31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Rheumatologic immune-related adverse events (irAE) in patients (pts) with genitourinary (GU) malignancies treated with immune checkpoint inhibitors (CPI).

652 Background: Rheumatologic irAEs in pts treated with CPIs present a clinical challenge. We describe the clinical characteristics, treatment, and outcomes of rheumatologic irAEs in CPI-treated GU malignancy pts. Methods: Pts with GU malignancies who were treated with CPIs and developed grade ≥ 2 (per CTCAEv4) rheumatologic irAEs (i.e., arthralgias and myalgias) were retrospectively reviewed. Patient-, disease-, and rheumatologic-related data were collected and analyzed. Results: Twenty-three pts were identified; 19 (83%) had renal cell carcinoma (RCC) and 4 (17%) had urothelial carcinoma (UC). The majority (70%) were male; median age at diagnosis was 56 (range, 36-78). All RCC pts had clear cell histology and all had prior nephrectomy; 1 UC pt had prior cystectomy. Most RCC pts (58%) received antiangiogenic therapy prior to CPI treatment and 50% of UC pts received prior chemotherapy. CPI therapy included anti-PD-L1 (30%), anti-PD-1 (43%), and combined PD-1 / CTLA-4 antibodies (26%). Median time from CPI initiation to rheumatologic irAE was 5.1 months (range, 0.23 – 51.3). Most (74%) patients had 2-4 muscle or joint groups involved. CPI was held in in 20 (87%) pts who developed rheumatologic irAEs. Most (96%) pts were treated with prednisone. Median initial prednisone dose was 40mg/d (range, 10-90mg/d) and median duration of prednisone therapy was 43.6 weeks (range, 2.5–206). Treatment intensification with methotrexate (14%), infliximab (14%), tocilizumab (9%), and etanercept (9%) was required in some pts for rheumatologic symptom control. Of the patients whose CPI was held for rheumatologic irAEs, 30% restarted CPI therapy following symptoms improvement, 15% switched to a subsequent therapy, and 55% have an ongoing sustained response to therapy (median 9.1 months; range, 0.63 - 46.1) despite no subsequent anti-cancer therapy. Conclusions: Rheumatologic irAEs in CPI-treated GU malignancy pts vary in timing of presentation, severity, and treatment. Multidisciplinary teams that include a rheumatologist are critical for optimal pt management. Larger pt populations are needed to assess the predictive/prognostic impact of these irAEs on outcome. </jats:p

Atezolizumab (atezo) and subsequent therapies in patients (Pts) with metastatic urothelial carcinoma (mUC) outside clinical trials.

432 Background: The use of immune checkpoint inhibitors (ICI) has revolutionized treatment of mUC. Little is known about the outcomes and safety profile of pts treated with ICI outside of clinical trials, as well as about responses to subsequent therapies. Methods: A retrospective analysis of consecutive mUC pts who received ≥1 dose of atezo 1200 mg every 3 weeks from May 2016 through April 2017 was conducted. Exploratory assessments included overall response rate according to RECIST v1.1, progression-free survival (PFS) and overall survival (OS) since time of treatment initiation, and treatment-related adverse events (TRAE) according to CTCAE v4.03. Results: A total of 79 pts were identified; median age 72 (29-93), 71% men, 27% never smokers, 66% pure urothelial histology, 49% visceral disease, 76% ECOG PS 0-1 and 61% with 1-2 Bellmunt risk factors. Most pts (79%) had primary tumor in bladder, 62% prior surgery and 75% ≥ 1 prior treatment. Most pts (71%) had 1-2 prior lines of treatment, 4% of pts had 3 lines, and 25% of pts had no prior systemic treatment. Pts received a median of 4 atezo doses (1-18) and median treatment duration was 3.2 months (95%CI 1.9-4.5). In 55 pts evaluable for response, 25% had partial response, 36% stable disease and 38% progressive disease, with a median time to best response of 2.7 months (1.3-7.4) and median PFS 4.5 months (95%CI 3.4-5.6). Estimated OS for the entire cohort was 8.3 months (median not reached) and was not significantly different based on prior therapy. TRAE of any grade were noted in 89% of pts and mostly included fatigue (63%) and anorexia (28%). Two pts had grade 4 hyperbilirubinemia, and no toxic deaths were noted. At time of data analysis, 34% of pts remained on atezo, 16% received 1-2 subsequent treatments with median duration of 1.3 months ( 95%CI 0.5-2.2) and 8% PR as best response, 41% were referred to hospice or died, and 9% were lost to follow-up. Conclusions: Pts with mUC treated with atezo had comparable outcomes and toxicity to those reported in clinical trials. Pts who progressed on atezo were unlikely to receive subsequent treatment and the benefit of such treatment was limited. Results may impact clinical trial designs and timing in regard to ICI. </jats:p

Adjuvant enzalutamide (Enza) for men with non-metastatic high-risk prostate cancer (HRPCa) after radical prostatectomy (RP).

