Race-Related Differences in Sipuleucel-T Response among Men with Metastatic Castrate-Resistant Prostate Cancer.

Sipuleucel-T is an autologous cellular immunotherapy that targets prostatic acid phosphatase (PAP) and is available for treatment of men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). In this single-arm, two-cohort, multicenter clinical study, potential racial differences in immune responses to sipuleucel-T in men with mCRPC were explored. Patients' blood samples were obtained to assess serum cytokines, humoral responses, and cellular immunity markers before and after treatment. Baseline cumulative product parameters (total nucleated and CD54+ cell counts and CD54 upregulation) were evaluated. IgM titers against the immunogen PA2024, the target antigen PAP, prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) were quantified by ELISA. Cytotoxic T-lymphocyte activity was determined by ELISpots, and cytokine and chemokine concentrations were determined by Luminex.Twenty-nine African American (AA) men and 28 non-African American (non-AA) men with mCRPC received sipuleucel-T. Baseline total nucleated cell count, CD54+ cell count, CD54 expression, and cumulative product parameters were higher in non-AA men. Although PSA baseline levels were higher in AA men, there were no racial differences in IgM antibody and IFNγ ELISpots responses against PA2024, PAP, PSA, and PSMA before and after treatment. Expression of co-stimulatory receptor ICOS on CD4+ and CD8+ T cells, and the levels of Th1 cytokine granulocyte-macrophage colony-stimulating factor and chemokines CCL4 and CCL5, were significantly higher in AA men before and/or after treatment. Despite no difference in the overall survival, PSA changes from baseline were significantly different between the two races. The data suggest that immune correlates in blood differ in AA and non-AA men with mCRPC pre- and post-sipuleucel-T. SIGNIFICANCE: Our novel findings of higher expression of co-stimulatory receptor ICOS on CD4+ and CD8+ T cells in African American patients with metastatic castrate-resistant prostate cancer (mCRPC) prior and post-sipuleucel-T suggest activation of CD4+ and CD8+ T cells. The data indicate that racial differences observed in these and other immune correlates before and after sipuleucel-T warrant additional investigation to further our understanding of the immune system in African American men and other men with mCRPC.

Phase II Trial of Pembrolizumab and Anti-CD3 x Anti-HER2 Bispecific Antibody-Armed Activated T Cells in Metastatic Castration-Resistant Prostate Cancer.

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.

Priming of pancreatic cancer cells with bispecific antibody armed activated T cells sensitizes tumors for enhanced chemoresponsiveness.

In this study, we investigated the ability of bispecific antibody armed activated T cells to target drug resistant pancreatic cancer cells and whether or not "priming" these resistant cancer cells with bispecific antibody armed activated T cells could enhance subsequent responsiveness to chemotherapeutic drugs. Chemotherapeutic responses for pancreatic cancer are either limited or the tumors develop resistance to chemotherapy regimens. The impetus for this study was the remarkable clinical response seen in our earlier phase I/II clinical trial: a pancreatic cancer patient with drug resistant tumors who showed progression of disease following three infusions of anti-CD3 x anti-EGFR bispecific antibody armed activated T cells (EGFR BATs) was restarted on the initial low dose of 5-fluorouracil showed complete response, suggesting that BATs infusions may have sensitized patient's tumor for chemoresponsiveness. In the current study, we tested the hypothesis that BATs can sensitize tumors for chemoresponsiveness. Gemcitabine or cisplatin-resistant MiaPaCa-2 and L3.6 cell lines were effectively targeted by EGFR BATs. Priming of drug sensitive or resistant cells with EGFR BATs followed by retargeting with lower concentrations of 50% inhibitory concentration of gemcitabine or cisplatin showed enhanced cytotoxicity. Gemcitabine or cisplatin-resistant cell lines show an increased proportion of CD44+/CD24+/EpCAM+ cancer stem like cells as well as an increased number of ABC transporter ABCG2 positive cells compared to the parental cell lines. These data suggest that bispecific antibody armed activated T cells can target and kill chemo-resistant tumor cells and also markedly augment subsequent chemotherapeutic responsiveness, possibly by modulating the expression of ABC transporters.