The Fc Domain of Immunoglobulin Is Sufficient to Bridge NK Cells with Virally Infected Cells.

Clearance of pathogens or tumor cells by antibodies traditionally requires both Fab and Fc domains of IgG. Here, we show the Fc domain of IgG alone mediates recognition and clearance of herpes simplex virus (HSV1)-infected cells. The human natural killer (NK) cell surface is naturally coated with IgG bound by its Fc domain to the Fcγ receptor CD16a. NK cells utilize the Fc domain of bound IgG to recognize gE, an HSV1-encoded glycoprotein that also binds the Fc domain of IgG but at a site distinct from CD16a. The bridge formed by the Fc domain between the HSV1-infected cell and the NK cell results in NK cell activation and lysis of the HSV1-infected cell in the absence of HSV1-specific antibody in vitro and prevents fatal HSV1 infection in vivo. This mechanism also explains how bacterial IgG-binding proteins regulate NK cell function and may be broadly applicable to Fcγ-receptor-bearing cells.

GD2-directed CAR-T cells in combination with HGF-targeted neutralizing antibody (AMG102) prevent primary tumor growth and metastasis in Ewing sarcoma.

Ewing sarcoma (EWS) is the second most common and aggressive type of metastatic bone tumor in adolescents and young adults. There is unmet medical need to develop and test novel pharmacological targets and novel therapies to treat EWS. Here, we found that EWS expresses high levels of a p53 isoform, delta133p53. We further determined that aberrant expression of delta133p53 induced HGF secretion resulting in tumor growth and metastasis. Thereafter, we evaluated targeting EWS tumors with HGF receptor neutralizing antibody (AMG102) in preclinical studies. Surprisingly, we found that targeting EWS tumors with HGF receptor neutralizing antibody (AMG102) in combination with GD2-specific, CAR-reengineered T-cell therapy synergistically inhibited primary tumor growth and establishment of metastatic disease in preclinical models. Furthermore, our data suggested that AMG102 treatment alone might increase leukocyte infiltration including efficient CAR-T access into tumor mass and thereby improves its antitumor activity. Together, our findings warrant the development of novel CAR-T-cell therapies that incorporate HGF receptor neutralizing antibody to improve therapeutic potency, not only in EWS but also in tumors with aberrant activation of the HGF/c-MET pathway.

Immunotherapies for pediatric cancer: current landscape and future perspectives.

The advent of immunotherapy has revolutionized how we manage and treat cancer. While the majority of immunotherapy-related studies performed to date have focused on adult malignancies, a handful of these therapies have also recently found success within the pediatric space. In this review, we examine the immunotherapeutic agents that have achieved the approval of the US Food and Drug Administration for treating childhood cancers, highlighting their development, mechanisms of action, and the lessons learned from the seminal clinical trials that ultimately led to their approval. We also shine a spotlight on several emerging immunotherapeutic modalities that we believe are poised to have a positive impact on the treatment of pediatric malignancies in the near future.

Pediatric cancer research: Surviving COVID-19.

A diverse panel of pediatric cancer advocates and experts, whose collective experience spans the continuum of international academic medicine, industry, government research, and cancer advocacy, recently discussed challenges for pediatric cancer research in the context of coronavirus disease 2019 (COVID-19). Specifically, this special report addresses the following focus areas: (a) the critical role that translational research has played in transforming pediatric cancer outcomes; (b) the current and potential future impact of COVID-19 on pediatric cancer research; (c) target areas of COVID-19 research that may have application in immunity, oncogenesis, and therapeutic discovery; and (d) future considerations and directions in maintaining pediatric cancer research during and after COVID-19.

First-in-Human Intravenous Seprehvir in Young Cancer Patients: A Phase 1 Clinical Trial.

Seprehvir (HSV1716) is an oncolytic herpes simplex virus-1 (HSV-1) previously demonstrated to be well tolerated in pediatric patients when administered intratumorally. To determine the safety of administering Seprehvir systemically, we conducted the first-in-human phase I trial of intravenous injection in young patients with relapsed or refractory extra-cranial solid cancers. We delivered a single dose of 5 × 104 infectious units (iu)/kg (maximum dose of 2 × 106) or 2.5 × 105 iu/kg (maximum dose of 1 × 107 iu) of Seprehvir via the peripheral vein, monitored adverse events, and measured tumor responses by imaging. We monitored HSV-1 serology as well as viremia and shedding by PCR and culture. We administered a single dose of Seprehvir to seven patients and multiple doses to two patients. We did not observe any dose-limiting toxicities. All five HSV-1 seronegative patients seroconverted by day 28. Four of nine patients had detectable HSV-1 genomes in peripheral blood appearing on day +4 consistent with de novo virus replication. Two patients had stable disease in response to Seprehvir. Intravenous Seprehvir is well tolerated without viral shedding in children and young adults with late-stage cancer. Viremia consistent with virus replication holds promise for future Seprehvir studies at higher doses and/or in combination with other anti-neoplastic therapies.

