CD40 ligation has been shown to induce antitumor effects in mice and cancer patients. Most of the studies have focused on the ability of an agonistic anti-CD40 mAb to either directly kill CD40-positive tumor cells or activate T-cell immune responses. In this review the authors focus on the ability of CD40 ligation to activate antitumor effector mechanisms of the cells of innate immunity such as macrophages and NK cells.

Phase I testing of the hu14.18-IL2 immunocytokine in melanoma patients (pts) showed immune activation, reversible toxicities, and a maximal tolerated dose of 7.5 mg/m2/day. In this phase II study, fourteen pts with measurable metastatic melanoma were scheduled to receive hu14.18-IL2 at 6 mg/m2/day as 4-hour intravenous infusions on days 1, 2 and 3 of each 28 day cycle. Pts with stable disease (SD) or regression following cycle 2 could receive 2 additional treatment cycles. The primary objective was to evaluate anti-tumor activity and response duration. Secondary objectives evaluated adverse events and immunologic activation. All pts received 2 cycles of treatment. One pt had a partial response (PR) [1 PR of 14 pts = response rate of 7.1%; confidence interval 0.2%−33.9%] and 4 pts had SD and received cycles 3 & 4. The PR and SD responses lasted 3–4 months. All toxicities were reversible and those resulting in dose reduction included grade 3 hypotension (2 pts) and grade 2 renal insufficiency with oliguria (1 pt). Pts had a peripheral blood lymphocytosis on day 8 and increased C-reactive protein. While one PR in 14 pts met protocol criteria to proceed to stage 2 and enter 16 additional pts, we suspended stage 2 due to limited availability of hul 4.18-IL2 at that time and the brief duration of PR and SD. We conclude that subsequent testing of hu14.18-IL2 should involve melanoma patients with minimal residual disease based on compelling preclinical data and the confirmed immune activation with some antitumor activity in this study.

Autologous melanoma associated antigens (MAA) on murine melanoma cells can elicit a protective anti-tumor immune response following a variety of vaccine strategies. Most require effective uptake by antigen presenting cells (APC). APC transport and process internalized MAA for activation of anti-tumor T cells. One potential problem with clinical melanoma vaccines against autologous tumors may be that often tumor cells do not express surface markers that label them for uptake by APC. Effective uptake of melanoma cells by APC might be achieved by exploiting the natural anti-Gal antibody which constitutes ~1% of immunoglobulins in humans. This approach has been developed in a syngeneic mouse model using mice capable of producing anti-Gal. Anti-Gal binds specifically to α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R). Injection of glycolipids carrying α-gal epitopes (α-gal glycolipids) into melanoma lesions results in glycolipid insertion into melanoma cell membranes, expression of α-gal epitopes on the tumor cells and binding of anti-Gal to these epitopes. Interaction between the Fc portions of bound anti-Gal and Fcγ receptors on APC induces effective uptake of tumor cells by APC. The resulting anti-MAA immune response can be potent enough to destroy distant micrometastases. A clinical trial is now open testing effects of intratumoral α-gal glycolipid injections in melanoma patients.

Purpose

To assess associations of soluble IL-2 receptor alpha (sIL-2rα) concentration with outcomes in pediatric acute myeloid leukemia in a phase 3 trial of IL-2 therapy.

Procedures

We randomized 289 children with AML in first remission after intensive chemotherapy to receive IL-2 infused on days 0-3 and 8-17 (IL-2 group) or no further therapy (AML control group). We measured sequential serum sIL-2rα concentrations in both groups before, during and after therapy in both groups and in reference controls without AML.

Results

Before treatment, mean sIL-2rα concentrations were similar in the IL-2 group and AML controls, but significantly higher than in reference controls. Both AML groups experienced reduction in sIL-2rα concentration after chemotherapy. Thereafter in the IL-2 group, mean sIL-2rα concentration increased from 2669 pg/ml before IL-2 to 15,534 pg/ml on day 4 (p<0.001) and 10,585 pg/ml on day 18 (p<0.001). In the control group sIL-2rα concentration did not change after 28 days of follow-up. Five-year disease-free survival (DFS) was 51% in the IL-2 group and 58% in the controls (p=0.489) and overall survival was 70% and 73% respectively (p=0.727).

