Background: Chimeric antigen receptor (CAR)-based T cell therapy is in early clinical trials to target the neuroectodermal tumor, neuroblastoma. No preclinical or clinical efficacy data are available for retinoblastoma to date. Whereas unilateral intraocular retinoblastoma is cured by enucleation of the eye, infiltration of the optic nerve indicates potential diffuse scattering and tumor spread leading to a major therapeutic challenge. CAR-T cell therapy could improve the currently limited therapeutic strategies for metastasized retinoblastoma by simultaneously killing both primary tumor and metastasizing malignant cells and by reducing chemotherapy-related late effects. Methods: CD171 and GD2 expression was flow cytometrically analyzed in 11 retinoblastoma cell lines. CD171 expression and T cell infiltration (CD3⁺) was immunohistochemically assessed in retrospectively collected primary retinoblastomas. The efficacy of CAR-T cells targeting the CD171 and GD2 tumor-associated antigens was preclinically tested against three antigen-expressing retinoblastoma cell lines. CAR-T cell activation and exhaustion were assessed by cytokine release assays and flow cytometric detection of cell surface markers, and killing ability was assessed in cytotoxic assays. CAR constructs harboring different extracellular spacer lengths (short/long) and intracellular co-stimulatory domains (CD28/4-1BB) were compared to select the most potent constructs. Results: All retinoblastoma cell lines investigated expressed CD171 and GD2. CD171 was expressed in 15/30 primary retinoblastomas. Retinoblastoma cell encounter strongly activated both CD171-specific and GD2-specific CAR-T cells. Targeting either CD171 or GD2 effectively killed all retinoblastoma cell lines examined. Similar activation and killing ability for either target was achieved by all CAR constructs irrespective of the length of the extracellular spacers and the co-stimulatory domain. Cell lines differentially lost tumor antigen expression upon CAR-T cell encounter, with CD171 being completely lost by all tested cell lines and GD2 further down-regulated in cell lines expressing low GD2 levels before CAR-T cell challenge. Alternating the CAR-T cell target in sequential challenges enhanced retinoblastoma cell killing. Conclusion: Both CD171 and GD2 are effective targets on human retinoblastoma cell lines, and CAR-T cell therapy is highly effective against retinoblastoma in vitro. Targeting of two different antigens by sequential CAR-T cell applications enhanced tumor cell killing and preempted tumor antigen loss in preclinical testing.

Background Neuroblastoma is the most common extracranial solid tumor of childhood. Patients with high-risk disease undergo extremely aggressive therapy and nonetheless have cure rates below 50%. Treatment with the ch14.18 monoclonal antibody (dinutuximab beta), directed against the GD2 disialoganglioside, improved 5-year event-free survival in high-risk patients when administered in postconsolidation therapy and was recently implemented in standard therapy. Relapse still occurred in 57% of these patients, necessitating new therapeutic options. Bispecific trifunctional antibodies (trAbs) are IgG-like molecules directed against T cells and cancer surface antigens, redirecting T cells (via their CD3 specificity) and accessory immune cells (via their functioning Fc-fragment) toward tumor cells. We sought proof-of-concept for GD2/CD3-directed trAb efficacy against neuroblastoma. Methods We used two GD2-specific trAbs differing only in their CD3-binding specificity: EKTOMUN (GD2/human CD3) and SUREK (GD2/mouse Cd3). This allowed trAb evaluation in human and murine experimental settings. Tumor-blind trAb and the ch14.18 antibody were used as controls. A coculture model of human peripheral blood mononuclear cells (PBMCs) and neuroblastoma cell lines was established to evaluate trAb antitumor efficacy by assessing expression of T-cell surface markers for activation, proinflammatory cytokine release and cytotoxicity assays. Characteristics of tumor-infiltrating T cells and response of neuroblastoma metastases to SUREK treatment were investigated in a syngeneic immunocompetent neuroblastoma mouse model mimicking minimal residual disease. Results We show that EKTOMUN treatment caused effector cell activation and release of proinflammatory cytokines in coculture with neuroblastoma cell lines. Furthermore, EKTOMUN mediated GD2-dependent cytotoxic effects in human neuroblastoma cell lines in coculture with PBMCs, irrespective of the level of target antigen expression. This effect was dependent on the presence of accessory immune cells. Treatment with SUREK reduced the intratumor Cd4/Cd8 ratio and activated tumor infiltrating T cells in vivo. In a minimal residual disease model for neuroblastoma, we demonstrated that single-agent treatment with SUREK strongly reduced or eliminated neuroblastoma metastases in vivo. SUREK as well as EKTOMUN demonstrated superior tumor control compared with the anti-GD2 antibody, ch14.18. Conclusions Here we provide proof-of-concept for EKTOMUN preclinical efficacy against neuroblastoma, presenting this bispecific trAb as a promising new agent to fight neuroblastoma.

