Preclinical Development of CAR T Cells with Antigen-Inducible IL18 Enforcement to Treat GD2-Positive Solid Cancers.

PURPOSE: Cytokine-engineering of chimeric antigen receptor-redirected T cells (CAR T cells) is a promising principle to overcome the limited activity of canonical CAR T cells against solid cancers. EXPERIMENTAL DESIGN: We developed an investigational medicinal product, GD2IL18CART, consisting of CAR T cells directed against ganglioside GD2 with CAR-inducible IL18 to enhance their activation response and cytolytic effector functions in the tumor microenvironment. To allow stratification of patients according to tumor GD2 expression, we established and validated immunofluorescence detection of GD2 on paraffin-embedded tumor tissues. RESULTS: Lentiviral all-in-one vector engineering of human T cells with the GD2-specific CAR with and without inducible IL18 resulted in cell products with comparable proportions of CAR-expressing central memory T cells. Production of IL18 strictly depends on GD2 antigen engagement. GD2IL18CART respond to interaction with GD2-positive tumor cells with higher IFNγ and TNFα cytokine release and more effective target cytolysis compared with CAR T cells without inducible IL18. GD2IL18CART further have superior in vivo antitumor activity, with eradication of GD2-positive tumor xenografts. Finally, we established GMP-compliant manufacturing of GD2IL18CART and found it to be feasible and efficient at clinical scale. CONCLUSIONS: These results pave the way for clinical investigation of GD2IL18CART in pediatric and adult patients with neuroblastoma and other GD2-positive cancers (EU CT 2022-501725-21-00).

Inotuzumab ozogamicin combined with chemotherapy in pediatric B-cell precursor CD22+ acute lymphoblastic leukemia: results of the phase IB ITCC-059 trial.

Inotuzumab Ozogamicin (InO) is a CD22-directed antibody conjugated with calicheamicin. The Phase 1B of the ITCC-059 trial tested InO combined with chemotherapy in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Relapsed /refractory CD22+ BCP-ALL pediatric patients were enrolled. The primary objective was to establish the Recommended Phase 2 Dose (RP2D). Secondary objectives included preliminary efficacy and tolerability. InO was combined with 1.5 mg/m2 of vincristine (days 3, 10, 17, 24), 20 mg/m2 of dexamethasone (two 5-day blocks, then amended), and intrathecal therapy. A rolling-6 design was used testing InO from 0.8 to 1.8 mg/m2/cycle. Between May-2020 and Apr-2022, 30 patients were treated, and 29 were evaluable for dose limiting toxicities (DLTs). At 1.1 mg/m2/cycle, two out of four patients had DLTs (liver toxicity). InO was de-escalated to 0.8 mg/m2/cycle (n=6) without DLTs while awaiting a protocol amendment to reduce dexamethasone dose to 10 mg/m2. Post amendment, InO was re-escalated to 1.1 mg/m2/cycle (n=6, 1 DLT), then to 1.4 mg/m2/cycle (n=3, no DLTs), and finally to 1.8 mg/m2/cycle (n=7, 1 DLT). Three additional patients were treated in an expansion cohort. The pooled response rate was 80% (24/30; 95%CI: 61.4% to 92.3%) and, among responders, 66.7% achieved minimal residual disease negativity. The RP2D of InO combined with vincristine, dexamethasone and IT therapy was declared at 1.8 mg/m2/cycle (1.5 mg/m2/cycle after remission) in a fractionated schedule. This combination showed an response rate similar to the single agent cohorts of this trial, with liver toxicity issues at the initial higher dexamethasone dose. #NTR5736.

Stopping antibacterial prophylaxis in pediatric allogeneic hematopoietic cell transplantation: An internal audit.

