First-line avelumab treatment in patients with metastatic Merkel cell carcinoma: 4-year follow-up from part B of the JAVELIN Merkel 200 study

BACKGROUND

Results from the JAVELIN Merkel 200 study led to the approval of avelumab [an anti-programmed death-ligand 1 (PD-L1) antibody] for the treatment of metastatic Merkel cell carcinoma (mMCC) in multiple countries and its inclusion in the treatment guidelines as a preferred or recommended therapy in this setting. Here, we report 4-year follow-up results from the cohort of patients with mMCC who received avelumab as first-line treatment.

PATIENTS AND METHODS

In part B of JAVELIN Merkel 200, a single-arm, open-label, phase II study, patients with mMCC who had not received prior systemic therapy for metastatic disease received avelumab 10 mg/kg via intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxicity, or withdrawal. In this analysis, long-term overall survival (OS), patient disposition, and subsequent treatment were analyzed.

RESULTS

In total, 116 patients received first-line avelumab. At the data cutoff (2 February 2022), the median follow-up was 54.3 months (range 48.0-69.7 months). Seven patients (6.0%) remained on treatment and an additional 21 patients remained in follow-up (18.1%); 72 patients (62.1%) had died. The median OS was 20.3 months [95% confidence interval (CI) 12.4-42.0 months], with a 4-year OS rate of 38% (95% CI 29% to 47%). In patients with PD-L1+ or PD-L1- tumors, the 4-year OS rate was 48% (95% CI 26% to 67%) and 35% (95% CI 25% to 45%), respectively. In total, 48 patients (41.4%) received poststudy anticancer drug therapy, most commonly etoposide (20.7%), carboplatin (19.0%), and avelumab (12.1%).

CONCLUSIONS

Avelumab first-line monotherapy in patients with mMCC resulted in meaningful long-term OS, which compared favorably with historical studies of first-line chemotherapy. These results further support the role of avelumab as a standard of care for patients with mMCC.

Afamitresgene autoleucel for advanced synovial sarcoma and myxoid round cell liposarcoma (SPEARHEAD-1): an international, open-label, phase 2 trial

BACKGROUND

Afamitresgene autoleucel (afami-cel) showed acceptable safety and promising efficacy in a phase 1 trial (NCT03132922). The aim of this study was to further evaluate the efficacy of afami-cel for the treatment of patients with HLA-A*02 and MAGE-A4-expressing advanced synovial sarcoma or myxoid round cell liposarcoma.

METHODS

SPEARHEAD-1 was an open-label, non-randomised, phase 2 trial done across 23 sites in Canada, the USA, and Europe. The trial included three cohorts, of which the main investigational cohort (cohort 1) is reported here. Cohort 1 included patients with HLA-A*02, aged 16-75 years, with metastatic or unresectable synovial sarcoma or myxoid round cell liposarcoma (confirmed by cytogenetics) expressing MAGE-A4, and who had received at least one previous line of anthracycline-containing or ifosfamide-containing chemotherapy. Patients received a single intravenous dose of afami-cel (transduced dose range 1·0 × 109-10·0 × 109 T cells) after lymphodepletion. The primary endpoint was overall response rate in cohort 1, assessed by a masked independent review committee using Response Evaluation Criteria in Solid Tumours (version 1.1) in the modified intention-to-treat population (all patients who received afami-cel). Adverse events, including those of special interest (cytokine release syndrome, prolonged cytopenia, and neurotoxicity), were monitored and are reported for the modified intention-to-treat population. This trial is registered at ClinicalTrials.gov, NCT04044768; recruitment is closed and follow-up is ongoing for cohorts 1 and 2, and recruitment is open for cohort 3.

FINDINGS

Between Dec 17, 2019, and July 27, 2021, 52 patients with cytogenetically confirmed synovial sarcoma (n=44) and myxoid round cell liposarcoma (n=8) were enrolled and received afami-cel in cohort 1. Patients were heavily pre-treated (median three [IQR two to four] previous lines of systemic therapy). Median follow-up time was 32·6 months (IQR 29·4-36·1). Overall response rate was 37% (19 of 52; 95% CI 24-51) overall, 39% (17 of 44; 24-55) for patients with synovial sarcoma, and 25% (two of eight; 3-65) for patients with myxoid round cell liposarcoma. Cytokine release syndrome occurred in 37 (71%) of 52 of patients (one grade 3 event). Cytopenias were the most common grade 3 or worse adverse events (lymphopenia in 50 [96%], neutropenia 44 [85%], leukopenia 42 [81%] of 52 patients). No treatment-related deaths occurred.

INTERPRETATION

Afami-cel treatment resulted in durable responses in heavily pre-treated patients with HLA-A*02 and MAGE-A4-expressing synovial sarcoma. This study shows that T-cell receptor therapy can be used to effectively target solid tumours and provides rationale to expand this approach to other solid malignancies.

FUNDING

Adaptimmune.

Sarcoma microenvironment cell states and ecosystems are associated with prognosis and predict response to immunotherapy

Characterization of the diverse malignant and stromal cell states that make up soft tissue sarcomas and their correlation with patient outcomes has proven difficult using fixed clinical specimens. Here, we employed EcoTyper, a machine-learning framework, to identify the fundamental cell states and cellular ecosystems that make up sarcomas on a large scale using bulk transcriptomes with clinical annotations. We identified and validated 23 sarcoma-specific, transcriptionally defined cell states, many of which were highly prognostic of patient outcomes across independent datasets. We discovered three conserved cellular communities or ecotypes associated with underlying genomic alterations and distinct clinical outcomes. We show that one ecotype defined by tumor-associated macrophages and epithelial-like malignant cells predicts response to immune-checkpoint inhibition but not chemotherapy and validate our findings in an independent cohort. Our results may enable identification of patients with soft tissue sarcomas who could benefit from immunotherapy and help develop new therapeutic strategies.

Therapy-Induced Senescence Contributes to the Efficacy of Abemaciclib in Patients with Dedifferentiated Liposarcoma

PURPOSE

We conducted research on CDK4/6 inhibitors (CDK4/6i) simultaneously in the preclinical and clinical spaces to gain a deeper understanding of how senescence influences tumor growth in humans.

PATIENTS AND METHODS

We coordinated a first-in-kind phase II clinical trial of the CDK4/6i abemaciclib for patients with progressive dedifferentiated liposarcoma (DDLS) with cellular studies interrogating the molecular basis of geroconversion.

RESULTS

Thirty patients with progressing DDLS enrolled and were treated with 200 mg of abemaciclib twice daily. The median progression-free survival was 33 weeks at the time of the data lock, with 23 of 30 progression-free at 12 weeks (76.7%, two-sided 95% CI, 57.7%-90.1%). No new safety signals were identified. Concurrent preclinical work in liposarcoma cell lines identified ANGPTL4 as a necessary late regulator of geroconversion, the pathway from reversible cell-cycle exit to a stably arrested inflammation-provoking senescent cell. Using this insight, we were able to identify patients in which abemaciclib induced tumor cell senescence. Senescence correlated with increased leukocyte infiltration, primarily CD4-positive cells, within a month of therapy. However, those individuals with both senescence and increased TILs were also more likely to acquire resistance later in therapy. These suggest that combining senolytics with abemaciclib in a subset of patients may improve the duration of response.

CONCLUSIONS

Abemaciclib was well tolerated and showed promising activity in DDLS. The discovery of ANGPTL4 as a late regulator of geroconversion helped to define how CDK4/6i-induced cellular senescence modulates the immune tumor microenvironment and contributes to both positive and negative clinical outcomes. See related commentary by Weiss et al., p. 649.

Anti-TIGIT Antibody Tiragolumab Alone or With Atezolizumab in Patients With Advanced Solid Tumors: A Phase 1a/1b Nonrandomized Controlled Trial

Importance

Inhibition of the T-cell immunoreceptor with Ig and ITIM domains (TIGIT)/poliovirus receptor pathway may amplify the antitumor immune response of atezolizumab in programmed death ligand 1-selected tumors.

Objective

To evaluate the safety and antitumor activity of the anti-TIGIT antibody tiragolumab and its combination with atezolizumab in patients with advanced solid tumors.

Design, Setting, and Participants

The GO30103 open-label, first-in-human phase 1a/1b dose-escalation and dose-expansion nonrandomized controlled trial was conducted at 13 sites in 6 countries (Australia, Canada, France, Korea, Spain, and the US). The start dates were May 23, 2016, for phase 1a and October 11, 2016, for phase 1b. Patients were aged 18 years or older with measurable disease at baseline. The clinical cutoff date was October 1, 2021. Data analysis was performed on January 24, 2022.

Interventions

Patients received fixed-dose intravenous tiragolumab on day 1 of each 21-day cycle (2 mg escalating to 1200 mg) in phase 1a, plus fixed-dose intravenous atezolizumab (1200 mg every 3 weeks) in phase 1b. Patients were treated until disease progression, loss of clinical benefit, or development of unacceptable toxicity.

Main Outcomes and Measures

The primary end points included the safety, tolerability, and recommended phase 2 dose (RP2D) of tiragolumab or combination tiragolumab plus atezolizumab. The secondary end point included the investigator-assessed objective response rate (ORR). Counts and percentages are used for categorical variables, and medians and ranges are used for continuous variables.

Results

Among the phase 1a (n = 24) and 1b (n = 49) dose-escalation cohorts, the median age was 60 (range, 40-77) and 54 (range, 25-81) years, respectively. More than half of patients were women (14 of 24 [58%] and 25 of 49 [51%]), and more than a third (10 [42%] and 18 [37%]) had received 4 or more prior cancer therapies. No dose-limiting toxicities occurred, and the maximum tolerated dose of tiragolumab was not reached (NR). The most frequent treatment-related adverse events (AEs) were fatigue (5 of 24 [21%]) in phase 1a and pruritus (5 of 49 [10%]) in phase 1b; the majority of AEs were grade 1 or 2. Immune-mediated AEs occurred in 4 of 24 (17%) and 29 of 49 (59%) patients during phases 1a and 1b, respectively (primarily grade 1 or 2). The RP2D of tiragolumab was 600 mg intravenously every 3 weeks, which was tested in phase 1b dose expansion. The confirmed ORR was 0% during phase 1a, with evidence of antitumor activity in 6% of patients (n = 3) during phase 1b. The safety profile of combination tiragolumab plus atezolizumab in phase 1b was similar in the dose-escalation and dose-expansion cohorts. The confirmed ORR was 46% (6 of 13) in the non-small cell lung cancer (NSCLC) cohort (median duration of response [DOR], NR) and 28% (5 of 18) in the esophageal cancer (EC) cohort (median DOR, 15.2 [95% CI, 7.0 to NR] months).

Conclusions and Relevance

In this nonrandomized controlled trial, tiragolumab was well tolerated with or without atezolizumab; no new safety signals were observed. Preliminary antitumor activity was demonstrated for the combination regimen in patients with cancer immunotherapy-naive metastatic NSCLC or EC.

Trial Registration

ClinicalTrials.gov Identifier: NCT02794571.

