BACKGROUND-Patients with advanced urothelial carcinoma that progresses after platinumbased chemotherapy have a poor prognosis and limited treatment options.

PURPOSE Pembrolizumab has previously shown antitumor activity against programmed death ligand 1 (PD-L1)–positive metastatic castration-resistant prostate cancer (mCRPC). Here, we assessed the antitumor activity and safety of pembrolizumab in three parallel cohorts of a larger mCRPC population. METHODS The phase II KEYNOTE-199 study included three cohorts of patients with mCRPC treated with docetaxel and one or more targeted endocrine therapies. Cohorts 1 and 2 enrolled patients with RECIST-measurable PD-L1–positive and PD-L1–negative disease, respectively. Cohort 3 enrolled patients with bone-predominant disease, regardless of PD-L1 expression. All patients received pembrolizumab 200 mg every 3 weeks for up to 35 cycles. The primary end point was objective response rate per RECIST v1.1 assessed by central review in cohorts 1 and 2. Secondary end points included disease control rate, duration of response, overall survival (OS), and safety. RESULTS Two hundred fifty-eight patients were enrolled: 133 in cohort 1, 66 in cohort 2, and 59 in cohort 3. Objective response rate was 5% (95% CI, 2% to 11%) in cohort 1 and 3% (95% CI, < 1% to 11%) in cohort 2. Median duration of response was not reached (range, 1.9 to ≥ 21.8 months) and 10.6 months (range, 4.4 to 16.8 months), respectively. Disease control rate was 10% in cohort 1, 9% in cohort 2, and 22% in cohort 3. Median OS was 9.5 months in cohort 1, 7.9 months in cohort 2, and 14.1 months in cohort 3. Treatment-related adverse events occurred in 60% of patients, were of grade 3 to 5 severity in 15%, and led to discontinuation of treatment in 5%. CONCLUSION Pembrolizumab monotherapy shows antitumor activity with an acceptable safety profile in a subset of patients with RECIST-measurable and bone-predominant mCRPC previously treated with docetaxel and targeted endocrine therapy. Observed responses seem to be durable, and OS estimates are encouraging.

PurposeSipuleucel-T, the first FDA-approved autologous cellular immunotherapy for treatment of advanced prostate cancer, is manufactured by activating peripheral blood mononuclear cells, including antigen presenting cells (APCs), with a fusion protein containing prostatic acid phosphatase. Analysis of data from three phase 3 trials was performed to immunologically characterize this therapy during the course of the three doses, and to relate the immunological responses to overall survival (OS).MethodsSipuleucel-T product characteristics [APC numbers, APC activation (CD54 upregulation), and total nucleated cell (TNC) numbers] were assessed in three randomized, controlled phase 3 studies (N = 737). Antigen-specific cellular and humoral responses were assessed in a subset of subjects. The relationships between these parameters and OS were assessed.ResultsAPC activation occurred in the first dose preparation [6.2-fold, (4.65, 7.70); median (25th, 75th percentile)] and increased in the second [10.6-fold (7.83, 13.65)] and third [10.5-fold (7.89, 13.65)] dose preparations. Cytokines and chemokines associated with activated APCs were produced during the manufacture of each dose; T-cell activation-associated cytokines were detected in the second and third dose preparations. Antigen-specific T cells were detectable after administration of the first sipuleucel-T dose. Cumulative APC activation, APC number, and TNC number correlated with OS (P < 0.05). Antigen-specific immune responses were observed in 78.8 % of monitored subjects and their presence correlated with OS (P = 0.003).ConclusionSipuleucel-T broadly engages the immune system by activating APCs ex vivo and inducing long-lived immune responses in vivo. These data indicate antigen-specific immune activation as a mechanism by which sipuleucel-T prolongs OS.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-012-1317-2) contains supplementary material, which is available to authorized users.

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The existence of tumor-specific T cells, as well as their ability to be primed in cancer patients confirms that the immune response can be deployed to combat cancer. However, there are obstacles that must be overcome to convert the ineffective immune response commonly found in the tumor environment to one that leads to sustained destruction of tumor. Members of the tumor necrosis factor (TNF) superfamily direct diverse immune functions. OX40 and its ligand, OX40L, are key TNF members that augment T-cell expansion, cytokine production, and survival. OX40 signaling also controls regulatory T cell differentiation and suppressive function. Studies over the past decade have demonstrated that OX40 agonists enhance anti-tumor immunity in preclinical models using immunogenic tumors; however, treatment of poorly immunogenic tumors has been less successful. Combining strategies that prime tumor-specific T cells together with OX40 signaling could generate and maintain a therapeutic anti-tumor immune response.

