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Purpose:To evaluate sitravatinib, an inhibitor of multiple receptor tyrosine kinases (RTK), for the treatment of well-differentiated/dedifferentiated liposarcoma (WD/DD LPS).Patients and Methods:This multicenter, open-label, Phase II trial enrolled patients with advanced WD/DD LPS who had received at least one prior systemic regimen and had progression within 12 weeks of enrollment. Patients received sitravatinib 150 mg (later amended to 120 mg) orally daily. A Simon two-stage design was used to evaluate for an improvement in the primary endpoint, progression-free rate at 12 weeks (PFR12), from 20% to 40%. Secondary endpoints included antitumor activity and safety. A subset of patients underwent paired biopsies analyzed using reverse-phase protein array.Results:Twenty-nine patients enrolled. Median age was 62 years and 31% had received 3 or more prior lines. Most patients (93%) had DDLPS or mixed WD/DD LPS. Overall, 12 of 29 patients (41%) were alive and progression-free at 12 weeks and the study met the primary endpoint. There were no confirmed responses. Median progression-free survival was 11.7 weeks [95% confidence interval (CI): 5.9–35.9] and median overall survival was 31.7 weeks (95% CI: 18.1–90.1). The most common treatment-related adverse events were diarrhea (59%), hypertension (52%), hoarseness (41%), mucositis (31%), and nausea (31%). Baseline expression of phospho-RTKs was not significantly different between patients with and without clinical benefit from sitravatinib, but the number of samples was small.Conclusions:Sitravatinib provided a PFR12 of 41% and meaningful disease control in a subset of patients with advanced, progressive WD/DD LPS.

Purpose:This phase I study assessed the safety, pharmacokinetics (PKs), and efficacy of MIW815 (ADU-S100), a novel synthetic cyclic dinucleotide that activates the stimulator of IFN genes (STING) pathway, in patients with advanced/metastatic cancers.Patients and Methods:Patients (n = 47) received weekly i.t. injections of MIW815, 50 to 6,400 μg, on a 3-weeks-on/1-week-off schedule.Results:A maximum tolerated dose was not reached. Most common treatment-related adverse events were pyrexia (17%), chills, and injection-site pain (each 15%). MIW815 was rapidly absorbed from the injection site with dose-proportional PK, a rapid terminal plasma half-life (approximately 24 minutes), and high interindividual variability. One patient had a partial response (PR; Merkel cell carcinoma); two patients had unconfirmed PR (parotid cancer, myxofibrosarcoma). Lesion size was stable or decreased in 94% of evaluable, injected lesions. RNA expression and immune infiltration assessments in paired tumor biopsies did not reveal significant on-treatment changes. However, increases in inflammatory cytokines and peripheral blood T-cell clonal expansion suggested systemic immune activation.Conclusions:MIW815 was well tolerated in patients with advanced/metastatic cancers. Clinical activity of single-agent MIW815 was limited in this first-in-human study; however, evidence of systemic immune activation was seen.

Immunohistochemistry of injected and noninjected lesions

Supplementary tables and figure legends

Chondrosarcomas are inherently resistant to chemotherapy and radiotherapy, pointing to an unmet need for new treatment options. Immune checkpoint inhibitors, which have shown remarkable promise in multiple solid cancer types, have limited efficacy in chondrosarcomas. Mutations in IDH1/2 genes, which result in progressive increases in DNA and histone methylation, are observed in 50% of conventional chondrosarcomas, suggesting that epigenetic dysregulation represents a potential barrier for tumor progression and target for therapeutic intervention. Here, we demonstrated that combined treatment of FDA-approved inhibitors of DNA methyltransferases (DNMTs) 5-aza-2′-deoxycytidine (5-aza), and histone deacetylases (HDACs) suberanilohydroxamic acid (SAHA) impaired the proliferation of chondrosarcoma cell lines in vitro and in xenograft studies. Transcriptomic analysis reveals that chondrosarcoma cells treated with 5-aza and SAHA markedly elevated the expression of IFN-stimulated genes including PD-L1, indicating that these epigenetic drugs induced a potent innate immune response. We demonstrated that 5-aza and SAHA resulted in both genomic and epigenomic instability, as shown by elevated DNA damage response and derepression of retrotransposons, respectively, which in turn activated pattern recognition receptors (PRRs) and the downstream IFN signaling pathways. Importantly, the cytotoxic effects of 5-aza and SAHA can be rescued by depletion of PRRs such as cGAS and MAVS, and potentiated by depletion of the RNA-editing enzyme ADAR1. Together, our results demonstrate preclinical activity of combined DNMT and HDAC inhibition against chondrosarcomas and suggest that targeted epigenetic therapies could represent a new therapeutic approach in the treatment of chondrosarcomas, and this is being tested in an ongoing clinical trial (NCT04340843).

Contains Figure S1-S6; Table S1-S2

Representativeness of Study Participants

Purpose:To evaluate sitravatinib, an inhibitor of multiple receptor tyrosine kinases (RTK), for the treatment of well-differentiated/dedifferentiated liposarcoma (WD/DD LPS).Patients and Methods:This multicenter, open-label, Phase II trial enrolled patients with advanced WD/DD LPS who had received at least one prior systemic regimen and had progression within 12 weeks of enrollment. Patients received sitravatinib 150 mg (later amended to 120 mg) orally daily. A Simon two-stage design was used to evaluate for an improvement in the primary endpoint, progression-free rate at 12 weeks (PFR12), from 20% to 40%. Secondary endpoints included antitumor activity and safety. A subset of patients underwent paired biopsies analyzed using reverse-phase protein array.Results:Twenty-nine patients enrolled. Median age was 62 years and 31% had received 3 or more prior lines. Most patients (93%) had DDLPS or mixed WD/DD LPS. Overall, 12 of 29 patients (41%) were alive and progression-free at 12 weeks and the study met the primary endpoint. There were no confirmed responses. Median progression-free survival was 11.7 weeks [95% confidence interval (CI): 5.9–35.9] and median overall survival was 31.7 weeks (95% CI: 18.1–90.1). The most common treatment-related adverse events were diarrhea (59%), hypertension (52%), hoarseness (41%), mucositis (31%), and nausea (31%). Baseline expression of phospho-RTKs was not significantly different between patients with and without clinical benefit from sitravatinib, but the number of samples was small.Conclusions:Sitravatinib provided a PFR12 of 41% and meaningful disease control in a subset of patients with advanced, progressive WD/DD LPS.

Background: INT230-6 is a novel formulation of cisplatin and vinblastine with an amphiphilic cell penetration enhancer that has been shown to enhance dispersion of the drug throughout tumors and allow diffusion into cells when given intratumorally. INT230-6 is being evaluated in monotherapy and in combination with immune checkpoint inhibitors (ICIs) in subjects with various advanced solid tumors, including advanced breast cancer. Methods: This phase 1/2 study evaluated INT230-6 in superficial and deep tumors with INT230-6 Q2W intratumoral injections for 5 doses alone or in combination with 200mg pembrolizumab IV Q3W for 2 years. Total INT230-6 injected in a subject ranged from 0.89 to 649 mL over 5 INT230-6 dosing sessions in each subject, except one subject who had only 2 dosing sessions. Subjects who had completed treatment in dose escalation cohorts were eligible for retreatment; and one subject was retreated with INT230-6 in multiple arms of the study. Advanced breast cancer subjects with an Eastern Cooperative Oncology Group (ECOG) performance status of 2 or below who have failed one or more approved therapies, or have no alternate approved therapy, were enrolled. Subjects must have adequate organ function and measurable disease by RECIST 1.1 criteria including one target tumor for injection. Tumor response using RECIST 1.1 was evaluated at 12 weeks from the first INT230-6 dose and then every 8 weeks. Tumor biopsies were taken prior to INT230-6 dosing on day 0 and on day 28 post dose. Results: 7 advanced triple negative breast cancer subjects (4 monotherapy, 3 pembrolizumab combination) were evaluable as of June 1, 2021. The median age was 56 (range 46-82) years old, with a median of 8 (2, 17) prior systemic therapies for metastatic disease. The intratumoral INT230-6 dose was up to 164 mL (82 mg of CIS, 16.4mg VIN) to tumors in a single dosing session. With INT230-6, 133-200% more volume is injected into the tumor and pharmacokinetics (PK) analysis shows that 95% of INT230-6 active agents remain in the tumor. Accordingly, assessment of tumor response using RECIST principles may be challenging, and even stable disease may represent a large decrease in viable tumor cells as indicated by biopsy evaluations. The most common (>20%) related treatment related adverse events (AE) were localized tumor related pain (71%), nausea (57%), anemia (29%), fatigue (29%), neck pain (29%), and vomiting (29%). AEs were mostly low grade and only one subject experienced grade 3 anemia (13%). There were no related grade 4 or 5 AEs or serious AEs. Disease control rate (DCR), defined as the percent of patients with a complete response, partial response, or stable disease at the first radiologic assessment, was 57%. Median overall survival was 12 months. Pre- and post- biopsy at 28 days after two INT230-6 doses (n= 3 evaluable, monotherapy, and combination with pembrolizumab) showed a 55% decrease in Ki67 and 69% reduction in viable cancer cells. In addition, multiplex immunofluorescence (n= 3 evaluable, combination with pembrolizumab) showed an influx of activated CD4 and CD8 T cells and in some cases a reduction in FoxP3 T-reg cells.. Conclusion: INT230-6 is a potential first-in-class intratumoral therapy for advanced breast cancer being developed in monotherapy and in combination with ICIs. There is a favorable safety profile in this population, similar to the broader metastatic solid tumor population presented elsewhere. There are early signs of cancer cell death in injected tumors and immune activation in heavily pre-treated patients. A Phase 2 expansion cohort of INT230-6 in combination with ICIs is ongoing. In addition, INT230-6 in being studied in a separate randomized Phase 2 neoadjuvant breast cancer study. Citation Format: Philippe Bedard, Lillian L Siu, Jacob Thomas, Diana Hanna, Anthony J Olszanski, Nilofer Azad, Giles Whalen, Matthew Ingham, Syed Mahmood, Lewis H Bender, Ian B Walters, Anthony El-Khoueiry. Safety and efficacy of INT230-6, a potential first-in-class intratumoral therapy, in monotherapy and in combination with pembrolizumab: Results from the IT-01 study [KEYNOTE-A10] in subjects with locally advanced, unresectable and metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-16-13.