Conclusion

SIL-2r α concentration was elevated in AML at diagnosis and tended to normalize after chemotherapy. IL-2 infusion significantly increased sIL-2rα concentration, but did not improve DFS or survival in pediatric AML. Furthermore, sIL-2rα concentration was not predictive of outcome before, during or after treatment for AML.

hu14.18–IL-2 (IC) is an immunocytokine consisting of human IL-2 linked to hu14.18 mAb, which recognizes the GD2 disialoganglioside. Phase 2 clinical trials of i.v. hu14.18–IL-2 (i.v.-IC) in neuroblastoma and melanoma are underway and have already demonstrated activity in neuroblastoma. We showed previously that intratumoral hu14.18–IL-2 (IT-IC) results in enhanced antitumor activity in mouse models compared with i.v.-IC. The studies presented in this article were designed to determine the mechanisms involved in this enhanced activity and to support the future clinical testing of intratumoral administration of immunocytokines. Improved survival and inhibition of growth of both local and distant tumors were observed in A/J mice bearing s.c. NXS2 neuroblastomas treated with IT-IC compared with those treated with i.v.-IC or control mice. The local and systemic antitumor effects of IT-IC were inhibited by depletion of NK cells or T cells. IT-IC resulted in increased NKG2D receptors on intratumoral NKG2A/C/E+ NKp46+ NK cells and NKG2A/C/E+ CD8+ T cells compared with control mice or mice treated with i.v.-IC. NKG2D levels were augmented more in tumor-infiltrating lymphocytes compared with splenocytes, supporting the localized nature of the intratumoral changes induced by IT-IC treatment. Prolonged retention of IC at the tumor site was seen with IT-IC compared with i.v.-IC. Overall, IT-IC resulted in increased numbers of activated T and NK cells within tumors, better IC retention in the tumor, enhanced inhibition of tumor growth, and improved survival compared with i.v.-IC.

Natural killer (NK) cells are powerful effector cells that can be directed to eliminate tumor cells through tumor-targeted monoclonal antibodies (mAbs). Some tumor-targeted mAbs have been successfully applied in the clinic and are included in the standard of care for certain malignancies. Strategies to augment the antitumor response by NK cells have led to an increased understanding of how to improve their effector responses. Next-generation reagents, such as molecularly modified mAbs and mAb-cytokine fusion proteins (immunocytokines, ICs) designed to augment NK-mediated killing, are showing promise in preclinical and some clinical settings. Continued research into the antitumor effects induced by NK cells and tumor-targeted mAbs suggests that additional intrinsic and extrinsic factors may influence the antitumor response. Therefore more research is needed that focuses on evaluating which NK cell and tumor criteria are best predictive of a clinical response and which combination immunotherapy regimens to pursue for distinct clinical settings.

Disease recurrence is frequent in high-risk neuroblastoma (NBL) patients even after multi-modality aggressive treatment [a combination of chemotherapy, surgical resection, local radiation therapy, autologous stem cell transplantation, and cis-retinoic acid (CRA)]. Recent clinical studies have explored the use of monoclonal antibodies (mAbs) that bind to disialoganglioside (GD2), highly expressed in NBL, as a means to enable immune effector cells to destroy NBL cells via antibody-dependent cell-mediated cytotoxicity (ADCC). Preclinical data indicate that ADCC can be more effective when appropriate effector cells are activated by cytokines. Clinical studies have pursued this by administering anti-GD2 mAb in combination with ADCC-enhancing cytokines (IL2 and GM-CSF), a regimen that has demonstrated improved cancer-free survival. More recently, early clinical studies have used a fusion protein that consists of the anti-GD2 mAb directly linked to IL2, and anti-tumor responses were seen in the Phase II setting. Analyses of genes that code for receptors that influence ADCC activity and natural killer (NK) cell function [Fc receptor (FcR), killer immunoglublin-like receptor (KIR), and KIR-ligand (KIR-L)] suggest patients with anti-tumor activity are more likely to have certain genotype profiles. Further analyses will need to be conducted to determine whether these genotypes can be used as predictive markers for favorable therapeutic outcome. In this review, we discuss factors that affect response to mAb-based tumor therapies such as hu14.18-IL2. Many of our observations have been made in the context of NBL; however, we will also include some observations made with mAbs targeting other tumor types that are consistent with results in NBL. Therefore, we hypothesize that the NBL observations discussed here may also be relevant to mAb therapy for other cancers, in which ADCC is known to play a role.