Immune-related Adverse Events after Immune Checkpoint Blockade-based Therapy Are Associated with Improved Survival in Advanced Sarcomas

The association between immune-related AEs (irAE) and outcome in patients with sarcoma is not known. We retrospectively reviewed a cohort of patients with advanced sarcoma treated with immune checkpoint blockade (ICB)-based therapy. Association of irAEs with survival was assessed using a Cox regression model that incorporated irAE occurrence as a time-dependent covariate. Tumor samples with available RNA sequencing data were stratified by presence of an irAE to identify patterns of differential gene expression. A total of 131 patients were included. Forty-two (32%) had at least one irAE of any grade and 16 (12%) had at least one grade ≥ 3 irAE. The most common irAEs were hypothyroidism (8.3%), arthralgias (5.3%), pneumonitis (4.6%), allergic reaction (3.8%), and elevated transaminases (3.8%). Median progression-free survival (PFS) and overall survival (OS) from the time of study entry were 11.4 [95% confidence interval (CI), 10.7-15.0) and 74.6 weeks (CI, 44.9-89.7), respectively. On Cox analysis adjusting for clinical covariates that were significant in the univariate setting, the HR for an irAE (HR, 0.662; CI, 0.421-1.041) approached, but did not reach statistical significance for PFS (P = 0.074). Patients had a significantly lower HR for OS (HR, 0.443; CI, 0.246-0.798; P = 0.007) compared with those without or before an irAE. Gene expression profiling on baseline tumor samples found that patients who had an irAE had higher numbers of tumor-infiltrating dendritic cells, CD8+ T cells, and regulatory T cells as well as upregulation of immune and inflammatory pathways.

SIGNIFICANCE

irAE after ICB therapy was associated with an improved OS; it also approached statistical significance for improved PFS. Patients who had an irAE were more likely to have an inflamed tumor microenvironment at baseline.

Stereotactic body radiation therapy for sarcoma pulmonary metastases

BACKGROUND/PURPOSE

Stereotactic body radiation therapy (SBRT) is standard for patients with inoperable early-stage NSCLC. We hypothesized that SBRT for sarcoma pulmonary metastases would achieve high rates of local control with acceptable toxicity and that patients with oligometastatic disease may achieve prolonged survival following SBRT.

MATERIALS/METHODS

This retrospective review included consecutive patients at our institution treated with SBRT for sarcoma pulmonary metastases. Cumulative incidence of local failure (LF) was estimated using a competing risks framework.

RESULTS

We identified 66 patients treated to 95 pulmonary metastases with SBRT. The median follow-up from the time of SBRT was 36 months (95% CI 34 - 53 months). The cumulative incidence of LF at 12 and 24 months was 3.1% (95% CI 0.9 - 10.6%) and 7.4% (95% CI 4.0% - 13.9%), respectively. The 12- and 24-month overall survival was 74% (95% CI 64 - 86%) and 49% (38 - 63%), respectively. Oligometastatic disease, intrathoracic only disease, and performance status were associated with improved survival on univariable analysis. Three patients had grade 2 pneumonitis, and one patient had grade 2 esophagitis. No patients had ≥ grade 3+ toxicities.

CONCLUSION

To the best of our knowledge, this is the largest series of patients treated with SBRT for pulmonary sarcoma metastases. We observed that SBRT offers an effective alternative to surgical resection with excellent local control and low proportions of toxicity.

Undifferentiated and Dedifferentiated Metastatic Melanomas Masquerading as Soft Tissue Sarcomas: Mutational Signature Analysis and Immunotherapy Response

The distinction between undifferentiated melanoma (UM) or dedifferentiated melanoma (DM) from undifferentiated or unclassifiable sarcoma can be difficult and requires the careful correlation of clinical, pathologic, and genomic findings. In this study, we examined the utility of mutational signatures to identify patients with UM/DM with particular attention as to whether this distinction matters for treatment because the survival of patients with metastatic melanoma has dramatically improved with immunologic therapy, whereas durable responses are less frequent in sarcomas. We identified 19 cases of UM/DM that were initially reported as unclassified or undifferentiated malignant neoplasm or sarcoma and submitted for targeted next-generation sequencing analysis. These cases were confirmed as UM/DM by harboring melanoma driver mutations, UV signature, and high tumor mutation burden. One case of DM showed melanoma in situ. Meanwhile, 18 cases represented metastatic UM/DM. Eleven patients had a prior history of melanoma. Thirteen of 19 (68%) of the tumors were immunohistochemically completely negative for 4 melanocytic markers (S100, SOX10, HMB45, and MELAN-A). All cases harbored a dominant UV signature. Frequent driver mutations involved BRAF (26%), NRAS (32%), and NF1 (42%). In contrast, the control cohort of undifferentiated pleomorphic sarcomas (UPS) of deep soft tissue exhibited a dominant aging signature in 46.6% (7/15) without evidence of UV signature. The median tumor mutation burden for DM/UM vs UPS was 31.5 vs 7.0 mutations/Mb (P < .001). A favorable response to immune checkpoint inhibitor therapy was observed in 66.6% (12/18) of patients with UM/DM. Eight patients exhibited a complete response and were alive with no evidence of disease at the last follow-up (median 45.5 months). Our findings support the usefulness of the UV signature in discriminating DM/UM vs UPS. Furthermore, we present evidence suggesting that patients with DM/UM and UV signatures can benefit from immune checkpoint inhibitor therapy.

A randomised phase II trial of a trivalent ganglioside vaccine targeting GM2, GD2 and GD3 combined with immunological adjuvant OPT-821 versus OPT-821 alone in metastatic sarcoma patients rendered disease-free by surgery

BACKGROUND

Recurrence after resection of metastatic sarcoma is common. The gangliosides GM2, GD2 and GD3 are strongly expressed across sarcoma subtypes. We hypothesised that generation of anti-ganglioside antibodies would control micrometastases and improve outcomes in sarcoma patients who were disease-free after metastasectomy.

METHODS

We conducted a randomised phase II trial of the immunological adjuvant OPT-821 with a KLH-conjugated ganglioside vaccine targeting GM2, GD2 and GD3, versus OPT-821 alone in patients with metastatic sarcoma following complete metastasectomy. Patients received 10 subcutaneous injections at Weeks 1, 2, 3, 8, 16, 28, 40, 52, 68 and 84 and were followed for evidence of recurrent disease. The primary end-point was relapse-free survival. Secondary end-points included overall survival and serologic response.

RESULTS

A total of 136 patients were randomised, 68 to each arm. The mean age was 51.2, 52.2% were male, 90.4% had relapsed disease, 86.8% had high-grade tumours and 14% had ≥4 metastases resected. Histologies included leiomyosarcoma (33%), spindle cell sarcoma (14%), undifferentiated pleomorphic sarcoma (13%), osteosarcoma (10%), synovial sarcoma (9%), liposarcoma (9%) and others (12%). Most adverse events were Grade ≤2 (83.8% and 70.6% in the vaccine and adjuvant arms, respectively). The most common (≥20% of patients) were injection site reaction (89.7%), fatigue (44.1%) and pyrexia (27.9%) on the vaccine arm, and injection site reaction (69.1%) on the adjuvant only arm. The 1-year relapse-free survival rate (34.5% and 34.8% in the vaccine and OPT-821 monotherapy arm, respectively) did not differ between arms (P = 0.725). One-year overall survival rates were 93.1% and 91.5% in the vaccine and OPT-821 monotherapy arm, respectively (P = 0.578). Serologic responses at week 9 were more frequent on the vaccine arm (96.5% of patients) than in the adjuvant arm (32.8%), and the difference between groups was durable.

CONCLUSIONS

A sustained serologic response to vaccination was induced with the vaccine, but no difference in recurrence-free or overall survival was observed between treatment arms.

CLINICALTRIALS

gov identifier: NCT01141491.

Retrospective observational studies in ultra-rare sarcomas: A consensus paper from the Connective Tissue Oncology Society (CTOS) community of experts on the minimum requirements for the evaluation of activity of systemic treatments

BACKGROUND

In ultra-rare sarcomas (URS) the conduction of prospective, randomized trials is challenging. Data from retrospective observational studies (ROS) may represent the best evidence available. ROS implicit limitations led to poor acceptance by the scientific community and regulatory authorities. In this context, an expert panel from the Connective Tissue Oncology Society (CTOS), agreed on the need to establish a set of minimum requirements for conducting high-quality ROS on the activity of systemic therapies in URS.

METHODS

Representatives from > 25 worldwide sarcoma reference centres met in November 2020 and identified a list of topics summarizing the main issues encountered in ROS on URS. An online survey on these topics was distributed to the panel; results were summarized by descriptive statistics and discussed during a second meeting (November 2021).

RESULTS

Topics identified by the panel included the use of ROS results as external control data, the criteria for contributing centers selection, modalities for ensuring a correct pathological diagnosis and radiologic assessment, consistency of surveillance policies across centers, study end-points, risk of data duplication, results publication. Based on the answers to the survey (55 of 62 invited experts) and discussion the panel agreed on 18 statements summarizing principles of recommended practice.

CONCLUSIONS

These recommendations will be disseminated by CTOS across the sarcoma community and incorporated in future ROS on URS, to maximize their quality and favor their use as control data when results from prospective studies are unavailable. These recommendations could help the optimal conduction of ROS also in other rare tumors.

Immunotherapy in Sarcoma: Where Do Things Stand?

Early experiences with modern immunotherapy have been disappointing in trials of unselected sarcoma subtypes. However, remarkable efficacy has been observed with immune checkpoint inhibitors (ICIs) in a subset of patients, with the most promising outcomes to date in alveolar soft part sarcoma, cutaneous angiosarcoma, undifferentiated pleomorphic sarcoma (UPS), and dedifferentiated liposarcoma (dLPS). Adoptive cellular therapies targeting cancer testis antigens have shown promising activity, but only synovial sarcoma (SS) and myxoid/round cell liposarcomas reliably express these targets. The majority of sarcomas are immunologically "cold" with sparse immune infiltration, which may explain the poor response to immunotherapy. Current immunotherapy trials for sarcomas explore combination therapies with checkpoint inhibitors to overcome immune evasion and novel targets in adoptive cellular therapies. The role of tertiary lymphoid structures, PD-L1 expression, tumor mutational burden, microsatellite instability, and tumor lymphocytes as biomarkers for response are areas of active investigation. In this review, we highlight prior and ongoing clinical efforts to improve outcomes with immunotherapy and discuss the current state of understanding for biomarkers to select patients most likely to benefit from this approach.

The Role of Immunotherapy in the Management of Soft Tissue Sarcomas: Current Landscape and Future Outlook

Soft tissue sarcomas (STS) are a subset of sarcoma, a rare group of heterogeneous malignancies of mesenchymal origin. Current standard of care involves surgical resection with systemic chemotherapy used to treat high-risk localized and metastatic disease. Though classically thought to be immunologically quiet tumors, STS interact with the immune system, undergoing immunoediting that alters tumor immunogenicity and the tumor microenvironment. Recent advances with immune checkpoint inhibition have led to clinical trials exploring the efficacy of immunotherapy in treating STS. Results from these trials point to histologic subtype-specific clinical activity of immune checkpoint blockade. In addition, combinatorial strategies adding immune checkpoint inhibition to local or systemic therapies for STS have further increased their efficacy. Targeted immunotherapies using engineered T-cell receptor-based approaches also show increasing promise as treatment options for some patients with STS. Adoptive transfer of autologous T cells targeting NY-ESO-1 and MAGE-A4 have high response rates in sarcomas expressing these antigens, although recurrence is often seen in responding patients. Future work must focus on identifying primary and acquired mechanisms of resistance to these therapies, and extend T-cell receptor discovery to other tumor-associated antigens.

