Myxoid/round Cell Liposarcoma Research Articles

T cells for advanced synovial sarcoma or myxoid round cell liposarcoma

T cells for advanced synovial sarcoma or myxoid round cell liposarcoma

Metastatic myxoid round cell liposarcoma of the buttock: a case report

Metastatic myxoid round cell liposarcoma of the buttock: a case report

Abstract 892: Afamitresgene autoleucel (afami-cel; formerly ADP-A2M4) demonstrates durable clinical responses by inducing broad immune engagement with anti-tumor activity

Abstract Afami-cel is a mixed CD4+ CD8+ autologous T-cell therapy engineered to target the cancer testis antigen melanoma-associated antigen A4 in HLA-A*02-positive patients with advanced/metastatic synovial sarcoma or myxoid/round cell liposarcoma (MRCLS). Pooled data from the Phase 1 (NCT03132922) and Phase 2 (SPEARHEAD-1, NCT04044768) trials of afami-cel showed an acceptable benefit to risk profile with an overall response rate of 36.2% and a median duration of response of 52.0 weeks.1 To support the continued investigation of potential mechanisms of durable anti-tumor activity, we previously showed that afami-cel induces broad and enduring peripheral cytokine responses2 and that afami-cel tumoral infiltration is associated with increased presence of activated and proliferative cytotoxic T-cells in the tumor microenvironment.3 Here, we report the results of translational analyses exploring the cooperation between afami-cel-induced innate and adaptive immune responses pooled from the Phase 1 and 2 trials. Methods included measurement of 92 biomarkers related to apoptosis, chemotaxis, metabolism, tumor immunity promotion/suppression, and vascular/tissue remodeling in pre- and post-infusion serum samples from 38 patients. We also conducted multiplex immunofluorescence and gene set variation analysis of Reactome immune system pathway categories and microenvironment cell populations in RNA sequencing data from pre- and post-infusion biopsies from ≥15 patients. Serum analyses showed that patients with a clinical benefit as defined by RECIST v1.1 had significantly greater post-infusion levels of chemotactic markers (Kruskal-Wallis; p<0.05 for partial response [PR] compared to progressive disease, p<0.01 for PR compared to stable disease), indicating higher signaling related to immune-cell recruitment towards lesions. Tumor analyses showed increased expression of genes associated with innate and adaptive immunity, and cytokine signaling, in post-infusion biopsies, including T-cell receptor signaling-related expression, which was consistent with relatively greater spatial protein detection of pro-immune infiltrate. This profile was associated with longer progression-free survival. In conclusion, our data suggest that afami-cel induces peripheral and tumoral innate and adaptive immune responses, a hallmark of durable anti-tumor activity. Updated patient sample data will be presented. 1. D'Angelo SP, et al. J Clin Oncol. 2022;40:16_suppl:11562. 2. D’Angelo SP, et al. Poster 146 presented at: CTOS 2021; Virtual. 3. Van Tine, BA et al. Paper 61 presented at: CTOS 2022; Vancouver, BC, Canada. Citation Format: Cheryl McAlpine, Martin Isabelle, Robyn Broad, Revashnee Naidoo, Ashley Liddle, Elizabeth Duperret, Paul Noto, Ruoxi Wang, Dzmitry Batrakou, Sumit Middha, Chris Evans. Afamitresgene autoleucel (afami-cel; formerly ADP-A2M4) demonstrates durable clinical responses by inducing broad immune engagement with anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 892.

Myxoid Liposarcomas: Systemic Treatment Options.

Myxoid/round-cell liposarcoma (MRCL) account for 30% of liposarcomas and are the most chemo-sensitive subtype of liposarcoma. The 5-year local relapse and distant metastasis rates are 10% and 20%, respectively. In the advanced setting, the first-line median progression-free survival and overall survival is 9 and 30months, respectively. The overall response rate (ORR) by RECIST with anthracycline-based chemotherapy is around 40% and with trabectedin is 20%, although response is higher when captured by CHOI criteria. Anthracycline-based combination chemotherapy regimens remain the standard of care first-line treatment option. However, trabectedin is also effective and may be considered in the first-line setting when anthracyclines cannot be prescribed. Beyond chemotherapy, new therapeutic classes are being developed, including autologous adoptive modified T cell receptor cellular therapies which have shown promising results thus far. These new therapies utilize the immunogenic potential of cancer testis antigens, NY-ESO-1 and MAGE-A4, which are expressed in the vast majority of MRCL. Early phase trials have shown encouraging results with up to 40% ORR and a median progression-free survival up to 8.7months. Other innovative strategies are being developed, tailored to the molecular biology of MRCL. This review summarizes current evidence for the use of standard chemotherapy and the new biomarker-selected treatments under development.

Myxoid pleomorphic liposarcoma is distinguished from other liposarcomas by widespread loss of heterozygosity and significantly worse overall survival: a genomic and clinicopathologic study