BACKGROUND: Antibacterial prophylaxis in children and adolescents undergoing allogeneic hematopoietic cell transplantation (HCT) is controversial and not recommended by international guidelines. We analyzed relevant posttransplant outcomes following discontinuation of antibacterial prophylaxis at a major European pediatric transplant center. METHODS: The single-center retrospective audit included all pediatric allogeneic HCT patients (pts) transplanted between 2011 and 2020 before (≤2014) and after (≥2015) stopping routine antibacterial prophylaxis with penicillin, metronidazole, and ciprofloxacin upon start of the conditioning regimen. The primary endpoint was overall survival until the first hospital discharge. Secondary endpoints included the occurrence of fever; bacterial infections; and cumulative days with antibacterial agents until discharge. RESULTS: A total of 257 HCT procedures were performed in 249 pts (median age: 10 years, range, 0.2-22.5) for leukemia/lymphoma (n = 150) and nonmalignant disorders (n = 107). Of these, 104 procedures were performed before (cohort 1) and 153 after (cohort 2) stopping prophylaxis. Overall survival until discharge was 90.4% in cohort 1 and 96.1% in cohort 2 (p = .06). No differences were observed in the occurrence of fever (92.3 vs. 94.1%; p = .57) and bacterial infections (34.6 vs. 25.5%; p = .11). The median number of days on antibacterial agents was significantly lower in cohort 2 (39 vs. 34; p = .002). Detection rates of resistant organisms were overall low. CONCLUSION: In this single-center audit, the stop of routine antibacterial prophylaxis had no effect on the occurrence of fever, bacterial infections, resistant organisms, and GVHD. Overall antibiotic use was significantly reduced, and survival was noninferior to the historical control cohort.

INSPIRED Symposium Part 4A: Access to CAR T Cell Therapy in Unique Populations with B Cell Acute Lymphoblastic Leukemia.

The approval of tisagenlecleucel (tisa-cel) for use in children with B cell acute lymphoblastic leukemia (B-ALL) was based on the phase 2 ELIANA trial, a global registration study. However, the ELIANA trial excluded specific subsets of patients facing unique challenges and did not include a sufficient number of patients to adequately evaluate outcomes in rare subpopulations. Since the commercialization of tisa-cel, data have become available that support therapeutic indications beyond the specific cohorts previously eligible for chimeric antigen receptor (CAR) T cells targeted to CD19 (CD19 CAR-T) therapy on the registration clinical trial. Substantial real-world data and aggregate clinical trial data have addressed gaps in our understanding of response rates, longer-term efficacy, and toxicities associated with CD19 CAR-T in special populations and rare clinical scenarios. These include patients with central nervous system relapsed disease, who were excluded from ELIANA and other early CAR-T trials owing to concerns about risk of neurotoxicity that have not been born out. There is also interest in the use of CD19 CAR-T for very-high-risk patients earlier in the course of therapy, such as patients with persistent minimal residual disease after 2 cycles of upfront chemotherapy and patients with first relapse of B-ALL. However, these indications are not specified on the label for tisa-cel and historically were not included in eligibility criteria for most clinical trials; data addressing these populations are needed. Populations at high risk of relapse, including patients with high-risk cytogenetic lesions, infants with B-ALL, patients with trisomy 21, and young adults with B-ALL, also may benefit from earlier treatment with CD19 CAR-T. It is important to prospectively study patient-reported outcomes given the differential toxicity expected between CD19 CAR-T and the historic standard of care, hematopoietic cell transplantation. Now that CD19 CAR-T therapy is commercially available, studies evaluating potential access disparities created by this very expensive novel therapy are increasingly pressing.

CAR T cells as micropharmacies against solid cancers: Combining effector T-cell mediated cell death with vascular targeting in a one-step engineering process.