To evaluate Sitravatinib, an inhibitor of multiple receptor tyrosine kinases (RTKs), for the treatment of well-differentiated/dedifferentiated liposarcoma (WD/DD LPS).This multi-center, open-label, phase 2 trial enrolled patients with advanced WD/DD LPS who had received at least one prior systemic regimen and had progression within 12 weeks of enrollment. Patients received Sitravatinib 150 mg (later amended to 120 mg) orally daily. A Simon 2-stage design was used to evaluate for an improvement in the primary endpoint, progression-free rate at 12 weeks (PFR12), from 20% to 40%. Secondary endpoints included antitumor activity and safety. A subset of patients underwent paired biopsies analyzed using reverse phase protein array.Twenty-nine patients enrolled. Median age was 62 years and 31% had received 3 or more prior lines. Most patients (93%) had DDLPS or mixed WD/DD LPS. Overall, 12 of 29 patients (41%) were alive and progression-free at 12 weeks and the study met the primary endpoint. There were no confirmed responses. Median PFS was 11.7 weeks (95% CI: 5.9 - 35.9) and median OS was 31.7 weeks (95% CI: 18.1 - 90.1). The most common treatment-related adverse events were diarrhea (59%), hypertension (52%), hoarseness (41%), mucositis (31%) and nausea (31%). Baseline expression of phospho-RTKs was not significantly different between patients with and without clinical benefit from Sitravatinib but the number of samples was small.Sitravatinib provided a progression-free rate at 12 weeks of 41% and meaningful disease control in a subset of patients with advanced, progressive WD/DD LPS.

Chondrosarcomas are inherently resistant to chemotherapy and radiotherapy, pointing to an unmet need for new treatment options. Immune checkpoint inhibitors, which have shown remarkable promise in multiple solid cancer types, have limited efficacy in chondrosarcomas. Mutations in IDH1/2 genes, which result in progressive increases in DNA and histone methylation, are observed in 50% of conventional chondrosarcomas, suggesting that epigenetic dysregulation represents a potential barrier for tumor progression and target for therapeutic intervention. Here, we demonstrated that combined treatment of FDA-approved inhibitors of DNA methyltransferases (DNMTs) 5-aza-2′-deoxycytidine (5-aza), and histone deacetylases (HDACs) suberanilohydroxamic acid (SAHA) impaired the proliferation of chondrosarcoma cell lines in vitro and in xenograft studies. Transcriptomic analysis reveals that chondrosarcoma cells treated with 5-aza and SAHA markedly elevated the expression of IFN-stimulated genes including PD-L1, indicating that these epigenetic drugs induced a potent innate immune response. We demonstrated that 5-aza and SAHA resulted in both genomic and epigenomic instability, as shown by elevated DNA damage response and derepression of retrotransposons, respectively, which in turn activated pattern recognition receptors (PRRs) and the downstream IFN signaling pathways. Importantly, the cytotoxic effects of 5-aza and SAHA can be rescued by depletion of PRRs such as cGAS and MAVS, and potentiated by depletion of the RNA-editing enzyme ADAR1. Together, our results demonstrate preclinical activity of combined DNMT and HDAC inhibition against chondrosarcomas and suggest that targeted epigenetic therapies could represent a new therapeutic approach in the treatment of chondrosarcomas, and this is being tested in an ongoing clinical trial (NCT04340843).

Purpose: This phase I study assessed the safety, pharmacokinetics (PKs), and efficacy of MIW815 (ADU-S100), a novel synthetic cyclic dinucleotide that activates the stimulator of IFN genes (STING) pathway, in patients with advanced/metastatic cancers. Patients and Methods: Patients (n = 47) received weekly i.t. injections of MIW815, 50 to 6,400 μg, on a 3-weeks-on/1-week-off schedule. Results: A maximum tolerated dose was not reached. Most common treatment-related adverse events were pyrexia (17%), chills, and injection-site pain (each 15%). MIW815 was rapidly absorbed from the injection site with dose-proportional PK, a rapid terminal plasma half-life (approximately 24 minutes), and high interindividual variability. One patient had a partial response (PR; Merkel cell carcinoma); two patients had unconfirmed PR (parotid cancer, myxofibrosarcoma). Lesion size was stable or decreased in 94% of evaluable, injected lesions. RNA expression and immune infiltration assessments in paired tumor biopsies did not reveal significant on-treatment changes. However, increases in inflammatory cytokines and peripheral blood T-cell clonal expansion suggested systemic immune activation. Conclusions: MIW815 was well tolerated in patients with advanced/metastatic cancers. Clinical activity of single-agent MIW815 was limited in this first-in-human study; however, evidence of systemic immune activation was seen.

Soft tissue sarcomas are heterogeneous mesenchymal neoplasms and account for 1% of all cancers in adults. Over 50 sarcomas subtypes have been classified and many have very limited treatment options which include surgery, chemotherapy and radiation. Two of the most common sarcomas are liposarcoma and leiomyosarcoma which are often treated with chemotherapies such as doxorubicin, dacarbazine and gemcitabine with low response rates. There is now more than ever an urgent need for new therapies for sarcoma. PCNA (Proliferating Cell Nuclear Antigen) is considered to be a key regulator of DNA and cell cycle control. In addition, it has been implicated to have roles in metabolism, cellular signaling and some immunological functions. PCNA forms complexes with proteins bearing a novel PCNA-interacting Peptide Motif called APIM (AlkB homolog 2 PCNA Interacting Motif). This binding usually occurs during stress responses such as those achieved during cancer therapy or cancer development. By preventing stress proteins from repairing or defending themselves, cancer therapies can be made more effective. We examined the in vitro effects of ATX-101, a PCNA-APIM protein interaction blocking peptide, on liposarcoma cell lines LS141, DDLS, SW872, 93T449 and 94T778 and leiomyosarcoma cell lines SK-LMS, SK-UT1 and SK-UT-1B. Cell survival, as measured by cell proliferation assays, indicated IC50s of 7.5-15µM with ATX-101. Enhanced combination effects with ATX-101 and chemotherapies such as doxorubicin, irinotecan and gemcitabine were also observed by proliferation assay. Synergism, with ATX-101 and gemcitabine, was indicated with SynergyFinder analysis. Cell cycle changes exhibited increases of S and G2 phases when treated with ATX-101 and gemcitabine. This correlated with increase of cell cycle proteins, cyclin B1 and cyclin A2. Western blot observations included increase of apoptotic marker, cleaved caspase 3, and DNA damage marker, pH2A.X. In addition, immunofluorescence assay showed increasing pH2A.X with ATX-101 and gemcitabine. In vivo studies revealed ATX-101 enhanced gemcitabine decrease of tumor volume in leiomyosarcoma cell line xenograft, SK-UT1. Tumor target inhibition by western blot showed increased pH2A.X and cleaved PARP along with decreased RAD51 API protein with combination treatment. Taken these observations and results, there is strong evidence of combining gemcitabine with ATX-101 in liposarcoma and leiomyosarcoma. Citation Format: Elgilda Musi, Tahir Sheikh, Matthew Ingham, Sminu Bose, Gary K. Schwartz. ATX-101, a peptide drug targeting PCNA, enhances the effect of gemcitabine in liposarcoma and leiomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6174.

