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Abstract Background: Post-transplant lymphoproliferative disorder (PTLD) occurs in up to 30% of high-risk solid organ transplant recipients and is strongly associated with the intensity and duration of immunosuppression. While Epstein-Barr virus (EBV)-positive monomorphic PTLD and diffuse large B-cell lymphoma (DLBCL) share overlapping morphologic features and expression of canonical B-cell markers, they exhibit distinct EBV transcriptional programs. Immunosuppressive regimens, essential for preventing graft rejection, impair EBV-specific cytotoxic T lymphocyte (CTL) responses, thereby promoting EBV-driven lymphomagenesis. We hypothesized that these differences in viral transcription and immune evasion reflect fundamentally distinct immune microenvironments and host responses in EBV-positive PTLD compared to DLBCL. Methods This prospective, non-interventional study has been conducted at Moffitt Cancer Center since 2019. To characterize tumor-specific T-cell responses in EBV-positive PTLD versus DLBCL, peripheral blood mononuclear cells (PBMCs) from enrolled patients were infected with EBV (ATCC VR-1492) to generate autologous, immortalized lymphoblastoid B-cell lines (LCLs). EBV antigen-specific immune responses were quantified using an IFN-γ ELISpot assay targeting EBNA1, LAMP1, LAMP2A, BARF1, and a CEF peptide pool as a control. To optimize cell viability and functional readout post-thaw, we implemented an overnight resting protocol for PBMCs, which demonstrated superior IFN-γ release compared to the conventional 1-hour rest. Results We present pilot data from 11 consecutive patients (55% male; median age 63.4 years), including 3 with PTLD (2 EBV-positive; 2 monomorphic) and 8 with EBV-negative DLBCL. A total of 12 evaluable PBMC samples were analyzed: 7 pre-treatment, 1 mid-treatment, and 4 post-treatment. Successful generation of autologous LCLs was predominantly achieved using pre-treatment samples, whereas samples collected after B-cell–targeted therapy (Rituximab ± CHOP) showed reduced transformation efficiency. Notably, early pre-treatment samples exhibited a relative enrichment of CD27⁺ memory B cells. Baseline flow cytometric profiling of B cells undergoing LCL transformation revealed low CD19 expression (range <1%–15%). Repeat immunophenotyping at 3 weeks identified residual T cells within cultures, suggesting ongoing B-cell clearance. In matched flow cytometry and ELISpot assays from 7 evaluable patients with pre-treatment samples, EBV-positive PTLD cases demonstrated pronounced overexpression of PD-1 and TIM-3, but not LAG-3, alongside markedly diminished T-cell responses to EBV antigens. This distinct immunophenotypic and functional signature suggests T-cell exhaustion or dysfunction, likely driven by prior immunosuppression, which may impair immune surveillance and facilitate EBV-driven lymphomagenesis. Conclusions Our findings reveal distinct immunologic profiles in EBV-positive monomorphic PTLD compared to EBV-negative DLBCL, characterized by immune exhaustion and impaired T-cell functionality. Specifically, overexpression of PD-1 and TIM-3—but not LAG-3—in EBV-positive PTLD correlated with diminished antigen-specific T-cell responses, as measured by ELISpot, underscoring the role of prior immunosuppression in shaping ineffective tumor-specific immunity. Successful generation of autologous LCLs was predominantly achieved from pre-treatment PBMCs, highlighting the impact of B-cell–depleting therapies (Rituximab ± CHOP) on downstream immune profiling feasibility. The persistence of residual T cells in long-term LCL cultures suggests ongoing B-cell clearance and may reflect previously unrecognized immune dynamics in PTLD. Collectively, these data provide novel insights into the immune landscape of EBV-driven PTLD and support the rationale for therapeutic strategies aimed at reversing T-cell exhaustion—such as immune checkpoint blockade or adoptive T-cell therapies—to restore anti-EBV immunity in transplant recipients.