Pilot study of bempegaldesleukin in combination with nivolumab in patients with metastatic sarcoma

PD-1 blockade (nivolumab) efficacy remains modest for metastatic sarcoma. In this paper, we present an open-label, non-randomized, non-comparative pilot study of bempegaldesleukin, a CD122-preferential interleukin-2 pathway agonist, with nivolumab in refractory sarcoma at Memorial Sloan Kettering/MD Anderson Cancer Centers (NCT03282344). We report on the primary outcome of objective response rate (ORR) and secondary endpoints of toxicity, clinical benefit, progression-free survival, overall survival, and durations of response/treatment. In 84 patients in 9 histotype cohorts, all patients experienced ≥1 adverse event and treatment-related adverse event; 1 death was possibly treatment-related. ORR was highest in angiosarcoma (3/8) and undifferentiated pleomorphic sarcoma (2/10), meeting predefined endpoints. Results of our exploratory investigation of predictive biomarkers show: CD8 + T cell infiltrates and PD-1 expression correlate with improved ORR; upregulation of immune-related pathways correlate with improved efficacy; Hedgehog pathway expression correlate with resistance. Exploration of this combination in selected sarcomas, and of Hedgehog signaling as a predictive biomarker, warrants further study in larger cohorts.

Clinical sequencing of soft tissue and bone sarcomas delineates diverse genomic landscapes and potential therapeutic targets

The genetic, biologic, and clinical heterogeneity of sarcomas poses a challenge for the identification of therapeutic targets, clinical research, and advancing patient care. Because there are > 100 sarcoma subtypes, in-depth genetic studies have focused on one or a few subtypes. Herein, we report a comparative genetic analysis of 2,138 sarcomas representing 45 pathological entities. This cohort is prospectively analyzed using targeted sequencing to characterize subtype-specific somatic alterations in targetable pathways, rates of whole genome doubling, mutational signatures, and subtype-agnostic genomic clusters. The most common alterations are in cell cycle control and TP53, receptor tyrosine kinases/PI3K/RAS, and epigenetic regulators. Subtype-specific associations include TERT amplification in intimal sarcoma and SWI/SNF alterations in uterine adenosarcoma. Tumor mutational burden, while low compared to other cancers, varies between and within subtypes. This resource will improve sarcoma models, motivate studies of subtype-specific alterations, and inform investigations of genetic factors and their correlations with treatment response.

A pilot study of lenvatinib plus pembrolizumab in patients with advanced sarcoma

TPS11588

Background: New treatment options are needed for sarcomas. Pazopanib is the only targeted agent approved for multiple soft tissue sarcoma (STS) subtypes with a response rate of 6% and a PFS of 4.6 months. Immunotherapy has a limited role in STS, as the SARC028 study of pembrolizumab demonstrated an overall response rate of 18%, with the highest response rate seen in the undifferentiated pleomorphic sarcoma (UPS) cohort at 23%. Lenvatinib is an oral, multi-tyrosine kinase inhibitor approved for the treatment of multiple cancer types including progressive, radioiodine-refractory thyroid cancer and unresectable hepatocellular carcinoma with inhibitory activity against the receptor tyrosine kinases VEGFR 1-3, FGFR 1-3, KIT, PDGFR alpha/beta, and RET. Early outcomes with the combination of lenvatinib and pembrolizumab suggest that this regimen could be broadly superior to PD-1 targeting alone for several tumor types as high rates of objective response have been noted. The rationale for this study is based on preclinical work demonstrating the immunosuppressive effects of VEGF in the tumor immune microenvironment including inhibition of dendritic cell maturation, recruitment of immunosuppressive Tregs, MDSCs and TAMs and up-regulation of PD-1 on CD8+ cells. Methods: This is a pilot study evaluating the efficacy of lenvatinib and pembrolizumab in the treatment of select metastatic and/or unresectable sarcomas. Patients will be enrolled in one of five cohorts: Cohort A: leiomyosarcoma; Cohort B: UPS; Cohort C: vascular sarcomas (including angiosarcoma and epithelioid hemangioendothelioma); Cohort D: synovial sarcoma and malignant peripheral nerve sheath tumor; and Cohort E: bone sarcomas (limited to osteosarcoma and chondrosarcoma). Eligible patients should have had at least one prior therapy for unresectable and/or metastatic disease, but no more than three prior lines of therapy. Prior treatment with angiogenesis inhibitors or immunotherapy is excluded. Archival tissue is required for eligibility. Patients enrolled in the study will be treated initially with a 2 week run-in of lenvatinib 20 mg orally daily which will be continued daily thereafter. Subsequently, they will start pembrolizumab 200 mg intravenously every 21 days. The primary endpoint for each cohort is best overall response rate documented by RECIST v1.1 Criteria at 27 weeks. A sample size of 10 patients is planned for each of the five histological cohorts. If 2 or more confirmed responses are observed among the 10 patients in an arm, the drug combination will be considered positive and worthy of further investigation for that arm. Secondary endpoints are PFS, OS, duration of response and safety/tolerability of the combination. On-treatment biopsy and blood samples will be required for correlative assessments. Accrual in all cohorts is ongoing. Clinical trial information: NCT04784247.

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.

A phase I/II study of prexasertib in combination with irinotecan in patients with relapsed/refractory desmoplastic small round cell tumor and rhabdomyosarcoma

11503

Background: Prexasertib (PRX) is an inhibitor of CHK1, prevents DNA repair leading to mitotic catastrophe, and can enhance the activity of DNA-damaging chemotherapy. Translocation driven sarcomas exhibit high levels of replication stress and have demonstrated susceptibility to CHK1 inhibition in preclinical models. Desmoplastic small round cell tumor (DSRCT) and rhabdomyosarcoma (RMS) are aggressive sarcomas of children, adolescents and young adults for which novel therapies are urgently required. Methods: We conducted a phase I/II trial of PRX with irinotecan (irino) in patients ≥ 12 months of age with relapsed or refractory DSRCT or RMS. Eligible patients could have any number of prior therapies, including irino. Dose level 1 was PRX 80 mg/m2 on day 1 + irino 20 mg/m2 for 10 days. Dose levels 2 and 2A were PRX 105 or 150 mg/m2 (>21 years or ≤ 21 years) on day 1 and irino 20 mg/m2 for 10 (level 2) or 5 (level 2A) days. All cycles were 21 days. The primary objectives were to determine the RP2D of PRX with irino, and to determine the best overall response rate (ORR) in 6 months at the RP2D (RECIST v1.1) in DSRCT, with 3 or more responses out of 16 considered promising. Results: 21 patients were enrolled (DSRCT: 19; 2 RMS:2). The RP2D was dose level 2A. Treatment was well tolerated with the most common adverse events being neutropenia (48%), nausea (48%), and fatigue (52%). Cytopenias were managed with the aid of growth factor support in all patients once the RP2D was established. The DSRCT expansion enrolled 13 of 16 planned patients due to discontinuation of PRX supply prior to study completion. Four patients remain on therapy at the time of this submission. Responses in DSRCT patients at all dose levels are shown in Table. Sixteen of 21 enrolled patients, and 5 of 6 patients achieving PR had previously received irino. The median (range) number of cycles was 7 (2-26). Both RMS patients treated at the RP2D experienced SD as best response. The estimated ORR at the RP2D was 23%, and lower boundary of the one-sided 90% confidence interval was 9%, exceeding the unpromising rate of 5%. The two-sided 90% confidence interval was 7 to 49%. In addition, 3 patients had a PR at doses lower than the RP2D, bringing the ORR for all dose levels (n = 19) to 32% (90%CI: 15 to 53%). Conclusions: The RP2D of PRX in combination with irino is PRX 105 or 150 mg/m2 (>21 years or ≤ 21 years) on day 1 and irino 20 mg/m2 for 5 days in 21 day cycles with myelosuppression successfully managed with growth factor support. The study met its primary objective to consider PRX + irino promising in DSRCT and should be further investigated. Clinical trial information: NCT04095221. [Table: see text]

Presence of immune infiltrates, increased expression of transposable elements, and viral response pathways in sarcoma associate with response to checkpoint inhibition

11510

Background: Response to checkpoint inhibition (CPI) in sarcoma is overall low and varies between and within subtypes. Understanding tumor intrinsic determinants of this response may improve efficacy and patient selection. The de-repression of transposable elements (TEs), which are epigenetically silenced repetitive DNA elements of viral origin, is linked to anti-tumor immunity through an antiviral inflammatory response. We hypothesize that baseline expression of TEs and epigenetic regulators correlates with overall response rate (ORR) in sarcoma CPI clinical trials. Methods: This is a retrospective analysis of bulk RNA-sequencing data from pre-treatment biopsies of patients on CPI trials in sarcoma (pembrolizumab plus talimogene laherparepvec, nivolumab plus bempegaldesleukin, and pembrolizumab plus epacadostat). Sixty-seven samples from unique patients representing 12 subtypes were analyzed. The MCP counter deconvolution method and unsupervised clustering were used to group samples by immune phenotypes resulting in immune ‘hot’ and ‘cold’ clusters. ORR was defined by RECIST. To determine if baseline expression of TEs and epigenetic regulators significantly predicted immune types, we implemented a lasso penalized logistic regression. Results: Immune ‘hot’ tumors were characterized by increased immune infiltrates including CD8+ T-cells, B-cells, and NK cells vs ‘cold’ tumors. Patients with ‘hot’ vs ‘cold’ tumors had an ORR of 30.5% (11/36) vs. 3.2% (1/31) (p = 0.003; chi-squared). The best predictors of ‘hot vs ‘cold’ was the increased expression of multiple TE families including MER45A, MER57F, and LTR21B (respective lasso coefficients, 0.27, 0.07, and 0.07). Expression of IKZF1, a chromatin-interacting transcription factor, was also predictive (lasso coefficient, 0.35) and increased expression correlated with improved ORR (p = 0.003; unpaired t-test). TE and IKFZ1 expression was significantly correlated with CD8+ T-cell signaling and antiviral response pathways such as cGAS-STING (MER57F, r2= 0.43, padj = 1.75E-4; IKZF1, r2= 0.63, padj = 6.28E-9) and type II interferon (MER57F, r2= 0.67, padj = 2.51E-10; IKZF1, r2= 0.60, padj = 7.19E-8). Increased expression of cGAS-STING (p = 3.9E-4; unpaired t-test) and type II interferon pathways (p = 1.89E-10; unpaired t-test) was significant in ‘hot’ tumors. Conclusions: Immune ‘hot’ baseline immune profiles of sarcoma are associated with improved ORR to CPI and with increased expression of TEs and IKZF1. These differences in gene expression correlate with increased inflammatory signaling, which suggests a response to TE-encoded viral-like sequences that are typically epigenetically silenced. Induction of TE de-repression and IKZF1 expression through epigenetic targeting warrants pre-clinical investigation as a strategy to promote CPI response in sarcomas.

