J A Hank

Soluble interleukin-2 receptor α activation in a Children's Oncology Group randomized trial of interleukin-2 Therapy for Pediatric Acute Myeloid Leukemia†‡

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

In Vivo Effects of Multiple Cycles of Recombinant Interleukin-2 (IL2) on Peripheral Granulocyte-macrophage Hematopoietic Progenitors Circulating in the Blood of Cancer Patients

The numbers of peripheral blood (PB) granulocyte-macrophage colony forming units (CFU-GM) were evaluated in five patients treated with multiple weekly cycles of recombinant interleukin-2 (IL2). A 4.5-12 fold increase in the number of CFU-GM was evident within 8 days after the beginning of the treatment. The maximal increase in the absolute numbers of CFU-GM/ml blood caused by the IL2 treatment, ranged from 14 to 57 times the baseline values and was reached after two or three cycles of IL2. IL2-activated PBMC, added in vitro to the PBMC of a normal donor did not modify the number of CFU-GM present in the donor PBMC. CFU-GM were also recovered from frozen samples of in vivo IL2-activated PBMC.

A human T cell clone that mediates the monocyte procoagulant response to specific sensitizing antigen

A panel of human purified protein derivative of the tubercle bacillus (PPD)-reactive T cell clones was derived by cloning out of soft agar followed by cultivation on inactivated feeder cells in the presence of interleukin-2. 1 of 4 clones tested was able to mediate an increase in monocyte procoagulant activity (PCA) in response to PPD. All four clones had identical surface marker phenotypes (T4+, T8-) and proliferated in response to antigen. The reactive T cell clone possessed no PCA of its own, but upon being presented with PPD was able to instruct monocytes to increase their expression of PCA. Antigen presentation could be performed only by autologous monocytes; allogeneic monocytes from donors unrelated to the donor of the reactive clone could not present antigen to cells of the clone in a way that would initiate the procoagulant response. Cells of the reactive clone did not mediate increased monocyte PCA in response to Candida, even though peripheral blood mononuclear cells from the donor demonstrated increased PCA to both Candida and PPD. Thus, the PCA response to specific antigen can be mediated by a single clone of cells that shows specificity in the recognition of both antigen and antigen presenting cell.

Evaluation of novel immunocytokines that preferentially target high or intermediate affinity IL-2 receptors

The parental hu14.18-IL-2 immunocytokine (ICp) is a fusion protein where one human IL-2 molecule is attached to each of the heavy chains of the intact humanized form of the anti-GD2 monoclonal antibody (mAb). Early clinical trials have shown that ICp treatment can lead to complete responses; however, dosing is limited by IL-2-induced toxicity. Evidence suggests that the anti-tumor efficacy of IL-2 is achieved through activation of immune cells expressing high-affinity IL-2 receptors (abg IL-2Rs) while IL-2 induced toxicity is related to over-stimulation of immune cells expressing intermediate affinity IL-2 receptors (bg IL-2Rs). We have shown that ICp stimulates murine bg IL-2R to a lesser degree than the human form, but is still able to induce potent anti-tumor effects in vivo. We believe this difference in the ICp selectivity profile for murine IL-2Rs may account for the successful retention of the anti-tumor effect and reduced IL-2 toxicity observed in mice. To study the effect of IL-2R selectivity on efficacy and toxicity we have created IC35 and ICSK, a novel generation of anti-GD2 ICs with varying levels of affinity for bg IL-2Rs. These two new constructs, IC35 and ICSK, have the IL-2 molecules fused to the C-terminus of the light chains of the hu14.18 mAb rather than to the heavy chains. This modification limits access to a critical contact residue of IL-2 by the b-chain thereby hindering the ability of IC35 to bind to bg IL-2Rs. In contrast to IC35, ICSK contains a mutated IL-2 protein with increased affinity for bg IL-2Rs. Here, we evaluated the ability of IC35 and ICSK to bind and induce proliferation of mouse and human cells expressing abg or bgIL-2Rs. We found that IC35 and ICSK maintained binding and activation of both human and mouse abg IL-2Rs. In contrast, IC35 had a ~50-fold reduction or complete loss of its ability to stimulate proliferation of human and mouse cells expressing bg IL-2Rs, respectively. Notably, ICSK had an increased ability to stimulate mouse cells expressing bg IL-2Rs resulting in similar receptor activity and selectivity that IC35 has for human immune cells. Overall, our data indicate that ICSK can be used in mouse models to study the effects of over stimulation of bg IL-2Rs and its relation to IL-2 induced toxicity. In addition, IC35’s reduced ability to stimulate human bg IL-2Rs suggests it may be a candidate for retaining anti-tumor activity with less dose-limiting IL-2 toxicity in clinical trials.

In vivo synergy of radiation and hu14.18-IL2 immunocytokine results in a memory T cell response in a syngeneic murine melanoma model

Purpose Tumor-specific monoclonal antibodies (mAb) are a common type of immunotherapy capable of engaging innate immune cells to elicit antibody-dependent cell-mediated cytotoxicity (ADCC). We recently demonstrated in vivo synergy between radiation (RT) and ADCC using the anti-GD2 hu14.18 mAb. We now investigate the potential of hu14.18-IL2 immunocytokine (IC) to augment this synergy.