To enhance the potency of chimeric antigen receptor (CAR) engineered T cells in solid cancers, we designed a novel cell-based combination strategy with an additional therapeutic mode of action. CAR T cells are used as micropharmacies to produce a targeted pro-coagulatory fusion protein, truncated tissue factor (tTF)-NGR, which exerts pro-coagulatory activity and hypoxia upon relocalization to the vascular endothelial cells that invade tumor tissues. Delivery by CAR T cells aimed to induce locoregional tumor vascular infarction for combined immune-mediated and hypoxic tumor cell death. Human T cells that were one-vector gene-modified to express a GD2-specific CAR along with CAR-inducible tTF-NGR exerted potent GD2-specific effector functions while secreting tTF-NGR that activates the extrinsic coagulation pathway in a strictly GD2-dependent manner. In murine models, the CAR T cells infiltrated GD2-positive tumor xenografts, secreted tTF-NGR into the tumor microenvironment and showed a trend towards superior therapeutic activity compared with control cells producing functionally inactive tTF-NGR. In vitro evidence supports a mechanism of hypoxia-mediated enhancement of T cell cytolytic activity. We conclude that combined CAR T cell targeting with an additional mechanism of antitumor action in a one-vector engineering strategy is a promising approach to be further developed for targeted treatment of solid cancers.

Specific and safe targeting of glioblastoma using switchable and logic-gated RevCAR T cells.

Glioblastoma (GBM) is still an incurable tumor that is associated with high recurrence rate and poor survival despite the current treatment regimes. With the urgent need for novel therapeutic strategies, immunotherapies, especially chimeric antigen receptor (CAR)-expressing T cells, represent a promising approach for specific and effective targeting of GBM. However, CAR T cells can be associated with serious side effects. To overcome such limitation, we applied our switchable RevCAR system to target both the epidermal growth factor receptor (EGFR) and the disialoganglioside GD2, which are expressed in GBM. The RevCAR system is a modular platform that enables controllability, improves safety, specificity and flexibility. Briefly, it consists of RevCAR T cells having a peptide epitope as extracellular domain, and a bispecific target module (RevTM). The RevTM acts as a switch key that recognizes the RevCAR epitope and the tumor-associated antigen, and thereby activating the RevCAR T cells to kill the tumor cells. However, in the absence of the RevTM, the RevCAR T cells are switched off. In this study, we show that the novel EGFR/GD2-specific RevTMs can selectively activate RevCAR T cells to kill GBM cells. Moreover, we show that gated targeting of GBM is possible with our Dual-RevCAR T cells, which have their internal activation and co-stimulatory domains separated into two receptors. Therefore, a full activation of Dual-RevCAR T cells can only be achieved when both receptors recognize EGFR and GD2 simultaneously via RevTMs, leading to a significant killing of GBM cells both in vitro and in vivo.

Parvovirus B19 infection in pediatric allogeneic hematopoietic cell transplantation - Single-center experience and review.

BACKGROUND: Parvovirus B19 (B19V) infection following pediatric hematopoietic cell transplantation (HCT) is a rare complication and available data is scarce. Therefore, we present the experience with B19V Infection in allogeneic pediatric HCT recipients at our transplant center together with a systematic review of the literature. METHODS: Pediatric HCT patients with Parvovirus B19 infection treated at the University Children's Hospital Münster between 1999 and 2021 were retrospectively identified and clinical data were analyzed. Additionally, a systematic MEDLINE search to identify relevant articles was performed. RESULTS: We identified three out of 445 patients (0.6%) with B19V infection post-transplantation. B19V infection occurred in combination with other complications like Graft-versus-Host disease, additional infections, or autoimmune-mediated hemolysis potentially triggered by B19V. In one patient these complications lead to a fatal outcome. The review of the literature showed considerable morbidity of B19V infection with the potential for life-threatening complications. Most patients were treated by red blood cell transfusion and intravenous immunoglobulins (IVIG) with a high succession rate. CONCLUSION: Symptomatic B19V infection following HCT remains a rare but potentially challenging complication. A causal antiviral therapy does not exist as well as general recommendations on dosage and duration of IVIG therapy. Despite this, most patients are treated successfully with these measures. Additionally, transmission via blood or stem cell products is also rare and no general recommendations on B19V screenings exist.

CD19 CAR T cells are an effective therapy for posttransplant relapse in patients with B-lineage ALL: real-world data from Germany.