Uterine sarcomas reflect the diversity of sarcoma as a whole. The most common histologies include leiomyosarcoma, high- and low-grade endometrial stromal sarcoma, and adenosarcoma. These are clinically and biologically heterogeneous diseases that are challenging to treat in the advanced setting. Recent advances in our understanding of the cancer biology of uterine sarcomas has improved diagnostic evaluation and therapeutic management. Promising approaches for patients with advanced uterine leiomyosarcoma include targeting DNA damage repair pathways and depleting immunosuppressive macrophage populations. A subset of endometrial stromal sarcomas harbor potentially actionable alterations in the Wnt, cyclin D-CDK4/6-Rb, and MDM2-p53 pathways. There remains an urgent need to translate molecular findings into prospective clinical trials of novel agents for patients with these diseases; progress will depend on academic collaborations and enrollment of patients with uterine sarcoma in biomarker-driven basket studies.

Opinion statementLeiomyosarcoma is one of the most common subtypes of soft tissue sarcomas accounting for approximately 20% of sarcomas. As leiomyosarcoma patients frequently develop metastatic disease, effective systemic therapies are needed to improve clinical outcomes. The overall activity of the currently available conventional systemic therapies and the prognosis of patients with advanced and/or metastatic disease are poor. As such, the treatment of this patient population remains challenging. As a result, there is a clear unmet medical need, and designing and performing meaningful clinical studies are of utmost importance to improve the prognosis of this patient group. Therefore, the aim of this review is to briefly summarize state-of-the-art treatments for leiomyosarcoma patients and to describe trial characteristics needed for informative clinical studies.

Melanoma brain metastasis (MBM) frequently occurs in patients with advanced melanoma, yet our understanding of the underlying salient biology is rudimentary. Here, we performed single-cell/nucleus RNA-seq in 22 treatment-naïve MBM and 10 extracranial melanoma metastases (ECM), and matched spatial single-cell transcriptomics and T cell receptor (TCR)-seq. Cancer cells from MBM were more chromosomally unstable, adopted a neuronal-like cell state, and enriched for spatially variably expressed metabolic pathways. Key observations were validated in independent patient cohorts, patient-derived MBM/ECM xenograft models, RNA/ATAC-seq, proteomics, and multiplexed imaging. Integrated spatial analyses revealed distinct geography of putative cancer immune evasion, and evidence for more abundant intra-tumoral B to plasma cell differentiation in lymphoid aggregates in MBM. MBM harbored larger fractions of monocyte-derived macrophages and dysfunctional TOX(+)CD8(+) T cells with distinct expression of immune checkpoints. This work provides comprehensive insights into MBM biology and serves as a foundational resource for further discovery and therapeutic exploration.

Brain metastases are the most frequent malignancies in the brain and are associated with significant morbidity and mortality. Melanoma brain metastases (MBM) occur in most patients with advanced melanoma and are challenging to treat. Our understanding of the treatment-naïve landscape of MBM is still rudimentary, and there are no site-specific molecular therapies available. To gain comprehensive insights into the niche-specific biology of MBM, we performed multi-modal profiling of fresh and frozen samples using single-cell RNA-seq, single-cell TCR-seq, single-nuclei RNA-seq, and spatial transcriptional profiling. We evolved single-nucleus RNA-seq processing methods to enable profiling of minute amounts of archival, frozen specimens and compared data quality and structure between matched fresh and frozen MBM. We curated a treatment-naïve single-transcriptome atlas of MBM, collected either fresh samples over 1 year or profiled frozen samples dating back more than 15 years, and compared these samples to extracranial melanoma metastases (ECMM). In total, we profiled 25 samples with more than 114,000 transcriptomes. We identified more than 20 different cell types, including diverse tumor-infiltrating T-cell subsets and rare dendritic cell types, and tissue-specific cell types, such as activated microglia. Tumor cells in MBM showed an increase in copy number alterations (CNAs) compared to ECMM, which we validated using an external dataset of whole exome sequencing (WES) data including both MBM and ECMM. MBM-derived tumor cells show enrichment of genes involved in neuronal development and function, and site-specific metabolic programs (e.g., oxidative phosphorylation). Comparison with an external bulk RNA-seq dataset validated enriched key genes in MBM and ECMM as putative dependencies. We recovered cell-cell interactions between tumor and brain-resident cells involved in brain development, homeostasis, and disease. Similar to ECMM, the tumor microenvironment of MBM contained CD8+ T cells across a spectrum of differentiation, exhaustion and expansion, which was associated with loss of TCF7 expression and adoption of a TOX+ cell state. CD4+ T cells included T regulatory, T helper and T follicular-helper-like expression profiles. Plasma cells showed spatially localized expansion and limited heterogeneity. Myeloid cells largely adopted pro-tumorigenic cell states, including microglia, the brain-resident myeloid cells, which showed an activation trajectory characterized by expression of SPP1 (osteopontin). Spatial transcriptional analysis revealed restricted expression of antigen presentation genes with only a subset of these locations showing a type I interferon response. In summary, this work presents a multi-modal single-cell approach to dissect and compare the landscape of treatment-naïve MBM and ECMM. Citation Format: Johannes C. Melms, Jana Biermann, Amit Dipak Amin, Yiping Wang, Somnath Tagore, Massimo Andreatta, Ajay Nair, Meri Rogava, Patricia Ho, Lindsay A. Caprio, Zachary H. Walsh, Shivem Shah, Daniel H. Vacarro, Blake Caldwell, Adrienne M. Luoma, Joseph Driver, Matthew Ingham, Suthee Rapisuwon, Jennifer Wargo, Craig L. Slinguff, Evan Z. Macosco, Fei Chen, Richard Carvajal, Michael B. Atkins, Michael A. Davies, Elham Azizi, Santiago J. Carmona, Hanina Hibshoosh, Peter D. Canoll, Jeffrey N. Bruce, Wenya L. Bi, Gary K. Schwartz, Benjamin Izar. Dissecting the ecosystem of treatment-naïve melanoma brain metastasis using multi-modal single-cell analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 984.

11515 Background: INT230-6 is a novel intratumoral (IT) agent with a dual anti-cancer mechanism (tumor cytoreduction while stimulating antigen presentation and recruitment of T-cells). The drug is comprised of cisplatin (CIS) and vinblastine (VIN) co-formulated with an amphiphilic molecule that enables drug dispersion throughout tumors and passive diffusion into cancer cells following IT delivery. In the neoadjuvant setting, a single injection can cause necrosis in > 95% of the tumor and recruit TILs. Combining with anti-CTLA-4 improved responses in preclinical models. Methods: INT230-6 dose is set by the tumor’s longest diameter and is proportional to the injected disease volume. INT230-6 is administered IT Q2W for 5 treatment sessions followed by maintenance every 9 weeks as monotherapy or with IPI 3mg/kg IV Q3W for 4 doses. Biopsies from injected tumors are obtained pretreatment and Day 28 for immunoprofiling. Results: 22 subjects with various advanced STS histologies with a median age of 64 and a median of 3 prior systemic therapies were enrolled (11 INT230-6 alone, 11 IPI combination). There were 178 image-guided IT INT230-6 injections (107 to deep tumors) at INT230-6 doses ranging from 5 to 242 mL (121mg CIS, 24.2mg VIN, doses which vastly exceed the usual IV doses of these drugs). PK analysis showed that > 95% of drug agents remain in the tumor. The most common (> 25%) all-grade related adverse events (AEs) in evaluable monotherapy subjects (n = 10) were pain (80%), decreased appetite (40%), nausea (40%), anemia (30%), fatigue (30%) and vomiting (30%). Tolerability was similar for the combination with IPI. Most events were low grade. The incidence of grade 3 AEs for the INT230-6 arm was 30% and for the IPI combination was 10%. There were no related grade 4 or 5 AEs in either cohort. RECIST metrics may not accurately reflect clinical benefit with this treatment given large volumes of INT230-6 is repeatedly injected into a tumor and local inflammation may occur. Paired biopsies showed reduction in proliferating tumor cells and an increase in T-cell infiltrates. The disease control rate at the first imaging timepoint for evaluable INT230-6 subjects (n = 9) was 56% and for evaluable IPI combination (n = 5) was 80%. Abscopal effects were seen in 2 monotherapy subjects, though most uninjected tumors were not tracked. The estimated 1-year overall survival was 88% for the IPI combo and 60% for the monotherapy cohort. Conclusions: IT INT230-6 is well tolerated as monotherapy and combined with IPI. STS, which is typically not sensitive to immunotherapy, may be amenable to INT230-6 or IPI combo to create antigens and promote a systemic immune response. Preliminary efficacy using INT230-6 alone is encouraging and will be evaluated in a global phase 3 trial. Further evaluation is needed to determine whether the addition of IPI may improve patient outcomes. Clinical trial information: NCT03058289.