We evaluated the anti-tumor effect of Resveratrol (RV) on M21 and NXS2 tumor cell lines and its immunosuppressive activity on human and murine immune cells to determine the potential for combining RV and immunotherapy. In vitro, concentrations of RV ≥ 25mcM, inhibited cell proliferation, blocked DNA synthesis and induced G1 phase arrest in tumor and immune cells. RV at 12–50mcM inhibited antibody dependent cell mediated cytotoxicity (ADCC) of tumor cells facilitated by the hu14.18-IL2 immunocytokine (IC). The in vivo anti-tumor and immunomodulating activity of RV given systemically were assessed in mice. Results showed that this RV regimen inhibited the growth of NXS2 tumors in vivo but did not appear to interfere with blood cell count, splenocyte or macrophage function. Thus, RV may be a candidate for combining with immunotherapy.

We investigated the anti-tumor effect of peritumoral resveratrol in combination with immunotherapy in vivo in neuroblastoma-bearing mice. Subcutaneous NXS2 tumors were induced in A/J mice. On day 10 some mice received 15mcg of intravenous immunocytokine for 5 days, mice received of 20mg of peritumoral resveratrol twice a week (starting on day 12) for a total of 5 injections, and a separate group received a combination of both regimens. Tumor progression and survival were assessed every 3–4 days. Blood and primary tumor tissue samples were collected on day 20 for Complete Blood Count and CD45 immunohistochemistry and histology, respectively. The primary tumor regressed in all mice receiving peritumoral resveratrol. Most of these mice receiving peritumoral resveratrol alone developed metastatic tumors and recurrence of the primary tumor after cessation of therapy. When resveratrol and immunocytokine regimens were combined, 61% of the mice receiving this combination therapy resolved their primary tumors and survived without developing metastatic tumors, compared to 15% and 13% receiving resveratrol or immunocytokine alone, respectively. None of the therapeutic regimes prevented lymphocyte infiltration or affected the Complete Blood Count. Greater necrosis was observed microscopically in tumors from mice receiving the combination therapy. These results demonstrate that the combination therapy of peritumoral resveratrol plus intravenous immunocytokine provides better anti-tumor effects in this model than either therapy alone.

Tumor growth is often accompanied by the accumulation of myeloid cells in the tumors and lymphoid organs. These cells can suppress T cell immunity, thereby posing an obstacle to T cell-targeted cancer immunotherapy. In this study, we tested the possibility of activating tumor-associated myeloid cells to mediate antitumor effects. Using the peritoneal model of B16 melanoma, we show that peritoneal cells (PEC) in tumor-bearing mice (TBM) had reduced ability to secrete nitric oxide (NO) following in vitro stimulation with interferon gamma and lipopolysaccharide, as compared to PEC from control mice. This reduced function of PEC was accompanied by the influx of CD11b+ Gr-1+ myeloid cells to the peritoneal cavity. Nonadherent PEC were responsible for most of the NO production in TBM, whereas in naïve mice NO was mainly secreted by adherent CD11b+ F4/80+ macrophages. Sorted CD11b+ Gr-1− monocytic and CD11b+ Gr-1+ granulocytic PEC from TBM had a reduced ability to secrete NO following in vitro stimulation (compared to naïve PEC), but effectively suppressed proliferation of tumor cells in vitro. In vivo, treatment of mice bearing established peritoneal B16 tumors with anti-CD40 and CpG resulted in activation of tumor-associated PEC, reduction in local tumor burden and prolongation of mouse survival. Inhibition of NO did not abrogate the antitumor effects of stimulated myeloid cells. Taken together, the results indicate that in tumor-bearing hosts, tumor-associated myeloid cells can be activated to mediate antitumor effects.

We have previously demonstrated T cell-independent antitumor effects of a combination of anti-CD40 mAb and CpG oligodeoxynucleotides (CpG) which involved macrophages. As some immunotherapeutic treatments can be potentiated by chemotherapy, we tested if cyclophosphamide (CY) would enhance the antitumor effect of anti-CD40 mAb + CpG. Treatment of B16 melanoma-bearing mice with CY and anti-CD40 mAb + CpG resulted in a significant reduction in tumor growth in immunocompetent mice compared to either CY alone or anti-CD40 mAb with CpG. This enhanced antitumor effect was maintained in SCID mice, as measured by both tumor growth and overall survival. NK cells were not required for this antitumor effect as it was also observed in SCID/beige mice. Moreover, while CY treatment of immunocompetent mice suppressed NK cell activity, it did not negatively affect the antitumor activity of their macrophages when assayed in vitro. Depletion of macrophages in vivo reduced the antitumor effect of CY and anti-CD40 mAb + CpG. These results suggest that therapeutic strategies to activate macrophages may have potential for clinical application in cancer patients receiving chemotherapy.