AbstractMyxoid pleomorphic liposarcoma (MPLPS) is a recently described and extremely rare subtype of liposarcoma with a predilection for the mediastinum. However, the genomic features of MPLPS remain poorly understood. We performed comprehensive genomic profiling of MPLPS in comparison with pleomorphic liposarcoma (PLPS) and myxoid/round cell liposarcoma (MRLPS). Of the 8 patients with MPLPS, 5 were female and 3 were male, with a median age of 32 years old (range 10–68). All except one were located in the mediastinum, with invasion of surrounding anatomic structures, including chest wall, pleura, spine, and large vessels. All cases showed an admixture of morphologies reminiscent of PLPS and MRLPS, including myxoid areas with plexiform vasculature admixed with uni- and/or multivacuolated pleomorphic lipoblasts. Less common features included well-differentiated liposarcoma-like areas, and in one case fascicular spindle cell sarcoma reminiscent of dedifferentiated LPS. Clinically, 4 experienced local recurrence, 4 had distant metastases and 5 died of disease. Compared to PLPS and MRLPS, patients with MPLPS had worse overall and progression-free survival. Recurrent TP53 mutations were present in all 8 MPLPS cases. In contrast, in PLPS, which also showed recurrent TP53 mutations (83%), RB1 and ATRX losses were more common. MRLPS was highly enriched in TERT promoter mutations (88%) and PI3K/AKT pathway mutations. Copy number profiling in MPLPS revealed multiple chromosomal gains with recurrent amplifications of chromosomes 1, 19 and 21. Importantly, allele-specific copy number analysis revealed widespread loss of heterozygosity (80% of the genome on average) in MPLPS, but not in PLPS or MRLPS. Our findings revealed genome-wide loss of heterozygosity co-existing with TP53 mutations as a characteristic genomic signature distinct from other liposarcoma subtypes, which supports the current classification of MPLPS as a stand-alone pathologic entity. These results further expand the clinicopathologic features of MPLPS, including older age, extra-mediastinal sites, and a highly aggressive outcome.

Abstract A038: Enrollment of pediatric and adolescent patients with MAGE-A4+ advanced synovial sarcoma into cohort 2 of SPEARHEAD-1: a phase 2 trial of afamitresgene autoleucel (“afami-cel” [formerly ADP-A2M4

Abstract Background: Afami-cel is an autologous, specific peptide enhanced affinity receptor T-cell therapy genetically engineered to target MAGE-A4+ solid tumors in HLA-A*02+ patients. SPEARHEAD-1 (NCT04044768) is a Phase 2, two-cohort, single-arm, open-label trial evaluating afami-cel in patients with advanced/metastatic synovial sarcoma or myxoid/round cell liposarcoma (MRCLS) and is the largest trial in metastatic synovial sarcoma to date. Preliminary data from Cohort 1 in 47 heavily pre-treated patients aged 16–75 years from 22 centers in North America and Europe, showed an overall response rate (ORR) per independent review of 34.0% (14/39 [35.9%] in synovial sarcoma; 2/8 [25%] in MRCLS) and a favorable benefit–risk profile with mainly low-grade cytokine release syndrome and tolerable/reversible hematologic toxicities.1 The reported ORR in synovial sarcoma in Cohort 1 was higher than reported ORRs for current standard-of-care therapies, such as pazopanib and trabectedin, in the second-line metastatic setting.2 As synovial sarcoma is the most common malignant nonrhabdomyosarcoma soft-tissue sarcoma in children and adolescents with few treatment options, especially for recurrent disease, the trial opened a second cohort to allow enrollment of pediatric patients with MAGE-A4+ synovial sarcoma who experienced disease progression post first-line chemotherapy, and to better understand MAGE-A4 tumor expression in children. Methods: Cohort 2 of the SPEARHEAD-1 trial is enrolling patients with advanced synovial sarcoma who are at least 10 years old and weigh at least 40 kg. The planned enrollment is 45 patients, including up to 13 children, to enable a pooled analysis of ORR in >90 patients across Cohorts 1 and 2. HLA and MAGE-A4+ screening in Cohort 2 is conducted at a central laboratory using the same method as Cohort 1; MAGE-A4 testing is done using a clinical trial assay. All patients enrolled in Cohort 2 undergo apheresis and their isolated T-cells are then transduced with the MAGE-A4c1032 TCR using a lentivirus vector, followed by ex vivo expansion. Prior to afami-cel infusion of 1–10 × 109 transduced T-cells, patients will receive lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day for 4 days) and cyclophosphamide (600 mg/m2/day for 3 days). Disease will be assessed by independent review per RECIST v1.1 using computerized tomography or magnetic resonance imaging at weeks 4, 8, 12, 16, 24, and every 2 months thereafter until confirmed disease progression. Patients enter long-term follow-up for 15 years. 1. Van Tine BA, et al. Paper 30: CTOS 2021; Virtual 2. Carroll C, et al. Cancer Res 2021;81(13_Suppl): Abstract nr 2630. Citation Format: Colin Lunt, Sandra P. D’Angelo, Albiruni Ryan Abdul Razak, Michael J. Wagner, Brian A. Van Tine, Kristen Ganjoo, Jean-Yves Blay, Dejka M. Araujo, Mark Agulnik, John W. Glod, Erin Van Winkle, Erica Elefant, Swethajit Biswas, Dennis Williams, Axel Le Cesne. Enrollment of pediatric and adolescent patients with MAGE-A4+ advanced synovial sarcoma into cohort 2 of SPEARHEAD-1: a phase 2 trial of afamitresgene autoleucel (“afami-cel” [formerly ADP-A2M4]) [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A038.

Abstract 5857: Systematic literature review of prognostic factors associated with overall survival among advanced synovial sarcoma and myxoid/round cell liposarcoma subjects