e23518 Background: Single-cell RNA-seq is an enabling technology that may inform the molecular underpinnings of drug response and resistance in patient biopsies. This method is difficult to implement in the study of rare diseases such as sarcomas due to specimen requirements and technical limitations. Methods: Here, we evolved novel methods that we recently reported in melanoma ( Wang, Fan, et al., bioRxiv, 2022), which enable single-nucleus RNA, T cell receptor (snRNA/TCR)-seq, and pool-matched whole-genome sequencing (WGS) from archival, frozen sarcoma tissue. Results: This enabled profiling of 75,716 cells and 788 matched TCR clonotypes from six patients with intimal sarcoma (INS) and undifferentiated pleomorphic sarcomas (UPS), including two matched pair samples from pre/post-immune checkpoint inhibitor (ICI). Our analysis revealed substantial transcriptional cancer cell heterogeneity driven by varying copy number alterations (CNAs). In one patient with INS with a complete response to ICI followed by an isolated recurrence, we identified a rare cancer cell clone defined by CNA (confirmed with WGS) and resulting transcriptional outputs that pre-existed and emerged during resistance. Furthermore, in a patient with UPS with intrinsic resistance to ICI, we find adequate T cell clonal expansion and activation, suggesting appropriate T cell response to ICI dampened by intrinsic mechanisms of ICI resistance within the cancer cells. Non-negative matrix factorization (NMF) analysis identified cell states associated with either intrinsic or adaptive resistance to ICI that was distinct from resistance to doxorubicin. These observations are consistent with those previously reported from sequential biopsies obtained from KEYNOTE-001 in metastatic melanoma ( Wang, Fan, et al., bioRxiv, 2022), which also revealed emergence of pre-existing populations of resistant clones defined by their underlying aneuploidy patterns. Conclusions: Together, these results demonstrate feasibility of implementing single-cell genomics from archival tissue to study sarcoma and propel our understanding of drug resistance. Conceptually, this work suggests that large-scale CNAs may drive cell sub-populations associated with ICI resistance in sarcoma and in other diseases.

11509 Background: uLMS is an aggressive sarcoma subtype of smooth muscle origin. Chemotherapy provides limited benefit for advanced disease. 18-25% of uLMS harbor deleterious alterations in homologous recombination (HR) DNA repair genes. uLMS exhibits high levels of replicative stress. These findings prompted a phase 2 study of O+T in pretreated uLMS where O+T demonstrated activity: ORR 27%, mPFS 6.9 mos (Ingham M. et. al. ASCO 2021: #11506) Methods: NCI protocol #10250 is a single-arm, multicenter, phase 2 trial evaluating O+T in advanced uLMS pts with progression on ≥1 prior line. Pre-treatment (Pre) and on-treatment (On) biopsies were collected from 22 pts. In prespecified analysis, we evaluated for a relationship between clinical outcomes and HR gene alterations by whole exome sequencing (WES), SLFN11/MGMT expression by RNAseq, and RAD51 foci formation (functional assay). HRD scores were calculated from WES using scarHRD. Gene expression was evaluated using a Spearman rank-order correlation analysis to identify genes associated with PFS (p < 0.01) and overexpressed in sensitive (S: PFS > 240d) or resistant (R: PFS < 240d) pts. Gene set enrichment analysis (GSEA) was performed (q = FDR-adjusted p value). Pts with available results: WES/RNAseq (16), Pre HRD score (13), Pre RAD51 foci (12). Results: 31% (5/16) pts had a mutation (Mut) or homozygous deletion (Hd) in the HR panel: ATRX Mut (2), ATR Mut, PALB2 Hd, RAD51B Hd. Pts with PALB2 and RAD51B Hd had longest PFS on study. Recurrent alterations also occurred in TP53 (56%) and RB1 (19%). Median HRD score in Pre samples was 51 (range 36-66) and 10/13 had HRD scores ≥ 42. Pre and On SLFN11 and MGMT RNA expression were not correlated with ORR/PFS. 6/13 Pre samples were HR-deficient by the RAD51 foci assay. Of pts with PFS ≥ 200d, 4/6 were HR-deficient. In Pre samples, 81 genes were overexpressed in S pts and 73 in R pts. In On samples, 146 genes were overexpressed in S pts and 127 in R pts. In On samples, GSEA identified the epithelial-mesenchymal transition enriched in S pts (q = 3.38e-7) and cell cycle pathways (E2F targets, G2M checkpoint) in R pts (q = 7.43e-4). Only 2 genes, CXCL10 and PCDH15, were differentially expressed between paired Pre and On samples (both increased in On). Gene expression signatures for replicative stress showed borderline association with worse PFS. Conclusions: Most uLMS tumors exhibit HR defects as measured by HRD scores. A subset of pts with greater benefit from O+T were identified by WES for HR genes and the RAD51 assay. There was no correlation between SLFN11 and MGMT expression and outcomes. GSEA identified pathways differentially expressed in S and R pts in On samples. O+T induced CXCL10 which has been associated with T-cell trafficking to tumors. A randomized phase 3 trial of O+T versus investigator’s choice is planned. These results provide insight into which pts may benefit most from this novel drug combination. Clinical trial information: NCT03880019.

11507 Background: Leiomyosarcoma (LMS) is one of the most common subtypes of soft tissue sarcoma and is associated with high risk of relapse and a poor prognosis for advanced disease. In preclinical LMS models, unesbulin, a microtubule polymerization inhibitor, potentiated the activity of dacarbazine (DTIC) (Jernigan F, et al. Mol Cancer Ther. 2021;20:1846–1857). Here, we report preliminary safety and efficacy results from a Phase 1b dose escalation study evaluating the combination of unesbulin with DTIC in patients with advanced LMS (NCT03761095). Methods: In this single-arm, open-label, Phase 1b clinical trial, patients with advanced LMS received unesbulin orally at 200, 300, or 400 mg twice weekly (BIW) in combination with intravenous DTIC at 1,000 mg/m2 once every 21 days. The primary objectives were to determine the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) of unesbulin in combination with DTIC and to characterize the safety profile of the combination. The time-to-event continual reassessment model (TITE-CRM) was used for dose finding. An expansion cohort with up to 12 additional patients is currently being enrolled. Results: As of the data cutoff on January 6, 2022, 29 LMS patients have been treated. Median prior lines of therapy were 3 (range 1–6). Of 27 evaluable patients, 12 had non-uterine and 15 had uterine LMS. The MTD/RP2D of unesbulin was determined to be 300 mg BIW with DTIC 1,000 mg/m2 every 21 days using the TITE-CRM. At the RP2D, the most common treatment-related adverse events included fatigue, diarrhea, neutropenia, and thrombocytopenia. In the intent-to-treat population, the overall response rate (ORR) was 17.2% (5/29) and the disease control rate (DCR) (DCR = complete response + partial response + stable disease at 12 weeks) was 58.6%. At the 300 mg dose level, the ORR was 19% (4/21) and the DCR was 57.1%. Patients received a median of four cycles (range 1–12). The study is ongoing, with patients continuing to receive treatment. Conclusions: Unesbulin 300 mg BIW in combination with DTIC 1,000 mg/m2 every 21 days was well tolerated and demonstrated promising efficacy in a heavily pre-treated patient population with advanced LMS; these results support further investigation. Updated clinical results will be presented as the data mature. A randomized, placebo-controlled, Phase 2/3 trial is planned. Clinical trial information: NCT03761095.