Graft-versus-host disease (GVHD) represents a major cause of morbidity and mortality following conventional allogeneic hematopoietic stem cell transplantation (HSCT). A study in mice (see related article on pages 101–108) demonstrates that the selective administration of donor memory CD4+ T cells results in immune reconstitution without GVHD, a result that, if translatable to humans, has important clinical implications for HSCT.

The prognosis for advanced neuroblastoma remains poor with high risk of recurrence after consolidation. Therapies based on monoclonal antibodies that specifically target disialoganglioside GD2 on tumor cells are improving treatment results for high-risk neuroblastoma. This article reviews the use of anti-GD2 antibodies either as monotherapy or as part of a larger and more complex treatment approach for advanced neuroblastoma. We review how anti-GD2 antibodies can be combined with other treatments or strategies to enhance their clinical effects. Tumor resistance and other problems that decrease the efficacy of anti-GD2 antibodies are discussed. Future developments in the area of anti-GD2 immunotherapies for neuroblastoma are also addressed.

Patients with high risk melanoma and neuroblastoma frequently recur despite surgical resection and appropriate adjuvant therapies. Immunotherapy with the immunocytokine, hu14.18-IL2, was developed via fusion of two molecules of IL2 to the monoclonal antibody, 14.18, that recognizes GD2, expressed on the above malignancies. This article will discuss the results of preclinical work utilizing hu14.18-IL2 therapy, including data suggesting that intratumoral therapy may have enhanced antitumor benefit compared with IV therapy. Initial clinical trials in adult melanoma and pediatric neuroblastoma have demonstrated acceptable toxicity profiles in dosing that induces immune activation. Preclinical and initial clinical data suggest greater efficacy in the setting of minimal residual disease, therefore future clinical testing is planned to test the benefit of hu14.18-IL2 in this setting.

Purpose

Immunocytokine (IC) hu14.18-IL2 is a fusion protein of humanized anti-disialoganglioside (GD2) antibody (hu14.18) and interleukin-2. Sixty-one melanoma and neuroblastoma patients received IC in Phase I/Ib studies. Patient sera were examined in enzyme-linked immunosorbent assay (ELISA) to determine if an anti-IC antibody response occurred during treatment.

Experimental Design

Serum was assayed for anti-idiotypic antibody based on ability to bridge biotinylated hu14.18 to plate-bound hu14.18 and ability to inhibit binding of hu14.18 to GD2 antigen and/or murine anti-id antibody. ELISA was also used to detect antibodies to the Fc-IL2 end of hu14.18-IL2.

Results

Thirty-two patients (pts) (52%) developed an anti-id antibody response (OD > 0.7) in the bridge ELISA. Twelve pts (20%) had an intermediate response while 17pts (28%) were negative (OD < 0.3). The development of antibody to hu14.18-IL2 detected in the bridge ELISA was not related to the dose of Hu14.18-IL2. Twenty of 33 adult pts (61%) demonstrated anti-id based on binding inhibition ELISA. The anti-id response was inversely correlated (p<0.002) with IC measured during the second course of treatment, indicating that development of anti-id antibodies interfered with detection of circulating Hu14.18-IL2. All pts developed some inhibitory activity in the binding inhibition assay designed to detect antibodies to the Fc-IL2 region of the IC. There was a positive correlation between the peak serum level of IC in course 1 and the anti-Fc-IL2 response.

Conclusions

Pts treated with hu14.18-IL2 developed anti-idiotypic antibodies and anti Fc-IL2 antibodies. No association was seen between development of anti-IC antibodies and clinical toxicity.

Purpose

Radiofrequency ablation (RFA) is a common treatment modality for surgically unresectable tumors. However, there is a high rate of both local and systemic recurrence.

Experimental Design

In this pre-clinical study, we sought to enhance the antitumor effect of RFA by combining it with huKS-IL2 immunocytokine (tumor-specific monoclonal antibody fused to interleukin 2) in mice bearing CT26-KS colon adenocarcinoma. Mice were treated with RFA, huKS-IL2 via intratumoral injection, or combination therapy.