Abstract Objective: Synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCLS) are rare subtypes of soft tissue sarcoma. Reported prognostic factors of survival for SS and MRCLS include tumor size/grade, tumor depth, and round cell component specifically for MRCLS. However, these publications refer to both localized and advanced disease, and there is a lack of a systematic review of these factors. The objective is to systematically review prognostic factors associated with overall survival (OS) in subjects with advanced (metastatic or unresectable) SS and MRCLS. Methods: Literature searches were conducted in PubMed and Embase using search strings for advanced/metastatic SS and MRCLS, and survival, and included English language articles (2000-2020), complemented with clinical trial registry summaries and oncology conference proceedings (most recent 3 years). Studies with multivariable (MV) analyses were prioritized. Results: Sixteen studies investigated prognostic factors associated with OS (13 SS, 2 MRCLS and 1 SS/MRCLS). Five studies were conducted in the US, two in the UK and three in the EU; three SS studies and one MRCLS study included at least 100 subjects in the analyses. Advanced SS: Among six studies with MV analyses of OS, the factors in the models varied by study. Age was studied in three analyses with older age being associated with worse OS in one analysis. Metastasectomy was included in two analyses and found to be associated with longer OS in one analysis. Larger primary tumor size was associated with shorter survival in two analyses. Other factors associated with worse OS and occurring in one analysis include: males, no chemotherapy/radiotherapy/surgery of primary tumor, extra-pulmonary metastasis, lymph node metastasis, shorter time to metastasis and higher performance status. Univariate analyses showed similar results. Advanced MRCLS: While no MV analyses were conducted, the following factors were investigated in two univariate analyses each but had p-values >0.05: primary tumor grade, primary tumor size, percentage of round cells and location of metastases. Only one study identified factors associated with worse OS: stage IV at diagnosis, ≥3 metastatic lesions at start of first-line therapy and a high number of organs involved during first-line therapy. Conclusion: Limited evidence exists for prognostic factors of OS among advanced SS and MRCLS subjects. Large tumor size was the most common factor associated with poor OS in MV analyses among advanced SS subjects; other factors associated with poorer prognosis included older age, males, and metastasis characteristics. Among advanced MRCLS subjects, there were very few prognostic factors reported and all stemmed from univariate analyses in a single study, underscoring the scarcity of data available and the need for further explorations with this subtype. Funding: GSK Citation Format: Samantha St Laurent, Judith van den Bosch, Hilde Vroling, Huifen Wang, Shibani Pokras. Systematic literature review of prognostic factors associated with overall survival among advanced synovial sarcoma and myxoid/round cell liposarcoma subjects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5857.

Abstract 5415: Glypican-3 immunohistochemistry precision, validation, and prevalence in selected solid tumors to identify target populations for CAR T cell therapy

Abstract Background: Glypican-3 (GPC3) is an oncofetal tumor antigen that is an attractive target for chimeric antigen receptor (CAR) T cell therapy due to its highly restricted expression on normal tissue and high prevalence in several adult and pediatric solid tumors. Aberrant GPC3 expression is implicated in tumorigenesis, and GPC3+ cancers are characterized by a highly immunosuppressive landscape which induces exhaustion in tumor-resident T cells. We sought to assess the validity of a GPC3 antibody clone in immunohistochemistry (IHC) and then measure GPC3+ prevalence in selected solid tumors. Methods: We evaluated GPC3 transcripts in human normal and tumor tissue specimens from The Cancer Genome Atlas (TCGA) and the Genome-Tissue Expression Project. GPC3 IHC was performed on formalin fixed paraffin embedded tumor tissues: hepatocellular (HCC), squamous cell lung (SCC), colorectal (CRC), serous ovarian (OC), Merkel cell carcinomas (MCC) and liposarcoma (LS) using antibody clone GC33 and scored using H-score (range 0-300), with appropriate positive and negative controls. Accuracy and precision of GPC3 antibody clone GC33 were tested in GPC3+ high prevalence tumor types compared to a validated anti-GPC3 clone (1G12). GPC3+ cutoff was set as H-score ≥ 30 (GC33) compared to >20 (1G12). The prevalence of GPC3 expression measured by IHC was also used to calculate the theoretical mRNA cutoff value from the TCGA data for GPC3+ indications represented in the database. Results: GPC3 mRNA was expressed at low levels predominantly in lung, adipose, tibial nerve, kidney and breast. GPC3 IHC of normal tissue showed predominantly faint, cytoplasmic staining in a few tissues including heart, kidney and stomach and no expression in lung or breast. HCC, SCC, LS, CRC, and OC showed high and varying levels of GPC3 mRNA expression in TCGA samples. The theoretical mRNA expression cutoff value based on IHC were HCC=1396 RSEM, SCC= 2675 RSEM, Sarcoma= 4126 RSEM; and OC 4486 RSEM; respectively. A cutoff for CRC could not be determined because the prevalence of GPC3 by IHC was <10%. GPC3 IHC using GC33 showed a higher prevalence of positive cases in myxoid/round cell LS (MRCLS) relative to other LS subtypes (15/45 vs. 8/75). HCC (n=110), SCC (n=73), MRCLS (n=45), and MCC (n=20) had a prevalence of 69%, 33%, 33%, and 70%; respectively. However, <10% of CRC (n=80) or OC (n=31) were GPC3+. GPC3 IHC assay using clone GC33 was fully validated for use as a lab-developed test by assessing accuracy, sensitivity, specificity, and precision in SCC, HCC, MCC and LS specimens. Conclusions: GPC3 has a high prevalence in selected tumors with low level expression in some normal tissues, making it an attractive target for CAR T cell therapy. The GC33 clone performs similarly to 1G12 and could be used for IHC screening for CAR T cell therapy. MRCLS has higher prevalence of GPC3+ expression relative to other LS subtypes. Citation Format: Glen J. Weiss, Amy Jensen-Smith, Sujatha Muralidharan. Glypican-3 immunohistochemistry precision, validation, and prevalence in selected solid tumors to identify target populations for CAR T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5415.

Identification of response stratification factors from pooled efficacy analyses of afamitresgene autoleucel (“Afami-cel” [Formerly ADP-A2M4]) in metastatic synovial sarcoma and myxoid/round cell liposarcoma phase 1 and phase 2 trials.