88 Background: Management of HRPCa is a clinical challenge. Novel AR inhibitors could potentially impact outcome in HRPCa men following RP. We conducted a phase II study evaluating the efficacy/safety of Enza in men with HRPCa following RP. Methods: HRPCa pts (≥pT3a, GS≥8, iPSA ≥20 ng/mL, +ve lymph nodes (LN), or ≥35% chance of biochemical recurrence (BCR) at 5 yrs based on MSKCC’s nomogram) with undetectable PSA within 3 months from RP were eligible. Enza 160mg PO daily was given in 28-day cycles until disease progression, intolerability, consent withdrawal, or study completion at 24 months. Accrual goal was N=40 to provide 80% power to detect a 75% decrease in the risk of BCR from historical 55% rate. BCR was defined as PSA ≥0.2ng/mL on 2 consecutive lab results or any PSA rise that resulted in subsequent therapy. Results: 42 men enrolled. Median age 59 (range 43-70), based on biopsy 45% were GS7; 36% GS8, 19% GS9. 76% men had cT1, 24% cT2, median iPSA was 8.2 (range 2-77). On prostatectomy pathology: 50% had pT3b; 52% +ve margins; 50% SVI; 24% had +LN. 37 (88%) pts completed 24 planned cycles. Of the 5 pts who did not complete all cycles, 3 withdrew consent for toxicity (2 had G3 fatigue, 1 had G3 fatigue and arthralgias/myalgias), 1 had rising PSA requiring subsequent therapy, and 1 had financial concerns. With median follow-up of 31 months (range 2.5-44.5), 37 (88%) pts remain free of BCR. Of the 5 pts who developed BCR, 4 completed all 24 months on therapy. Median time to BCR was 31 months (range 13-40). Most common adverse events (AE) are listed (Table). Conclusions: Adjuvant Enza in men with HRPCa following RP is safe and relatively well-tolerated. Long-term safety, efficacy, and genomic correlations (including tumor RNA expression) are ongoing. Clinical trial information: NCT01927627. [Table: see text] </jats:p

Correlation of myeloid derived suppressor cell (MDSC) populations with clinicopathologic features in urothelial carcinoma (UC).

434 Background: MDSC are a heterogeneous population of potent immunosuppressive cells with potential predictive/prognostic significance in solid tumors. The association between MDSC and clinicopathologic features in patients (pts) with UC was investigated. Methods: Peripheral blood from 26 non-metastatic UC pts scheduled to undergo cystectomy or nephroureterectomy at Cleveland Clinic was collected. MDSC were enumerated in fresh unfractionated blood (WB) and in peripheral blood mononuclear cells (PBMC). (T)otal MDSC were defined as CD33+/HLADR-; out of T-MDSC, (G)ranulocytic (CD15+CD14-), (M)onocytic (CD15-CD14+) and (I)mmature (CD15-CD14-) MDSC were identified. CD11b MDSC (Linlo/HLADR-/CD33+/CD11b+) were identified in WB. MDSC populations were presented as % of live nucleated blood cells and as absolute numbers from WB. Wilcoxon rank sum test was used to assess associations between MDSC populations and clinicopathologic features. Due to the exploratory nature of the study, p &lt; .10 was considered significant. Results: Of 26 pts, 25 had surgery and 1 is under surveillance. 24 had both WB and PBMC data. 23/26 were men; median age 67. Of 26 pts, all had primarily UC histology; 7 had mixed UC histology, 11 had prior intravesical BCG, 12 neoadjuvant therapy (10 Gem/Cis, 1 Gem/Carbo, 1 unknown). Of 25 pts who had surgery, 5 had pT3/4 stage; 5 had LVI; 9 had CIS. All but 1 had negative LN. Higher levels of specific WB MDSC populations were associated with mixed histology (including squamous), CIS, and higher pT-stage (Table). When compared to a separate cohort of 11 pts with metastatic UC, the % G-MDSC in PBMC was lower in non-metastatic pts (median 0.3 vs. 1.47; p = .05). Conclusions: Although no single MDSC population correlated with all the evaluated clinicopathologic features, higher levels of certain MDSC populations appear to correlate with histology and pT stage. Further validation of blood and tissue is ongoing in a larger cohort. [Table: see text] </jats:p