Oncolytic Viruses and Their Potential as a Therapeutic Opportunity in Osteosarcoma.

Osteosarcoma remains an unmet medical need. Oncolytic viruses are gaining traction as novel cancer therapeutics. These viruses are either naturally nonpathogenic or engineered to be safe by specific genetic deletions yet retain the ability to infect and kill human cancer cells and elicit anticancer immunity. Some versions are being specifically designed and tested in patients with osteosarcoma, though due to their generalized mechanism of action most are being tested in patients across a broad range of cancer types. The activity of these viruses is impacted not only by the susceptibility of tumor cells to infection but also by the tumor microenvironment (TME) and by tumor immunogenicity. Here we review the field of oncolytic viruses with a particular emphasis on highlighting any available data in preclinical osteosarcoma models or in patients with osteosarcoma. While in general the viruses have been shown safe to administer to patients by a variety of routes, their therapeutic efficacy to date has been limited. Given the low rate of adverse events and the likely absence of long-term side effects, the utility of oncolytic viruses will most likely be realized when used in combination with other agents.

Immunotherapy for osteosarcoma: Where do we go from here?

Osteosarcoma is the most common bone tumor in children and young adults, with few advances in survival and treatment, especially for metastatic disease, in the last 30 years. Recently, immunotherapy has begun to show promise in various adult cancers, but the utility of this approach for osteosarcoma remains relatively unexplored. In this review, we outline the mechanisms and status of immunotherapies currently in clinical trials as well as future therapies on the horizon, and discuss their potential application for osteosarcoma.

Immune profiles of desmoplastic small round cell tumor and synovial sarcoma suggest different immunotherapeutic susceptibility upfront compared to relapse specimens.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) and synovial sarcoma are rare tumors with dismal outcomes requiring new therapeutic strategies. Immunotherapies have shown promise in several cancer types, but have not been evaluated in DSRCT and synovial sarcoma. Because the immune microenvironment can provide indications of the inflammatory nature of tumors, immunohistochemical staining is able to assess the tumor immune infiltrates in both tumor types. PROCEDURE: Using tissue microarrays of DSRCT and synovial sarcoma tumor samples, we detected tumoral HLA-A/B/C, beta-2-microglobulin(B2M), and PD-L1 expression, and quantified tumor-infiltrating lymphocytes expressing CD4, CD8, CD56, CD45RO, or FOXP3 by immunohistochemistry. We used staining intensity on a scale of 0-3 and percentage of tumor stained to determine HLA, B2M, and PD-L1 scores. We calculated the cytotoxic T lymphocyte (CTL) target score as HLA score × B2M score/100. RESULTS: In diagnostic samples, we found high HLA and CTL target scores and low PD-L1 expression with decreased scores in recurrence for both tumor types. We found an increase in CD56+ natural killer cells in DSRCT samples from diagnosis to recurrence. CONCLUSIONS: We found similar immunostimulatory profiles in DSRCT and synovial sarcoma. Our findings suggest that DSRCT and synovial sarcoma may be amenable to immunotherapies, albeit there was significant heterogeneity. Interestingly, HLA and CTL target scores decreased at recurrence, possibly reflecting immunoevasion. Our findings suggest both tumor types may be amendable to CTL-based therapies at diagnosis but less so at relapse. Our results support further investigation into the prognostic and predictive value of these findings in a larger dataset.

A multiyear quality improvement project to increase influenza vaccination in a pediatric oncology population undergoing active therapy.

BACKGROUND: In an effort to reduce morbidity and mortality from vaccine preventable influenza infection, national consensus guidelines recommend vaccination of patients who are immunocompromised as a result of receiving cancer therapy. Quality improvement (QI) processes are a proven method used to improve vaccination rates. PROCEDURE: We conducted a QI initiative aimed at increasing influenza vaccination in oncology patients undergoing active treatment. Primary drivers for the project focused on patient education, staff and provider education, and communication regarding vaccine-eligible patients. We performed a retrospective analysis of influenza infection among the vaccine-eligible population. This approach has validity at our institution because of the consistent follow-up and hospital admission pattern of cancer patients on active therapy such that nearly all follow-up care is delivered at our institution. RESULTS: We successfully achieved greater than 87% vaccination of eligible patients each vaccine season (September to March). During the recommended timeframe for delivering influenza vaccine between September and December of each vaccine season, we offered the vaccine to 100% of patients on active therapy and vaccinated >90%. Barriers to success, including vaccine refusals, increased late in the vaccine season. Influenza infection was documented in 0.5-7.3% of the vaccine-eligible group. CONCLUSION: A robust influenza vaccination program implemented using a standardized QI approach can sustain a high vaccination rate in a pediatric oncology population receiving active treatment. The influenza infection rate was under 10% in the vaccinated group.