11562 Background: Afami-cel is an autologous, HLA-A*02-restricted, specific peptide enhanced affinity receptor, T-cell therapy engineered to target MAGE-A4+ solid tumors. The pivotal, 2-cohort, single-arm, Phase 2, SPEARHEAD-1 trial (NCT04044768) with afami-cel met its primary endpoint based on Cohort 1 data. As of September 1, 2021, in 47 patients (pts) with metastatic synovial sarcoma (SyS) or myxoid/round cell liposarcoma (MRCLS), the overall response rate (ORR) per independent review was 34% with encouraging durability (Van Tine, et al. Paper 30: CTOS 2021; Virtual). To identify potential stratification factors for response and assess whether response is a proxy for progression-free survival (PFS), we present pooled analyses using data from the prior Phase 1 trial (NCT03132922) and Cohort 1 of the SPEARHEAD-1 trial. Methods: Eligible pts (16–75 years) were HLA-A*02+ with MAGE-A4+ tumors. Pts received afami-cel after lymphodepleting chemotherapy. The pooled analyses evaluated ORR per RECIST v1.1 by investigator review, stratified by 7 factors, and safety. Results: In the pooled data, 69 pts received afami-cel (2.12–9.99×109 transduced T-cells) and were evaluable for response (Phase 1, n = 18; Phase 2, n = 51); all expressed one eligible HLA-A*02 allele. Median (range) for: age was 42 years (19–76), number of prior lines of therapy was 2 (1–12), and tumor MAGE-A4 H-score was 230 (60–300). Median (range) H-score was higher in SyS (256 [60–300]) than in MRCLS (180 [112–230]). The pooled investigator-assessed ORR was 36.2% (40.7% in SyS; 10.0% in MRCLS). Responses occurred across a wide MAGE-A4 H-score range (134–300). Median (range) duration of response was 52 weeks (8.29–75.14). Response rate was higher in the 59 pts with SyS: with ≤2 vs ≥3 prior lines of therapy (55.2% vs 26.7%), baseline target lesion sum of longest diameters <10cm vs ≥10cm (53.1% vs 25.9%), MAGE-A4 H-score ≥200 vs <200 (46.3% vs 27.8%), without vs with bridging therapy (48.6% vs 29.2%), who were female vs male (46.4% vs 35.5%), aged ≥40 vs <40 years (45.7% vs 33.3%), and from North America vs Europe (42.6% vs 33.3%). In responders vs non-responders with SyS, respectively, median PFS was 58.3 vs 11. 0 weeks (log-rank p-value <0.0001); the probability of being progression-free at 24 weeks was 0.8 vs 0.2. The pooled benefit:risk profile of afami-cel was similar to that in the SPEARHEAD-1 trial (Van Tine, et al. Paper 30: CTOS 2021; Virtual.). Conclusions: We show that baseline tumor burden, prior systemic treatment history, and MAGE-A4 tumor expression levels are potential factors associated with response to afami-cel, although their true predictive value for response status awaits confirmation. Our findings will inform the ongoing clinical development of afami-cel in sarcoma, especially for prognostic studies with PFS or overall survival endpoints. Clinical trial information: NCT04044768, NCT03132922.

ZENYTH-ESO: Master protocol to assess the safety and recommended phase II dose of next generation NY-ESO-1-specific TCR T-cells in HLA-A*02 patients with synovial sarcoma and myxoid/round cell liposarcoma [Substudy 3, GSK4427296

TPS2681 Background: Letetresgene autoleucel (lete-cel; GSK3377794) is an autologous T-cell therapy expressing an affinity-enhanced T-cell receptor (TCR) to improve recognition of cancer cells expressing NY-ESO-1 and/or LAGE-1a. Next generation NY-ESO-1 TCR T-cell therapy, GSK4427296, utilizes the same TCR as lete-cel, as well as an epigenetic reprogramming process (Epi-R) developed by Lyell Immunopharma to alter the phenotypic T-cell profile of the manufactured product, and is intended to increase the proportion of cells with properties of durable stemness. T cells with properties of durable stemness are able to proliferate, persist, and self-renew with anti-tumor functionality. A first-time-in-human master protocol (NCT04526509) is underway to evaluate the safety, tolerability, and recommended phase II dose (RP2D) of next generation NY-ESO-1 TCR T-cell therapies. Substudy 3 is added to this master protocol to assess GSK4427296 in patients with advanced synovial sarcoma (SS) or myxoid/round cell liposarcoma (MRCLS). Methods: This substudy includes a dose confirmation stage to assess RP2D and a dose expansion stage, aiming to dose 10 participants at the RP2D. Key inclusion criteria: age ≥18 years; measurable disease per RECIST v1.1; HLA-A*02:01, A*02:05, or A*02:06 positivity; NY-ESO-1/LAGE-1a tumor expression; advanced (metastatic/unresectable) SS with t(X;18) translocation or MRCLS with a translocation involving DDIT3 and/or FUS and/or EWSR1 genes; and anthracycline-based therapy receipt/completion/intolerance. Key exclusion criteria: prior malignancy that is not in complete remission or clinically significant systemic illness; prior receipt of gene or allogenic stem cell/solid organ transplant; and central nervous system metastases. Primary endpoints: safety (adverse events) and tolerability (dose-limiting toxicities). Secondary endpoints: investigator-assessed overall response rate, duration of response, maximum transgene expansion (Cmax), Tmax, and AUC(0-t). Analyses will be descriptive. The master protocol is open for recruitment. Clinical trial information: NCT04526509.

Improving Immunotherapy Efficacy in Soft-Tissue Sarcomas: A Biomarker Driven and Histotype Tailored Review.

