Blogs

Correlation of tertiary lymphoid structures with survival benefits in patients treated with first line atezolizumab for metastatic lung cancer

606. IMpower110: Tertiary lymphoid structures (TLS) and clinical outcomes in advanced non-small cell lung cancer (NSCLC) treated with first-line atezolizumab

Barzin Nabet (Genentech, South San Francisco, CA, USA) presented an analysis to evaluate the clinical utility of tertiary lymphoid structures (TLS) as a biomarker associated with clinical benefits from immunotherapy in patients with untreated metastatic non-small cell lung cancer (mNSCLC). Prior studies have indicated that B-cell and plasma-cell gene expression signatures as well as the presence of TLS are associated with improved overall survival outcomes in patients with mNSCLC treated with atezolizumab in the second line setting. This study analyzed patient baseline samples from IMpower110, a Phase III study of first line atezolizumab vs chemotherapy in PD-L1-selected mNSCLC. Digital images of baseline samples in patients were reviewed for the presence of dense lymphoid aggregates with at least one distinct germinal center (TLS), lymphoid aggregates without any germinal centers (LA), or absence of both (neither). Of 422 patients in TLS biomarker-evaluable population, 62 samples were characterized as TLS, 151 as LA and 209 neither. TLS distributions were similar across treatment arms and across key patient subgroups. The TLS subgroup showed numerically improved progression free survival (PFS) and overall survival (OS) in the atezolizumab arm compared to the chemotherapy arm (PFS HR 0.47; OS HR 0.55). PFS benefit within atezolizumab arm greater in TLS than LA or neither group. The TLS subgroup showed improved PFS across PD-L1 subgroups in the atezolizumab arm compared to the chemotherapy arm, especially in the PD-L1 intermediate/low subgroup (HR 0.44). Similar results were observed for OS. The TLS subgroup also showed PFS benefits associated with atezolizumab across histology subgroups. This study represents the first large-scale analysis of TLS/LA in the context of a Phase III clinical trial of immune checkpoint blockade vs chemotherapy for mNSCLC. Although additional NSCLC clinical data sets should be analyzed to validate these findings, these data indicate that the presence of TLS in baseline tumor tissues may identify patients with mNSCLC who are most likely to benefit from first-line PD-(L)1 inhibitors, especially those with tumors with intermediate or low levels of PD-L1 expression.

Phase I trial of pressure-enabled drug delivery of TLR9 agonist SD-110 for liver metastases

1534. Clinical activity of SD-101 with immune checkpoint inhibition (ICI) in metastatic uveal melanoma liver metastasis (MUM-LM) from the PERIO-01 Phase 1 trial

Sapna Patel (The University of Texas MD Anderson Cancer Center, Houston, TX, USA) presented results from PERIO-01, a Phase I trial of pressure-enabled drug delivery (PEDD) of SD-110, a TLR9 agonist, for metastatic uveal melanoma liver metastasis (MUM-LM). Previous studies indicate that SD-101 leads to depletion of myeloid-derived suppressor cells (MDSC) and recruitment and activation of T cells in the tumor microenvironment (TME). 56 patients who were heavily pretreated for MUM-LM were assigned to three dose escalation cohorts. Patients in Cohort A (n=13) received SD-101 monotherapy, Cohort B (n=26) received SD-101 + nivolumab, and Cohort C (n=17) received SD-101 + nivolumab + ipilimumab. 6 patients experienced treatment related adverse events (TRAEs) of grade 3 or higher, and five of these patients were in Cohort C, who received nivolumab and ipilimumab in addition to SD-101. Pharmacokinetic analyses indicated that SD-101 was detected in high levels in the liver but at low, transient levels in the peripheral blood. At day 57, tumors from patients in cohort B exhibited increased levels of tumor-infiltrating CD4+ and CD8+ T cells and NK cells.  SD-101 at a dose of 2 mg was associated with decreased regulatory T cells and MDSCs and increased Granzyme B in the tumor as well as increased IL-15 signaling, so 2 mg SD-101 with nivolumab was identified as the optimal dose. Although SD-101 was detected at low levels outside of the liver, peripheral blood from patients showed increases in T cell activation, inflammatory cytokine signaling, and NK cell activation, indicating SD-101 induced systemic immune activation. 86% of all patients experienced a decrease in circulating tumor DNA (ctDNA), and 59% of patients experienced ctDNA clearance. Among patients who received 2 mg SD-101 + nivolumab, the median progression free survival was 11.7 months, and one-year overall survival was 86%. No patients who received 2 mg SD-101 + nivolumab experienced TRAEs of grade 3 or higher. The safety and clinical efficacy of SD-101 are promising, indicating that PEDD of SD-101 with nivolumab may have potential to address a significant unmet clinical need of patients with liver metastases. A larger trial of 2 mg SD-101 + nivolumab for MUM-LM is currently enrolling patients.