Patients with precursor B-cell acute lymphoblastic leukemia (pB-ALL) who have relapsed after allogeneic hematopoietic stem cell transplantation (allo-HSCT), have relapsed more than once, or are resistant upfront have a dismal prognosis. CD19-targeted chimeric antigen receptor (CAR) T cells have evolved as potent immune therapies. Tisagenlecleucel (Tisa-cel) is a commercially available autologous CD19-directed CAR T-cell product. We performed a retrospective study inviting all CAR T-cell centers in Germany to participate. Eighty-one patients with pB-ALL were included. Twenty-eight days after CAR T-cell infusion, 71 patients (87.7%) were in complete response, and 8 (9.9%) were in nonremission. At 2 years, the probabilities of event-free survival (pEFS), relapse-free survival (pRFS), and overall survival (pOS) were 45.3%, 51.7%, and 53.2%, respectively. pEFS was not different in patients without (n = 16, 55.0%) vs with prior allo-HSCT (n = 65, 43.4%). In patients treated after allo-HSCT, the time to relapse after allo-HSCT was a strong predictor of outcome. Patients relapsing within 6 months of allo-HSCT had a disappointing pEFS of 18.4% (pOS = 16.0%); the pEFS for those relapsing later was 55.5% (pOS = 74.8%). Our study provides real-world experience in pediatric, adolescent, and young adult patients with ALL treated with Tisa-cel, where most patients were treated after having relapsed after allo-HSCT. A total of 45.3% were rescued with a single dose of Tisa-cel. Our novel finding that patients with ALL after allo-HSCT had by far a better pEFS if relapse occurred beyond 6 months might be helpful in clinical decision-making and motivates studies to uncover the reasons.

Electrostatic anti-CD33-antibody-protamine nanocarriers as platform for a targeted treatment of acute myeloid leukemia.

BACKGROUND: Acute myeloid leukemia (AML) is a fatal clonal hematopoietic malignancy, which results from the accumulation of several genetic aberrations in myeloid progenitor cells, with a worldwide 5-year survival prognosis of about 30%. Therefore, the development of more effective therapeutics with novel mode of action is urgently demanded. One common mutated gene in the AML is the DNA-methyltransferase DNMT3A whose function in the development and maintenance of AML is still unclear. To specifically target "undruggable" oncogenes, we initially invented an RNAi-based targeted therapy option that uses the internalization capacity of a colorectal cancer specific anti-EGFR-antibody bound to cationic protamine and the anionic siRNA. Here, we present a new experimental platform technology of molecular oncogene targeting in AML. METHODS: Our AML-targeting system consists of an internalizing anti-CD33-antibody-protamine conjugate, which together with anionic molecules such as siRNA or ibrutinib-Cy3.5 and cationic free protamine spontaneously assembles into vesicular nanocarriers in aqueous solution. These nanocarriers were analyzed concerning their physical properties and relevant characteristics in vitro in cell lines and in vivo in xenograft tumor models and patient-derived xenograft leukemia models with the aim to prepare them for translation into clinical application. RESULTS: The nanocarriers formed depend on a balanced electrostatic combination of the positively charged cationic protamine-conjugated anti-CD33 antibody, unbound cationic protamine and the anionic cargo. This nanocarrier transports its cargo safely into the AML target cells and has therapeutic activity against AML in vitro and in vivo. siRNAs directed specifically against two common mutated genes in the AML, the DNA-methyltransferase DNMT3A and FLT3-ITD lead to a reduction of clonal growth in vitro in AML cell lines and inhibit tumor growth in vivo in xenotransplanted cell lines. Moreover, oncogene knockdown of DNMT3A leads to increased survival of mice carrying leukemia patient-derived xenografts. Furthermore, an anionic derivative of the approved Bruton's kinase (BTK) inhibitor ibrutinib, ibrutinib-Cy3.5, is also transported by this nanocarrier into AML cells and decreases colony formation. CONCLUSIONS: We report important results toward innovative personalized, targeted treatment options via electrostatic nanocarrier therapy in AML.

Correlation of Transcriptomics and FDG-PET SUVmax Indicates Reciprocal Expression of Stemness-Related Transcription Factor and Neuropeptide Signaling Pathways in Glucose Metabolism of Ewing Sarcoma.

