Bohac, Gerry C.

e22520 Background: Outcomes of patients (pts) with advanced synovial sarcoma (SS) and myxoid/round cell sarcoma (MRCL) is lacking. Current data is limited to single institution studies or post hoc analyses of clinical trials. To understand the natural history of these subtypes of soft tissue sarcoma we performed a systematic analysis of SS and MRCL patients from large medical institutions. Methods: Data was abstracted at 7 U.S. centers for pts treated from 2005 to 2015. Advanced SS or MRCL were eligible if they had received chemotherapy and were 18 years or older. The primary endpoint was overall survival, and secondary endpoints were progression free survival, time to next treatment, time to new distant metastasis. Results: 350 pts with locally advanced (LA), unresectable and/or or metastatic (Met) SS (n = 249) and MRCL (n = 101) were analyzed. The median age at diagnosis was 40 years for SS pts (58.2% male). The median age of MRCL pts was 50 years (67.3% male). 249 SS pts all had ≥ 1line of therapy, 74.7% had ≥2 lines of treatment. All MRCL pts received ≥1 line of treatment, 72.3% had ≥2 lines. The clinical outcomes (median overall survival (OS), progression free survival (PFS), time to next treatment (TTNT) and time to distant metastasis (TTDM)) from start of first-line chemotherapy are: The OS and PFS from second line chemotherapy decreased for all evaluable pts (n = 259) was 17.9 months (mos) [95% confidence interval (CI) (15.0, 22.3)]; 3.9 mos (3.4, 4.8), respectively. A similar trend toward shortened OS and PFS were seen with each subsequent line of chemotherapy. Conclusions: This registry analyzing real-world clinical outcomes among advanced SS and MRCL pts is the most comprehensive performed to date. It provides data on clinical outcomes depending on line of therapy and can provide the backbone for better patient management and design of future clinical trials.[Table: see text]

11011 Background: CMB305 (C) is an immunotherapy designed to generate an anti-NY-ESO-1 immune response (IR). C consists of a dendritic cell-targeting lentiviral vector encoding NY-ESO-1 gene (LV305), and a TLR-4 agonist NY-ESO-1 recombinant protein plus GLA-SE (G305). A Phase 1 study demonstrated C is safe, generates IR and conveys a median overall survival (mOS) of 23.7 months (15.5, not reached [NR]) for soft tissue sarcomas & 29.2 months (12.2, NR) for synovial sarcoma (SS) (ESMO 2018). We evaluated efficacy and safety of C and atezolizumab (A) vs A alone in NY-ESO-1+ SS and myxoid round cell liposarcoma (MRCL). Methods: A prospective randomized open label phase 2 study of C (LV305 Intradermal Days 0, 14, 42, 70 + G305 Intramuscular Days 28, 56, 84 then q 6wk up to one year (yr)) + A (1200mg IV q3wk) vs A alone in advanced NY-ESO-1+ SS/MRCL. Primary endpoints of OS and progression-free survival (PFS); secondary endpoints of safety, IR, and response rate and post hoc analysis by line of therapy. Results: 88 patients (pts) were enrolled and dosed. Arm C+A: median age 48 yrs, 73% SS, 98% relapsed metastatic, 73% ≥2 prior lines chemotherapy; Arm A: 47 yrs, 67% SS, 84% relapsed metastatic, 53% ≥2 prior lines chemotherapy. Most treatment-related adverse events (TRAE) Grade 1/2, no treatment related deaths. Summary of clinical outcomes. Conclusions: Despite no major differences in PFS and OS between the treatment arms (Arm C+A had more advanced disease and more prior lines of chemotherapy), Arm A +C achieved PRs, a higher level of anti-NY-ESO-1 IR, and pts with IR had numerically superior outcomes. Moreover, the clinical benefit of C+A in earlier lines of therapy warrant further study. Clinical trial information: NCT02609984. [Table: see text]