The immunosuppressive tumour microenvironment (TME) remains a central barrier to effective immunotherapy in solid tumours. We present a gene-therapeutic strategy that enables localized remodelling of the TME via tumour-intrinsic cytokine expression. Central to this approach is CancerPAM, a multi-omics bioinformatics pipeline that identifies and ranks patient-specific, tumour-exclusive CRISPR-Cas9 knock-in sites with high specificity and integration efficiency. Using neuroblastoma as a model, CancerPAM analysis of tumour sequencing data identifies optimal knock-in sites for pro-inflammatory cytokines (CXCL10, CXCL11, IFNG), and CancerPAM rankings correlate strongly with target-site specificity and knock-in efficiency, validating its predictive performance. CRISPR-mediated CXCL10 knock-in enhances CAR T cell infiltration and antitumour efficacy in vitro and in vivo, including humanized CD34⁺ HuNOG mice, where CXCL10-expressing tumours show stronger immune infiltration and prolonged tumour control within a reconstituted human immune microenvironment. Our findings establish a framework for safe and effective CRISPR-based cytokine delivery, integrating localized TME remodelling with cellular immunotherapies to enhance CAR T cells and other treatments in immune-refractory solid tumours.

Introduction: Despite advances in treating high-risk neuroblastoma, 50-60% of patients still suffer relapse, necessitating new treatment options. Bispecific trifunctional antibodies (trAbs) are a promising new class of immunotherapy. TrAbs are heterodimeric IgG-like molecules that bind CD3 and a tumor-associated antigen simultaneously, whereby inducing a TCR-independent anti-cancer T cell response. Moreover, via their functional Fc region they recruit and activate cells of the innate immune system like antigen-presenting cells potentially enhancing induction of adaptive tumor-specific immune responses.Methods: We used the SUREK trAb, which is bispecific for GD2 and murine Cd3. Tumor-blind trAb and the monoclonal ch14.18 antibody were used as controls. A co-culture model of murine dendritic cells (DCs), T cells and a neuroblastoma cell line was established to evaluate the cytotoxic effect and the T cell effector function in vitro. Expression of immune checkpoint molecules on tumor-infiltrating T cells and the induction of an anti-neuroblastoma immune response using a combination of whole cell vaccination and trAb therapy was investigated in a syngeneic immunocompetent neuroblastoma mouse model (NXS2 in A/J background). Finally, vaccinated mice were assessed for the presence of neuroblastoma-directed antibodies. We show that SUREK trAb-mediated effective killing of NXS2 cells in vitro was strictly dependent on the combined presence of DCs and T cells. Results: Using a syngeneic neuroblastoma mouse model, we showed that vaccination with irradiated tumor cells combined with SUREK trAb treatment significantly prolonged survival of tumor challenged mice and partially prevent tumor outgrowth compared to tumor vaccination alone. Treatment led to upregulation of programmed cell death protein 1 (Pd-1) on tumor infiltrating T cells and combination with anti-Pd-1 checkpoint inhibition enhanced the NXS2-directed humoral immune response.Conclusion: Here, we provide first preclinical evidence that a tumor vaccination combined with SUREK trAb therapy induces an endogenous anti-neuroblastoma immune response reducing tumor recurrence. Furthermore, a combination with anti-Pd-1 immune checkpoint blockade might even further improve this promising immunotherapeutic concept in order to prevent relapse in high-risk neuroblastoma patients.