BACKGROUND: In Ewing sarcoma (EwS), long-term treatment effects and poor survival rates for relapsed or metastatic cases require individualization of therapy and the discovery of new treatment methods. Tumor glucose metabolic activity varies significantly between patients, and FDG-PET signals have been proposed as prognostic factors. However, the biological basis for the generally elevated but variable glucose metabolism in EwS is not well understood. METHODS: We retrospectively included 19 EwS samples (17 patients). Affymetrix gene expression was correlated with maximal standardized uptake value (SUVmax) using machine learning, linear regression modelling, and gene set enrichment analyses for functional annotation. RESULTS: Expression of five genes correlated (MYBL2, ELOVL2, NETO2) or anticorrelated (FAXDC2, PLSCR4) significantly with SUVmax (adjusted p-value ≤ 0.05). Additionally, we identified 23 genes with large SUVmax effect size, which were significantly enriched for "neuropeptide Y receptor activity (GO:0004983)" (adjusted p-value = 0.0007). The expression of the members of this signaling pathway (NPY, NPY1R, NPY5R) anticorrelated with SUVmax. In contrast, three transcription factors associated with maintaining stemness displayed enrichment of their target genes with higher SUVmax: RNF2, E2F family, and TCF3. CONCLUSION: Our large-scale analysis examined comprehensively the correlations between transcriptomics and tumor glucose utilization. Based on our findings, we hypothesize that stemness may be associated with increased glucose uptake, whereas neuroectodermal differentiation may anticorrelate with glucose uptake.

Relevance of Abnormal KCNN1 Expression and Osmotic Hypersensitivity in Ewing Sarcoma.

Ewing sarcoma (EwS) is a rare and highly malignant bone tumor occurring mainly in childhood and adolescence. Physiologically, the bone is a central hub for Ca2+ homeostasis, which is severely disturbed by osteolytic processes in EwS. Therefore, we aimed to investigate how ion transport proteins involved in Ca2+ homeostasis affect EwS pathophysiology. We characterized the expression of 22 candidate genes of Ca2+-permeable or Ca2+-regulated ion channels in three EwS cell lines and found the Ca2+-activated K+ channel KCa2.1 (KCNN1) to be exceptionally highly expressed. We revealed that KCNN1 expression is directly regulated by the disease-driving oncoprotein EWSR1-FL1. Due to its consistent overexpression in EwS, KCNN1 mRNA could be a prognostic marker in EwS. In a large cohort of EwS patients, however, KCNN1 mRNA quantity does not correlate with clinical parameters. Several functional studies including patch clamp electrophysiology revealed no evidence for KCa2.1 function in EwS cells. Thus, elevated KCNN1 expression is not translated to KCa2.1 channel activity in EwS cells. However, we found that the low K+ conductance of EwS cells renders them susceptible to hypoosmotic solutions. The absence of a relevant K+ conductance in EwS thereby provides an opportunity for hypoosmotic therapy that can be exploited during tumor surgery.

Osteosarcoma and causes of death: A report of 1520 deceased patients from the Cooperative Osteosarcoma Study Group (COSS).

PURPOSE: Most aspects of osteosarcoma have been addressed in detail, but there is no comprehensive analysis of deceased patients and causes of death. METHODS: The database of the Cooperative Osteosarcoma Study Group COSS (1980-03/31/2021; 4475 registered high-grade central osteosarcoma patients) was searched deaths from any cause. Affected patients were analyzed for demographic and baseline variables and disease-status at the time of demise. Deaths from causes other than osteosarcoma were analyzed in detail. RESULTS: A total of 1520 deceased patients were identified (median age (range) at osteosarcoma diagnosis 16 (2-78) years; 908 (59.7%) male, 612 (40.3%) female; primary tumor: extremities 1263 (83.1%), trunk 208 (13.7%), craniofacial 47 (3.1%) (site unknown 2); metastases at registration: absent 1.051 (69.1%), present 466 (30.7%) (3 no data). The median time from diagnosis to death was 2.22 (0.08-32.02) years. 1286 (84.6%) patients succumbed to osteosarcoma (370 without achieving complete remission, 488 first, 428 more than one recurrences), 146 (9.6%) to other, 88 (5.8%) to unknown causes. Chemotherapy-related infections (40), secondary malignancies (39), and perioperative complications (19) were among the most frequent potentially treatment-related causes, and high-dose methotrexate (19), doxorubicin (17), and ifosfamide (15) were the drugs most commonly held responsible. Patients with unknown causes of death had an unusually long median follow-up. CONCLUSION: The major cause of death of patients after osteosarcoma is this malignancy, mostly from one of its multiple relapses. However, almost 10% of fatalities are due to other documented causes. Some of these deaths may be preventable with the knowledge gained from comprehensive analyses such as this.