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We have recently shown that effector T cells (TE) lacking either perforin or IFN-γ are highly effective mediators of tumor regression. To rule out compensation by either mechanism, TE deficient in both perforin and IFN-γ (perforin knockout (PKO)/IFN-γ knockout (GKO)) were generated. The adoptive transfer of PKO/GKO TE mediated complete tumor regression and cured wild-type animals with established pulmonary metastases of the B16BL6-D5 (D5) melanoma cell line. PKO/GKO TE also mediated tumor regression in D5 tumor-bearing PKO, GKO, or PKO/GKO recipients, although in PKO/GKO recipients efficacy was reduced. PKO/GKO TE exhibited tumor-specific TNF-α production and cytotoxicity in a 24-h assay, which was blocked by the soluble TNFRII-human IgG fusion protein (TNFRII:Fc). Blocking TNF in vivo by administering soluble TNFR II fusion protein (TNFRII:Fc) significantly reduced the therapeutic efficacy of PKO/GKO, but not wild-type TE. This study identifies perforin, IFN-γ, and TNF as a critical triad of effector molecules that characterize therapeutic antitumor T cells. These insights could be used to monitor and potentially tune the immune response to cancer vaccines.

11 Background: Preclinical studies have shown combined anti-tumor effect through interactions between poly(adenosine diphosphate–ribose) polymerase and androgen receptor signaling pathways. A Phase II trial (NCT01972217) in pts with mCRPC unselected by homologous recombination repair (HRR) status who previously received docetaxel demonstrated improved radiographic progression-free survival (rPFS) for pts treated with ola + abi vs pbo + abi (Clarke N, 2018). The Phase III PROpel study (NCT03732820) evaluates the efficacy and safety of ola + abi in the 1L mCRPC setting. Methods: PROpel is a randomized, double-blind, placebo-controlled Phase III trial in pts with mCRPC undergoing 1L treatment after failure of primary androgen deprivation therapy, enrolled independent of HRR status. Pts were randomized 1:1 to receive ola (300 mg twice daily [bid]) or pbo, and abi (1000 mg once daily) + prednisone or prednisolone (5 mg bid). The primary endpoint was investigator-assessed rPFS with multiple secondary endpoints, including overall survival (OS). Results:796 pts were randomized to ola + abi (n=399) or pbo + abi (n=397).In this planned interim analysis, 1L treatment with ola + abi significantly prolonged rPFS vs pbo + abi in pts with mCRPC irrespective of HRR status (24.8 vs 16.6 months; hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.54–0.81; P <0.0001). Predefined subgroup analyses showed rPFS improvement across all subgroups, including pts with (HR 0.54, 95% CI 0.36–0.79) and without (HR 0.76, 95% CI 0.59–0.97) HRR mutations detected by circulating tumor DNA testing. A sensitivity analysis of rPFS by blinded independent central review was consistent with the primary analysis (HR 0.61, 95% CI 0.49–0.74; P=0.004). OS is currently immature with 228 deaths (28.6%). A trend in OS favoring ola + abi was observed (HR 0.86, 95% CI 0.66–1.12). Secondary endpoints of time to first subsequent treatment (HR 0.74, 95% CI 0.61–0.90) and time to second progression-free survival or death (HR 0.69, 95% CI 0.51–0.94) were supportive of long-term benefits. The most common grade ≥3 adverse event (AE) reported was anemia (15.1 vs 3.3%) for ola + abi vs pbo + abi; 13.8 vs 7.8% pts, respectively, discontinued ola/pbo because of an AE. The rate of AEs leading to abi discontinuation were similar in both arms (8.5 vs 8.8%). Conclusions: At interim analysis, PROpel met its primary objective, demonstrating significant improvement in rPFS for ola + abi vs pbo + abi in pts with newly detected mCRPC who had not received prior 1L therapy, irrespective of HRR status. The safety and tolerability profile of ola + abi was consistent with the known safety profiles of the individual drugs. These results demonstrate the benefit of ola + abi without the need for HRR stratification in 1L treatment of mCRPC. Pt follow-up is ongoing for the planned OS analysis. Clinical trial information: NCT03732820.