A phase I/II trial of the PD-1 inhibitor retifanlimab (R) in combination with gemcitabine and docetaxel (GD) as first-line therapy in patients (Pts) with advanced soft-tissue sarcoma (STS)

11516

Background: In a phase III trial, GD had similar response and survival rates to doxorubicin when administered as first-line therapy to advanced STS pts. G and D have each demonstrated synergy with PD-1 blockade in pre-clinical or clinical studies. We hypothesized that GD plus R would be safe, tolerable, and have synergistic activity in STS. Methods: This is an ongoing open-label, single-center, phase I/II trial of R (INCMGA00012) combined with GD in pts with treatment-naïve unresectable or metastatic high-grade STS. Herein, we report the phase I results, which included a safety run-in followed by a 3+3 dose de-escalation design. G (900 mg/m2) was administered on days 1 and 8 and D (75 mg/m2) on day 8, in 21-day cycles. R (210 mg IV flat dose on the run-in portion and 375 mg on the dose de-escalation portion) was administered on day 1 of each cycle starting in cycle 2 and continued as monotherapy after completion of 6 cycles of GD. The primary endpoint of the phase I was to determine the recommended phase 2 dose (RP2D) of R plus GD. Secondary endpoints included describing the safety, assessing best overall response rate (ORR) by RECIST 1.1, disease control rate (DCR), and progression-free survival (PFS). Results: Thirteen pts were treated, 7on the run-in and 6 on the de-escalation portion. One pt progressed prior to starting R and was replaced. Median pt age was 53 (range 28 – 74) and 7 were female. Histologies included leiomyosarcoma (n = 6), undifferentiated pleomorphic sarcoma (2), dedifferentiated liposarcoma (2), pleomorphic liposarcoma (1), angiosarcoma (1), and myxofibrosarcoma (1). The Table lists treatment-related adverse events (TRAEs) that occurred in ≥ 20% pts in descending order of frequency. Additional Grade (Gr) 3 TRAEs occurring in 1 pt each, included: infusion reaction, leukopenia, anorectal infection, neutropenia, and pyelonephritis. Gr 3 pyelonephritis was the only dose-limiting toxicity. There were no Gr ≥ 4 TRAEs. One pt (Gr 3 elevated AST/ALT) required corticosteroids and cessation of study therapy. The RP2D was determined to be 375 mg of R plus GD. Twelve pts were evaluable for response. ORR was 17% (1 of 6; 95% CI 1 - 64%) and 50% (3 of 6; 95% CI 19% - 81%) in the run-in and de-escalation cohorts, respectively. DCR was 100% (6 of 6; 95% CI 52 - 100%) and 83% (5 of 6; 95% CI: 36 - 99%). PFS rates at 24 weeks were 60% (95% CI: 29 - 100%) and 44% (95% CI: 17 - 100%). Conclusions: R plus GD was generally safe and well tolerated with no unexpected safety signals to date. The phase II portion evaluating efficacy of R plus GD at the RP2D is ongoing. Clinical trial information: NCT04577014. [Table: see text]

Primary efficacy and safety of letetresgene autoleucel (lete-cel; GSK3377794) pilot study in patients with advanced and metastatic myxoid/round cell liposarcoma (MRCLS)

11500

Background: Lete-cel is an autologous T-cell therapy targeting NY-ESO-1 tumors using a genetically modified, high-affinity T-cell receptor. MRCLS is a sarcoma with poor response to current immunotherapy approaches and limited treatment options. The cancer testis antigen NY-ESO-1 is expressed in 80‒90% of MRCLS tumors, making this a promising target. This report summaries the primary efficacy and safety results of a pilot study of lete-cel in patients (pts) with advanced or metastatic MRCLS. Methods: This is an open label, study of lete-cel in pts with advanced or metastatic MRCLS following reduced-dose (Cohort 1 [C1]; 30 mg/m2 fludarabine [flu] x 3d + 600 mg/m2 cyclophosphamide [cy] x 3d) or standard dose (Cohort 2 [C2]; 30 mg/m2 flu x 4d + 900 mg/m2 cy x 3d) lymphodepletion (LD). Key eligibility criteria were: age ≥18 y; HLA-A*02:01; A*02:05, or A*02:06; advanced or metastatic NY-ESO-1+ MRCLS (≥30% of cells 2+/3+ by IHC); prior anthracycline treatment, and measurable disease. The transduced T cell dose range was 1– 8 × 109. Response was assessed at weeks 4, 8, 12, 24, then every 3 months (mo) until disease progression, death, or withdrawal. Investigator-assessed (IA) ORR by RECIST v1.1 was the primary efficacy endpoint. Secondary endpoints included safety, independently assessed ORR by RECIST v1.1, time to response (TTR), duration of response (DOR), progression-free survival (PFS). Overall survival (OS) was an exploratory endpoint. Results: 23 pts enrolled from March 2017 to February 2020. The median age was 47.0 yrs (range 33 to 72). 20 pts were dosed with T cells, 10 in each cohort with a median transduced T cell dose of 4.6 x 109. 8 of 20 pts (40%) had 1 line of prior therapy, 6 pts (30%) had 2 lines, and 6 pts (30%) had ≥3 lines. The median follow-up was 5.6 (C1) and 12.9 (C2) mo. In C1 the IA ORR was 20%, with best response (BR) of partial response (PR) in 2 pts and BR of stable disease (SD) in 8 pts. The median TTR was 1.9 mo, median DOR was 5.3 mo (95% CI: 1.9-8.7), and median PFS was 5.4 mo (95% CI: 2.0-11.5). In C2 the IA ORR was 40%, with BR of PR in 4 pts and BR of SD in 5 pts. The median TTR was 1.9 mo, median DOR was 7.5 mo (95% CI: 6.0-NE), and median PFS was 8.7mo (95% CI: 0.9-NE). OS is not yet mature. All pts experienced at least 1 treatment-emergent adverse event (TEAE). 55% of pts experienced serious TEAEs. 90% of pts had Gr ≥3 TE neutropenia, with 83% probability of resolution of initial Gr ≥3 occurrence by Day 30. Cytokine release syndrome occurred in 80% of pts, of which 25% were Gr 3, with 1st onset within 5d of infusion and median duration 7.5d. No Graft-vs-host disease, immune effector cell–associated neurotoxicity syndrome, Guillain-Barré Syndrome were reported. Conclusions: Treatment with a single dose of lete-cel showed anti-tumor activity, including response and long median PFS with an acceptable safety profile in pts with advanced and metastatic MRCLS. Clinical trial information: NCT02992743.

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.

Phase Ib Trial of the Combination of Imatinib and Binimetinib in Patients with Advanced Gastrointestinal Stromal Tumors

PURPOSE

This phase Ib trial was designed to evaluate the safety and early efficacy signal of the combination of imatinib and binimetinib in patients with imatinib-resistant advanced gastrointestinal stromal tumors (GISTs).

PATIENTS AND METHODS

This trial used a standard 3 + 3 design to determine the recommended phase II dose (RP2D). Additional patients were enrolled on an expansion cohort at the RP2D enriching for succinate dehydrogenase (SDH)-deficient GISTs to explore potential efficacy.

RESULTS

The trial enrolled nine patients in the dose-escalation cohort and 14 in the dose-expansion cohort including six with SDH-deficient GISTs. Imatinib 400 mg daily with binimetinib 45 mg twice daily was established as the RP2D. Dose-limiting toxicity (DLT) was asymptomatic grade 4 creatinine phosphokinase (CPK) elevation. The most common non-DLT grade 3/4 toxicity was asymptomatic CPK elevation (69.6%). Other common ≥grade 2 toxicities included peripheral edema (17.4%), acneiform rash (21.7%), anemia (30.4%), hypophosphatemia (39.1%), and aspartate aminotransferase (AST) increase (17.4%). Two serious adverse events occurred (grade 2 dropped head syndrome and grade 3 central retinal vein occlusion). No unexpected toxicities were observed. Limited clinical activity was observed in KIT-mutant GIST. For SDH-deficient GISTs, one of five had confirmed RECIST1.1 partial response (PR). The median progression-free survival (mPFS) in patients with SDH-deficient GIST was 45.1 months [95% confidence interval (CI), 15.8-not estimable (NE)]; the median overall survival (mOS) was not reached (95% CI, 31.6 months-NE). One patient with a refractory metastatic SDH-deficient GIST had an exceptional pathologic response and durable clinical benefit.

CONCLUSIONS

The combination of imatinib and binimetinib is safe with manageable toxicity and has encouraging activity in SDH-deficient but not imatinib-refractory KIT/PDGFRA-mutant GISTs. The observed clinical benefits provide a motivation for a larger trial of the combination strategy in SDH-deficient GISTs.

Phase II Trial of Imatinib Plus Binimetinib in Patients With Treatment-Naive Advanced Gastrointestinal Stromal Tumor

PURPOSE

Dual targeting of the gastrointestinal stromal tumor (GIST) lineage-specific master regulators, ETV1 and KIT, by MEK and KIT inhibitors were synergistic preclinically and may enhance clinical efficacy. This trial was designed to test the efficacy and safety of imatinib plus binimetinib in first-line treatment of GIST.

METHODS

In this trial (NCT01991379), treatment-naive adult patients with confirmed advanced GISTs received imatinib (400 mg once daily) plus binimetinib (30 mg twice daily), 28-day cycles. The primary end point was RECIST1.1 best objective response rate (ORR; complete response plus partial response [PR]). The study was designed to detect a 20% improvement in the ORR over imatinib alone (unacceptable rate of 45%; acceptable rate of 65%), using an exact binomial test, one-sided type I error of 0.08 and type II error of 0.1, and a planned sample size of 44 patients. Confirmed PR or complete response in > 24 patients are considered positive. Secondary end points included Choi and European Organisation for Research and Treatment of Cancer Response Rate, progression-free survival (PFS), overall survival (OS), pathologic responses, and toxicity.

RESULTS

Between September 15, 2014, and November 15, 2020, 29 of 42 evaluable patients with advanced GIST had confirmed RECIST1.1 PR. The best ORR was 69.0% (two-sided 95% CI, 52.9 to 82.4). Thirty-nine of 41 (95.1%) had Choi PR approximately 8 weeks. Median PFS was 29.9 months (95% CI, 24.2 to not estimable); median OS was not reached (95% CI, 50.4 to not estimable). Five of eight patients with locally advanced disease underwent surgery after treatment and achieved significant pathologic response (≥ 90% treatment effect). There were no unexpected toxicities. Grade 3 and 4 toxicity included asymptomatic creatinine phosphokinase elevation (79.1%), hypophosphatemia (14.0%), neutrophil decrease (9.3%), maculopapular rash (7.0%), and anemia (7.0%).

CONCLUSION

The study met the primary end point. The combination of imatinib and binimetinib is effective with manageable toxicity and warrants further evaluation in direct comparison with imatinib in frontline treatment of GIST.

Comparison of tumor assessments using RECIST 1.1 and irRECIST, and association with overall survival

Background

Patients treated with immune checkpoint inhibitors (ICIs) may experience pseudoprogression, which can be classified as progressive disease (PD) by Response Evaluation Criteria in Solid Tumors (RECIST) V.1.1 and could lead to inappropriate treatment discontinuation. Immune-response criteria were developed to better capture novel response patterns seen with ICIs.

Methods

We pooled data from 1765 patients with 12 types of advanced solid tumors treated with avelumab (an anti-programmed death ligand 1 (PD-L1) monoclonal antibody) monotherapy in the JAVELIN Solid Tumor and JAVELIN Merkel 200 trials, conducted a comparative analysis of tumor assessments by investigators according to RECIST 1.1 and immune-related RECIST (irRECIST), and evaluated the correlation between progression-free survival (PFS) and overall survival (OS).

Results

In total, 147 patients (8.3%) had a best overall response (BOR) of PD by RECIST 1.1 but had immune-related disease control by irRECIST (defined as immune-related BOR (irBOR) of immune-related stable disease or better). This discordance was seen irrespective of PD-L1 status and observed across all tumor types. Overall, PFS and immune-related PFS showed similar imputed rank correlations with OS.