Abstract Introduction Diffuse large B-cell lymphoma (DLBCL) is a heterogenous disease with varied expressions of CD30. Brentuximab vedotin (BV) is a CD30-directed antibody-drug conjugate approved for treatment of patients with relapsed or refractory DLBCL in combination with lenalidomide (Len) and rituximab (R). In the phase 3 ECHELON-3 study (NCT04404283), BV + Len + R showed significant overall survival (OS) benefit compared with placebo + Len + R in patients with relapsed or refractory DLBCL. Subgroup analysis from this study showed that BV + Len + R provided clinical benefit regardless of CD30 expression level. We hypothesized that even sub-threshold levels of CD30 expression, below the detection limits of immunohistochemistry (IHC), may be sufficient to elicit the antitumor activity of BV. Here, we further investigated whether trace amounts of CD30 staining are required for patients to benefit from BV + Len + R. Methods In the ECHELON-3 study, patients with relapsed or refractory DLBCL were randomized 1:1 to receive BV + Len + R or placebo + Len + R. The primary endpoint was OS, with progression-free survival (PFS) and objective response rate (ORR), per Lugano 2014, as key secondary endpoints. CD30 expression was assessed by IHC by central and/or local testing. CD30 positivity was scored as the percentage of CD30 positive cells out of neoplastic cells or out of total lymphocytes, when neoplastic cells could not be distinguished. In this updated analysis, patients with CD30 <1% staining by central laboratory IHC were further grouped into CD30 <1% with trace staining and CD30 <1% with no staining. Results Overall, 60 patients in the BV + Len + R group had CD30 <1% expression; of these, 34 had CD30 <1% with trace staining and 26 had CD30 <1% with no staining. In the placebo + Len + R group, 63 patients had CD30 <1% expression; of these, 36 had CD30 <1% with trace staining and 27 had CD30 <1% with no staining. In the overall CD30 <1% groups, numerically greater OS and PFS benefits were observed with BV + Len + R vs placebo + Len + R (HR for OS, 0.57; 95% CI, 0.36-0.89 and HR for PFS, 0.53; 95% CI, 0.34-0.82). In patients with CD30 <1% with trace staining, BV + Len + R showed a numerically higher OS compared with placebo + Len + R, with HR of 0.48 (95% CI, 0.26-0.90); median OS was 15.6 vs 5.2 months. In patients with CD30 <1% with no staining, there was a trend toward higher OS with BV + Len + R vs placebo + Len + R, with HR of 0.66 (95% CI, 0.34-1.28); median OS was 14.8 vs 11.8 months. Similarly, in patients with CD30 <1% with trace staining, BV + Len + R showed a trend toward longer PFS compared with placebo + Len + R, with HR of 0.60 (95% CI, 0.33-1.11); median PFS was 2.8 vs 1.5 months. In patients with CD30 <1% with no staining, a numerically longer PFS benefit was observed with BV + Len + R vs placebo + Len + R, with HR of 0.41 (95% CI, 0.21-0.79); median PFS was 4.2 vs 2.7 months. In the overall groups, ORR was 60.0% with BV + Len + R and 34.9% with placebo + Len + R. Higher ORR was observed with BV + Len + R compared with placebo + Len + R in both CD30 <1% with trace staining (55.9% vs 25.0%) and CD30 <1% with no staining (65.4% vs 48.1%) groups. Conclusions Results from this updated analysis indicate that visible CD30 detection by IHC is not required for response to BV + Len + R in patients with relapsed or refractory DLBCL. Treatment with BV + Len + R showed efficacy benefit compared with placebo + Len + R regardless of CD30 expression level, including in patients with no visible CD30 IHC staining. These results are consistent with those from the overall ECHELON-3 study population, in which significant improvement in OS was demonstrated with BV + Len + R compared with placebo + Len + R.

Abstract Clinical and preclinical research has demonstrated that iPSC-derived NK (iNK) cells have a high therapeutic potential, yet poor understanding of the detailed process of their differentiation in vitro and their counterpart cell development in vivo has hindered therapeutic iNK cell production and engineering. Here we dissect the crucial differentiation of both fetal liver NK cells and iNK cells to enable the rational design of advanced iNK production protocols. We use a comparative analysis of single-cell RNA-seq (scRNA-seq) to pinpoint key factors lacking in the induced setting which we hypothesized would hinder iNK differentiation and/ or functionality. By analyzing key transcription factor regulatory networks, we discovered the importance of TBX21, EOMES, and STAT5A in the differentiation timeline. This analysis provides a blueprint for further engineering new iPSC lines to obtain iNK cells with enhanced functions. We validated this approach by creating a new line of STAT5A-iPSCs which can be differentiated to STAT5A-expressing macrophages with both NK cell and macrophage features such as perforin production, phagocytosis, and anti-tumor functions.