Purine nucleoside phosphorylase (PNP) deficiency causes inadequate purine metabolite detoxification, which leads to combined immunodeficiency and variable neurologic symptoms. Hematopoietic stem cell transplantation (HSCT) cures the immunodeficiency, but large studies on the long-term outcomes are lacking. In a retrospective study of the European Society for Blood and Marrow Transplantation, we investigated 46 patients with PNP deficiency from 21 centers. We analyzed the presenting clinical signs and outcomes after HSCT. Cognition (0-3), hearing (0-3), interaction (0-4), movement (0-4), and occupation (0-3) (CHIMO) were scored at the last follow-up (FU) visit (no impairment, 17; mild, 15-16; moderate, 12-14; and severe impairment, 50%-100%)/low-level donor chimerism (11%-50%) was observed in 85%/15% of patients, respectively, leading to resolution of T lymphopenia. The median overall CHIMO score was 14 (6-17), while the median scores for each component were 3 (0-3), 3 (1-3), 4 (1-4), 3 (1-4), and 2 (0-3), respectively. Patients who underwent HSCT before 24 months after the initial presentation demonstrated superior OS (P = .049). Neurological symptoms that occurred before 11 months of age were associated with reduced OS (P = .027). While the overall results were satisfactory, earlier diagnosis could further improve outcomes.

Hematopoietic stem cell transplantation (HSCT) serves as a therapeutic intervention for various pediatric diseases. Acute and chronic graft-versus-host disease (GVHD) are decisive determinants for allogeneic HSCT success. The immunosuppressive agent, ciclosporin A, is most often used to prevent GVHD in pediatric patients, but is known to be nephrotoxic. Acute kidney injury afflicts 21-84% of pediatric HSCT cases, compromising clinical outcomes. This retrospective single-institution analysis scrutinized the practice of substituting nephrotoxic ciclosporin A with an everolimus/mycophenolate mofetil combination as GVHD prophylaxis in 57 patients with acute kidney injury (n=53) or central nervous system side effects due to calcineurin inhibitor treatment (n=4) following first allogeneic HSCT. This retrospective cohort study analyzes clinical courses in 57 children switched from calcineurin inhibitor-based GVHD prophylaxis (ciclosporin A or tacrolimus in single cases) to the everolimus/mycophenolate mofetil combination (n=48) or everolimus alone (n=9) after first allogeneic HSCT at the Charité University Medicine Berlin. Serving as control cohort were 74 patients undergoing first allogeneic HSCT during the same period, who did not receive everolimus at any date post-transplantation. Patients undergoing mismatched family donor transplantation without subsequent calcineurin inhibitor treatment for GVHD prophylaxis were excluded. Study endpoints encompassed the retention parameter course subsequent to GVHD prophylaxis switch, overall survival, incidence of underlying disease relapse and acute and chronic GVHD in both treatment groups. Renal function significantly improved after switching from ciclosporin A treatment to the everolimus/mycophenolate mofetil combination. Crucially, the transition to everolimus did not adversely affect overall survival following HSCT (HR 1.6; 95% CI: 0.74 - 3.5; p=0.23), especially for patients afflicted with non-malignant diseases (HR 1.4; 95% CI: 0.34 - 5.9; p=0.64). Incidences of grade 3-4 acute GVHD (HR: 1.82; 95% CI: 0.45 - 7.4; p=0.40) and severe chronic GVHD (HR 2.76, 95% CI: 0.69 - 11.0; p=0.15) in patients treated with the everolimus/mycophenolate mofetil combination were comparable to standard ciclosporin A treatment in patients in the control group. Overall survival in patients with malignant underlying diseases was lower in the everolimus cohort (HR: 2.7; 95% CI: 1.1 - 6.9, P=0.03), however, event-free survival was similar in patients with an underlying malignant disease, who were treated with either the everolimus/mycophenolate mofetil combination or ciclosporin A (HR 0.87, 95% CI: 0.39-1.9, p=0.73). Among patients who switched immunosuppression regimen from cyclosporin A to everolimus, with or without mycophenolate mofetil co-treatment after diagnosis of AKI, renal function significantly improved. Patient outcomes in the everolimus cohort were comparable to those in the control cohort. This study provides compelling real-world clinical evidence to replace ciclosporin A with the everolimus/mycophenolate mofetil combination in the management of acute kidney injury following HSCT in children.