Background: Metastatic human epidermal growth receptor II (HER2) negative breast cancer remains incurable. Our phase I study showed that anti-CD3 × anti-HER2 bispecific antibody armed activated T cells (HER2 BATs) may be effective against HER2-tumors. This phase II trial evaluates the efficacy and immune responses of HER2 BATs given to patients with metastatic HER2-estrogen and/or progesterone receptor positive (HR+) and triple negative breast cancer (TNBC) as immune consolidation after chemotherapy. The primary objective of this study was to increase the traditional median time to progression after failure of first-line therapy of 2–4 months with the secondary endpoints of increasing overall survival (OS) and immune responses. Methods: HER2- metastatic breast cancer (MBC) patients received 3 weekly infusions of HER2 BATs and a boost after 12 weeks. Results: This phase II study included 24 HER2-HR+ and 8 TNBC patients who received a mean of 3.75 and 2.4 lines of prior chemotherapy, respectively. Eight of 32 evaluable patients were stable at 4 months after the first infusion. There were no dose limiting toxicities. Tumor markers decreased in 13 of 23 (56.5%) patients who had tumor markers. The median OS was 13.1 (95% CI 8.6 to 17.4), 15.2 (95% CI 8.6 to 19.8), and 12.3 (95% CI 2.1 to 17.8) months for the entire group, HER2-HR+, and TNBC patients, respectively. Median OS for patients with chemotherapy-sensitive and chemotherapy-resistant disease after chemotherapy was 14.6 (9.6–21.8) and 8.6 (3.3–17.3) months, respectively. There were statistically significant increases in interferon-γ immunospots, Th₁ cytokines, Th₂ cytokines, and chemokines after HER2 BATs infusions. Conclusions: In heavily pretreated HER2-patients, immune consolidation with HER2 BATs after chemotherapy appears to increase the proportion of patients who were stable at 4 months and the median OS for both groups as well as increased adaptive and innate antitumor responses. Future studies combining HER2 BATs with checkpoint inhibitors or other immunomodulators may improve clinical outcomes.

Purpose: A phase II study was conducted to evaluate the safety and efficacy of the combination of HER2 bispecific antibody (HER2Bi)-armed activated T cells (HER2 BAT) and programmed death 1 inhibitor, pembrolizumab. Patients and Methods: Patients with metastatic castration-resistant prostate cancer (mCRPC) with 0 to 1 performance status and normal liver, kidney, and marrow function, pre- or post-docetaxel chemotherapy were eligible. Primary endpoint was 6-month progression-free survival (PFS). Peripheral blood mononuclear cells were obtained by a single apheresis, shipped to University of Virginia, activated with OKT3 and expanded for 14 days in IL2, harvested, and armed with HER2Bi and cryopreserved. HER2 BATs were infused twice weekly for 4 weeks and pembrolizumab was administered every 21 days for a maximum duration of 6 months starting 1 to 3 weeks prior to HER2 BATs infusion. Results: Fourteen patients were enrolled with a median age of 69 (range 57–82 years) and median PSA of 143.4 (range 8.2–4210 ng/dL). Two patients had peritoneal metastases, 1 had lymph node (LN) only metastases and 11 had bone metastases of which 7 had bone and LN metastases. All were pretreated with androgen receptor axis targeted agents and 7 (50%) had prior docetaxel chemotherapy. The toxicities were grade1–2 infusion reactions with fever, chills, headaches, nausea and/or myalgias. Primary endpoint of 6 month PFS was achieved in 5 of 14 patients (38.5%; 95% confidence interval, 19.5%–76.5%). Median PFS was 5 months and median survival was 31.6 months. Conclusions: The safety and promising efficacy makes this combination worthy of future investigation in mCRPC.

