A Phase 1 Clinical Trial of NKTR-255 with CD19-22 CAR-T Cell Therapy for Refractory B-cell Acute Lymphoblastic Leukemia.

While chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of B-cell malignancies, many patients relapse and therefore strategies to improve antitumor immunity are needed. We previously designed a novel autologous bispecific CAR targeting CD19 and CD22 (CAR19-22), which was well tolerated and associated with high response rates but relapse was common. Interleukin-15 (IL15) induces proliferation of diverse immune cells and can augment lymphocyte trafficking. Here, we report the results of a phase 1 clinical trial of the first combination of a novel recombinant polymer-conjugated IL15 receptor agonist (NKTR-255), with CAR19-22, in adults with relapsed / refractory B-cell acute lymphoblastic leukemia. Eleven patients were enrolled, nine of whom successfully received CAR19-22 followed by NKTR-255. There were no dose limiting toxicities, with transient fever and myelosuppression as the most common possibly related toxicities. We observed favorable efficacy with eight out of nine patients (89%) achieving measurable residual disease negative remission. At 12 months, progression-free survival for NKTR-255 was double that of historical controls (67% vs 38%). We performed correlative analyses to investigate the effects of IL15 receptor agonism. Cytokine profiling showed significant increases in IL15 and the chemokines CXCL9 and CXCL10. The increase in chemokines was associated with decreases in absolute lymphocyte counts and CD8+ CAR T-cells in blood and ten-fold increases in CSF CAR-T cells, suggesting lymphocyte trafficking to tissue. Combining NKTR-255 with CAR19-22 was safe, feasible and associated with high rates of durable responses (NCT03233854).

Sequential intravenous and intracerebroventricular GD2-CAR T-cell therapy for H3K27M-mutated diffuse midline gliomas.

H3K27M-mutant diffuse midline gliomas (DMGs) express high levels of the GD2 disialoganglioside and chimeric antigen receptor modified T-cells targeting GD2 (GD2-CART) eradicate DMGs in preclinical models. Arm A of the Phase I trial NCT04196413 administered one IV dose of autologous GD2-CART to patients with H3K27M-mutant pontine (DIPG) or spinal (sDMG) diffuse midline glioma at two dose levels (DL1=1e6/kg; DL2=3e6/kg) following lymphodepleting (LD) chemotherapy. Patients with clinical or imaging benefit were eligible for subsequent intracerebroventricular (ICV) GD2-CART infusions (10-30e6 GD2-CART). Primary objectives were manufacturing feasibility, tolerability, and identification of a maximally tolerated dose of IV GD2-CART. Secondary objectives included preliminary assessments of benefit. Thirteen patients enrolled and 11 received IV GD2-CART on study [n=3 DL1(3 DIPG); n=8 DL2(6 DIPG/2 sDMG). GD2-CART manufacturing was successful for all patients. No dose-limiting toxicities (DLTs) occurred on DL1, but three patients experienced DLT on DL2 due to grade 4 cytokine release syndrome (CRS). Nine patients received ICV infusions, which were not associated with DLTs. All patients exhibited tumor inflammation-associated neurotoxicity (TIAN). Four patients demonstrated major volumetric tumor reductions (52%, 54%, 91% and 100%). One patient exhibited a complete response ongoing for >30 months since enrollment. Eight patients demonstrated neurological benefit based upon a protocol-directed Clinical Improvement Score. Sequential IV followed by ICV GD2-CART induced tumor regressions and neurological improvements in patients with DIPG and sDMG. DL1 was established as the maximally tolerated IV GD2-CART dose. Neurotoxicity was safely managed with intensive monitoring and close adherence to a management algorithm.

Mesothelin CAR T Cells Secreting Anti-FAP/Anti-CD3 Molecules Efficiently Target Pancreatic Adenocarcinoma and its Stroma.

PURPOSE: Targeting solid tumors with chimeric antigen receptor (CAR) T cells remains challenging due to heterogenous target antigen expression, antigen escape, and the immunosuppressive tumor microenvironment (TME). Pancreatic cancer is characterized by a thick stroma generated by cancer-associated fibroblasts (CAF), which may contribute to the limited efficacy of mesothelin-directed CAR T cells in early-phase clinical trials. To provide a more favorable TME for CAR T cells to target pancreatic ductal adenocarcinoma (PDAC), we generated T cells with an antimesothelin CAR and a secreted T-cell-engaging molecule (TEAM) that targets CAF through fibroblast activation protein (FAP) and engages T cells through CD3 (termed mesoFAP CAR-TEAM cells). EXPERIMENTAL DESIGN: Using a suite of in vitro, in vivo, and ex vivo patient-derived models containing cancer cells and CAF, we examined the ability of mesoFAP CAR-TEAM cells to target PDAC cells and CAF within the TME. We developed and used patient-derived ex vivo models, including patient-derived organoids with patient-matched CAF and patient-derived organotypic tumor spheroids. RESULTS: We demonstrated specific and significant binding of the TEAM to its respective antigens (CD3 and FAP) when released from mesothelin-targeting CAR T cells, leading to T-cell activation and cytotoxicity of the target cell. MesoFAP CAR-TEAM cells were superior in eliminating PDAC and CAF compared with T cells engineered to target either antigen alone in our ex vivo patient-derived models and in mouse models of PDAC with primary or metastatic liver tumors. CONCLUSIONS: CAR-TEAM cells enable modification of tumor stroma, leading to increased elimination of PDAC tumors. This approach represents a promising treatment option for pancreatic cancer.