Results

Treatment of mice bearing subcutaneous tumors with RFA and huKS-IL2 resulted in significantly greater tumor growth suppression and enhanced survival, compared to mice treated with RFA or huKS-IL2 alone. When subtherapeutic regimens of RFA or huKS-IL2 were used, tumors progressed in all treated mice. In contrast, the combination of RFA and immunocytokine resulted in complete tumor resolution in 50% of mice. Treatment of a tumor with RFA and intratumoral huKS-IL2 also demonstrated antitumor effects against a distant untreated tumor. Tumor-free mice following treatment with RFA and huKS-IL2 demonstrated immunological memory based on their ability to reject subsequent challenges of CT26-KS and the more aggressive parental CT26 tumors. Flow cytometry analysis of tumor-reactive T-cells from mice with complete tumor resolution demonstrated that treatment with RFA and huKS-IL2 resulted in a greater proportion of cytokine-producing CD4 T-cells and CD8 T-cells compared to mice treated with RFA or huKS-IL2 alone.

Conclusions

These results show that the addition of huKS-IL2 to RFA significantly enhances the antitumor response in this murine model, resulting in complete tumor resolution and induction of immunological memory.

Improvements in adult cancer survivorship can be achieved from behavioral changes and adopting screening programs. Yet, these approaches cannot be readily applied to lower the morbidity and mortality from childhood cancers. Rather, pediatric oncologists must rely on procedures and therapies to treat, rather than prevent malignancies. The systematic application of chemotherapy, radiation therapy, and surgery has led to remarkable advances in survival but these improvements have come at a cost. Children routinely receive chemotherapy agents that were designed decades ago, and these drugs have predictable side effects that result in the loss of potential for long-term survivors. The advent of targeted applications of immune-based therapies offers children with cancer a new class of oncolytic therapies that may be used to treat disease refractory to conventional approaches and lessen the toxicity of current treatment regimens without compromising remission. This review explores how 3 components of the immune system—T cells, natural killer (NK) cells, and antibodies—can be used for therapy of pediatric malignancies.

The Eμ-TCL1 transgenic mouse spontaneously develops a CD5+ B cell lymphoproliferative disorder similar to human chronic lymphocytic leukemia (CLL). Given the ineffectual T cell antitumor responses in this mouse model of CLL, we sought to determine whether combined treatment with anti-CD40 mAb (αCD40) and CpG-containing oligodeoxynucleotides (CpG) could exert immunotherapeutic effects. We have previously shown that macrophages activated by sequential ligation of CD40 and TLR9 could become cytotoxic against solid tumor cell lines both in vitro and in vivo. In the current study, we find that αCD40 plus CpG-activated macrophages induce tumor B cell apoptosis in vitro and that αCD40 plus CpG treatment markedly retards tumor growth in immunodeficient SCID/Beige mice following transplantation of primary tumor B cells. Our results suggest a novel immunotherapeutic strategy for CLL that may be effective even in the face of tumor or chemotherapy-induced T cell immunodeficiency.

The first annual conference on immunotherapy in pediatric oncology was held in Bethesda, MD, USA, from September 9–10, 2008 to discuss the state-of-the-art of immunotherapeutic strategies currently being explored in pediatric oncology. Major topics included targeting cell surface receptors, understanding and improving T cell-based therapies, augmenting innate immune strategies and enhancing graft-versus-leukemia for pediatric malignancies. As can be seen in the summaries of the individual presentations, significant progress has been made in developing preclinical models of pediatric tumors while a variety of novel immunobiologic therapies are approaching, or already in, the clinic. While there is much excitement about the potential utility of these agents, a great deal of challenges lie ahead in improving the efficacy of each of these modalities as well as getting them to patients in a timely fashion. The resulting discussions will hopefully lead to new collaborations and insight for further translational and clinical studies.