Cobimetinib in Pediatric and Young Adult Patients with Relapsed or Refractory Solid Tumors (iMATRIX-cobi): A Multicenter, Phase I/II Study.

BACKGROUND: The MAPK pathway is an emerging target across a number of adult and pediatric tumors. Targeting the downstream effector of MAPK, MEK1, is a proposed strategy to control the growth of MAPK-dependent tumors. OBJECTIVE: iMATRIX-cobi assessed the safety, pharmacokinetics, and anti-tumor activity of cobimetinib, a highly selective MEK inhibitor, in children and young adults with relapsed/refractory solid tumors. PATIENTS AND METHODS: This multicenter Phase I/II study enrolled patients aged 6 months to < 30 years with solid tumors with known/expected MAPK pathway involvement. Patients received cobimetinib tablet or suspension formulation on Days 1-21 of a 28-day cycle. Dose escalation followed a rolling 6 design. The primary endpoint was safety; secondary endpoints were pharmacokinetics and anti-tumor activity. RESULTS: Of 56 enrolled patients (median age 9 years [range 3-29]), 18 received cobimetinib tablets and 38 cobimetinib suspension. Most common diagnoses were low-grade glioma (LGG; n = 32, including n = 12 in the expansion cohort) and plexiform neurofibroma within neurofibromatosis type 1 (n = 12). Six patients (11 %) experienced dose-limiting toxicities (including five ocular toxicity events), which established a pediatric recommended Phase II dose (RP2D) of 0.8 mg/kg tablet and 1.0 mg/kg suspension. Most frequently reported treatment-related adverse events were gastrointestinal and skin disorders. Steady state mean exposure (Cmax, AUC0-24) of cobimetinib at the RP2D (1.0 mg/kg suspension) was ~ 50 % lower than in adults receiving the approved 60 mg/day dose. Overall response rate was 5.4 % (3/56; all partial responses in patients with LGG). CONCLUSIONS: The safety profile of cobimetinib in pediatrics was similar to that reported in adults. Clinical activity was observed in LGG patients with known/suspected MAPK pathway activation. Cobimetinib combination regimens may be required to improve response rates in this pediatric population. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT02639546, registered December 24, 2015.

SS18-SSX drives CREB activation in synovial sarcoma.

PURPOSE: Synovial sarcoma (SySa) is a rare soft tissue tumor characterized by a reciprocal t(X;18) translocation. The chimeric SS18-SSX fusion protein represents the major driver of the disease, acting as aberrant transcriptional dysregulator. Oncogenic mechanisms whereby SS18-SSX mediates sarcomagenesis are incompletely understood, and strategies to selectively target SySa cells remain elusive. Based on results of Phospho-Kinase screening arrays, we here investigate the functional and therapeutic relevance of the transcription factor CREB in SySa tumorigenesis. METHODS: Immunohistochemistry of phosphorylated CREB and its downstream targets (Rb, Cyclin D1, PCNA, Bcl-xL and Bcl-2) was performed in a large cohort of SySa. Functional aspects of CREB activity, including SS18-SSX driven circuits involved in CREB activation, were analyzed in vitro employing five SySa cell lines and a mesenchymal stem cell model. CREB mediated transcriptional activity was modulated by RNAi-mediated knockdown and small molecule inhibitors (666-15, KG-501, NASTRp and Ro 31-8220). Anti-proliferative effects of the CREB inhibitor 666-15 were tested in SySa avian chorioallantoic membrane and murine xenograft models in vivo. RESULTS: We show that CREB is phosphorylated and activated in SySa, accompanied by downstream target expression. Human mesenchymal stem cells engineered to express SS18-SSX promote CREB expression and phosphorylation. Conversely, RNAi-mediated knockdown of SS18-SSX impairs CREB phosphorylation in SySa cells. Inhibition of CREB activity reduces downstream target expression, accompanied by suppression of SySa cell proliferation and induction of apoptosis in vitro and in vivo. CONCLUSION: In conclusion, our data underline an essential role of CREB in SySa tumorigenesis and provides evidence for molecular targeted therapies.