Preclinical studies of tissue-targeted liquid nanoparticle delivery of bispecific T cell engager mRNA

1358. Tissue-targeted lipid nanoparticle delivery for mRNA encoding bispecific T-cell engager demonstrated potent antitumor effects on both hematological malignancies and solid tumors

Xin Kai (Hopewell Therapeutics Inc., Woburn, MA, USA) reported results from preclinical studies of a next-generation tissue-targeted lipid nanoparticle delivery of mRNA encoding a bispecific T cell engager (ttLNP-BiTE mRNA). HTX-L01-008 (LNP-mRNA GPC3/CD3 BiTE), which targeted the liver, was shown to have an extended pharmacokinetic profile in mice and induced T cell killing against HepG2-Luc, luciferase-tagged hepatocellular carcinoma (HCC) cells. HTX-L01-008 exhibited significantly higher anti-tumor efficacy in an orthotopic HCC xenograft mouse model compared to a GPC x CD3 BiTE, and mice receiving HTX-L01-008 exhibited no adverse effects. HTX-L01-003 (LNP-mRNA CD19/CD3 BiTE), which targeted lymphoid organs, was administered to non-human primates, exhibited dose-dependent protein expression, transient T cell activation, and sustained depletion of B cells and plasma cells. Like HTX-L01-008, HTX-L01-003 was well-tolerated. These studies suggest that tissue-targeting LNP-mRNA encoding BiTE provides a unique platform with enhanced anti-tumor activity and reduced toxicity for the treatment of both hematological and solid tumors. This platform may potentially represent a simple and cost-effective alternative for the manufacturing of different BiTEs to treat a variety of cancers.

Vaccination with high doses of MHC-II neoantigens induce a novel class of inhibitory cytolytic CD4+ T cells

1006. High doses of MHC-II neoantigens in peptide cancer vaccines induce tumor-specific inhibitory cytolytic CD4+ T cells

Hussein Sultan (Washington University School of Medicine, Saint Louis, MO, USA) presented results from a study of synthetic long peptide (SLP) cancer neoantigen vaccines in a syngeneic mouse cancer model. Previous work has indicated that vaccine efficacy depends on the quantity and quality of MHC-II neoantigens in the vaccine. Mouse sarcoma lines that never express MHC-II were implanted into syngeneic mice and treated with tumor-specific SLP neoantigen vaccines containing varying amounts of MHC-II neoantigens. Vaccines containing tumor-specific MHC-I neoantigens plus low doses of MHC-II neoantigens (LDVax) promoted tumor rejection, but vaccines with high doses of MHC-II neoantigens (HDVax) were ineffective. HDVax inhibited the anti-tumor efficacy of anti-PD-1 and anti-4-1BB therapies but not anti-CTLA4 therapy, suggesting HDVax induced an inhibitory immune cell population. Adoptive transfer of antigen-specific HDVax-induced CD4+ T cells also blocked T3 tumor rejection. To address the nature of these inhibitory HDVax tumor-specific CD4+ T cells, single cell RNA sequencing identified a cluster of CD4+ T cells expressing high levels of LILRB4, Granzyme-B (GZMB), Perforin and CCL5 that were enriched after HDVax treatment. Anti-LILRB4 reduced expression of GZMB and CCL5 expression and blocked the inhibitory activity of the HDVax-induced CD4+ T cells. HDVax-induced CD4⁺ T cells inhibited tumor immunity by killing type 1 conventional dendritic cells (cDC1), as evidenced by in vitro killing assays and by low recovery of cDC1 from tumors in HDVax-treated mice compared to LDVax-treated or control mice. Treatment with anti-LILRB4 partially restored cDC1 loss in HDVax-treated tumors. Although this novel subset of inhibitory CD4+ T cells needs to be identified in humans, results from this study may provide new insights to improving the efficacy of cancer vaccines and other immunotherapies.

Using RNA splicing mutations to identify new targets for T cell-directed therapies

1399. Identification of alternative splicing-derived targets for TCR-T cell therapies

Elise Wilcox (Fred Hutchinson Cancer Center, Seattle, WA, USA) reported a study using RNA splicing mutations to identify clinically targetable peptides for TCR-T cell therapy. The P95H mutation in SRSF2, a protein involved in pre-mRNA splicing, is prevalent across multiple types of high-risk myeloid neoplasms and results in recurrent missplicing of hundreds of RNA transcripts. The ARTEMIS single chain dimer peptide discovery pipeline was used to identify HLA-presented neopeptides that result from splicing errors. HLA-specific single chain dimers (SCDs), which express the His-Tag to allow for secretion, were transduced into SRSF2 wild type cell line or a cell line with the SRSF2 P95H mutation. SCDs that were secreted during the culture period were collected and identified using mass spectrometry. Thousands of peptides were eluted from three HLAs (HLA-A2, HLA-A11, and HLA-A24) that represent 71% of the patient population in the United States, and 10.4% of the peptides were exclusive to the splicing mutant cells. Initial analyses identified targetable peptides that stimulated T cell responses. Current analyses are underway to identify and validate target peptides, especially those that span exon-exon junctions and elicit strong, specific immune responses. This study identifies a novel method to identify HLA-presented peptides, extending the range of engineered TCR-T cell therapies. Work is currently underway to construct patient-derived xenograft mouse model with SRSF2 P95H patient samples. This methodology can be adapted to other mutations associated with RNA processing and could also be applied to other anti-cancer treatment modalities, including peptide-based vaccines and CAR T cells.