TPS11587 Background: Soft tissue sarcoma (STS) is a heterogeneous malignancy of mesenchymal origin; leiomyosarcoma (LMS) and liposarcoma (LPS), two of the most common adult STS, are treated with first-line chemotherapy with objective response rates (ORRs) of 15-20%. There is an urgent need for novel therapeutics. ATX-101 is a small peptide comprised of a novel human AlkB homolog 2 proliferating cell nuclear antigen (PCNA) interacting motif termed APIM coupled to cellular and nuclear delivery domains. Via APIM, PCNA interacts with many cellular proteins important in the cellular stress and DNA damage responses, as well as intracellular signaling, apoptosis, metabolism, and anti-tumor immunity. In preclinical studies, ATX-101 demonstrated single-agent activity and potentiated other cytotoxic and targeted agents across multiple cancer models in vitro and in vivo, including LMS and LPS. In a phase I safety and pharmacokinetic study in solid tumors, ATX-101 was well tolerated and demonstrated prolonged disease stabilization in patients (pts) with heavily pretreated malignancies. This study will evaluate preliminary efficacy and further establish the safety profile of ATX-101 in advanced LMS and LPS. Methods: This is a single-arm, open-label, Simon 2-stage, phase II clinical trial of ATX-101 in pts with advanced LMS and LPS. Eligible pts have ECOG PS ≤2, progression on ≥1 prior line of therapy and disease measurable by RECIST v1.1 and amenable to image-guided biopsy. Pts receive ATX-101 60 mg/m2 IV weekly in continuous 21-day cycles. The 1° endpoint is progression free rate at 12 weeks (PFR12). A Simon 2-stage design is used to evaluate for improvement in PFR12 of ≤ 30% (null hypothesis) versus ≥ 55% (alternative hypothesis). The design calls for 34 pts with a safety lead-in among the first 10 pts enrolled. If 15/34 meet the PFR12 endpoint, the treatment is promising. This design yields 85% power and 1-sided type I error of 5%. 2° endpoints include progression free survival, ORR, and safety. 10 pts undergo tumor biopsies pre-treatment and during cycle 2. Tissue is used for correlative analysis interrogating ATX-101’s effects on the immune microenvironment through multiplex immunohistochemistry, DNA damage response through whole exome sequencing/RNAseq to evaluate for alterations in HR pathway component genes, and intracellular signaling pathways by Western blot for AKT/mTOR components. The study opened to accrual 12/2021. Clinical trial information: NCT05116683.

2520 Background: INT230-6 is a new product with a unique dual anti-cancer mechanism. The drug is comprised of cisplatin (CIS) and vinblastine (VIN) co-formulated with an amphiphilic molecule that enables drug dispersion throughout a tumor and passive diffusion into cancer cells following intratumoral (IT) delivery. A neoadjuvant study in breast cancer confirms that a single injection can kill 95% of an injected tumor and recruit TILs. Methods: INT230-6 treatments are Q2W for up to 5 treatments followed by maintenance dosing every 9 weeks. Dose is set by the tumor’s longest diameter or volume. One arm received INT230-6 plus PEM 200mg IV Q3W. Biopsies from injected tumor are taken pretreatment and Day 28 for immunohistochemistry (IHC) analysis. Results: Sixty-two subjects received INT230-6 alone (median age 61, with 4 prior treatments), and 21 INT230-6 + PEM (median age 70, with 3 prior treatments). To these subjects over 575 image guided INT230-6 IT injections were given (320 to visceral tumors such as lung, liver, pancreas). Doses ranged from 0.14 to 175mL (87.5 mg of CIS, 17.5 mg VIN - higher than typical IV doses). Pharmacokinetic data shows > 95% of the INT230-6 active agents remain in the tumor. The most common ( > 25%) adverse events (AEs) related to INT230-6 were localized pain (58%), nausea (40%), and fatigue (29%). The most common AEs attributed to the PEM combination were nausea (62%), localized pain (57%), vomiting (57%), decreased appetite (43%), fatigue (43%) and constipation (29%). The incidence of grade 3 AEs for the INT230-6 arm was 11% and for the PEM combination was 14%. There were no related grade 4 or 5 AEs in the INT230-6 arm; and one grade 4 neutrophil count decrease was seen on the PEM combination. There were no dose limiting adverse events. No patient discontinued therapy due to toxicities related to either drug or injection procedure. The monotherapy arm enrolled patients from 17 tumor types; while the PEM combo recruited primarily pancreatic, CRC, triple negative breast, or bile duct cancer. IHC results confirm a marked reduction in proliferating tumor cells with influx of CD4 and CD8 T-cells. Seven of the INT230-6 monotherapy patients had non injected tumor shrinkage in 9 visceral/deep lesions. Estimated median overall survival (mOS) was over 1 year for both arms. Conclusions: In this clinical trial, deep and superficial tumor injections into patients with widely metastatic disease was feasible and well tolerated. Biopsies confirm the dual anti-cancer mechanism, and study patients live longer than would be expected for these refractory populations. INT230-6’s rapid tumor killing and immune activation properties may offer an alternative to control refractory patients (even those that are chemotherapy refractory) and the product is moving into randomized controlled registration trials. Clinical trial information: NCT03058289.

Background INT230-6 is a novel formulation of cisplatin and vinblastine with an amphiphilic cell penetration enhancer that has been shown to enhance dispersion of the drug throughout tumors and allow diffusion into cells when given intratumorally. In preclinical models, INT230-6 has resulted in cell death, dendritic cell influx, antigen presentation and T-cell engagement with strong synergy when combined with checkpoint inhibitors Methods This phase 1/2 study evaluated Q2week injections of INT230-6 x 5 dosed by tumor volume alone or with 200 mg pembrolizumab IV Q3 weeks. Eligble patients had any advanced malignancy refractory to standard therapy with an injectable tumor. Results Sixty subjects (median 3 prior therapies (range 0–10)) were enrolled (53 monotherapy, 7 combo). Median age was 60 (42–85). 19 different cancer types were accrued with breast cancer and sarcoma being the most frequent. Over 200 deep tumor injections were administered at doses of up to 172 ml of INT230-6 (86 mg of CIS, 17 mg of Vin). PK analysis revealed Conclusions INT230-6 is well tolerated when administered intratumorally alone or in combination with pembrolizumab. Pharmacodynamic assessments provides proof of concept that this drug can reduce viable cancer cells and increases CD4/CD8 T-cell infiltrates leading to durable clinical benefit off treatment. Trial Registration NCT 03058289 Ethics Approval The study was approved by USC, Princess Margaret Cancer Center, Fox Chase, UMass, Columbia, and Johns Hopkins Institution’s Ethics Board Consent Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal

Although degree of T-cell infiltration in CRC was shown to correlate with a positive prognosis, the contribution of phenotypically and functionally distinct T cell subtypes within tumors remains unclear. We analyzed 37,931 single T cells with respect to transcriptome, TCR sequence and 23 cell surface proteins, from tumors and adjacent normal colon of 16 patients. Our comprehensive analysis revealed two phenotypically distinct cytotoxic T cell populations within tumors, including positively prognostic effector memory cells and non-prognostic resident memory cells. These cytotoxic T cell infiltrates transitioned from effector memory to resident memory in a stage-dependent manner. We further defined several Treg subpopulations within tumors. While Tregs overall were associated with positive clinical outcomes, CD38+ peripherally-derived Tregs, phenotypically related to Th17 cells, correlated with poor outcomes independent of cancer stage. Thus, our data highlight the diversity of T cells in CRC and demonstrate the prognostic significance of distinct T cell subtypes, which could inform therapeutic strategies.

BackgroundBackground: Study IT-01 (KEYNOTE-A10) evaluates INT230-6, a novel formulation of cisplatin (CIS) and vinblastine (VIN) with an amphiphilic cell penetration enhancer designed for intratumoral (IT) administration, as monotherapy and in combination with pembrolizumab (PEM). In preclinical studies, INT230-6 increases drug dispersion throughout the tumor, allows drug diffusion into cancer cells and recruits dendritic, CD4 and CD8 T cells. The addition of PEM improves these responses in mouse models.MethodsIT-01 is an open-label phase 1/2 study, currently enrolling adult subjects with solid tumors in phase 2. The study assesses the safety and efficacy of INT230-6 IT Q2W up to 5 doses as monotherapy or with PEM 200mg Q3W. Biopsies from injected tumor are taken pretreatment and Day 28 for immunohistochemistry (IHC) analysis.ResultsFifty-seven INT230-6, two INT230-6 then PEM combination, and thirteen INT230-6 + PEM combination subjects were enrolled having a median of 4 prior therapies (0, 10). Median age was 62. 20+ cancer types were accrued; breast cancer and sarcoma were the most frequent. Over 500 image guided INT230-6 IT injections were given (253 to deep tumors) at doses of 0.3 to 172mL (86 mg CIS, 17.2 mg VIN) in a single session (contains higher amounts than typical IV chemo doses). PK shows that 95% of INT230-6 active agents remain in the tumor.1 The most common (>25%) related adverse events (AEs) for INT230-6 alone were localized pain (59%), nausea (37%), and fatigue (29%). Safety profile of the PEM combination was similar. There were no related grade 4 or 5 AEs in either arm. The median overall survival (mOS) estimated with removal of 700cm3 tumor burdens was 433 days for monotherapy (n=51) and 513 days for PEM combination (n=12), which compares favorably to results seen in basket studies of patients having similar prognostic factors (ECOG, LDH, # of metastatic sites).2 IHC results indicate influx of CD4 and CD8 T-cells in injected lesions. No meaningful changes were observed in circulating inflammatory cytokines. Abscopal effects in the monotherapy arm were observed in 15 visceral/deep lesions in 11 patients, primarily who received an INT230-6 dose >50% of their total tumor burden (TTB).ConclusionsINT230-6 is well tolerated when administered IT as monotherapy and combined with PEM. Data suggests that INT230-6 prolongs survival compared to published basket studies in patients with similar prognostic factors. IHC and abscopal results indicate dosing INT230-6 may also activate a T-cell mediated immune response.AcknowledgementsN/ATrial RegistrationNCT# 03058289ReferencesOwelien. Historical PK data from IV administration. J Cancer Res 1977; 8.Abstract. Wagner M, et al. Validation of the Royal Marsden Hospital (RMH) prognostic score in 100 patients with advanced sarcoma enrolled in early phase clinical trials at a major cancer center. JCO 2015. https://ascopubs.org/doi/abs/10.1200/jco.2015.33.15_suppl.10558Ethics ApprovalThe protocol was approved by an institutional review board, independent ethics committee, or research ethics board at each institution. All subjects or their legally acceptable representative provided written informed consent before screening. The study was designed, undertaken, and reported in accordance with the Declaration of Helsinki, and is registered with clinicaltrial.gov with registration no NCT03058289.