Adoptive T cell therapies for solid tumors is challenging. We generated metabolically enhanced co-activated-T cells by transducing intracellular co-stimulatory (41BB, ICOS or ICOS-27) and CD3ζ T cell receptor signaling domains followed by arming with bispecific antibodies (BiAbs) to produce armed “Headless CAR T cells” (hCART). Various hCART armed with BiAb directed at CD3ϵ and various tumor associated antigens were tested for: 1) specific cytotoxicity against solid tumors targets; 2) repeated and dual sequential cytotoxicity; 3) survival and cytotoxicity under in vitro hypoxic condition; and 4) cytokine secretion. The 41BBζ transduced hCART (hCART_41BBζ) armed with HER2 BiAb (HER2 hCART_41BBζ) or armed with EGFR BiAb (EGFR hCART_41BBζ) killed multiple tumor lines significantly better than control T cells and secreted Th₁ cytokines/chemokines upon tumor engagement at effector to target ratio (E:T) of 2:1 or 1:1. HER2 hCART serially killed tumor targets up to 14 days. Sequential targeting of EGFR or HER2 positive tumors with HER2 hCART_41BBζ followed by EGFR hCART_41BBζ showed significantly increased cytotoxicity compared single antigen targeting and continue to kill under in vitro hypoxic conditions. In summary, metabolically enhanced headless CAR T cells are effective serial killers of tumor targets, secrete cytokines and chemokines, and continue to kill under in vitro hypoxic condition.

Mounting evidence links systemic innate immunity with cancer immune surveillance. In advanced metastatic castration-resistant prostate cancer (mCRPC), Black patients have been found to have increased inflammatory markers and longer survival after sipuleucel-T (sip-T) therapy, an FDA-approved, autologous cell therapy. We hypothesized these differences may be explained by previously reported ancestral differences in pattern recognition receptor signaling, which broadly governs innate inflammation to control adaptive immune cell activation, chemotaxis, and functionality. We discovered that peripheral blood mononuclear cell IFN-β responses to Toll-like receptor 1/2 (TLR1/2), a sensor of bacterial and gut microbiome constituents, associated with significantly longer survival after sip-T therapy in two separate cohorts of men with mCRPC (discovery cohort: n = 106, HR = 0.12; P = 0.019; validation cohort: n = 28, HR < 0.01; P = 0.047). Higher IFN-β induction after TLR1/2 stimulation was associated with lower HRs than biomarkers of vaccine potency and other prognostic factors in mCRPC. TLR1/2-dependent cytokine induction was stronger in Black individuals (1.2-fold higher for IFN-β; P = 0.04) but was associated with survival independently of race or numbers of vaccine-induced tumor antigen–specific T cells. IFN-β responses to TLR1/2 signaling correlated with increased numbers of IFN-γ producing T cells after broad, tumor antigen–independent stimulation. Thus, peripheral innate immunity differs by race, may predict survival after sip-T, and associates with peripheral T-cell functionality in men with mCRPC. Significance: The identification of factors that determine successful cancer immunotherapy, particularly in refractory tumor types like mCRPC, is urgently needed: both to identify patients that may benefit from such therapies and to uncover routes to sensitize patients with cancer to immunotherapy. Our work links functional peripheral immune responses with race and survival after cellular immunotherapy in men with mCRPC.

4108Background: Conventional chemotherapy (CT) for advanced pancreatic cancer (PC) is associated with dismal response rates and poor survival. Arming anti-CD3 activated T cells (ATC) with anti-CD3 x anti-EGFR bispecific antibody (EGFRBi) makes every ATC into a non-MHC-restricted EGFR-specific cytotoxic T lymphocyte. Engagement of CD3 on T cells and EGFR on PC cell lines leads to cytokine secretion, proliferation, cytotoxicity by ATC, and inhibition of tumor growth. Methods: We report on 9 LAPC and MPC patients (pts) (5 phase I and 4 phase I/II pts). In our phase I study at Karmanos Cancer Institute (KCI) on NCT0140874, EGFRBi-armed T cells (EGFR BATs) were used to target EGFR in 5 pts with unresectable or metastatic PC in a phase I dose escalation involving 3 weekly infusions of 10, 20, and 40 x 109 BATs per infusion followed by a booster infusion 3 months later for up to 80 x 109 BATs if they were stable or better. In a phase II study performed at KCI on NCT02620865 and continued at the University of Vir...