Anti-PD-(L)1 therapies yield a disappointing response rate of 15% across soft-tissue sarcomas, even if some subtypes benefit more than others. The proportions of TAMs and TILs in their tumor microenvironment are variable, and this heterogeneity correlates to histotype. Tumors with a richer CD8+ T cell, M1 macrophage, and CD20+ cells infiltrate have a better prognosis than those infiltrated by M0/M2 macrophages and a high immune checkpoint protein expression. PD-L1 and CD8+ infiltrate seem correlated to response to immune checkpoint inhibitors (ICI), but tertiary lymphoid structures have the best predictive value and have been validated prospectively. Trials for combination therapies are ongoing and focus on the association of ICI with chemotherapy, achieving encouraging results especially with pembrolizumab and doxorubicin at an early stage, or ICI with antiangiogenics. A synergy with oncolytic viruses is seen and intratumoral talimogene laherpavec yields an impressive 35% ORR when associated to pembrolizumab. Adoptive cellular therapies are also of great interest in tumors with a high expression of cancer-testis antigens (CTA), such as synovial sarcomas or myxoid round cell liposarcomas with an ORR ranging from 20 to 50%. It seems crucial to adapt the design of clinical trials to histology. Leiomyosarcomas are characterized by complex genomics but are poorly infiltrated by immune cells and do not benefit from ICI. They should be tested with PIK3CA/AKT inhibition, IDO blockade, or treatments aiming at increasing antigenicity (radiotherapy, PARP inhibitors). DDLPS are more infiltrated and have higher PD-L1 expression, but responses to ICI remain variable across clinical studies. Combinations with MDM2 antagonists or CDK4/6 inhibitors may improve responses for DDLPS. UPS harbor the highest copy number alterations (CNA) and mutation rates, with a rich immune infiltrate containing TLS. They have a promising 15-40% ORR to ICI. Trials for ICB should focus on immune-high UPS. Association of ICI with FGFR inhibitors warrants further exploration in the immune-low group of UPS. Finally translocation-related sarcomas are heterogeneous, and although synovial sarcomas a poorly infiltrated and have a poor response rate to ICI, ASPS largely benefit from ICB monotherapy or its association with antiangiogenics agents. Targeting specific neoantigens through vaccine or adoptive cellular therapies is probably the most promising approach in synovial sarcomas.

391 Biomarker correlates of response in patients with advanced myxoid/round cell liposarcoma (MRCLS) treated with NY-ESO-1 TCR T cells (Letetresgene autoleucel)

BackgroundThis is an open label pilot study (NCT02992743) on letetresgene autoleucel (lete-cel; GSK3377794), an NY-ESO-1-specific autologous CD4+ and CD8+ T cells expressing a high affinity T-cell receptor which recognizes the NY-ESO-1 antigen epitope in complex with specific HLA- alleles A*02, which exhibited anti-tumor activity and manageable safety profiles in patients with advanced MRCLS based on interim analysis (IA) data.1 Lymphodepletion has been shown to enhance the expansion, persistence, and homing of therapeutically infused T-cells, thereby potentiating therapeutic efficacy against malignant diseases.2 Initial T-cell kinetics data from this study demonstrated that lymphodepletion regimen (LDR)-B robustly depleted lymphocytes at infusion and was trended with higher peak cell expansion (Cmax) vs. LDR-A. The peak expansion was significantly associated with weight-normalized transduced cell dose and trended with response.1 Here, we will be discussing additional cell kinetics data and other exploratory biomarker correlates of response.MethodsPatients with advanced MRCLS were enrolled to 2 cohorts and received either planned A (N=10) or B (N=10) LDRs prior to lete-cel infusion (table 1). Response was assessed per RECIST v1.1. Transduced cell kinetics were measured by quantitative PCR of transgene vector copies in DNA from peripheral blood mononuclear cells (PBMCs). Serum cytokines (Meso Scale Discovery immunoassay) as pharmacodynamic (PD) markers of response and their association with T cell kinetics will be discussed. Phenotypic characterization of the cell product (pre- and post- infusion) via Flow cytometry using Cytek Aurora (23 color panel), to help understand correlation of response with engineered cell product attributes, will be presented. Potential biomarker correlates of clinical response were tested using generalized linear models.ResultsFive out of 6 responders with available lab data exhibited robust lymphocyte depletion at infusion (0–25 cell/µL) and high Cmax (>50,000 vector copies/µg gDNA) with LDR. Only 6/14 non-responders exhibited low lymphocytes counts at infusion and high Cmax. LDR-B also induced strong depletion of monocytes at infusion (p=0.03) vs. LDR-A, but depletion of monocytes did not show association with response. Higher Cmax was correlated with exposure (AUC0–28d) (Adj. R2=0.606). AUC0–28d was a better predictor of response in patients receiving LDR-B (p=0.0182), with AUC0–28d trending towards predicting response in the LDR-A cohort. AUC0–28d was associated with tumor volume reduction (p=0.0569).Abstract 391 Table 1ConclusionsExposure–response analysis of this study reveals that efficacy appears to be driven by weight-normalized transduced cell dose and LDR via AUC0–28d. Higher AUC0–28d was correlated with Cmax and maximum tumor volume reduction.AcknowledgementsThis study (208469; NCT02992743) was funded by GlaxoSmithKline.Trial RegistrationNCT02992743ReferencesD’Angelo SP, et al. J Clin Oncol 2021;39:15_suppl:11521.Bechman, Maher. Expert Opin Biol Ther 2021;21(5):627–637.Ethics ApprovalThis study was approved by institutional review boards (IRB) at the six participating sites.

Safety and efficacy of letetresgene autoleucel (lete-cel; GSK3377794) in advanced myxoid/round cell liposarcoma (MRCLS) following high lymphodepletion (Cohort 2): Interim analysis.