BackgroundStudy IT-01 evaluates INT230-6, a novel formulation of cisplatin (CIS) and vinblastine (VIN) with an amphiphilic cell penetration enhancer designed for intratumoral (IT) administration, as monotherapy or in combination with ipilimumab (IPI). In preclinical studies, INT230-6 increases drug dispersion throughout the tumor, allows drug diffusion into cancer cells and recruits dendritic, CD4 and CD8 T-cells. Further, the addition of IPI has shown to improve INT230-6 responses in preclinical models.1MethodsIT-01 is an open-label phase 1/2 study, currently enrolling adult subjects with locally advanced, unresectable or metastatic solid tumors, including soft tissue sarcoma (STS). The study assesses the safety and efficacy of INT230-6 administered IT Q2W up to 5 treatment sessions as monotherapy or with IPI 3mg/kg IV Q3W for 4 doses. Biopsies from injected tumor are taken pretreatment and Day 28 for immunohistochemistry (IHC) analysis.Results22 subjects with STS (14 INT230-6 monotherapy, 8 IPI combination) have been enrolled with a median age was 65, having a median of 4 (2,10) prior therapies. INT230-6 doses of up to 175 mL (87.5 mg of CIS, 17.5 mg VIN) were injected in one or more tumors at a single dosing session, which contains doses exceeding the typical IV doses of the cytotoxic drugs.2 PK analysis estimates that 95% of INT230-6 active agents remain in the tumor. The most common (>25%) related adverse events (AEs) in evaluable monotherapy subjects (n=13) were localized pain (77%), fatigue (39%), decreased appetite (31%), and nausea (31%). The most common (>25%) related AEs in evaluable IPI subjects (n=4) were anemia (50%), fatigue (50%), pruritus (50%), and rash maculo-papular (50%). There were no related grade 4 or 5 AEs in either cohort.The median overall survival (OS) estimate for the monotherapy population (n=14) has not been reached with a median follow-up of 425 days, which compares favorably to results seen in basket studies of patients with similar prognostic factors (ECOG, LDH, # of metastatic sites).3 4 IHC results indicate influx of CD4 and CD8 T-cells without meaningful changes in circulating inflammatory cytokines. Abscopal effects in the monotherapy arm were observed in multiple lesions in 4 subjects. OS data for the 8 IPI combination subjects is immature.ConclusionsIT INT230-6 is well tolerated when administered as monotherapy and combined with IPI in STS subjects. INT230-6 monotherapy survival compares favorably to published basket studies in STS with similar prognostic factors. IHC and abscopal effects indicate dosing may activate a T-cell mediated immune response.Trial RegistrationNCT # 03058289ReferencesBloom AC, et al. Intratumorally delivered formulation, INT230-6, containingpotent anticancer agents induces protective T cell immunity and memory. OncoImmunology 2019.Owelien. Historical PK data from IV administration. J Cancer Res 1977; 8.Livingston J, et al. Validation of prognostic scoring and assessment of clinical benefit for patients with bone sarcomas enrolled in phase I clinical trials. Oncotarget 2016;7: 64421–64430. https://www.oncotarget.com/article/10910/Abstract M, et al. Validation of the Royal Marsden Hospital (RMH) prognostic score in 100 patients with advanced sarcoma enrolled in early phase clinical trials at a major cancer center. JCO 2015. https://ascopubs.org/doi/abs/10.1200/jco.2015.33.15_suppl.10558WagnerEthics ApprovalThe protocol was approved by an institutional review board, independent ethics committee, or research ethics board at each institution. All subjects or their legally acceptable representative provided written informed consent before screening. The study was designed, undertaken, and reported in accordance with the Declaration of Helsinki, and is registered with clinicaltrial.gov with registration no NCT03058289.

BackgroundImmune checkpoint blockade has emerged as a highly effective treatment for patients with metastatic melanoma and cutaneous squamous cell carcinoma. Nivolumab blocks the interactions between programmed cell death protein 1 and programmed death ligand 1 allowing for activation of a latent immune response against the malignancy. Ipilimumab binds to and blocks cytotoxic T-lymphocyte-associated protein 4, alleviating the negative regulation of T-cell activation that is mediated by that checkpoint. Combination therapy with nivolumab and ipilimumab is associated with longer overall survival at 5 years compared with nivolumab monotherapy. Solid organ transplant recipients have a significantly higher risk of malignancies compared with the general population. There is limited data surrounding the efficacy of combination immunotherapy in solid organ transplant recipients, as these patients were excluded from seminal trials due to risk of organ rejection.Case presentationsHere we present four cases of combination immunotherapy in kidney transplant recipients. Three patients had metastatic melanoma, and one patient had metastatic cutaneous squamous cell carcinoma. Two patients had radiographic responses from immunotherapy, one patient had stable disease, and one patient had disease progression. Only one patient had biopsy-proven rejection. At last follow-up, three patients had functioning grafts, though one required hemodialysis after treatment, and one patient succumbed to disease, but graft function remained intact throughout her course.ConclusionsThese cases describe the use of ipilimumab and nivolumab combination immunotherapy for cutaneous malignancies in kidney transplant recipients. They highlight the potential to preserve kidney graft function while effectively treating the disease.Trial Registration numberNCT03816332.

Soft tissue and bone sarcomas are malignancies of mesenchymal origin, and more than 50 subtypes are defined. For most sarcomas, locally advanced or unresectable disease is still treated with cytotoxic chemotherapy. Recently, our understanding of subtype-specific cancer biology has expanded, and it has revealed distinct molecular alterations responsible for tumor initiation and progression. These findings have motivated the development of targeted therapies that are being evaluated in subtype-specific or biomarker-driven clinical trials. Indeed, the spectrum of targeted drug development in sarcoma now spans many of the most active paradigms in cancer research and includes agents that target cancer-related vulnerabilities in receptor tyrosine kinases and intracellular signaling pathways, epigenetics, metabolism, nuclear-cytoplasmic transport, and many others. Our understanding of the sarcoma immune microenvironment and heterogeneous mechanisms of tumor immune evasion has also expanded. Although a subset of sarcomas appears inflamed and responsive to immune checkpoint blockade with programmed death 1 (PD-1) targeted agents, novel immunotherapies and combinations likely will be needed for most subtypes. A variety of approaches—including targeting immune checkpoints other than PD-1; modulating tumor-associated macrophage phenotype from tumor-promoting to tumor-suppressive status; using cellular-based therapies, such as chimeric antigen and high-affinity T-cell receptors to deepen the adaptive immune response; and reinvigorating older approaches, such as vaccines and oncolytic virus-based treatments—are being investigated. The goal of these new approaches is to harness subtype-specific insights into cancer and immune biology to bring more effective and less toxic treatments to the clinic for the benefit of patients with sarcoma.