Conclusions

The use of irRECIST identified a subset of patients with a BOR of PD by RECIST 1.1 but an irBOR of immune-related disease control by irRECIST with a distinctive survival curve, thereby providing more clinically relevant information than RECIST 1.1 alone. However, as a surrogate endpoint for OS in the whole population, immune-related PFS by irRECIST did not show improved predictive value compared with PFS by RECIST 1.1.

A Phase Ib/II Randomized Study of RO4929097, a Gamma Secretase or Notch Inhibitor with or without Vismodegib, a Hedgehog Inhibitor, in Advanced Sarcoma

PURPOSE

Because the Hedgehog and Notch pathways are often overexpressed in mesenchymal malignancies, we evaluated the efficacy of concurrent inhibition of Notch and Hedgehog signaling using the gamma secretase inhibitor (GSI) RO4929097 and the smoothened antagonist vismodegib in unresectable or metastatic sarcoma.

PATIENTS AND METHODS

In this investigator-initiated trial, phase 1b employed standard 3+3 dose-escalation in which patients first received vismodegib once daily for 21 days, followed by the combination of RO4929097 concurrently with vismodegib in 21-day cycles. In phase II, patients were randomized to RO4929097 alone or in combination with vismodegib.

RESULTS

Nine patients were treated in phase Ib with no dose-limiting toxicities. RO4929097 at 15 mg daily in combination with 150 mg daily of vismodegib was declared the recommended phase 2 dose. Most adverse events (AEs) were grade {less than or equal to} 2. In phase II (closed early due to discontinuation of RO4929097 evaluation), 34 patients were randomized to RO4929097 alone and 33 to RO4929097 plus vismodegib. RO4929097 did not interfere with the steady-state concentration of vismodegib, while vismodegib reduced the plasma concentration of RO492909. No patients had an objective response. Neither progression-free nor overall survival differed significantly between treatment arms. Paired tumor biopsies from a subset of patients demonstrated inhibition of cleaved Notch.

CONCLUSIONS

The combination of RO4929097 plus vismodegib was generally well tolerated. Although accrual to this study was not completed, vismodegib did not meaningfully enhance the clinical efficacy of RO4929097 in an unplanned analysis. GSIs and GSIs plus vismodegib can inhibit intratumoral Notch and downstream pAkt signaling.

Long term follow-up and patterns of response, progression and hyperprogression in patients after PD-1 blockade in advanced sarcoma

PURPOSE

PD-1 blockade can mediate objective responses in advanced sarcomas, but their durability has not been established and it is unclear if hyperprogressive disease (HPD) occurs in sarcomas treated with PD-1 inhibitors.

METHODS

We pooled patients who were treated prospectively with nivolumab or pembrolizumab as monotherapy or with bempegaldesleukin, epacadostat, ipilimumab or Talimogene laherparepvec. We did a new independent assessment for HPD and analyzed clinical, pathologic and genomic data from baseline tumor biopsies. Our primary endpoint was the incidence of HPD; secondary endpoints were clinical or genomic correlates of response or HPD.

RESULTS

We treated 134 patients with advanced sarcoma from 2015 - 2019. Twenty-one patients (16%) had a complete or partial response (CR/PR), and 30% of responses were durable for over 2 years. Forty-eight (36%) patients had stable disease (SD), 45 (34%) had progressive disease without HPD (PD) and 15 (11%) had HPD. Five patients (4%) were not evaluable for HPD. The sarcoma subtypes, sites of metastasis, clinical course, and genomic alterations in patients with PD and HPD were similar, except HPD tumors were smaller at baseline.

CONCLUSIONS

In patients with advanced sarcoma, PD-1 blockade can mediate durable responses. HPD occurs in sarcoma at an incidence that is similar to what has been reported in other solid tumors, but patients with HPD were clinically and biologically similar to those who had PD. Further research is required to establish whether HPD is a biologically distinct phenomenon and whether a theoretical risk of HPD should influence patient management.

Case Report: Response to Regional Melphalan via Limb Infusion and Systemic PD1 Blockade in Recurrent Myxofibrosarcoma: A Report of 2 Cases

Treatment options for patients with advanced sarcoma remain limited. Promising responses to checkpoint inhibition have been observed, but responses to single-agent PD-1 inhibition are rare. We report on two patients with multiply recurrent myxofibrosarcoma treated with the combination of regionally administered melphalan (via isolated limb infusion) and pembrolizumab. Both patients had recurrent disease after multiple surgical resections and radiation. Analysis of primary tumors demonstrated microsatellite stable tumors with few mutations. After combination treatment, one patient had a significant partial response of 6 months duration, the second patient had a complete response of 2 years duration. Post treatment biopsies demonstrated immune infiltration into the tumor. These promising responses in patients with multiply recurrent myxofibrosarcoma have prompted the development of an investigator-initiated clinical trial to formally study the combination of regional melphalan and pembrolizumab in a systematic fashion (NCT04332874).

Avelumab in patients with previously treated metastatic Merkel cell carcinoma (JAVELIN Merkel 200): updated overall survival data after >5 years of follow-up

BACKGROUND

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that has a poor prognosis in patients with advanced disease. Avelumab [anti-programmed death-ligand 1 (PD-L1)] became the first approved treatment for patients with metastatic MCC (mMCC), based on efficacy and safety data observed in the JAVELIN Merkel 200 trial. We report long-term overall survival (OS) data after >5 years of follow-up from the cohort of patients with mMCC whose disease had progressed after one or more prior lines of chemotherapy.

PATIENTS AND METHODS

In Part A of the single-arm, open-label, phase II JAVELIN Merkel 200 trial, patients with mMCC that had progressed following one or more prior lines of chemotherapy received avelumab 10 mg/kg by intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxicity, or withdrawal. In this analysis, long-term OS was analyzed.

RESULTS

In total, 88 patients were treated with avelumab. At data cut-off (25 September 2020), median follow-up was 65.1 months (range 60.8-74.1 months). One patient (1.1%) remained on treatment, and an additional patient (1.1%) had reinitiated avelumab after previously discontinuing treatment. Median OS was 12.6 months [95% confidence interval (CI) 7.5-17.1 months], with a 5-year OS rate of 26% (95% CI 17% to 36%). In patients with PD-L1+ versus PD-L1- tumors, median OS was 12.9 months (95% CI 8.7-29.6 months) versus 7.3 months (95% CI 3.4-14.0 months), and the 5-year OS rate was 28% (95% CI 17% to 40%) versus 19% (95% CI 5% to 40%), respectively (HR 0.67; 95% CI 0.36-1.25).

CONCLUSION

Avelumab monotherapy resulted in meaningful long-term OS in patients with mMCC whose disease had progressed following chemotherapy. These results further support the role of avelumab as a standard of care for patients with mMCC.

18F-FDG PET/CT for post-treatment surveillance imaging of patients with stage III Merkel cell carcinoma

To investigate diagnostic and prognostic value of ¹⁸F-FDG PET/CT for surveillance imaging in patients treated for Stage III Merkel cell carcinoma (MCC). Methods: This retrospective study included 61 consecutive stage III MCC patients, who were clinically asymptomatic and underwent surveillance FDG-PET/CT. Findings were correlated with either pathology and/or clinical/imaging follow-up. Median follow-up period was 4.8 years. Statistical analyses were performed. Results: FDG-PET/CT detected unsuspected recurrences in 33% patients (20/61) with lesion-based sensitivity, specificity, and accuracy of 92%, 93%, and 93%, respectively. Mean±SD SUV for malignant and benign lesions was 7.5±3.9 and 3.8±2.0, respectively. Unknown distant metastases, as first recurrence site, were noted in 12 of 61 patients. Those with positive disease on FDG-PET/CT within one year of definitive treatment had relatively worse overall survival (p<0.0001). After adjustment on stage, risk of death increased with higher SUV_max (HR for one unit=1.17;P = 0.006) and with a higher number of positive lesions on FDG-PET/CT (HR for one additional lesion = 1.60;p<0.001). Conclusion: Post-definitive treatment surveillance FDG-PET/CT scan detects unsuspected recurrences and has prognostic value. Inclusion of FDG-PET/CT within the first 6 months after definitive treatment would be appropriate for surveillance and early detection of recurrence. Our data merits further studies to evaluate the prognostic implications.

First-line avelumab in a cohort of 116 patients with metastatic Merkel cell carcinoma (JAVELIN Merkel 200): primary and biomarker analyses of a phase II study

Background

Avelumab (anti-programmed death ligand 1 (PD-L1)) is approved in multiple countries for the treatment of metastatic Merkel cell carcinoma (mMCC), a rare and aggressive skin cancer. We report efficacy and safety data and exploratory biomarker analyses from a cohort of patients with mMCC treated with first-line avelumab in a phase II trial.

Methods

Patients with treatment-naive mMCC received avelumab 10 mg/kg intravenously every 2 weeks. The primary endpoint was durable response, defined as objective response (complete or partial response; assessed by independent review) lasting ≥6 months. Additional assessments included progression-free survival (PFS), overall survival (OS), safety, and biomarker analyses.

Results

In 116 patients treated with avelumab, median follow-up was 21.2 months (range: 14.9–36.6). Thirty-five patients had a response lasting ≥6 months, giving a durable response rate of 30.2% (95% CI: 22.0% to 39.4%). The objective response rate was 39.7% (95% CI: 30.7% to 49.2%). Median PFS was 4.1 months (95% CI: 1.4 to 6.1) and median OS was 20.3 months (95% CI: 12.4 to not estimable). Response rates were numerically higher in patients with PD-L1+ tumors, Merkel cell polyomavirus (MCPyV)-negative tumors, and tumors with increased intratumoral CD8⁺ T-cell density. Exploratory analyses did not identify a biomarker that could reliably predict a response to first-line treatment with avelumab; however, a novel gene expression signature to identify the presence of MCPyV+ tumors was derived. Treatment-related adverse events (any grade) occurred in 94 (81.0%) patients, including grade 3/4 events in 21 (18.1%) patients; no treatment-related deaths occurred.

Conclusion

In patients with mMCC, first-line treatment with avelumab led to responses in 40% and durable responses in 30%, and was associated with a low rate of grade 3/4 treatment-related adverse events.

The impact of MYC amplification on clinicopathologic features and prognosis of radiation-associated angiosarcomas of the breast

AIMS

Radiation-associated angiosarcomas (RT-AS) of the breast are rare tumours with poor prognosis. MYC amplification is considered the hallmark of RT-AS and is sometimes used as a diagnostic tool to distinguish from other radiation-associated vascular lesions. However, a small subset of RT-AS lacks MYC amplification, which may be associated with better outcome. Loss of H3K27me3 expression by immunohistochemistry (IHC) has been recently postulated as an additional diagnostic marker for RT-AS. This study aimed to evaluate the impact of MYC amplification as detected by fluorescence in situ hybridization and/or next-generation sequencing on clinicopathologic features and outcome in a large cohort of RT-AS, compare outcome with radiation-associated sarcomas of the breast (RT-S) other than angiosarcoma, and evaluate expression of H3K27me3 IHC in these groups.