11521 Background: Cancer testis antigen NY-ESO-1 is expressed in multiple tumor types, including 80‒90% of MRCLS [1,2]. Overall response rates (ORRs) to MRCLS treatment are low (1L, <20%; 2L, <10%) [2]. Lete-cel, an autologous T-cell therapy, targets NY-ESO-1/LAGE-1a+ tumors using a genetically modified, high-affinity T-cell receptor. High-dose lymphodepletion (LD) was linked with better responses in synovial sarcoma [3]; the current study tested this hypothesis in MRCLS. Methods: This open label, pilot study evaluates lete-cel efficacy and safety in advanced MRCLS following low-dose (Cohort 1 [C1]; 30 mg/m2 fludarabine [flu] x 3d + 600 mg/m2 cyclophosphamide [cy] x 3d) or high-dose (Cohort 2 [C2]; 30 mg/m2 flu x 4d + 900 mg/m2 cy x 3d; initiated based on C1 data) LD. Key eligibility: age ≥18 y; HLA-A*02:01; A*02:05, or A*02:06; advanced high-grade NY-ESO-1+ MRCLS (≥30% of cells 2+/3+ by IHC); prior anthracycline; measurable disease; specified washouts; and active/chronic/intercurrent illness restrictions. Stages include screening, leukapheresis, lete-cel manufacture, LD, lete-cel infusion (1– 8 × 109 transduced T cells), follow-up. Response is assessed at wk 4, 8, 12, and 24, then every 3 mo to disease progression/death/withdrawal. The primary efficacy endpoint is investigator-assessed ORR by RECIST v1.1. In C1 (n=10 patients [pts]), lete-cel was well tolerated and linked with 2 confirmed partial responses (PR; ORR, 20%) and stable disease (SD) in 8 pts. Planned interim analysis for C2, shown here, was done once all 10 treated pts had ≥3 post-baseline disease assessments or progressed/died/withdrew. Efficacy data will be correlated with transduced cell kinetics and pharmacodynamics marker profiles. Results: Durable (1.0–7.8 mo) PR (4/10 pts [ORR, 40%]; 2 ongoing) and prolonged (2.7–10.6 mo) SD (5/10 pts; 3 ongoing) with tumor regression were observed. Treatment-emergent cytopenias occurred in all pts. All experienced T-cell related cytokine release syndrome (5 serious adverse events; 30% Grade 3), with onset ≤5d of infusion and median duration 7.5d. Graft-vs-host disease, immune effector cell–associated neurotoxicity syndrome, pancytopenia, or aplastic anemia were not reported. Conclusions: A single lete-cel infusion after high LD showed antitumor activity in advanced MRCLS and a manageable safety profile consistent with other lete-cel studies. The trial is active but no longer recruiting (NCT02992743). MRCLS is included in a separate, ongoing lete-cel study (NCT03967223).

IGNYTE-ESO: A master protocol to assess safety and activity of letetresgene autoleucel (lete-cel; GSK3377794) in HLA-A*02+ patients with synovial sarcoma or myxoid/round cell liposarcoma (Substudies 1 and 2).

TPS11582 Background: Letetresgene autoleucel (lete-cel; GSK3377794) is an autologous T-cell product using a genetically modified T-cell receptor to target cancer cells expressing the cancer testis antigen New-York esophageal squamous cell carcinoma 1 (NY-ESO-1). Lete-cel is currently being investigated alone and in combination in multiple tumor types [1,2]. NY-ESO-1 is expressed in 70‒80% of synovial sarcoma (SS) and 80‒90% of myxoid/round cell liposarcoma (MRCLS) tumors [3,4], suggesting these tumors may be prime lete-cel targets. This master protocol design (IGNYTE-ESO; NCT03967223) enables evaluation of multiple cell therapies in multiple tumor types and treatment stages in separate substudies, beginning with lete-cel in Substudies 1 and 2 for SS and MRCLS. Methods: Substudy 1 is a single-arm study assessing lete-cel in treatment-naïve patients (pts; ie, anthracycline therapy-naïve for metastatic disease) with advanced (metastatic/unresectable) NY-ESO-1+ SS or MRCLS as a first line of therapy (n=10 planned). Substudy 2 is a pivotal, single-arm study assessing lete-cel in pts with NY-ESO-1+ SS or MRCLS who progressed after anthracycline therapy (n=70 planned). Key eligibility criteria are age ≥10 y and NY-ESO-1 and HLA-A*02 positivity. Exclusion criteria include prior NY-ESO-1–specific/gene therapy, allogeneic stem cell transplant, and central nervous system metastases. Screened pts undergo leukapheresis for lete-cel manufacture, lymphodepletion, lete-cel infusion, and follow-up (FU). Long-term FU (15 y) may be done under a separate protocol. The Substudy 2 primary endpoint is overall response rate (ORR) per RECIST v1.1 assessed by central independent review. Substudy 1 is not testing any formal hypotheses; statistical analysis will be descriptive. Substudy 2 is comparing ORR with the historical control assuming at least 90% power with 0.025 one-sided type I error. Secondary endpoints include efficacy (time to/duration of response, disease control rate, progression-free survival), safety (adverse event [AE] frequency/severity, serious AEs, AEs of special interest), and pharmacokinetic (maximum transgene expansion [Cmax], time to Cmax, area under the time curve from zero to time t as data permit). Enrollment began in December 2019.

SPEARHEAD-1: A phase 2 trial of afamitresgene autoleucel (Formerly ADP-A2M4) in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma.