The Cellular Tumor Immune Microenvironment of Childhood Solid Cancers: Informing More Effective Immunotherapies.

Common pediatric solid cancers fail to respond to standard immuno-oncology agents relying on preexisting adaptive antitumor immune responses. The adoptive transfer of tumor-antigen specific T cells, such as CAR-gene modified T cells, is an attractive strategy, but its efficacy has been limited. Evidence is accumulating that local barriers in the tumor microenvironment prevent the infiltration of T cells and impede therapeutic immune responses. A thorough understanding of the components of the functional compartment of the tumor microenvironment and their interaction could inform effective combination therapies and novel engineered therapeutics, driving immunotherapy towards its full potential in pediatric patients. This review summarizes current knowledge on the cellular composition and significance of the tumor microenvironment in common extracranial solid cancers of childhood and adolescence, such as embryonal tumors and bone and soft tissue sarcomas, with a focus on myeloid cell populations that are often present in abundance in these tumors. Strategies to (co)target immunosuppressive myeloid cell populations with pharmacological anticancer agents and with selective antagonists are presented, as well as novel concepts aiming to employ myeloid cells to cooperate with antitumor T cell responses.

Targeting CD10 on B-Cell Leukemia Using the Universal CAR T-Cell Platform (UniCAR).

Chimeric antigen receptor (CAR)-expressing T-cells are without a doubt a breakthrough therapy for hematological malignancies. Despite their success, clinical experience has revealed several challenges, which include relapse after targeting single antigens such as CD19 in the case of B-cell acute lymphoblastic leukemia (B-ALL), and the occurrence of side effects that could be severe in some cases. Therefore, it became clear that improved safety approaches, and targeting multiple antigens, should be considered to further improve CAR T-cell therapy for B-ALL. In this paper, we address both issues by investigating the use of CD10 as a therapeutic target for B-ALL with our switchable UniCAR system. The UniCAR platform is a modular platform that depends on the presence of two elements to function. These include UniCAR T-cells and the target modules (TMs), which cross-link the T-cells to their respective targets on tumor cells. The TMs function as keys that control the switchability of UniCAR T-cells. Here, we demonstrate that UniCAR T-cells, armed with anti-CD10 TM, can efficiently kill B-ALL cell lines, as well as patient-derived B-ALL blasts, thereby highlighting the exciting possibility for using CD10 as an emerging therapeutic target for B-cell malignancies.

Using stroma-anchoring cytokines to augment ADCC: a phase 1 trial of F16IL2 and BI 836858 for posttransplant AML relapse.