METHODS AND RESULTS

Eighty-one RT-AS were identified, including 73 MYC amplified and 8 (10%) non-amplified. MYC amplified RT-AS were diagnosed in older patients (median age 69 vs 61 years). The 5-year disease specific survival and overall survival were 56% and 47%, respectively. Older age, larger tumour size, positive margin and MYC amplification were associated with worse prognosis. None of the RT-AS showed complete loss of H3K27me3 IHC expression. All 18 RT-S were MYC non-amplified, and complete loss of H3K27me3 expression was seen in 2. We found no difference in prognosis between RT-AS and RT-S.

CONCLUSIONS

RT-AS is associated with a poor prognosis. Older age at diagnosis, larger tumour size, positive margin at excision and MYC amplification are associated with worse prognosis.

Avelumab in patients with previously treated metastatic Merkel cell carcinoma: long-term data and biomarker analyses from the single-arm phase 2 JAVELIN Merkel 200 trial

Background

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer associated with a high risk of metastasis. In 2017, avelumab (anti–programmed death-ligand 1 (PD-L1)) became the first approved treatment for patients with metastatic MCC (mMCC), based on the occurrence of durable responses in a subset of patients. Here, we report long-term efficacy and safety data and exploratory biomarker analyses in patients with mMCC treated with avelumab.

Methods

In a cohort of this single-arm, phase 2 trial (JAVELIN Merkel 200), patients with mMCC and disease progression after prior chemotherapy received avelumab 10 mg/kg intravenously every 2 weeks. The primary endpoint was confirmed objective response rate (ORR) by independent review per Response Evaluation Criteria in Solid Tumors V.1.1. Other assessments included duration of response, progression-free survival, overall survival (OS), safety and biomarker analyses.

Results

As of 14 September 2018, 88 patients had been followed up for a median of 40.8 months (range 36.4–49.7 months). The ORR was 33.0% (95% CI 23.3% to 43.8%), including a complete response in 11.4% (10 patients), and the median duration of response was 40.5 months (95% CI 18.0 months to not estimable). As of 2 May 2019 (≥44 months of follow-up), the median OS was 12.6 months (95% CI 7.5 to 17.1 months) and the 42-month OS rate was 31% (95% CI 22% to 41%). Of long-term survivors (OS >36 months) evaluable for PD-L1 expression status (n=22), 81.8% had PD-L1+ tumors. In exploratory biomarker analyses, high tumor mutational burden (≥2 non-synonymous somatic variants per megabase) and high major histocompatibility complex class I expression (30% of tumors with highest expression) were associated with trends for improved ORR and OS. In long-term safety assessments (≥36 months of follow-up), no new or unexpected adverse events were reported, and no treatment-related deaths occurred.

Conclusions

Avelumab showed continued durable responses and meaningful long-term survival outcomes in patients with mMCC, reinforcing avelumab as a standard-of-care treatment option for this disease.

Trial registration number

NCT02155647

Master protocol to assess safety and recommended phase 2 dose of next generation NY-ESO-1–specific TCR T-cells in HLA-A*02 patients with synovial sarcoma or non-small cell lung cancer (Substudies 1 and 2)

TPS2661

Background: Letetresgene autoleucel (lete-cel; GSK3377794) is an autologous T-cell therapy using a genetically modified T-cell receptor (TCR) to improve recognition of cancer cells expressing NY-ESO-1/LAGE-1a. Next generation NY-ESO-1 TCR T-cell therapies, such as GSK3901961 and GSK3845097, integrate added genetic modifications to enhance anticancer activity. GSK3901961 co-expresses the CD8α chain to stabilize TCR-human leukocyte A (HLA) class I interactions on CD4+ T cells, improving T-cell persistence and helper functions such as Type 1 T-helper antitumor responses. GSK3845097 co-expresses a dominant negative transforming growth factor-β (TGF-β) type II receptor to reduce TGF-β pathway activation and maintain T-cell proliferation, cytokine production, and cytotoxicity in the tumor microenvironment. A first-time-in-human master protocol (NCT04526509) will evaluate safety, tolerability, and recommended phase 2 dose (RP2D) of these and possible subsequent therapies. Substudy 1 will assess GSK3901961 in patients (pts) with advanced non-small cell lung cancer (NSCLC) or synovial sarcoma (SS). Substudy 2 will assess GSK3845097 in pts with advanced SS. Methods: Each substudy includes a dose confirmation stage to assess RP2D and a dose expansion stage. Key inclusion criteria are age ≥18 y; 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 and anthracycline-based therapy receipt/completion/intolerance (SS only); and Stage IV NSCLC, receipt of ≥1 prior line(s) of standard of care (SOC) therapy including programmed death receptor- or ligand-1 inhibitors, and SOC chemotherapy receipt/intolerance (Substudy 1 only). Key exclusion criteria are prior malignancy that is not in complete remission or clinically significant systemic illness; prior receipt of gene/NY-ESO-1–specific therapy or allogenic stem cell/solid organ transplant; central nervous system metastases (SS only); and actionable genetic aberration and receipt/failure of ≥3 systemic therapy lines (Substudy 1 only). Primary endpoints are safety (adverse events) and tolerability (dose-limiting toxicities). Secondary endpoints include investigator-assessed overall response rate, duration of response, and maximum expansion/persistence and phenotype of infiltrating transduced T cells. Exploratory endpoints include laboratory parameters, overall survival, and anti-GSK3901961 or -GSK3845097 titers as applicable. Analyses will be descriptive. The substudies are enrolling. Funding: GSK (209012; NCT04526509). Editorial support was provided by Eithne Maguire, PhD, of Fishawack Indicia, part of Fishawack Health; funded by GSK. Previously presented at AACR 2021 (CT219). Clinical trial information: NCT04526509.

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. References: 1. Reckamp KL, et al. Ann Oncol 2019;30(Suppl_5):v602–v660. 2. Rapoport A, et al. J Clin Oncol 2020 38:15_suppl, TPS8555. 3. D’Angelo SP, et al. Cancer Discov 2018;8(8):944–957. 4. D’Angelo SP, et al. J Clin Oncol 2018 36:15_suppl, 3005. Funding: GSK. Editorial support was provided by Eithne Maguire, PhD, of Fishawack Indicia, part of Fishawack Health, and funded by GSK. Previously presented at BSG 2021 (P914542). Clinical trial information: NCT03967223.

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). References: 1. D’Angelo SP, et al. J Clin Oncol 2018;36:15_suppl, 3005. 2. Pollack SM, et al. Cancer Med 2020;9(13):4593–602. 3. D’Angelo SP, et al. J Immunother Cancer 2020;8:P298. Funding: GSK (208469; NCT02992743). Editorial support was provided by Eithne Maguire, PhD, of Fishawack Indicia, part of Fishawack Health, and funded by GSK. Clinical trial information: NCT02992743.

Avelumab in patients with previously treated Merkel cell carcinoma (JAVELIN Merkel 200): Updated overall survival data after more than five years of follow up

9517

Background: Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer. Although MCC is considered chemosensitive, patients typically have limited survival benefit with chemotherapy. Before the approval of immune checkpoint inhibitors, patients with metastatic MCC (mMCC) had a poor prognosis, with a historical 5-year overall survival (OS) rate of approximately 14%. Avelumab (anti–PD-L1) became the first approved treatment for patients with mMCC, based on efficacy and safety data observed in the phase 2 JAVELIN Merkel 200 trial (NCT02155647), in which patients with mMCC received avelumab monotherapy. We report the long-term OS data from the cohort of patients with mMCC whose disease had progressed after ≥1 prior line of chemotherapy. Methods: Eligible patients had histologically confirmed, measurable (per RECIST 1.1) stage IV MCC. Patients received avelumab 10 mg/kg by intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxicity, or withdrawal. Long-term OS was analyzed; updated data for other efficacy endpoints, including response and progression-free survival, were not obtained. Results: A total of 88 patients were enrolled and received avelumab treatment. As of September 25, 2020 (data cutoff), median follow-up was 65.1 months (range, 60.8-74.1 months). Median OS was 12.6 months (95% CI, 7.5-17.1 months); the 48- and 60-month OS rates were 30% (95% CI, 20%-40%) and 26% (95% CI, 17%-36%), respectively. At data cutoff, treatment was ongoing in 1 patient (1.1%) and an additional patient (1.1%) had reinitiated avelumab after previously discontinuing treatment. Reasons for treatment discontinuation were disease progression (n = 45 [51.1%]), adverse event (AE; n = 11 [12.5%]), death (n = 10 [11.4%]), withdrawal of consent (n = 9 [10.2%]), loss to follow-up (n = 1 [1.1%]), protocol noncompliance (n = 1 [1.1%]), and other reason (n = 10 [11.4%]). At data cutoff, 19 patients (21.6%) had discontinued treatment but remained in follow-up, and 63 patients (71.6%) had died; causes of death were disease progression (n = 49 [55.7%]), unknown reason (n = 9 [10.2%]), AE not related to study treatment (n = 3 [3.4%]), and other reason (n = 2 [2.3%]). In total, 26 patients (29.5%) received subsequent anticancer therapy; the most common subsequent therapies after trial discontinuation were avelumab (n = 4 [4.5%]), carboplatin and etoposide (n = 4 [4.5%]), and pembrolizumab (n = 4 [4.5%]). Conclusions: Avelumab monotherapy led to meaningful long-term OS in a subset of patients with mMCC whose disease had progressed after chemotherapy. These results further support the role of avelumab as a standard-of-care treatment for patients with mMCC. Clinical trial information: NCT02155647.

A phase 1b study of avelumab plus DCC-3014, a potent and selective inhibitor of colony stimulating factor 1 receptor (CSF1R), in patients with advanced high-grade sarcoma

11549

Background: Select sarcomas are infiltrated with immunosuppressive myeloid cells. DCC-3014 is an inhibitor of the CSF1R kinase that decreases tumor infiltrating myeloid cells in preclinical models. We hypothesized that DCC-3014 combined with the anti-PDL1 inhibitor avelumab would be safe and tolerable, decrease immunosuppressive myeloid cells, and increase cytotoxic T cells. Methods: This investigator initiated, open label, single center, phase I study of DCC-3014 plus avelumab in patients (pts) with unresectable or metastatic sarcoma utilized a standard 3+3 dose escalation design. DCC-3014 was administered on days 1-3 (loading dose of 20, 30, or 50 mg) followed by oral daily maintenance (10, 14, or 20 mg) in 28-day cycles; 800 mg of IV avelumab was administered q2weeks. The primary endpoint was to determine the recommended phase 2 dose (RP2D). Secondary endpoints defined the adverse event (AE) profile and assessed clinical efficacy. Peripheral blood CD14+Lin-HLA-DRlo myeloid-derived suppressor cells (MDSCs) were measured by flow cytometry. Results: 13 pts were treated; median age was 61 (range 32 – 71), 8 were female, and median prior lines of therapy was 5 (range 2 – 10). Histologic subtypes included leiomyosarcoma (LMS, n = 7), undifferentiated pleomorphic sarcoma (2), dedifferentiated liposarcoma (LPS, 2), synovial sarcoma (1), and pleomorphic LPS (1). The Table lists treatment-related AEs (TRAEs) of any grade (G) occurring in ≥ 10% of pts and all G ≥ 3 TRAEs, sorted by frequency. All pts had at least 1 TRAE. Seven pts (54%) had a G ≥ 3 TRAE. Most TRAEs were either G ≤ 2 or expected on-target effects of CSF1R inhibition. 1 of 6 pts on the highest dose level had a dose limiting toxicity (G4 elevated AST with abdominal pain) that resolved with treatment cessation. The highest dose level was declared the RP2D. Best objective response by RECIST 1.1 was stable disease in 3 pts; 2 had LMS and were treated at the highest dose level. At baseline, the mean proportion of monocytes in peripheral blood samples with an MDSC phenotype was 12.2% (range 7.1 – 19.9). 5 of 7 pts with serial blood samples had decreased circulating MDSCs (mean decrease of 26.9% from baseline to last time point). Conclusions: DCC-3014 combined with avelumab was safe and tolerable. Study therapy decreased circulating MDSCs in select patients; T cell analyses will be reported. Study expansion at the RP2D is ongoing. Clinical trial information: NCT04242238. [Table: see text]