11504 Background: This phase 2, open-label trial (SPEARHEAD-1; NCT04044768) is designed to evaluate the efficacy, safety, and tolerability of afamitresgene autoleucel in 45 patients (pts) with advanced/metastatic synovial sarcoma or Myxoid/Round Cell Liposarcoma (MRCLS). Methods: Eligible pts are HLA-A*02 positive with MAGE-A4-expressing tumors. Pts undergo leukapheresis for collection of autologous T-cells for processing and manufacture into afamitresgene autoleucel cells. Pts were treated with afamitresgene autoleucel doses between 1–10 × 109 transduced T-cells after receiving lymphodepleting chemotherapy. The primary endpoint is overall response rate per RECIST v1.1 by independent review. An independent Data Safety Monitoring Board reviews ongoing safety and benefit: risk during the interventional phase. Results: As of Feb 4, 2021, 32 pts received afamitresgene autoleucel. Of these pts, 59% were male, 87.5% had synovial sarcoma, the median age was 43 yrs (range: 24–73), and they had a median of 3 prior systemic lines of therapy. The MAGE-A4 antigen expression level (histoscore) ranged from 112–300, and the transduced cell dose ranged from 2.7–9.9 x 109. At the data cutoff, 25 pts were evaluable for preliminary efficacy (23 with synovial sarcoma and 2 with MRCLS) and 7 pts (5 with synovial sarcoma and 2 with MRCLS) had insufficient follow-up (<8 weeks follow-up and/or awaiting first scan). Of the 25 evaluable pts, the investigator-assessed responses were: complete response (2 pts), partial response (8 pts), stable disease (11 pts), and progressive disease (4 pts). All responses were confirmed. Nine of the 10 responders had ongoing response at the data cutoff and 3 responders had MAGE-A4 antigen histoscores <200. The most common AEs of any grade (>30% pts) were neutropenia, lymphopenia, nausea, cytokine release syndrome, leukopenia, fatigue, pyrexia, and anemia. Cytokine release syndrome of any grade occurred in 19/32 pts; 95% of those events were ≤Grade 2. No immune effector cell-associated neurotoxicity syndrome (ICANS) has been reported to date. Cytopenia (≥G3) at 4 wks post-infusion was observed in 6 pts (anemia 3 pts, neutropenia 2 pts, and thrombocytopenia 1 pt). Conclusion: These preliminary data demonstrate afamitresgene autoleucel is efficacious and well tolerated in heavily pre-treated pts. Objective responses are reported across a wide range of MAGE-A4 antigen levels and deep responses have been observed. Initial durability data is encouraging. Preliminary response data in SPEARHEAD-1 is comparable to the findings of the prior Phase 1 trial [1]. To date, the safety profile of afamitresgene autoleucel has been favorable, with mainly low-grade cytokine release syndrome and tolerable/reversible hematologic toxicities. [1]. Van Tine BA, et al. CTOS; November 18-21, 2020; Virtual. Clinical trial information: NCT04044768.

SPEARHEAD-1: A phase II trial of ADP-A2M4 SPEAR T cells in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma.

TPS11569 Background: ADP-A2M4 specific peptide enhanced affinity receptor (SPEAR) T-cells are genetically engineered to target MAGE-A4+ tumors in the context of HLA-A*02. MAGE-A4 has been described as having high expression in synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCLS) [1, 2]. This Phase 2 trial was initiated based on the favorable benefit:risk profile of ADP-A2M4 observed in a Phase 1 trial (NCT03132922) of ADP-A2M4 which demonstrated compelling clinical responses in patients with SS. Methods: This Phase 2, open-label trial (SPEARHEAD-1; NCT04044768) is designed to evaluate the efficacy, safety and tolerability of ADP-A2M4 in patients with advanced/metastatic SS or MRCLS who are HLA-A*02 positive and whose tumors express the MAGE-A4 protein. Enrolled patients are to undergo apheresis, and their isolated T-cells are then transduced with the MAGE-A4c1032 TCR, and expanded. Prior to ADP-A2M4 infusion, patients are to receive lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day x 4 days) and cyclophosphamide (600 mg/m2/day x 3 days). Patients are to receive 1 – 10 × 109 transduced T-cells. An independent Data Safety Monitoring Board will review ongoing safety and benefit:risk during the interventional phase of the study. Disease will be assessed by independent review per RECIST v1.1 by CT/MRI at weeks 4, 8, 12, 16, 24, and every 2 months thereafter until confirmed disease progression. As of 24 Jan 2020, there were 17 clinical sites open in the US, one in Canada, and two in Spain.

Clinical outcomes of patients with advanced synovial sarcoma or myxoid/round cell liposarcoma treated at major cancer centers in the United States.

BackgroundOutcomes data regarding advanced synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCL) are limited, consisting primarily of retrospective series and post hoc analyses of clinical trials.MethodsIn this multi‐center retrospective study, data were abstracted from the medical records of 350 patients from nine sarcoma centers throughout the United States and combined into a registry. Patients with advanced/unresectable or metastatic SS (n = 249) or MRCL (n = 101) who received first‐line systemic anticancer therapy and had records of tumor imaging were included. Overall survival (OS), time to next treatment, time to distant metastasis, and progression‐free survival (PFS) were evaluated using the Kaplan‐Meier method and Cox regression.ResultsAt start of first‐line systemic anticancer therapy, 92.4% of patients with SS and 91.1% of patients with MRCL had metastatic lesions. However, 74.7% of patients with SS and 72.3% of patients with MRCL had ≥2 lines of systemic therapy. Median OS and median PFS from first‐line therapy for SS was 24.7 months (95% CI, 20.9‐29.4) and 7.5 months, respectively (95% CI, 6.4‐8.4). Median OS and median PFS from start of first‐line therapy for MRCL was 29.9 months (95% CI, 27‐44.6) and 8.9 months (95% CI 4.5‐12.0).ConclusionsTo the best of our knowledge, this is the largest retrospective study of patients with SS and MRCL. It provides an analysis of real‐world clinical outcomes among patients treated at major sarcoma cancer centers and could inform treatment decisions and design of clinical trials. In general, the survival outcomes for this selected population appear more favorable than in published literature.