Natural killer (NK) cells are key effectors in cancer immunosurveillance and posttransplant immunity, but deficiency of environmental signals and insufficient tumor recognition may limit their activity. We hypothesized that the antibody-mediated anchoring of interleukin-2 (IL-2) to a spliced isoform of the extracellular matrix (ECM) glycoprotein tenascin-C would potentiate NK-cell-mediated antibody-dependent cellular cytotoxicity against leukemic blasts. In this novel-novel combination, dose-escalation, phase 1 trial, we enrolled patients with posttransplant acute myeloid leukemia (AML) relapse to evaluate the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of the antibody-cytokine fusion F16IL2 (10 × 106 to 20 × 106 IU IV; days 1, 8, 15, and 22 of each 28-day cycle) in combination with the anti-CD33 antibody BI 836858 (10-40 mg IV, 2 days after each F16IL2 infusion). Among the 15 patients (median [range] age, 50 [20-68] years) treated across 4 dose levels (DLs), 6 (40%) had received 2 or 3 prior transplantations. The most frequent adverse events were pyrexia, chills, and infusion-related reactions, which were manageable, transient and of grade ≤2. One dose-limiting toxicity occurred at each of DLs 3 (pulmonary edema) and 4 (graft-versus-host disease). Three objective responses were observed among 7 patients treated at the 2 higher DLs, whereas no responses occurred at the 2 starting DLs. Combination therapy stimulated the expansion and activation of NK cells, including those expressing the FcγRIIIA/CD16 receptor. ECM-targeted IL-2 combined with anti-CD33 immunotherapy represents an innovative approach associated with acceptable safety and encouraging biologic and clinical activity in posttransplant AML relapse. This trial was registered at EudraCT as 2015-004763-37.

Inotuzumab ozogamicin as single agent in pediatric patients with relapsed and refractory acute lymphoblastic leukemia: results from a phase II trial.

Inotuzumab Ozogamicin is a CD22-directed antibody conjugated to calicheamicin, approved in adults with relapsed or refractory (R/R) B cell acute lymphoblastic leukemia (BCP-ALL). Patients aged 1-18 years, with R/R CD22 + BCP-ALL were treated at the RP2D of 1.8 mg/m2. Using a single-stage design, with an overall response rate (ORR) ≤ 30% defined as not promissing and ORR > 55% as expected, 25 patients needed to be recruited to achieve 80% power at 0.05 significance level. Thirty-two patients were enrolled, 28 were treated, 27 were evaluable for response. The estimated ORR was 81.5% (95%CI: 61.9-93.7%), and 81.8% (18/22) of the responding subjects were minimal residual disease (MRD) negative. The study met its primary endpoint. Median follow up of survivors was 16 months (IQR: 14.49-20.07). One year Event Free Survival was 36.7% (95% CI: 22.2-60.4%), and Overall Survival was 55.1% (95% CI: 39.1-77.7%). Eighteen patients received consolidation (with HSCT and/or CAR T-cells therapy). Sinusoidal obstructive syndrome (SOS) occurred in seven patients. MRD negativity seemed correlated to calicheamicin sensitivity in vitro, but not to CD22 surface expression, saturation, or internalization. InO was effective in this population. The most relevant risk was the occurrence of SOS, particularly when InO treatment was followed by HSCT.

CD19 CAR T-cells for pediatric relapsed acute lymphoblastic leukemia with active CNS involvement: a retrospective international study.

Relapse of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) may occur in the central nervous system (CNS). Most clinical trials of CAR T-cell therapy excluded patients with active CNS leukemia, partially for concerns of neurotoxicity. Here, we report an international study of fifty-five children and adolescents who received CAR T-cell therapy for relapsed BCP-ALL with CNS involvement at the time of referral. All patients received bridging therapy, 16 still having active CNS disease at the time of lymphodepletion. Twelve patients received CD28-based CAR T-cells, 9 being subsequently treated with allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Forty-three patients received 4-1BB-based CAR T-cells. Cytokine-release syndrome (CRS) and neurotoxicity occurred in 65% and 38% of patients, respectively, more frequently following treatment with CD28-based CARs. Fifty-one of 54 evaluable patients (94%) achieved complete response following this therapy. Relapse occurred in 22 patients: 19/43 following 4-1BB-based CARs (12 CNS relapses), and 3/12 after CD28-based CARs with subsequent HSCT (no CNS relapse). Patients treated with tisagenlecleucel for an isolated CNS relapse had a high incidence of a subsequent CNS relapse (6 of 8). CAR T-cells were found to be effective in this cohort, though the risk of CNS relapse was not completely mitigated by this approach.