Under different circumstances, tumors can inhibit or activate macrophage (Mϕ) effector functions. We studied the mechanisms of tumor-Mϕ interactions leading to Mϕ activation. The results show that L5178Y mouse T-cell lymphoma cells can prime naïve mouse Mϕ to subsequent LPS stimulation, resulting in increased NO production and anti-lymphoma effects in vitro. L5178Y cells, but not naïve splenocytes, primed Mϕ respond to ligation of TLR4 but not TLR9. L5178Y-primed Mϕ incubated with LPS showed down-regulation of CD40 and up-regulation of NKG2D expression. While L5178Y T cell lymphoma cells prime naïve mouse Mϕ, mouse A20 B cell lymphoma, B16 melanoma, or NIH-3T3 fibroblasts, and human Jurkat T cell lymphoma, Daudi B cell lymphoma, or M21 melanoma tumor cells lines all failed to prime mouse Mϕ. Neither L5178Y-conditioned supernatants nor co-culture of Mϕ and L5178Y cells in transwells resulted in priming, indicating that direct L5178Y cell-Mϕ contact was needed. Several receptor-ligand pairs are reciprocally expressed on Mϕ and L5178Y cell membranes and can be potentially involved in Mϕ priming. Of these, the CD40-CD154 pair played the most important role, as blocking the interaction of these molecules substantially reduced in vitro Mϕ priming. Furthermore, simultaneous blocking of interactions between CD40–CD154, NKG2D–H60, and CD18–ICAM-1/-2 led to complete abrogation of Mϕ-mediated NO secretion and complete inhibition of Mϕ-mediated tumor cell cytostasis. The priming of Mϕ to LPS with L5178Y cells was also observed in vivo. These results suggest that contact with certain tumor cells via CD40, NKG2D, and CD18 molecules on the Mϕ may facilitate Mϕ-mediated anti-tumor immune surveillance.

Purpose

Recurrence of high-risk neuroblastoma is common despite multimodality therapy. ch14.18, a chimeric human/murine anti-GD2 antibody, lyses neuroblastoma cells. This study determined the maximum tolerable dose (MTD) and toxicity of ch14.18 given in combination with interleukin-2 (IL-2) after high-dose chemotherapy (HDC)/stem-cell rescue (SCR). Biologic correlates including ch14.18 levels, soluble IL-2 receptor levels, and human antichimeric antibody (HACA) activity were evaluated.

Patients and Methods

Patients were given ch14.18 for 4 days at 28-day intervals. Patients received IL-2 during the second and fourth courses of ch14.18 and granulocyte-macrophage colony-stimulating factor (GM-CSF) during the first, third, and fifth courses. The MTD was determined based on toxicities occurring with the second course. After the determination of the MTD, additional patients were treated to confirm the MTD and to clarify appropriate supportive care.

Results

Twenty-five patients were enrolled. The MTD of ch14.18 was determined to be 25 mg/m2/d for 4 days given concurrently with 4.5 × 106 U/m2/d of IL-2 for 4 days. IL-2 was also given at a dose of 3 × 106 U/m2/d for 4 days starting 1 week before ch14.18. Two patients experienced dose-limiting toxicity due to ch14.18 and IL-2. Common toxicities included pain, fever, nausea, emesis, diarrhea, urticaria, mild elevation of hepatic transaminases, capillary leak syndrome, and hypotension. No death attributable to toxicity of therapy occurred. No additional toxicity was seen when cis-retinoic acid (cis-RA) was given between courses of ch14.18. No patient treated at the MTD developed HACA.

Conclusion

ch14.18 in combination with IL-2 was tolerable in the early post-HDC/SCR period. cis-RA can be administered safely between courses of ch14.18 and cytokines.

Immunocytokines (IC), consisting of tumor-specific monoclonal antibodies fused to the immunostimulatory cytokine interleukin 2 (IL2), exert significant antitumor effects in several murine tumor models. We investigated whether intratumoral (IT) administration of IC provided enhanced antitumor effects against subcutaneous tumors. Three unique ICs (huKS-IL2, hu14.18-IL2, and GcT84.66-IL2) were administered systemically or IT to evaluate their antitumor effects against tumors expressing the appropriate IC-targeted tumor antigens. The effect of IT injection of the primary tumor on a distant tumor was also evaluated. Here, we show that IT injection of IC resulted in enhanced antitumor effects against B16-KSA melanoma, NXS2 neuroblastoma, and human M21 melanoma xenografts when compared to intravenous (IV) IC injection. Resolution of both primary and distant subcutaneous tumors, and a tumor-specific memory response were demonstrated following IT treatment in immunocompetent mice bearing NXS2 tumors. The IT effect of huKS-IL2 IC was antigen-specific, enhanced compared to IL2 alone, and dose-dependent. Hu14.18-IL2 also showed greater IT effects than IL2 alone. The antitumor effect of IT IC did not always require T cells since IT IC induced antitumor effects against tumors in both SCID and nude mice. Localization studies using radiolabeled 111In-GcT84.66-IL2 IC confirmed that IT injection resulted in a higher concentration of IC at the tumor site than IV administration. In conclusion, we suggest that IT IC is more effective than IV administration against palpable tumors. Further testing is required to determine how to potentially incorporate IT administration of IC into an antitumor regimen that optimizes local and systemic anticancer therapy.