TPS11578 Background: Conventional chondrosarcoma (cCS) accounts for ̃25% of primary bone cancers and is the second most common primary bone tumor after osteosarcoma. Surgical resection is the primary treatment for localized disease. No FDA approved therapy exists for advanced disease and chemotherapy has marginal efficacy with ORR < 12%. IDH1/2 mutation is seen in 50% of cases. Epigenetic dysregulation is central to oncogenesis in both IDH1/2 mutant and wild-type CS. Pre-clinical studies from our group show that combination treatment with HDAC and DNMT inhibitors is significantly more effective at suppressing the growth of CS models in vitro and in vivo compared to either therapy alone. The combination regimen mediates anti-tumor effects on CS by induction of apoptosis, induction of tumor suppressor genes (eg. E-cadherin), the induction of interferon responsive genes (eg. IRF7, OASL, ISG15, DDX58) and reversal of global hypomethylated state. Based on these findings we have designed a phase 2 clinical trial with an HDAC inhibitor (belinostat) and a DNMT inhibitor (guadecitabine) in patients with advanced cCS. Methods: NCI # 10330 is a single-arm, multi-center, Simon 2-stage, phase 2 clinical trial evaluating belinostat and guadecitabine in patients with advanced cCS. Eligible patients will have biopsy proven cCS which is measurable by RECIST v1.1 and amenable to biopsy, ECOG PS ≤ 2, any number of prior treatments (including none). Patients will receive guadecitabine 45 mg/m2 SC followed by belinostat 1000 mg/m2 IV once daily on days 1-5 of a 28-day cycle. A safety lead-in and continuous toxicity monitoring rule will be applied. The primary endpoint will be ORR. Since chemotherapy is associated with an ORR of 8-12% and targeted agents have shown an ORR of 0% in cCS, we will consider an ORR of 8% as inactive while an ORR of 28% will suggest promising activity. A Simon 2-stage design is employed. The design calls for 26 patients. If ≥ 2 responses are observed among 13 patients in stage I, the study will proceed to full accrual. If ≥ 5 responses are seen among 26 patients, the study treatment is considered promising. This design has 85% power with α of 0.054 to test for a response rate of 8% vs 28%. Secondary objectives include safety, tolerability and PFS. All patients will undergo pre-treatment and on-treatment tumor biopsies. Paired tissue will be used for correlative analysis including: 1) whole exome sequencing/RNAseq to evaluate changes in gene expression in response to treatment, 2) multiplex IHC to interrogate the effect of combination therapy on tumor immune microenvironment and 3) a global DNA methylation assay to better understand the changes in epigenetic landscape in response to treatment. This study is open throughout the ETCTN (NCT04340843). Six of the planned 26 patients in the safety lead-in have been enrolled without DLT. Further accrual is on hold pending completion of the safety lead-in. Clinical trial information: 04340843.

2592 Background: Study IT-01 (KEYNOTE-A10) evaluates INT230-6, a novel formulation of cisplatin (CIS) and vinblastine (VIN) with an amphiphilic cell penetration enhancer designed for intratumoral (IT) administration, alone or in combination with pembrolizumab (PEM), an antibody to PD-1. INT230-6 dosing is set by a tumor’s volume. In preclinical studies, INT230-6 increases drug dispersion throughout the tumor, allows drug diffusion into cancer cells and recruits dendritic, CD4 and CD8 T cells. The addition of PEM has been shown to improve these responses in models. Phase 1 data indicated INT230-6 alone induced tumor regression in both injected and non-injected lesions. Considering the large volume of drug injected and retained in the tumor, coupled with immune infiltration on biopsies, RECIST response methodology may not capture the benefit of INT230-6 treatment. Methods: IT-01 is an open-label phase 1/2 study, currently enrolling adult subjects with solid tumors in phase 2. INT230-6 was administered IT Q2W for 5 doses alone or with PEM 200mg Q3W. The study seeks to assess the safety and efficacy of IT INT230-6 alone and in combination with PEM. Results: 67 subjects have been enrolled (58 mono and 12 INT230-6 + PEM (3 started in mono, then received combo)) having a median of 3 prior therapies (0, 10). Median age was 60 (42, 85). 20+ cancer types were accrued; breast cancer and sarcoma were the most frequent. Over 500 image guided INT230-6 IT injections were given (253 to deep tumors) at doses of 0.3 to 172mL (86 mg CIS, 17.2 mg VIN) in a single session, which are higher amounts than typical IV doses. PK shows that 95% of INT230-6 active agents remain in the tumor. The most common (> 20%) related TEAEs for INT230-6 alone were localized pain (57%), nausea (36%), fatigue (29%) and vomiting (24%); with grade 3 TEAEs (> 1) of localized pain (5%) and anemia (3%). The safety in the combination was similar. There were no related grade 4 or 5 TEAEs. In evaluable monotherapy subjects (n = 43), the disease control rate (DCR) was 65% vs. 100% in PEM subjects (n = 5). Given the range of dose and entering tumor burden, an exploratory analysis of dose relative to tumor burden (TB) showed that subjects receiving a dose of INT230-6 < 50% of their reported TB (n = 30) had a mOS of 3.5 months. While in subjects receiving a dose of INT230-6 to ≥50% of TB (n = 37), mOS has not yet been reached after a median follow up of 9.5 months (HR: 0.26 (0.13,0.51)). Conclusions: INT230-6 is well tolerated when administered IT as monotherapy and combined with PEM. Given the challenge in assessing overall response rate following IT delivery, an exploratory analysis suggests prolonged survival for subjects receiving an INT230-6 dose ≥50% of their tumor burden compares favorably to the < 50% group and to literature accounting for prognostic factors (ECOG, LDH, # of metastatic sites). Clinical trial information: 03058289.

11508 Background: Soft tissue sarcoma (STS) is dependent on extracellular arginine as it often lacks expression of argininosuccinate synthase 1 (ASS1), the urea cycle enzyme needed to produce intracellular arginine. PEGylated arginine deiminase (ADI-PEG 20) is an extracellular arginine-degrading enzyme that causes ASS1 deficient tumors to enter the starvation state. Preclinical data demonstrated that addition of docetaxel (D) with ADI-PEG20 upregulates expression of the transporter for gemcitabine (G), overcoming transporter level resistance, and causing increased cell death. In vivo modeling demonstrated that the combination of ADI-PEG20 with G+D was superior to G+D alone. Therefore, we performed a phase 2 trial testing the addition of ADI-PEG20 to G+D. Methods: We performed an investigator-initiated, phase 2, multicenter, multi-arm clinical trial of ADI-PEG20 with G (90minute infusion)+D in STS, Ewing’s, osteosarcoma and small cell lung cancer. We are reporting Arm A, the STS arm. Eligible patients had STS that would be standardly treated with G+D that had progressed on at least one prior line of therapy with measurable disease by RECIST1.1 and had adequate organ function Based on a historic median PFS of 6.2 months for G+D, we targeted to enroll N = 75 patients in cohort A to detect a 2.8 month improvement with 80% power at a 5% alpha level. Primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), clinical benefit rate (CBR), safety, tolerability, cancer related mortality, and correlation with ASS1 expression by IHC. We evaluated PFS by Kaplan-Meier method and estimated overall response rate (ORR). Results: 75 patients were treated and deemed evaluable. The trial underwent two dose reductions by the data safety monitoring board due to prolonged neutropenia and thrombocytopenia preventing the use of day 8 G+D, consistent with preclinical mechanism of action data showing that ADI-PEG 20+D enhanced G uptake. Originally, the G dose was 900mg/m2 reduced first to 750mg/m2 then to 600mg/m2. D was dose reduced at the time of the second dose reduction from 75mg/m2 to 60mg/m2. ADI-PEG20 was given at a fixed intramuscular dose (36 mg/m2) weekly. The need for two dose reductions affected the PFS. The PFS/OS (months) were for the 600mg/m2 group (n = 31) was 6.0/N.D., leiomyosarcoma (LMS) (N = 33) 7.2/22.5, liposarcoma 5.1/17.4, and other (N = 36) 2.8/15.0. Responses were 8% complete (6/75) (3 LMS, 1 synovial and 2 angiosarcoma), 17% partial (13/75), and 43% stable disease (32/75), for an ORR of 25% (19/75) and CBR of 68% (51/75). There was a trend for ASS1 negative tumors to benefit more than ASS1 positive tumors. Conclusions: The combination of ADI-PEG20 with G+D can be safely and effectively given at a dose of 600mg/m2 G and 60mg/m2 D. Future randomized trials of ADI-PEG20 with G+D are planned. Clinical trial information: NCT03449901.