A novel autologous checkpoint of activated CD8+ T cells

916. Making their own off switch: Fgl2 produced by antigen-specific CD8+ T cells tempers the CD8+ T-cell response via apoptosis of FcγRIIB+ CD8+ T cells

Kelsey Bennion (Emory University, Atlanta, GA, USA) presented a study of FCγRIIB, a novel inhibitory IgG-Fc receptor that was recently found to be upregulated on effector-like memory CD8+ T cells at the tumor in mice and humans. CD8+ T cells expressing FCγRIIB exhibit strong anti-tumor function, and activation of FCγRIIB reduces cellular proliferation or induces apoptosis. Antigen specific CD8+ Fcgr2b knockout cells outcompete their wild-type counterparts, and this competitive advantage is dependent on Fgl2, a binding partner of FCγRIIB. Fgl2 is expressed by many cells, but single cell RNA sequencing of a dataset from melanoma patients indicated that tumors with exhausted CD8 +T cells expressing Fgl2 were associated with worse survival in patients. Studies from a separate dataset from melanoma patients indicate that Fgl2 is most expressed on PD-1+ CD8+ T cells with an exhausted phenotype. A mouse model was generated where Fgl2 wild type or Fgl2 knockout T cells were transferred to Fgl2 knockout mice, and mice were challenged with B16 melanoma cells. Mice that received Fgl2 knockout T cells exhibited more persistent anti-tumor activity, decreased exhaustion, and decreased tumor size compared to mice that received wild type T cells. Persistence of Fgl1 knockout cells may have been at least partly caused by the increased levels of apoptosis of FCγRIIB+ CD8+ T cells in mice that received wild type T cells. The data presented support a model in which exhausted CD8+ T cells make their own off switch. Fgl2, expressed by exhausted T cells, induces apoptosis of CD8+ T cells through interaction with FCγRIIB, thus decreasing T cell-mediated anti-tumor activity, increasing levels of Fgl2-expressing exhausted T cells, and negatively affecting patient outcomes. Discovery of this pathway provides a new immune checkpoint for which expressing and/or signaling can be manipulated to develop new treatment options for patients with cancer.

Lipid metabolism, lipid-associated macrophages, and PARP inhibitor therapy in breast cancer

1111. Targeting lipid metabolism to improve PARP inhibitor response in BRCA-associated TNBC

Carlos Wagner Wanderley (Brigham and Women’s Hospital, Alston, MA, USA) presented results from a study of lipid metabolism and poly (ADP-ribose) polymerase inhibitor (PARPi) therapy. PARPi therapy induces DNA damage in tumor to activate cGAS/STING signaling, increasing tumor antigen and immune infiltration. The efficacy of PARPi therapy is dependent on the recruitment of CD8+ T cells to the tumor and T cell activity in the tumor microenvironment. Previous studies have shown that depletion of macrophages with anti-CSF1R enhances PARPi therapy, and lipid-associated macrophages found in breast tumors confer a pro-tumorigenic environment. The goal of this study was to determine whether PARPi therapy reprograms the immunometabolic landscape of breast cancer tumors by increasing lipid-associated macrophages, which act to inhibit the anti-tumor response. Single-cell analyses of patient samples pre- and post-PARPi therapy indicate that PARPi therapy is associated with increased levels of suppressive macrophage markers, suggesting PARPi therapy recruits and induces suppressive macrophages to the tumor. PARPi therapy also induced upregulation of inflammatory pathways as well as metabolic pathways involved in lipid metabolism. Using a mouse model of breast cancer, PARPi therapy was associated with an influx of CD8 T cells, macrophages, and other immune cells to the tumor as well as upregulation of genes associated with lipid and carbohydrate metabolism. Tumors in mice treated with PARPi also exhibited an increase in lipid levels, and this effect was abrogated with anti-CSF1-R to deplete macrophages. Inhibition of lipid metabolism with fatostatin reduced fatty acid synthesis in the tumor and improved response to PARPi therapy, indicated by decreased tumor burden and increased survival. Results from this study provides new insights to deregulation of lipid metabolism, lipid-associated macrophages, and their roles in compromising the efficacy of PARPi therapy.