Chronic lymphocytic leukemia (CLL) is characterized by chronic clonal expansion of mature CD19-expressing B lymphocytes and global dysfunction of immune effectors, including natural killer (NK) cells. CLL remains incurable, and novel approaches to refractory CLL are needed. Our group has previously described trispecific killer engager (TriKE) molecules that redirect NK cell function against tumor cells. TriKE reagents simultaneously bind an activating receptor on NK cells, CD16, and a tumor antigen while also providing an NK cell expansion signal via an interleukin-15 moiety. Here we developed the novel CD19-targeting 161519 TriKE. We demonstrate that 161519 TriKE induced killing of a CD19-expressing Burkitt’s lymphoma cell line and examined the impact on primary CLL targets using healthy donor and patient NK cells. 161519 TriKE induced potent healthy donor NK cell activation, proliferation, and directed killing. Furthermore, 161519 TriKE rescued the inflammatory function of NK cells obtained from CLL patient peripheral blood samples. Finally, we show that 161519 TriKE induced better directed killing of CLL in vitro when compared with rituximab. In conclusion, 161519 TriKE drives a potent activating and proliferative signal on NK cells, resulting in enhanced NK cell expansion and CLL target killing. Our findings indicate the potential immunotherapeutic value of 161519 TriKE in CLL.

Natural killer (NK) cells are potent immune modulators that can quickly lyse tumor cells and elicit inflammatory responses. These characteristics make them ideal candidates for immunotherapy. However, unlike T cells, NK cells do not possess clonotypic receptors capable of specific antigen recognition and cannot expand via activating receptor signals alone. To enable NK cells with these capabilities, we created and have previously described a tri-specific killer engager (TriKE) platform capable of inducing antigen specificity and cytokine-mediated NK-cell expansion. TriKE molecules have three arms: (i) a single-chain variable fragment (scFv) against the activating receptor CD16 on NK cells to trigger NK-cell activation, (ii) an scFv against a tumor-associated antigen (CD33 here) to induce specific tumor target recognition, and (iii) an IL15 moiety to trigger NK-cell expansion and priming. Here, we demonstrate that by modifying the anti-CD16 scFv with a humanized single-domain antibody against CD16, we improved TriKE functionality. A CD33-targeting second-generation TriKE induced stronger and more specific NK-cell proliferation without T-cell stimulation, enhanced in vitro NK-cell activation and killing of CD33-expressing targets, and improved tumor control in preclinical mouse models. Given these improved functional characteristics, we propose rapid translation of second-generation TriKEs into the clinic.

BackgroundThe tumor microenvironment contains stromal cells, including endothelial cells and fibroblasts, that aid tumor growth and impair immune cell function. Many solid tumors remain difficult to cure because of tumor-promoting stromal cells, but current therapies targeting tumor stromal cells are constrained by modest efficacy and toxicities. TEM8 is a surface antigen selectively upregulated on tumor and tumor stromal cells, endothelial cells and fibroblasts that may be targeted with specific natural killer (NK) cell engagement.MethodsA Tri-specific Killer Engager (TriKE) against TEM8—‘cam1615TEM8’—was generated using a mammalian expression system. Its function on NK cells was assessed by evaluation of degranulation, inflammatory cytokine production, and killing against tumor and stroma cell lines in standard co-culture and spheroid assays. cam1615TEM8-mediated proliferation and STAT5 phosphorylation in NK cells was tested and compared with T cells by flow cytometry. NK cell proliferation, tumor infiltration, and tumor and tumor-endothelium killing by cam1615TEM8 and interleukin-15 (IL-15) were assessed in NOD scid gamma (NSG) mice.Resultscam1615TEM8 selectively stimulates NK cell degranulation and inflammatory cytokine production against TEM8-expressing tumor and stromal cell lines. The increased activation translated to superior NK cell killing of TEM8-expressing tumor spheroids. cam1615TEM8 selectively stimulated NK cell but not T cell proliferation in vitro and enhanced NK cell proliferation, survival, and tumor infiltration in vivo. Finally, cam1615TEM8 stimulated NK cell killing of tumor and tumor endothelial cells in vivo.ConclusionsOur findings indicate that the cam1615TEM8 TriKE is a novel anti-tumor, anti-stroma, and anti-angiogenic cancer therapy for patients with solid tumors. This multifunctional molecule works by selectively targeting and activating NK cells by costimulation with IL-15, and then targeting that activity to TEM8+ tumor cells and TEM8+ tumor stroma.

IMPORTANCE Clinical trials and compassionate use agreements provide selected patients with access to potentially life-saving treatments before approval by the Food and Drug Administration (FDA). Approval from the FDA decreases a number of access barriers; however, it is unknown whether FDA approval is associated with increases in the equitable use of novel therapies and reductions in disparities in use among patients with cancer in the US. OBJECTIVETo assess the association between FDA drug approval and disparities in the use of immunotherapy across health, sociodemographic, and socioeconomic strata before and after approval of the first checkpoint inhibitors for the treatment of patients with cancer in the US. DESIGN, SETTING, AND PARTICIPANTSThis cohort study used data from the National Cancer Database to examine the use of immunotherapy across health, sociodemographic, and socioeconomic strata before and after FDA approval of the first checkpoint inhibitor therapies. A total of 402 689 patients 20 years or older who were diagnosed with stage IV non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), or melanoma of the skin between January 1, 2007, and December 31, 2018 (specific years varied by tumor type), were included. EXPOSURES Patient health (Charlson-Deyo comorbidity score and age), sociodemographic characteristics (sex, race, and ethnicity), and socioeconomic (insurance status and household income based on zip code of residence) characteristics. MAIN OUTCOMES AND MEASURESThe association of patient characteristics with receipt of immunotherapy was evaluated in the 4 years before and the 3 years immediately after FDA approval using multivariable logistic regression modeling. RESULTSAmong 402 689 patients (median [IQR] age, 68 [60-76 years]; 225 081 men [55.9%]), 347 233 had NSCLC, 43 714 had RCC, and 11 742 patients had melanoma. A total of 47 527 patients (11.8%) were Black, 15 763 (3.9%) were Hispanic, 375 874 (93.3%) were non-Hispanic, 335 833 (83.4%) were White, and 16 553 (4.1%) were of other races. Before FDA approval, 6271 patients (3.2%) with NSCLC, 1155 patients (4.8%) with RCC, and 504 patients (8.6%) with melanoma received immunotherapy compared with 23 908 patients (15.6%) with NSCLC, 3890 patients (19.7%) with RCC, and 1143 patients (19.3%) with melanoma after FDA approval. Before FDA approval, sociodemographic and socioeconomic characteristics were associated with variable immunotherapy administration by tumor type. For example, among those with NSCLC, Black patients were less likely to receive immunotherapy than White patients (odds ratio [OR], 0.78; 95% CI ,0.71-0.85; P < .001); among those with RCC, uninsured patients were less likely to receive immunotherapy than privately insured patients (OR, 0.31; 95% CI, 0.20-0.48; P < .001). After FDA approval, most disparities persisted, but several narrowed (eg, Black patients with NSCLC: OR, 0.87 [95% CI, 0.83-0.91; (continued) Key Points Question Is drug approval by the Food and Drug Administration (FDA) associated with a reduction in di...