PURPOSE CMB305 is a heterologous prime-boost vaccination regimen created to prime NY-ESO-1–specific CD8 T-cell populations and then activate the immune response with a potent TLR-4 agonist. This open-label randomized phase II trial was designed to investigate the efficacy and safety of adding the CMB305 regimen to atezolizumab (anti–programmed death ligand-1 therapy) in comparison with atezolizumab alone in patients with synovial sarcoma or myxoid liposarcoma. PATIENTS AND METHODS Patients with locally advanced, relapsed, or metastatic synovial sarcoma or myxoid liposarcoma (any grade) were randomly assigned to receive CMB305 with atezolizumab (experimental arm) or atezolizumab alone (control arm). The primary end points were progression-free survival (PFS) and overall survival (OS) analyzed using the Kaplan-Meier method. Safety and immune responses were assessed. RESULTS A total of 89 patients were enrolled; 55.1% had received ≥ 2 prior lines of chemotherapy. Median PFS was 2.6 months and 1.6 months in the combination and control arms, respectively (hazard ratio, 0.9; 95% CI, 0.6 to 1.3). Median OS was 18 months in both treatment arms. Patients treated with combination therapy had a significantly higher rate of treatment-induced NY-ESO-1–specific T cells ( P = .01) and NY-ESO-1–specific antibody responses ( P < .0001). In a post hoc analysis of all dosed patients, OS was longer (36 months) in the subset who developed anti-NY-ESO-1 T-cell immune response (hazard ratio, 0.3; P = .02). CONCLUSION Although the combination of CMB305 and atezolizumab did not result in significant increases in PFS or OS compared with atezolizumab alone, some patients demonstrated evidence of an anti-NY-ESO-1 immune response and appeared to fare better by imaging than those without such an immune response. Combining prime-boost vaccines such as CMB305 with anti–programmed death ligand-1 therapies merits further evaluation in other clinical contexts.

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]

Abstract Purpose: LV305 is a modified, third-generation, nonreplicating, integration-deficient lentivirus-based vector designed to selectively transduce dendritic cells in vivo. LV305 induces expression of the New York Esophageal Squamous Cell Carcinoma-1 (NY-ESO-1) cancer testis antigen in dendritic cells, promoting immune responses against NY-ESO-1–expressing tumors. This phase I study evaluated the safety, immunogenicity, and preliminary efficacy of LV305 in patients with sarcoma or other solid tumors. Patients and Methods: Adults with previously treated, advanced, NY-ESO-1–positive solid tumors and limited tumor burden were eligible. LV305 was administered every 3 weeks by intradermal injection in four dose cohorts (Cohort 1: 108 vector genomes (vg) x 3 doses; Cohorts 1A, 2, and 3: 108 vg, 109 vg, 1010 vg x 4 doses). Results: Thirty-nine patients were enrolled: 3 patients each in Cohorts 1, 1A, and 2, and 30 patients in Cohort 3. No dose-limiting toxicities were observed. Tumor types included sarcoma (n = 24), ovarian (n = 8), melanoma (n = 6), and lung cancer (n = 1). All treatment-related adverse events were grade 1 or 2. Common treatment-related adverse events were fatigue (49%), injection site reactions (46%), and myalgia (21%). The disease control rate was 56.4% in all patients and 62.5% in sarcoma patients. One patient with synovial sarcoma achieved a partial response lasting &gt;36 months. Anti–NY-ESO-1-specific CD4+ and/or CD8+ T cells were induced in 57% of evaluable sarcoma patients. Induction of an anti–NY-ESO-1 immune response was associated with improved 1-year survival in an exploratory analysis. Conclusions: This first-in-class, first-in-human study of LV305 demonstrated a favorable safety profile, induction of antigen-specific responses, and potential clinical activity in patients with advanced cancer.

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.