Reduction of cyclophosphamide dose for patients with subset 2 low-risk rhabdomyosarcoma is associated with an increased risk of recurrence: A report from the Soft Tissue Sarcoma Committee of the Children's Oncology Group.

BACKGROUND: Failure-free survival (FFS) and overall survival (OS) rates were found to improve on Intergroup Rhabdomyosarcoma Study (IRS) IV (IRS-IV) compared with IRS-III for patients with subset 2 (IRS stage 1, group III nonorbit or stage 3, group I/II) low-risk embryonal rhabdomyosarcoma with the addition of cyclophosphamide (total cumulative cyclophosphamide dose of 26.4 g/m2 ) to the combination of vincristine and dactinomycin (VAC). The goal of Children's Oncology Group ARST0331 for subset 2 low-risk patients was to reduce the total cumulative cyclophosphamide dose without compromising FFS. METHODS: Therapy included 4 cycles of VAC (total cumulative cyclophosphamide dose of 4.8 g/m2 ) followed by 12 cycles of vincristine and dactinomycin over 46 weeks. Patients with group II or III tumors received radiotherapy, except for girls with group III vaginal tumors who enrolled before September 2009 and achieved a complete response with chemotherapy with or without delayed surgical resection. RESULTS: Among 66 eligible patients who were followed for a median of 3.5 years, there were 20 failures versus 10.53 expected failures. The estimated 3-year FFS and OS rates were 70% (95% confidence interval [95% CI], 57%-80%) and 92% (95% CI, 83%-97%), respectively. The estimated 3-year FFS rate was 57% (95% CI, 33%-75%) for girls with subset 2 genital tract embryonal rhabdomyosarcoma (21 patients) and 77% (95% CI, 61%-87%) for all other subset 2 patients (45 patients) (P = .02). CONCLUSIONS: The authors observed suboptimal FFS among patients with subset 2 low-risk rhabdomyosarcoma using reduced total cyclophosphamide. Eliminating radiotherapy for girls with group III vaginal tumors in combination with reduced total cyclophosphamide appeared to contribute to the suboptimal outcome. Cancer 2017;123:2368-2375. © 2017 American Cancer Society.

Preparation and Evaluation of a Novel Class of Amphiphilic Amines as Antitumor Agents and Nanocarriers for Bioactive Molecules.

PURPOSE: We describe a novel class of antitumor amphiphilic amines (RCn) based on a tricyclic amine hydrophilic head and a hydrophobic linear alkyl tail of variable length. METHODS: We tested the lead compound, RC16, for cytotoxicity and mechanism of cell death in several cancer cell lines, anti tumor efficacy in mouse tumor models, and ability to encapsulate chemotherapy drugs. RESULTS: These compounds displayed strong cytotoxic activity against cell lines derived from both pediatric and adult cancers. The IC50 of the lead compound, RC16, for normal cells including human keratinocytes, human fibroblasts and human umbilical vein endothelial cells was tenfold higher than for tumor cells. RC16 exhibited significant antitumor effects in vivo using several human xenografts and a metastatic model of murine neuroblastoma by both intravenous and oral administration routes. The amphiphilic character of RC16 triggered a spontaneous molecular self-assembling in water with formation of micelles allowing complexation of Doxorubicin, Etoposide and Paclitaxel. These micelles significantly improved the in vitro antitumor activity of these drugs as the enhancement of their aqueous solubility also improved their biologic availability. CONCLUSIONS: RC16 and related amphiphilic amines may be useful as a novel cancer treatment.

Characterization of MHC Class I and ß-2-Microglobulin Expression in Pediatric Solid Malignancies to Guide Selection of Immune-Based Therapeutic Trials.