11006 Background: CMB305 is an active immunotherapy regimen designed to generate and expand anti-NY-ESO-1 T cells. It consists of LV305, a dendritic cell targeting lentiviral vector encoding NY-ESO-1, and a boost with G305, an NY-ESO-1 recombinant protein plus GLA-SE, a TLR-4 agonist. An LV305 phase 1 study demonstrated a 1-yr survival of 81% and induction of anti-NY-ESO-1 T cells in sarcoma patients (pts). This first-in-human study of CMB305 examined safety, immunogenicity, and efficacy in pts with NY-ESO-1 positive (+) solid tumors. Methods: Adults with previously treated NY-ESO-1+ sarcomas, NSCLC, ovarian cancer were enrolled in a 3+3 dose-escalation with an expansion phase 1 study. The CMB305 regimen included 4 intradermal injections of LV305 at 109 or 1010 vector genomes, alternating with 3 intramuscular G305 injections at 250 µg for 3 months, then bimonthly G305 injections up to 1 yr. Results: As of 31Dec2016, 25 pts with STS (15 synovial (SS), 8 myxoid/round cell liposarcoma (MRCL), 2 other) were evaluable for safety; 23 SS/MRCL pts were evaluable for immune response (IR) and efficacy. All SS and MRCL pts received prior therapy for locally advanced/metastatic disease, 67% > = 2 prior chemo regimens. No DLTs were observed; treatment related AEs were grade 1 and 2, except 1 pt with grade 3 SAE (prostatic pain). Of 11 SS/MRCL pts tested, 64% pts developed NY-ESO-1 specific T cells and 72% pts anti-NY-ESO-1 antibodies. T cell receptor sequencing indicated increased clonality, and antigen spreading after CMB305. Best response by immune related response criteria was stable disease in 8/15 (53%) SS pts and 6/8 (75%) MRCL pts. The 3 month PFS rate was 74% and 75% for SS and MRCL pts. Median survival has not been reached with 1-yr survival rate of 86% and 100% for SS and MRCL pts. Conclusions: CMB305 is safe, well tolerated, and demonstrates a survival rate that is favorable when compared with approved agents for recurrent STS. CMB305 resulted in a stronger and broader integrated IR than LV305, including antigen spreading. These data warrant further investigation of CMB305 as a monotherapy in a randomized clinical study in STS. A randomized study of CMB305 in combination with atezolizumab in SS/MRCL pts is ongoing. Clinical trial information: NCT02387125.

3090 Background: The correlation of immune response (IR) and clinical benefit in patients (pts) who receive active immunotherapy remains controversial. CMB305 is an active immunotherapy designed to generate and expand anti-NY-ESO-1 T cells, consisting of LV305 (a DC targeting lentiviral vector encoding NY-ESO-1) and a boost (NY-ESO-1 recombinant protein plus GLA-SE, a TLR-4 agonist). Phase 1 studies of LV305 and CMB305 evaluated the IR and survival of pts with NY-ESO-1 positive tumors. Methods: 62 pts with recurrent NY-ESO-1 expressing (by IHC) solid tumors were enrolled in 2 Phase 1 trials (31 pts each: 43 sarcomas, 12 ovarian, 4 melanomas, and 3 NSCLC). Peripheral blood was assessed pre and post therapy for anti-NY-ESO-1 T cell responses (IFNγ ELISPOT) and antibodies (Ab) (ELISA) (n = 62), TCR-β CDR3 repertoire and conserved (public) TCR (n = 28), and antigen spreading (ELISA, ELISPOT) (n = 23). Relationship between progression-free survival (PFS), overall survival (OS) and up to 15 biomarkers were analyzed by the Kaplan-Meier method. Results: Preexisting anti-NY-ESO-1 T cells and Ab were identified in 34% and 40% of pts. LV305 and CMB305 induced (de novo or increased) anti-NY-ESO-1 T-cells in 51% and 65% pts, and anti-NY-ESO-1 Ab responses in 13% and 68% pts, respectively. LV305 and CMB305 induced antigen spreading in 17% and 36% pts. TCR clonality increased after CMB305 as compared to LV305. The TCRβ-CDR3 amino acid sequences of three NY-ESO-1 specific TCR clones in a patient with a > 2-year response were fully conserved in 20/28 patients. Biomarkers showing the strongest association with OS and PFS were pre-existing anti-NY-ESO-1 T-cell response and Ab, integrated IR (T cells and antibodies), and NY-ESO-1 expression level. Presence of public TCRs was associated with longer survival, particularly in pts with high ( > 50%) NY-ESO-1 expression. Conclusions: While LV305 and CMB305 are both immunogenic, CMB305 resulted in a stronger and broader integrated IR, including antigen spreading. The three identified survival variables, preexisting and treatment-induced NY-ESO-1 IR and the presence of public TCRs, warrant validation in randomized studies of CMB305.