successful translation of OVs into the clinic.

Remission of Liquid Tumors and SARS-CoV-2 Infection: a Literature Review

The coronavirus disease 2019 (COVID-19) pandemic has produced a new global challenge for patients with cancer. The disease and the immunosuppression induced by cancer therapies have generated a perfect storm of conditions to increase the severity of the symptoms and worsen the prognosis. However, a few clinical reports showcased the power of viruses to induce remission in some patients suffering from liquid tumors. Here, we reviewed six cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that resulted in cancer remission, simultaneously highlighting the strengths and the unique challenges of oncolytic virotherapy. Virotherapy has become a special case of cancer immunotherapy. This paradigm-shifting concept suggests that oncolytic viruses are not only promising agents to combat particularly immunologically suppressed, immunotherapy-resistant tumors but also that the trigger of local inflammation, such as SARS-CoV-2 infection of the respiratory pathways, may trigger an abscopal effect sufficient to induce the remission of systemic cancer.

Immunovirotherapy for Pediatric Solid Tumors: A Promising Treatment That is Becoming a Reality

Immunotherapy has seen tremendous strides in the last decade, acquiring a prominent position at the forefront of cancer treatment since it has been proven to be efficacious for a wide variety of tumors. Nevertheless, while immunotherapy has changed the paradigm of adult tumor treatment, this progress has not yet been translated to the pediatric solid tumor population. For this reason, alternative curative therapies are urgently needed for the most aggressive pediatric tumors. In recent years, oncolytic virotherapy has consolidated as a feasible strategy for cancer treatment, not only for its tumor-specific effects and safety profile but also for its capacity to trigger an antitumor immune response. This review will summarize the current status of immunovirotherapy to treat cancer, focusing on pediatric solid malignancies. We will revisit previous basic, translational, and clinical research and discuss advances in overcoming the existing barriers and limitations to translate this promising therapeutic as an every-day cancer treatment for the pediatric and young adult populations.