Recombinant Interleukin-15(National Cancer Institute)

Adoptive transfer of chimeric antigen receptor (CAR)-expressing natural killer (NK) cells has demonstrated success against hematological malignancies. Efficacy against solid tumors has been limited by poor NK cell survival and function in the suppressive tumor microenvironment (TME). To enhance efficacy against solid tumors, stimulatory cytokines have been incorporated into CAR-NK cell therapeutic approaches. However, current cytokine strategies have limitations, including systemic toxicities, exogenous dependencies, and unwanted TME bystander effects. Here, we aimed to overcome these limitations by modifying CAR-NK cells to express a constitutively active interleukin (IL)-7 receptor, termed C7R, capable of providing intrinsic CAR-NK cell activation that does not rely on or produce exogenous signals nor activate bystander cells.

We examined persistence, antitumor function, and transcriptional profiles of CAR-NK cells coexpressing C7R in a novel tumor immune microenvironment (TiME) co-culture system and against hematologic and solid tumor xenografts in vivo.

Peripheral blood NK cells expressing a CAR directed against the solid tumor antigen GD2 and modified with C7R demonstrated enhanced tumor killing and persistence in vitro compared with CAR-NK cells without cytokine support and similar functions to CAR-NK cells supplemented with recombinant IL-15. C7R.CAR-NK cells exhibited enhanced survival and proliferation within neuroblastoma TiME xenografts in vivo but produced poor long-term tumor control compared with CAR-NK cells supplemented with IL-15. Similar results were seen using C7R-expressing CD19.CAR-NK cells against CD19+leukemia xenografts. Gene expression analysis revealed that chronic signaling via C7R induced a transcriptional signature consistent with intratumor stressed NK cells with blunted effector function. We identified gene candidates associated with chronic cytokine-stressed NK cells that could be targeted to reduce CAR-NK cell stress within the solid TME.

C7R promoted CAR-NK cell survival in hostile TMEs independent of exogenous signals but resulted in poor antitumor function in vivo. Our data reveals the detrimental role of continuous IL-7 signaling in CAR-NK cells and provides insights into proper application of cytokine signals when attempting to enhance CAR-NK cell antitumor activity.

Recombinant human interleukin-15 (rhIL-15) is an immunotherapeutic agent that enhances natural killer (NK) cells to augment the antibody-dependent cellular cytotoxicity (ADCC) of monoclonal antibodies. Mogamulizumab is a CC chemokine receptor 4-directed monoclonal antibody that exerts cytotoxicity through ADCC and depletes regulatory T cells within the tumor microenvironment. We conducted a phase 1 clinical trial of rhIL-15 in combination with mogamulizumab. Patients with relapsed or refractory adult T-cell leukemia/lymphoma (ATLL), mycosis fungoides (MF), and Sezary syndrome (SS) received a fixed dose mogamulizumab, combined with escalating doses of rhIL-15 to identify the maximum tolerated dose (MTD). Six patients were enrolled, 4 with ATLL and 2 with MF/SS. The most common adverse events were rash, infection, and fever (67% of all). Two patients (33%) had grade 4 acute kidney injury, and in 25% of cycles, grade 3 or higher anemia was present. The MTD was dose level 1. One patient with ATLL had a partial response despite receiving only 4 cycles because of grade 4 myositis. Circulating NK cells were increased in all patients during the first cycle and a rapid reduction in tumor cells within the peripheral circulation was noted. Ex vivo assessment demonstrated increased NK cell activation and increased cell lysis in the presence of monoclonal antibodies after only 5 days. Our small study suggests that rhIL-15, in combination with mogamulizumab, leads to effector NK cell activation and regulatory T-cell depletion but has an unfavorable safety profile. Future development of combinations of immunotherapy that target the microenvironment in relapsed or refractory T-cell lymphomas remains rational. This trial was registered at www.ClinicalTrials.gov as #NCT04185220.