11523 Background: Sarcoma pts often receive aggressive, highly immunosuppressive therapy and may be at high risk for severe COVID-19. Demographics, outcomes and risk factors for pts with sarcoma and COVID-19 are unknown. We aimed to describe the course of COVID-19 in sarcoma pts and to identify factors associated with adverse outcomes. Methods: The COVID-19 and Cancer Consortium (NCT04354701) is an international registry of pts with cancer and COVID-19. Adult pts (≥18 years old) with a diagnosis of sarcoma and laboratory confirmed SARS-CoV-2 were included from 50 participating institutions. Data including demographics, sarcoma diagnosis and treatment, and course of COVID-19 infection were analyzed. Primary outcome was the composite rate of hospitalization or death at 30 days from COVID-19 diagnosis. Secondary outcomes were 30 day all-cause mortality, rate of hospitalization, O2 need, and ICU admission. Descriptive statistics and univariate Fisher tests are reported. Results: From March 17, 2020 to February 6, 2021, N=204 pts were included. Median follow up was 42 days. Median age was 58 years (IQR 43-67). 97 (48%) were male. 30 (15%) had ECOG performance status ≥2. 104 (51%) received cancer treatment, including surgery or radiation, within 3 months of COVID-19 diagnosis. 153 (75%) had active cancer, of whom 34 (22%) had lung metastases. 100 (49%) pts met the composite primary endpoint; 96 (47%) were hospitalized and 18 (9%) died within 30 days from COVID-19 diagnosis. 64 (31%) required oxygen, and 16 (8%) required ICU admission. Primary endpoint rates were similar for pts who received cytotoxic chemotherapy (38/58, 66%) or targeted therapy (16/28, 57%). Pts with higher rates of the primary endpoint included patients ≥60 years old (59% vs 40%, OR 2.04, 95% CI 1.12-3.74, p=0.016), pts with ECOG PS ≥2 vs 0-1 (90% vs 41%, OR 12.2, 95% CI 3.44-66.8, p

11513 Background: Well-differentiated/dedifferentiated liposarcoma (WD/DD LPS), a sarcoma of adipocytic origin, lacks effective treatment options for advanced disease. Pazopanib, a receptor tyrosine kinase (RTK) inhibitor active upon angiogenic RTKs, is approved for non-adipocytic sarcomas but failed to show activity in LPS. In a phase 2 study, pazopanib provided a progression-free rate at 12 weeks of 26% in LPS. Our preclinical work implicated IGF1R, MET, and PDGFRα/ß in liposarcomagenesis. Sitravatinib (S) is a novel, orally available, potent, small molecule RTK inhibitor active upon these and related targets. In preclinical WD/DD LPS models, S demonstrated significant activity in vitro and in vivo and appeared superior in efficacy to pazopanib, imatinib and crizotinib. Methods: We performed a phase II, single-arm, multi-center, Simon 2-stage study to evaluate S in adult pts with unresectable/metastatic WD/DD LPS who had received ≥ 1 prior line of systemic therapy and had evidence of disease progression ≤ 12 wks prior to enrollment. Pts received S 120 mg PO daily in continuous 21-day cycles. Primary endpoint was the progression-free rate at 12 wks (PFR12). Secondary endpoints were objective response rate (ORR), progression free survival (PFS) and safety/tolerability. Based upon historical controls, PFR12 ≤ 20% was considered inactive whereas PFR12 ≥ 40% was considered promising. If ≥ 3/13 met PFR12 in stage 1, the study proceeded to full accrual. If ≥ 9/29 met PFR12 overall, S was considered promising. Design provided 85% power with α= 0.10. A subset of pts underwent paired biopsies. Results: 29 pts initiated treatment and are evaluable. Median age was 62 yrs (range: 28-88). 16 (55%) were male. 28/29 had DD LPS. 3 pts remain on treatment and 26 pts have discontinued (22 for disease progression, 2 for adverse events). In the first stage, 5/13 pts met the PFR12 endpoint; therefore, the study proceeded to full accrual. Overall, 12/29 pts (41%) were progression-free at 12 weeks and the study met the primary endpoint. ORR by RECIST was 3.4%. Median PFS was 11.7 weeks (95% CI: 5.9 - 35.9 wks). 12/29 (41%) of pts experienced grade 3 treatment-related adverse events. Common S-related grade 3 AEs were hypertension (24%), fatigue (7%) and hyponatremia (7%). There were 2 grade 4 events (hypertension, reversible posterior leukoencephalopathy syndrome). Hypertension was easily managed with medication. A subset of pts underwent paired tumor biopsies that will be analyzed using next generation sequencing and reverse phase protein array. Conclusions: S met the predefined efficacy endpoint with 12/29 pts (41%) progression-free at 12 weeks, indicating clinically meaningful activity potentially superior to pazopanib. The drug was well tolerated. Further study of S in WD/DD LPS is warranted. Clinical trial information: NCT02978859.

11557 Background: Patients have limited treatment options following initial chemotherapy failure. INT230-6, a novel formulation of cisplatin (CIS) and vinblastine (VIN) with an amphiphilic cell penetration enhancer, is designed for intratumoral (IT) administration. Study IT-01 (BMS # CA184-592, NCT 03058289) evaluates INT230-6 alone or in combination with ipilimumab (IPI), an antibody to CTLA-4. INT230-6 dosing is set by a % of the volume of the tumor to be injected. The product has been shown to disperse throughout an injected tumor and diffuse into cancer cells. Cell death leads to recruitment of dendritic and T cells, the effect of which may be augmented by CTLA-4 inhibition as evidenced by increased efficacy of the combination in preclinical models. Historically, checkpoint inhibitors have limited activity in sarcoma. Considering the large volume of drug injected and retained in the tumor, coupled with immune infiltration on biopsies, RECIST response methodology may not capture the benefits of INT230-6 treatment. Methods: IT-01 is an open-label phase 1/2 study that is enrolling adult subjects with locally advanced, unresectable or metastatic sarcoma. INT230-6 was administered IT Q2W for 5 doses alone or with IPI 3mg/kg IV Q3W for 4 doses. The study objectives are to assess the safety and efficacy of IT INT230-6 alone and in combination with IPI. Results: 16 heterogenous sarcoma subjects (13 monotherapy, 3 IPI combination) having a median of 3 prior therapies (0, 8) were enrolled to date. The INT230-6 dose was up to 145 mL (72.5 mg of CIS, 14.5 mg VIN) in a single session (an amount of each agent in excess of standard IV doses). The most common ( > 20%) related TEAEs in sarcoma subjects (n = 16) were localized pain (63%), fatigue (38%), decreased appetite (31%), nausea (31%), and vomiting (25%) most of which were low grade; with only grade 3 TEAE above 5% being anemia (13%). There were no related grade 4 or 5 TEAEs. In 11 evaluable monotherapy subjects, the disease control rate (DCR = CR+PD+SD) was 82%. Basket studies of sarcomas, including chordoma, with Royal Marsden Hospital index (RMHI) scores of 2 or higher report median overall survival (mOS) of 4 months. In this study 75% of monotherapy subjects had a RMHI score of 2 and preliminary estimates of mOS was 21.3 (4.67, NA) months. Pilot immunohistochemistry analysis of 5 paired (pre- and 28 days post-dose) biopsy samples showed substantial tumor necrosis, reduction of viable cancer, a decreased cancer proliferation as measured by Ki67, and increased TILs. Conclusions: Preliminary data shows that INT230-6 administered intratumorally alone or in combination with ipilimumab is well-tolerated in this small, heterogenous sarcoma population. The preclinical cancer cell death and immune infiltration mechanism of action appears to translate to sarcoma subjects. There are early signs of efficacy, DCR and potentially OS, that need to be confirmed in randomized studies. Clinical trial information: 03058289.

Simple Summary In this position paper, we aim to summarize state-of-the-art treatments for patients with leiomyosarcomas in order to identify knowledge gaps and current unmet needs, thereby guiding the community to design innovative clinical trials and basic research and close these research gaps. This white paper arose from a leiomyosarcoma research meeting in October 2020 hosted by the National LeioMyoSarcoma Foundation (NLMSF) and Sarcoma Patients EuroNet (SPAEN). Abstract As leiomyosarcoma patients are challenged by the development of metastatic disease, effective systemic therapies are the cornerstone of outcome. However, the overall activity of the currently available conventional systemic treatments and the prognosis of patients with advanced or metastatic disease are still poor, making the treatment of this patient group challenging. Therefore, in a joint effort together with patient networks and organizations, namely Sarcoma Patients EuroNet (SPAEN), the international network of sarcoma patients organizations, and the National LeioMyoSarcoma Foundation (NLMSF) in the United States, we aim to summarize state-of-the-art treatments for leiomyosarcoma patients in order to identify knowledge gaps and current unmet needs, thereby guiding the community to design innovative clinical trials and basic research and close these research gaps. This position paper arose from a leiomyosarcoma research meeting in October 2020 hosted by the NLMSF and SPAEN.