ENVASARC: A pivotal trial of envafolimab, and envafolimab in combination with ipilimumab, in patients with advanced or metastatic undifferentiated pleomorphic sarcoma or myxofibrosarcoma who have progressed on prior chemotherapy

TPS11581

Background: Metastatic undifferentiated Pleomorphic Sarcoma (UPS) and the genetically related myxofibrosarcoma (MFS) are soft tissue sarcoma (STS) subtypes with poor prognoses. While responses to front line chemotherapy can approach 20%, efficacy remains limited in the 2nd line setting and beyond. Pazopanib, the only approved treatment in the refractory setting, has demonstrated an objective response rate (ORR) of 4%. Envafolimab is a single domain PD-L1 antibody administered rapidly by subcutaneous (SQ) injection that is being studied in two additional pivotal trials: microsatellite instability-high (MSI-H) cancer and biliary tract cancer. The activity of envafolimab appears to be similar to other PD-1 antibodies administered i.v. Envafolimab demonstrated a 32% objective response rate (ORR) in MSI-H colorectal cancer patients who failed three approved chemotherapeutics, similar to the ORR of 28% and 33% with nivolumab and pembrolizumab in these patient populations, respectively. The rationale for the ENVASARC trial is based on the previously reported activity of checkpoint inhibition in UPS/MFS. Single agent pembrolizumab demonstrated a 23% ORR, while the combination of nivolumab and ipilimumab demonstrated a 29% ORR in refractory UPS/MFS. Methods: ENVASARC (NCT 04480502) is a pivotal multicenter (at ̃25 U.S. centers) open-label, randomized, non-comparative, parallel cohort study of treatment with envafolimab 300 mg every 3 weeks by SQ injection (cohort A; n = 80) or envafolimab 300 mg every 3 weeks by SQ injection combined with ipilimumab 1 mg/kg every 3 weeks i.v. for four doses (cohort B; n = 80) in patients with locally advanced, unresectable or metastatic UPS/MFS who have progressed on one or two lines of prior therapy. The primary objective of each of parallel cohort is to demonstrate an ORR with a lower limit of the 95% confidence interval that excludes 5.0% in each cohort. If ≥ 9 responders are observed of the 80 patients enrolled in each cohort, then the lower bound of the 95% confidence interval will exclude 5.0%. Secondary endpoints include duration of response (DOR), PFS and OS. Key inclusion criteria: ≤ 2 prior lines of therapy (neoadjuvant and adjuvant therapy excluded), ECOG ≤ 1. Clinical trial information: NCT 04480502.

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.

Selinexor, a First in Class, Nuclear Export Inhibitor for the Treatment of Advanced Malignant Peripheral Nerve Sheath Tumor

Malignant peripheral nerve sheath tumor (MPNST) is a highly malignant neoplasm arising from peripheral nerve or its attendant sheath and is derived from Schwann or pluripotent cells of neural crest origin. Patients with recurrent, unresectable, or advanced stage disease have limited treatment options, and current therapies are associated with little benefit. In this article, we report nine cases of MPNST treated with selinexor, an orally bioavailable, selective inhibitor of nuclear export, accompanied by tumor stabilization or regression.

Objective Response Rate Among Patients With Locally Advanced or Metastatic Sarcoma Treated With Talimogene Laherparepvec in Combination With Pembrolizumab: A Phase 2 Clinical Trial

Importance

Patients with advanced sarcoma have limited treatment options. Talimogene laherparepvec (T-VEC) has been shown to increase tumor-specific immune activation via augmenting antigen presentation and T-cell priming.

Objective

To examine whether T-VEC in combination with pembrolizumab is associated with increased tumor-infiltrating lymphocyte infiltration and programmed death-ligand 1 expression and thus with increased antitumor activity in patients with locally advanced or metastatic sarcoma.

Design, Setting, and Participants

This open-label, single-institution phase 2 interventional trial of T-VEC plus pembrolizumab enrolled 20 patients with locally advanced or metastatic sarcoma between March 16 and December 4, 2017, for whom at least 1 standard systemic therapy had failed. The median duration of therapy was 16 weeks (range, 7-67 weeks). Reported analyses include data through December 14, 2018.

Intervention

Patients received pembrolizumab (200-mg flat dose) intravenously and T-VEC (first dose, ≤4 mL × 106 plaque-forming units [PFU]/mL; second and subsequent doses, ≤4 mL × 108 PFU/mL) injected into palpable tumor site(s) on day 1 of each 21-day cycle.

Main Outcomes and Measures

The primary end point was objective response rate (ORR; complete response and partial response) at 24 weeks determined by Response Evaluation Criteria In Solid Tumors (RECIST), version 1.1, criteria. Secondary end points included best ORR by immune-related RECIST criteria, progression-free survival rate at 24 weeks, overall survival, and safety.

Results

All 20 patients (12 women [60%]; median age, 63.5 years [range, 24-90 years]) were evaluable for response. The study met its primary end point of evaluating the best ORR at 24 weeks determined by RECIST, version 1.1, criteria; the best ORR was 30% (95% CI, 12%-54%; n = 6). The ORR overall was 35% (95% CI, 15%-59%; n = 7). The incidence of grade 3 treatment-related adverse events was low (4 patients [20%]). There were no grade 4 treatment-related adverse events or treatment-related deaths.

Conclusions and Relevance

In this phase 2 clinical trial, treatment with T-VEC plus pembrolizumab was associated with antitumor activity in advanced sarcoma across a range of sarcoma histologic subtypes, with a manageable safety profile. This combination therapy met its predefined primary study end point; further evaluation of T-VEC in combination with pembrolizumab for patients with select sarcoma subtypes is planned.

Trial Registration

ClinicalTrials.gov identifier: NCT03069378.

Long-term clinical activity, safety and patient-reported quality of life for emactuzumab-treated patients with diffuse-type tenosynovial giant-cell tumour

OBJECTIVES

This study investigated the safety, clinical activity and patient-reported outcomes of patients with diffuse-type tenosynovial giant-cell tumour (dTGCT) of the soft tissue who were treated with emactuzumab, a humanised anti-colony stimulating factor 1 receptor (CSF1R) monoclonal antibody and were followed up for up to 2 years after the start of treatment.

METHODS

In this open-label phase 1 study (ClinicalTrials.govNCT01494688), patients received intravenous (IV) emactuzumab from 900 to 2000 mg every two weeks in the dose-escalation phase and at the optimal biological dose of 1000 mg with different schedules in the dose-expansion phase. Adverse event (AE) rates and biomarker assessments from tumour biopsies were analysed. Quality of life was assessed using a standard questionnaire (EuroQol-5D-3L) and the WOMAC® 3.1 Osteoarthritis Index. Tumour responses were determined with magnetic resonance imaging.

RESULTS

Altogether, 63 patients were enrolled into the study. The most frequently reported AEs were pruritus, asthenia and oedema. In 36 patients for whom biopsy tissue was available a substantial decrease of CSF1R-positive and CD68/CD163-positive macrophages was detected. The independently reviewed best overall objective response rate (ORR) (Response Evaluation Criteria in Solid Tumors version 1.1) was 71%. Responses were durable, and an ORR of 70% and 64% was determined after one or two years after enrolment into the study. Clinical activity was accompanied by an improvement in EuroQol-5D-3L and particularly the joint disorder-specific WOMAC score.

CONCLUSIONS

Systemic therapy of dTGCT patients with emactuzumab resulted in pronounced and durable responses associated with symptomatic improvement and a manageable safety profile.

Efficacy and immune-related adverse event associations in avelumab-treated patients

BACKGROUND

Adverse events (AEs) of special interest that arise during treatment with immune checkpoint inhibitors, including immune-related AEs (irAEs), have been reported to be associated with improved clinical outcomes. We analyzed patients treated with avelumab from the JAVELIN Solid Tumor and Merkel 200 trials, examining the association between AEs and efficacy while adjusting for confounding factors such as treatment duration and event order.

METHODS

We analyzed efficacy and safety data from 1783 patients treated with the programmed death ligand 1 inhibitor avelumab who were enrolled in expansion cohorts of the JAVELIN Solid Tumor and Merkel 200 trials. To analyze the association between irAEs and efficacy with regard to survival, we used a time-dependent Cox model with time-varying indicators for irAEs, as well as multistate models that accounted for competing risks and time inhomogeneity.

RESULTS

295 patients (16.5%) experienced irAEs and 454 patients (25.5%) experienced infusion-related reactions. There was a reduced risk of death in patients who experienced irAEs compared with those who did not (HR 0.71, 95% CI 0.59 to 0.85) using the time-dependent Cox model. The multistate model did not suggest that the occurrence of irAEs could predict response; however, it predicted a higher chance of irAEs occurring after a response. No association was observed between response and infusion-related reactions.

CONCLUSIONS

Patients who experience irAEs showed improved survival. Although irAEs are not predictors for response to immune checkpoint inhibitors, increased vigilance for irAEs is needed after treatment with avelumab.

TRIAL REGISTRATION NUMBERS

NCT01772004 and NCT02155647.

Health-related quality of life trajectory of treatment-naive patients with Merkel cell carcinoma receiving avelumab

Aim: To evaluate changes in health-related quality of life (HRQoL) in a Phase II trial (NCT02155647) of treatment-naive patients with metastatic Merkel cell carcinoma treated with avelumab (15-month follow-up). Materials & methods: Mixed-effect Models for Repeated Measures were applied to HRQoL data (FACT-M; EQ-5D-5L) to assess changes over time. Clinically derived progression-free survival was compared with HRQoL deterioration-free survival. Results: Overall, we saw relative stability in HRQoL among 116 included patients, with nonprogression associated with statistically and clinically meaningful better HRQoL compared with progressive disease. Deterioration-free survival rates (49-72% at 6 months, 40-58% at 12 months) were consistently higher/better compared with progression-free survival rates (41/31% at 6/12 months). Conclusion: These findings show unique longitudinal HRQoL data for treatment-naive metastatic Merkel cell carcinoma patients treated with avelumab. Clinical trial registration: NCT02155647 (ClinicalTrials.gov).

HLA Genotyping in Synovial Sarcoma: Identifying HLA-A*02 and Its Association with Clinical Outcome

PURPOSE

To determine if a targeted exome panel utilizing matched normal DNA can accurately detect germline and somatic HLA genes in patients with synovial sarcoma (SS) and whether select HLA-A*02 genotypes are prognostic or predictive of outcome in metastatic SS.