Characterization of autologous T cells engineered to express NY-ESO-1 TCR with multiplexed CRISPR/Cas9 editing (NYCE T Cells)

Background & Aim NY-ESO-1 is a cancer testis antigen with ectopic expression on multiple myeloma (MM), melanoma and sarcoma but restricted expression on normal tissues, rendering it a good candidate target for cancer immunotherapy. We recently reported a phase 1 pilot trial of multiplex CRISPR/Cas9 genome-edited NY-ESO-1 TCR cells (NYCE T cells; NCT03399448) for patients (pts) with advanced MM, synovial sarcoma and myxoid/round cell liposarcoma (MRCL) demonstrated safety and feasibility as well as persistence of T cells. Here, we characterize the phenotype and function of the ex vivo manufactured NYCE T cells from the 3 pts that were infused in the trial. Methods, Results & Conclusion The 3 infusion products (2 MM – pt #35 and Pt #7, and 1 MRCL – pt #39) were used to compare expanded T cells with either CRISPR/Cas9 editing without TCR transduction or with Mock-editing and TCR transduction from the same pt. We examined the phenotypic markers of T cell differentiation and checkpoint inhibitors by multicolor flow cytometry and assessed in vitro anti-tumor efficacy via a luciferase-based killing assay. We found heterogeneity in the composition of T cell subsets from all 3 infusion products with various CD4 and CD8 ratios, ranging from 0.12-1.1. Transduction efficiencies (determined by Vbeta8.1+ staining) varied between 1-11% and different levels of knockout efficiency in TRAC, TRBC and PDCD1 genes were observed by digital PCR. Three NYCE T cell infusion products displayed a terminally differentiated T cell phenotype similar to CRISPR/Cas9 edited counterpart. In contrast to Mock-edited T cells from the same pt, NYCE T cells exhibited lower levels of differing combinations of exhaustion-associated markers (PD1, TIM3, LAG3, EOMES and CTLA4) in both CD4+ and CD8+ T cell compartments. All 3 infusion products elicited antigen-specific killing of NY-ESO-1 expressing target cells. We demonstrate that NYCE T cells are heterogeneous in composition. Furthermore, we showed that CRISPR/Cas9 editing does not affect T cell differentiation and anti-tumor efficacy, but does reduce levels of exhaustion-associated markers expressed by the final products. This work provides an in-depth characterization of the heterogeneous product composition and function of the first multiplex CRISPR/Cas9-edited T cells tested in humans.

Can radiomics improve the prediction of metastatic relapse of myxoid/round cell liposarcomas?

The strongest adverse prognostic factor in myxoid/round cell liposarcomas (MRC-LPS) is the presence of a round cell component above 5% within the tumor bulk. Its identification is underestimated on biopsies and in the neoadjuvant setting. The aim was to improve the prediction of patients' prognosis through a radiomics approach. Thirty-five out of 89 patients with MRC-LPS managed at our sarcoma reference center from 2008 to 2017 were included in this IRB-approved retrospective study as they presented with a pre-treatment contrast-enhanced MRI (median age, 49 years old). Two radiologists reported usual conventional/semantic radiological variables. After signal intensity (SI) normalization, voxel size standardization of T2-WI, and whole tumor volume segmentation, 44 3D-radiomics features were extracted. Using least absolute shrinkage and selection operator penalized Cox regression on prefiltered features, a radiomics score based on 3 weighted radiomics features was generated. Four prognostic multivariate models for MRFS were compared using concordance index: (1) clinical model, (2) semantic radiological model, (3) radiomics model, and (4) radiomics + semantic radiological model. Twelve patients showed a metastatic relapse. The radiomics score included FOS_Skewness, GLRLM_LRHGE, and SHAPE_Volume and correlated with MRFS (hazard ratio = 19.37, p = 0.0009) and visual heterogeneity on T2-WI (p < 0.0001). A high score indicated a poorer prognosis. After adjustment, the best predictive performances were obtained with model (4) (concordance index = 0.937) and the lowest with model (1) (concordance index = 0.637). Adding selected radiomics features that quantify tumor heterogeneity and shape at baseline to a conventional radiological analysis improves prediction of MRC-LPS patients' prognosis. • Fourteen radiomics features quantifying shape and heterogeneity of myxoid/round cell liposarcomas on T2-WI were associated with metastatic relapse in univariate analysis. • A radiomics score based on 3 selected and weighted radiomics features was a strong and independent prognostic factor for metastatic relapse-free survival. • The best prediction of metastatic relapse-free survival for myxoid/round cell liposarcomas was achieved by combining the radiomics score to relevant radiological features.

First-in-Human Assessment of Feasibility and Safety of Multiplexed Genetic Engineering of Autologous T Cells Expressing NY-ESO -1 TCR and CRISPR/Cas9 Gene Edited to Eliminate Endogenous TCR and PD-1 (NYCE T cells) in Advanced Multiple Myeloma (MM) and Sarcoma

Stadtmauer: Celgene: Consultancy; Takeda: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Novartis: Consultancy, Research Funding; Tmunity: Research Funding; Abbvie: Research Funding. Cohen:Poseida Therapeutics, Inc.: Research Funding. Lacey:Novartis: Patents & Royalties: Patents related to CAR T cell biomarkers; Tmunity: Research Funding; Novartis: Research Funding. Melenhorst:Incyte: Research Funding; Novartis: Research Funding, Speakers Bureau; Parker Institute for Cancer Immunotherapy: Research Funding; Genentech: Speakers Bureau; Stand Up to Cancer: Research Funding; IASO Biotherapeutics, Co: Consultancy; Simcere of America, Inc: Consultancy; Shanghai Unicar Therapy, Co: Consultancy; Colorado Clinical and Translational Sciences Institute: Membership on an entity's Board of Directors or advisory committees; National Institutes of Health: Research Funding. Fraietta:Tmunity: Research Funding; Cabaletta: Research Funding; LEK Consulting: Consultancy. Mangan:amgen: Speakers Bureau; takeda: Speakers Bureau; celgene: Speakers Bureau; janssen: Speakers Bureau. Lancaster:novartis: Research Funding. Suhoski:novartis: Research Funding. Fesnak:Novartis: Research Funding. Young:novartis: Research Funding. Chew:tmunity: Other: Scientific Founder, Research Funding; novartis: Research Funding. Zhao:Tmunity: Membership on an entity's Board of Directors or advisory committees, Research Funding; novartis: Research Funding. Hwang:Novartis: Research Funding; Tmunity: Research Funding. Hexner:novartis: Research Funding. June:Novartis: Research Funding; Tmunity: Other: scientific founder, for which he has founders stock but no income, Patents & Royalties.