BACKGROUND: Over 10,000 US children are diagnosed with cancer yearly. Though outcomes have improved by optimizing conventional therapies, recent immunotherapeutic successes in adult cancers are emerging. Cytotoxic T lymphocytes (CTLs) are the primary executioners of adaptive antitumor immunity and require antigenic presentation in the context of major histocompatibility complex (MHC) class I and the associated ß-2-microglobulin (B2M). Loss of MHC I expression is a common immune escape mechanism in adult malignancies, but pediatric cancers have not been thoroughly characterized. The essential nature of MHC I expression in CTL-mediated cell death may dictate the success of immunotherapies, which rely on eliciting an adaptive response. PROCEDURE: We queried pediatric tumor microarray databases for MHC I and B2M gene expression. We detected MHC I in pediatric tumor cell lines by flow cytometry and characterized MHC I and B2M expression in patient samples by immunohistochemistry. To determine whether therapeutic approaches might enhance MHC I expression in selected models in vitro, we tested effects of exposure to IFN-γ and histone deacetylase inhibitors. RESULTS: Pediatric tumors overall, as well as samples within select individual tumor subtypes, exhibit wide ranges of MHC I and B2M gene and protein expression. For most cell lines tested, MHC I was inducible in vitro. CONCLUSIONS: MHC I and B2M expression vary among pediatric tumor types and should be evaluated as potential biomarkers, which might identify patients most likely to benefit from MHC I dependent immunotherapies. Modulation of MHC I expression may be a promising mechanism for enhancing MHC I dependent immunotherapeutic efficacy.

Use of miRNA response sequences to block off-target replication and increase the safety of an unattenuated, glioblastoma-targeted oncolytic HSV.

Glioblastoma multiforme (GBM) is an aggressive brain cancer for which there is no effective treatment. Oncolytic HSV vectors (oHSVs) are attenuated lytic viruses that have shown promise in the treatment of human GBM models in animals, but their efficacy in early phase patient trials has been limited. Instead of attenuating the virus with mutations in virulence genes, we engineered four copies of the recognition sequence for miR-124 into the 3'UTR of the essential ICP4 gene to protect healthy tissue against lytic virus replication; miR-124 is expressed in neurons but not in glioblastoma cells. Following intracranial inoculation into nude mice, the miR-124-sensitive vector failed to replicate or show overt signs of pathogenesis. To address the concern that this safety feature may reduce oncolytic activity, we inserted the miR-124 response elements into an unattenuated, human receptor (EGFR/EGFRvIII)-specific HSV vector. We found that miR-124 sensitivity did not cause a loss of treatment efficiency in an orthotopic model of primary human GBM in nude mice. These results demonstrate that engineered miR-124 responsiveness can eliminate off-target replication by unattenuated oHSV without compromising oncolytic activity, thereby providing increased safety.

Phase 1 study of intratumoral Pexa-Vec (JX-594), an oncolytic and immunotherapeutic vaccinia virus, in pediatric cancer patients.

Pexa-Vec (pexastimogene devacirepvec, JX-594) is an oncolytic and immunotherapeutic vaccinia virus designed to destroy cancer cells through viral lysis and induction of granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven tumor-specific immunity. Pexa-Vec has undergone phase 1 and 2 testing alone and in combination with other therapies in adult patients, via both intratumoral and intravenous administration routes. We sought to determine the safety of intratumoral administration in pediatric patients. In a dose-escalation study using either 10(6) or 10(7) plaque-forming units per kilogram, we performed one-time injections in up to three tumor sites in five pediatric patients and two injections in one patient. Ages at study entry ranged from 4 to 21 years, and their cancer diagnoses included neuroblastoma, hepatocellular carcinoma, and Ewing sarcoma. All toxicities were ≤ grade 3. The most common side effects were sinus fever and sinus tachycardia. All three patients at the higher dose developed asymptomatic grade 1 treatment-related skin pustules that resolved within 3-4 weeks. One patient showed imaging evidence suggestive of antitumor biological activity. The two patients tested for cellular immunoreactivity to vaccinia antigens showed strong responses. Overall, our study suggests Pexa-Vec is safe to administer to pediatric patients by intratumoral administration and could be studied further in this patient population.

Nothing but NET: a review of norepinephrine transporter expression and efficacy of 131I-mIBG therapy.

Neuroblastoma is unique amongst common pediatric cancers for its expression of the norepinephrine transporter (NET), enabling tumor-selective imaging and therapy with radioactive analogues of norepinephrine. The majority of neuroblastoma tumors are avid for (123)I-metaiodobenzaguanidine (mIBG) on imaging, yet the therapeutic response to (131) I-mIBG is only 30% in clinical trials, and off-target effects cause short- and long-term morbidity. We review the contemporary understanding of the tumor-selective uptake, retention, and efflux of meta-iodobenzylguanidine (mIBG) and strategies currently in development for improving its efficacy. Combination treatment strategies aimed at enhancing NET are likely necessary to reach the full potential of (131)I-mIBG therapy.