EXPERIMENTAL DESIGN

Patients with metastatic SS consented to HLA typing by a Clinical Laboratory Improvement Amendments (CLIA)-certified test to determine eligibility for a clinical trial of NY-ESO-1-specific engineered T cells restricted to carriers of HLA-A*02:01, -A*02:05, or -A*02:06 (HLA-A*02 eligible). HLA genotype was determined from Memorial Sloan Kettering Integrated Molecular Profiling of Actionable Cancer Targets (MSK-IMPACT), where feasible, and somatic loss of heterozygosity (LOH) in HLA alleles was identified. Overall survival (OS) was estimated and stratified by HLA-A*02 eligibility.

RESULTS

A total of 23 patients had HLA genotyping by a CLIA-certified lab and MSK-IMPACT. Ninety percent (108/110) of the sequenced alleles were concordant between IMPACT and the outside lab. LOH of HLA genes was detected in three tumors, one had loss of HLA-A*02:01. In total, 66 patients were screened for T-cell therapy and 20 (30%) were HLA-A*02 eligible on outside testing. Univariate analysis of OS from the time of metastasis found HLA-A*02 eligibility was marginally associated with shorter OS [HR = 1.95; 95% confidence interval (CI), 0.995-3.813; P = 0.052]. On multivariate analysis, older age and larger tumor size, but not HLA-A*02 eligibility, were significantly associated with decreased OS. HLA-A*02 eligibility did not impact OS after chemotherapy or pazopanib in the metastatic setting.

CONCLUSIONS

Targeted gene panels like MSK-IMPACT may accurately report HLA type and identify loss of somatic HLA alleles. In a multivariable model, HLA-A*02 eligibility was not significantly associated with OS in patients with metastatic SS.

Patient Experiences with Avelumab in Treatment-Naïve Metastatic Merkel Cell Carcinoma: Longitudinal Qualitative Interview Findings from JAVELIN Merkel 200, a Registrational Clinical Trial

BACKGROUND AND OBJECTIVE

Avelumab is approved for the treatment of metastatic Merkel cell carcinoma, a rare aggressive skin cancer with a poor prognosis. The aim of this qualitative study embedded in a clinical trial was to explore patient experiences while receiving avelumab.

METHODS

All treatment-naïve patients with metastatic Merkel cell carcinoma entering part B of the phase II, open-label, international, JAVELIN Merkel 200 trial (NCT02155647) were invited to participate in optional semi-structured phone interviews before avelumab administration (baseline) and at weeks 13 and 25. Interviews were conducted by trained professionals, audio-recorded, transcribed and analysed. Key concepts identified at baseline were assessed during follow-up interviews.

RESULTS

Twenty-nine patients completed the baseline interview; 19 had at least one follow-up interview. Baseline interviews described the patients' challenging journeys before being correctly diagnosed with Merkel cell carcinoma, the negative psychological burden of living with a symptomless disease and the hope for avelumab to be a successful therapy. During the trial, most patients reported an increased or continued sense of hope and willingness to fight metastatic Merkel cell carcinoma. Patients who self-reported disease improvement (n = 12) also reported stability or improvement in physical well-being and ability to do daily activities, having more energy, worrying less and being optimistic. Six patients who reported their condition as stable (n = 4) or worsened (n = 3) reported a worsening of physical well-being. Nine patients reported fatigue/tiredness on the day of and after receiving avelumab. Baseline and longitudinal experiences were similar across countries.

CONCLUSIONS

This study suggests that patients experience perceptible benefits in physical and psychological well-being following treatment success with first-line avelumab in metastatic Merkel cell carcinoma.

Association of immune-related adverse events (irAEs) with improved clinical outcome in sarcoma patients treated with immune checkpoint blockade (ICB)

11510

Background: IrAEs are associated with improved clinical outcomes after treatment with ICB in select epithelial malignancies. We hypothesized that sarcoma patients (pts) treated with ICB who developed an irAE would have improved outcomes compared to pts who had no irAE. Methods: Adverse events (AEs) from 3 sarcoma-specific ICB trials (nivolumab plus NKTR-214, pembrolizumab plus epacadostat, and pembrolizumab plus T-VEC) were reviewed. AEs probably or definitely related to ICB were classified as immune- or non-immune-related by the principal investigator. Endpoints of interest included best overall response (BOR) by RECIST 1.1 (complete response [CR]/partial response [PR]), durable clinical benefit (DCB; CR/PR/stable disease [SD] ≥ 16 weeks), and progression-free survival (PFS). Outcomes were stratified by the presence or absence of ≥ 1 irAE of any grade and by grade 1-2, grade 3-4, or no irAE (three-category comparison). Results: A total of 124 pts received ICB on these studies. Median pt age was 56 (range: 13-90); 53% were male; all but one pt had a performance status of ≤ 1. BOR was PR in 12 pts, SD in 41, and PD in 69. 2 pts were not evaluable. 40 pts (32%) had ≥ 1 irAE of any grade, 6 of whom had a grade 3-4 irAE. The most common irAEs (≥ 5% of pts) were rash (15%), arthralgia (11%), myalgia (9%), pruritis (8%), and hypothyroidism (6%). The proportion of pts with a CR/PR was higher in pts with than without an irAE (18% vs. 6%, respectively; P = 0.058). A significantly higher proportion of pts with an irAE had DCB compared to those without (53% and 29%, respectively; P = 0.017). The median PFS of pts with an irAE was 16.6 months compared to 10.6 in those without (P = 0.013). The proportion of pts with a grade 3-4 irAE and a CR/PR was highest (33%) compared to pts with grade 1-2 (15%) or no irAE (6%) (P = 0.048). More pts with grade 3-4 irAE achieved DCB (67%) than grade 1-2 (50%) or no irAE (29%) (P = 0.027). Median PFS was 22.6, 15, and 10.6 weeks in the grade 3-4, grade 1-2, and no irAE groups, respectively (P = 0.047). Conclusions: Approximately one-third of advanced sarcoma pts with ICB-based immunotherapy developed an irAE. As reported previously in select carcinomas, sarcoma pts with irAEs were more likely to have clinical benefit than those without irAEs. Further research is needed to understand the mechanism behind this association and to validate these findings prospectively.

Safety and activity of autologous T cells with enhanced NY-ESO-1–specific T-cell receptor (GSK3377794) in HLA-a*02+ previously-treated and -untreated patients with advanced metastatic/unresectable synovial sarcoma: A master protocol study design (IGNYTE-ESO)

TPS11571

Background: T cells modified to target NY-ESO-1 have shown encouraging activity in HLA-A*02+ patients with NY-ESO-1–positive synovial sarcoma. NY-ESO-1 is a cancer/testis antigen that is expressed across multiple tumor types and highly expressed in synovial sarcoma. NY-ESO-1 TCR T (GSK3377794) are autologous polyclonal T cells transduced by a self-inactivating lentiviral vector to express an affinity-enhanced TCR able to recognize NY-ESO-1 epitope in complex with HLA-A*02. Ongoing trials are evaluating GSK3377794 in multiple solid tumors and multiple myeloma. Methods: This study (NCT03967223) uses a Master Protocol design that allows investigation of GSK3377794 in multiple tumor types under the same protocol in separate substudies. The first two are single-arm substudies in patients with advanced metastatic or unresectable synovial sarcoma: treatment-naïve (1st line [1L], substudy 1; n = 10 planned) and progressing after anthracycline-based chemotherapy (2L+, substudy 2; n = 55 planned). Patients must be aged ≥10 years, have adequate organ function, ECOG performance status 0–1, measurable disease, and no central nervous system metastases. Excluded prior treatments include gene therapy with an integrating vector or NY-ESO-1–specific T cells, vaccine or targeting antibody, or allogeneic stem cell transplant. Patients will undergo leukapheresis and manufacture of GSK3377794; lymphodepletion then GSK3377794 infusion, followed by safety and disease assessments; and long-term follow-up for 15 years (under a separate protocol). The primary objective of substudy 2 is overall response rate per RECIST v1.1 by central independent review. Secondary objectives include time to response, duration of response, disease control rate, progression-free survival, overall survival, plus safety and tolerability. Exploratory objectives include assessment of the correlation of T-cell persistence with safety, clinical responses, and infused T-cell phenotype. Evaluation of quality of life and daily functioning of patients will also be assessed. Enrollment began in December 2019. These data are presented on behalf of the original authors with their permission. A similar presentation (P453) was presented at the SITC Annual Meeting, National Harbor, MD, USA, Nov 6–10, 2019. Funding: GlaxoSmithKline (208467) Clinical trial information: NCT03967223 .

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. References: 1. Iura K, et al. Cancer-testis antigen expression in synovial sarcoma: NY-ESO-1, PRAME, MAGEA4, and MAGEA1. Human Pathology 2017; 61:130-139. 2. Iura K, et al. MAGEA4 expression in bone and soft tissue tumors: its utility as a target for immunotherapy and diagnostic marker combined with NY-ESO-1. Virchows Archiv 2017;471:383–392. Clinical trial information: NCT04044768 .

HLA genotyping in synovial sarcoma: Identifying HLA-A*02 and its association with clinical outcome

e23560

Background: Patients (pts) with synovial sarcoma (SS) and an HLA-A*02 genotype whose tumors express NY-ESO-1 may be eligible for clinical trials of adoptive T cell therapy. We reasoned that a next generation tumor sequencing platform utilizing matched normal DNA (MSK-IMPACT) could accurately identify HLA genotype. Although HLA-A*02 is necessary for some adoptive T cell therapies, the prognosis of this genotype on clinical outcome has not been described in SS. Methods: Pts with metastatic SS who consented to screen for a clinical trial of engineered T cells had high-resolution HLA genotyping performed with a Clinical Laboratory Improvement Amendments (CLIA)-certified test. Where feasible, HLA genotype and loss-of-heterozygosity (LOH) of HLA alleles were determined from IMPACT samples. Overall survival (OS) was estimated in three overlapping cohorts and stratified by HLA-A*02 status: pts treated with anthracyclines or alkylators in the first line, pazopanib in the second line or beyond, and all pts from time of metastasis. Results: 66 pts with SS were screened, but not treated with T cells; 30% (n = 20) were HLA-A*02-positive on a CLIA-certified outside test. 23 pts had HLA genotyping both by IMPACT and an outside laboratory, 22 (96%) of whom had concordant results. 3 pts had LOH of at least 1 HLA allele, including one with LOH of HLA*02:01 in the primary tumor. Among pts treated chemotherapy (n = 36) or pazopanib (n = 37), OS did not significantly differ between HLA-A*02-positive or negative pts. Univariable analyses of OS from the time of metastasis in the whole cohort identified primary tumor size and time to metastasis as variables significantly associated with outcome (hazard ratio (HR) 1.2, 95% confidence interval (CI) 1.123 – 1.345 [P < 0.001] and HR 0.99, 95% CI 0.976 – 0.999 [P = 0.032], respectively). HLA-A*02-positive status and age did not reach the significance threshold (HR 1.95, 95% CI 0.995 – 3.813 [P = 0.052] and HR 1.021, 95% CI 0.999 – 1.044 [P = 0.061], respectively). Multivariable analysis found older age and larger tumor size were independently associated with significantly shorter OS (HR 1.03, 95% CI 1.002 – 1.049 [P = 0.037] and HR 1.2, 95% CI 1.127 – 1.37 [P < 0.001], respectively). Conclusions: Targeted exome panels like IMPACT that utilize matched tumor-normal DNA may accurately identify HLA genotype. Detection of LOH at HLA loci may identify a subgroup of pts who would be refractory to treatment with HLA-A*02-restricted engineered T cells. HLA-A*02 status was not associated with a statistically significant survival difference in pts with metastatic SS.