Purpose

To determine the response rate to oral capsular fenretinide in children with recurrent or biopsy proven refractory high-risk neuroblastoma.

Experimental Design

Patients received 7 days of fenretinide: 2475 mg/m2/day divided TID (<18 years) or 1800 mg/m2/day divided BID (≥18 years) every 21 days for a maximum of 30 courses. Patients with stable or responding disease after course 30 could request additional compassionate courses. Best response by course 8 was evaluated in Stratum 1 (measurable disease on CT/MRI +/− bone marrow and/or MIBG avid sites) and Stratum 2 (bone marrow and/or MIBG avid sites only).

Results

Sixty-two eligible patients, median age 5 years (range 0.6–19.9), were treated in Stratum 1 (n=38) and Stratum 2 (n=24). One partial response (PR) was seen in Stratum 2 (n=24 evaluable). No responses were seen in Stratum 1 (n=35 evaluable). Prolonged stable disease (SD) was seen in 7 patients in Stratum 1 and 6 patients in Stratum 2 for 4–45+ (median 15) courses. Median time to progression was 40 days (range 17–506) for Stratum 1 and 48 days (range 17–892) for Stratum 2. Mean 4-HPR steady state trough plasma concentrations were 7.25 µM (coefficient of variation 40–56%) at day 7 course 1. Toxicities were mild and reversible.

Conclusions

Although neither stratum met protocol criteria for efficacy, 1 PR + 13 prolonged SD occurred in 14/59 (24%) of evaluable patients. Low bioavailability may have limited fenretinide activity. Novel fenretinide formulations with improved bioavailability are currently in pediatric Phase I studies.

Conventional (cv) and germfree (gf) mice are able to give a good proliferative response to allogeneic cells in the mixed leukocyte culture (MLC) test, while the response to xenogeneic stimulating cells has been in question. Previous studies by others have suggested only a low MLC response in cv animals and none in gf ones. We have found that both cv and gf animals can give a good MLC response to xenogeneic as well as allogeneic cells. These findings are of importance for our understanding of both MLC stimulation and response.

Purpose

The hu14.18-IL2 fusion protein consists of interleukin-2 molecularly linked to a humanized monoclonal antibody that recognizes the GD2 disialoganglioside expressed on neuroblastoma cells. This phase II study assessed the antitumor activity of hu14.18-IL2 in two strata of patients with recurrent or refractory neuroblastoma.

Patients and Methods

Hu14.18-IL2 was given intravenously (12 mg/m2/daily) for 3 days every 4 weeks for patients with disease measurable by standard radiographic criteria (stratum 1) and for patients with disease evaluable only by [123I]metaiodobenzylguanidine (MIBG) scintigraphy and/or bone marrow (BM) histology (stratum 2). Response was established by independent radiology review as well as BM histology and immunocytology, and durability was assessed by repeat evaluation after more than 3 weeks.

Results

Thirty-nine patients were enrolled (36 evaluable). No responses were seen in stratum 1 (n = 13). Of 23 evaluable patients in stratum 2, five patients (21.7%) responded; all had a complete response (CR) of 9, 13, 20, 30, and 35+ months duration. Grade 3 and 4 nonhematologic toxicities included capillary leak, hypoxia, pain, rash, allergic reaction, elevated transaminases, and hyperbilirubinemia. Two patients required dopamine for hypotension, and one patient required ventilatory support for hypoxia. Most toxicities were reversible within a few days of completing a treatment course and were expected based on phase I results.

Conclusion

Patients with disease evaluable only by MIBG and/or BM histology had a 21.7% CR rate to hu14.8-IL2, whereas patients with bulky disease did not respond. Hu14.18-IL2 warrants further testing in children with nonbulky high-risk neuroblastoma.