Going back to class I: MHC and immunotherapies for childhood cancer.

After decades of unfulfilled promise, immunotherapies for cancer have reached a tipping point, with several FDA approved products now on the market and many more showing promise in both adult and pediatric clinical trials. Tumor cell expression of MHC class I has emerged as a potential determinant of the therapeutic success of many immunotherapy approaches. Here we review current knowledge regarding MHC class I expression in pediatric cancers including a discussion of prognostic significance, the opposing influence of MHC on T-cell versus NK-mediated therapies, and strategies to reverse or circumvent MHC down-regulation.

Phase I trial of Seneca Valley Virus (NTX-010) in children with relapsed/refractory solid tumors: a report of the Children's Oncology Group.

BACKGROUND: To determine the MTD of Seneca Valley Virus (NTX-010) in children with relapsed/refractory solid tumors. Patients (≥ 3-≤ 21 years) with neuroblastoma, rhabdomyosarcoma, or rare tumors with neuroendocrine features were eligible. PROCEDURE: Part A (single dose of NTX-010) enrolled 13 patients at three dose levels (1 × 10(9) viral particles (vp)/kg [n = 6], 1 × 10(10) vp/kg [n = 3], 1 × 10(11) vp/kg [n = 4]). Diagnoses included neuroblastoma (n = 9), rhabdomyosarcoma (n = 2), carcinoid tumor (n = 1), and adrenocorticocarcinoma (n = 1). Part B added cyclophosphamide (CTX) (oral CTX (25 mg/m(2) /day) days 1-14 and IV CTX (750 mg/m(2) ) days 8 and 29) to two doses of NTX-010 (1 × 10(11) vp/kg, days 8 and 29). Nine patients enrolled to Part B. Diagnoses included neuroblastoma (n = 3), rhabdomyosarcoma (n = 1), Wilms tumor (n = 3), and adrenocorticocarcinoma (n = 2). RESULTS: Twelve patients on Part A were evaluable for toxicity. There was a single DLT (grade 3 pain) at dose level 1. Additional grade ≥ 3 related adverse events (AEs) included leukopenia (n = 1), neutropenia (n = 3), lymphopenia (n = 3), and tumor pain (n = 1). No DLTs occurred on part B. Other grade ≥ 3 related AEs on Part B included: Leukopenia (n = 3), nausea (n = 1), emesis (n = 1), anemia (n = 1), neutropenia (n = 4), platelets (n = 1), alanine aminotransferase (n = 1), and lymphopenia (n = 2). All patients cleared NTX-010 from blood and stool by 3 weeks with 17/18 patients developing neutralizing antibodies. CONCLUSION: NTX-010 is feasible and tolerable at the dose levels tested in pediatric patients with relapsed/refractory solid tumors either alone or in combination with cyclophosphamide. However, despite the addition of cyclophosphamide, neutralizing antibodies appeared to limit applicability.

Radiation therapy may increase metastatic potential in alveolar rhabdomyosarcoma.

BACKGROUND: We previously determined that radiation could be safely administered using a mouse-flank in vivo model to both alveolar (Rh30) and embryonal (Rh18) rhabdomyosarcoma xenografts. Mice from both tumor lines in this experiment developed metastases, an event not previously described with these models. We sought to determine if radiation-induced changes in gene expression underlie an increase in the metastatic behavior of these tumor models. PROCEDURE: Parental Rh18 and Rh30 xenografts, as well as tumor that recurred locally after radiotherapy (Rh18RT and Rh30RT), were grown subcutaneously in the flanks of SCID mice and then subjected to either fractionated radiotherapy or survival surgery alone. Metastasis formation was monitored and recorded. Gene expression profiling was also performed on RNA extracted from parental, recurrent, and metastatic tissue of both tumor lines. RESULTS: Rh30 and Rh30RT xenografts demonstrated metastases only if they were exposed to fractionated radiotherapy, whereas Rh18 and Rh18RT xenografts experienced significantly fewer metastatic events when treated with fractionated radiotherapy compared to survival surgery alone. Mean time to metastasis formation was 40 days in the recurrent tumors and 73 days in the parental xenografts. Gene expression profiling noted clustering of Rh30 recurrent and metastatic tissue that was independent of the parental Rh30 tissue. Rh18RT xenografts lost radiosensitivity compared to parental Rh18. CONCLUSION: Radiation therapy can significantly decrease the formation of metastases in radio-sensitive tumors (Rh18) and may induce a more pro-metastatic phenotype in radio-resistant lines (Rh30).