Correlation of constitutive PD-1 resistance in HNC with GM-CSF expression and presence of myeloid derived suppressor cells (MDSCs)

6049

Background: PD-1 checkpoint blockade is active in head and neck squamous cell carcinomas (HNC) with a response rate of ~18% and significant impact on survival. However, only a subset of patients benefits (Seiwert, Lancet Oncol). Biomarkers such as PD-L1 IHC and the Interferon-Gamma gene expression profile (INF-G GEP) identify inflamed tumors with a higher chance of response (~35-40%). However, it remains unclear why the majority of INF-G inflamed tumors still do not respond, or how to overcome constitutive resistance. Methods: 50 anti-PD-1 treated recurrent/metastatic HNC patients were included. Tumor RNA was analyzed using a 638-gene immune panel on the Nanostring nCounter. HPV status was assessed by HPV E6/E7 mRNA. T-cell inflamed phenotype was calculated using the 6-gene INF-G GEP (geometric mean) using both a low (6) and a high cutpoint. Differential gene expression was determined between inflamed-benefitting (IB) patients (defined as OS ≥ 250days), and inflamed-non-benefitting (INB) patients. Candidate biomarkers were evaluated in the entire cohort. Results: CD8 correlated highly with INF-G GEP (R = 0.80), suggesting T cell-driven inflammation. Comparing inflamed benefitting with inflamed non-benefitting tumors, the most differentially expressed gene was CSF-2, encoding GM-CSF, with 4-fold higher expression in inflamed non-benefitting (INB) tumors (with both cutpoints). In the overall anti-PD-1 treated cohort of 50 patients, CSF-2/GM-CSF correlated strongly with poor overall survival (P = 0.02), outperforming both HPV status, or PD-L1 expression in cox PH multivariate analysis. GM-CSF expression has been linked to myeloid derived suppressor cells (MDSC); MDSC marker CD34, as well as JAK2/IL10 were significantly elevated in inflamed non-benefitting (INB) tumors. There was no difference in M2 macrophage marker CD163 between the two groups. Conclusions: Constitutive resistance to PD-1 checkpoint blockade in inflamed HNC associates with expression of GM-CSF and Myeloid Derived Suppressor Cell (MDSC) markers. Strategies to deplete MDSCs, such as chemotherapy, should be considered in combination or sequentially with anti-PD-1.

A pharmacodynamic study of sirolimus and metformin in patients with advanced solid tumors

TPS11628

Background: Sirolimus is an inhibitor of the mammalian target of rapamycin (mTOR). Metformin has shown anti-cancer activity through its cellular (e.g., AMPK activation) and systemic effects (e.g., inhibition of IGF-1). We conducted a pilot study to test the hypothesis that metformin may potentiate mTOR inhibition by sirolimus. Methods: An open-label, randomized study was conducted in which eligible patients with advanced solid tumors were started on sirolimus (3mg daily) alone for the first 7 days. On day 8, patients were randomized to either receive metformin XL (500 mg daily) plus sirolimus (Arm A) or sirolimus alone (Arm B) for until day 21. From day 22 onwards, all patients recieved metformin XL plus sirolimus. The pharmacodynamic (PD) biomarkers were collected at baseline, day 8 and day 22 of cycle 1. The primary endpoint was to compare the change in PD biomarker phospho-p70S6K, using a two-sample t test (log ratio D22/D8 in arm A vs. arm B). The phospho-p70S6K was measured in peripheral blood T cells using Western blot. The secondary endpoints were to assess objective response rate (RECIST 1.1), toxicity (CTCAE V4.0) and changes in the serum levels of PD biomarkers: fasting glucose, triglycerides, insulin, C-peptide, IGF-1, IGF-1R, IGF-BP, leptin and adiponectin using two-sample t tests. Results: 24 patients were enrolled, at which time an interim futility analysis was conducted. 18 patients were evaluable for the primary endpoint (8 in arm A; 10 in arm B). The mean log ratios D22/D8 in phospho-p70S6K in arms A and B were -0.12 (SD = 0.13) and -0.16 (SD = 0.29), respectively (P = 0.64). Of the 17 pts evaluable for response, the best response was stable disease in 9 patients and progressive disease in 8 patients. There were no dose-limiting or unexpected toxicities. Of the 21 patients evaluable for serum PD biomarkers, there were no significant differences between arms A and B in fasting glucose, triglycerides, insulin, C-peptide, IGF-1, IGF-BP1, IGF-BP3, leptin and adiponectin (P > 0.05 for all). Conclusions: The addition of metformin to sirolimus, although well-tolerated, was not associated with significant changes in phospho-p70S6k and other PD biomarkers. Based on the results of the interim analysis, the trial was terminated. Clinical trial information: NCT02145559.

Epacadostat plus pembrolizumab in patients with advanced RCC: Preliminary phase I/II results from ECHO-202/KEYNOTE-037

4515

Background: Epacadostat (E) is a potent oral inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1), a tryptophan-catabolizing enzyme that induces immune tolerance by T-cell suppression. Preclinical and clinical data suggest that epacadostat has antitumor activity when combined with checkpoint inhibitors, including the PD-1 inhibitor pembrolizumab (P). ECHO-202/KEYNOTE-037 is an ongoing open-label, phase 1/2 (P1/2) study evaluating E + P in multiple tumor types. We report preliminary P1/2 efficacy and safety data for the advanced renal cell carcinoma (RCC) cohort as of a 29OCT2016 data cutoff. Methods: Eligible patients (pts) had advanced clear-cell RCC, prior antiangiogenic therapy (tx), and no prior checkpoint inhibitor tx. In P1 dose escalation (3+3+3), pts received E (25, 50, 100, or 300 mg PO BID) + P (2 mg/kg or 200 mg IV Q3W); MTD was not exceeded. E (100 mg BID) + P (200 mg Q3W) dosing was selected for P2 cohort expansion. Response was assessed in RECIST 1.1 evaluable pts. Safety/tolerability was assessed in pts receiving ≥1 E + P dose. Results: 33 pts (P1, n = 11; P2, n = 22) were enrolled (median age, 63 years; 70% men; 97% white; MSKCC criteria of favorable, intermediate, and poor in 6%, 64%, and 12% of pts, respectively). Of 30 efficacy-evaluable pts, 63% (n = 19) had 0–1 prior tx and 37% (n = 11) had ≥2 prior tx for advanced disease. ORR (CR+PR) and DCR (CR+PR+SD) for pts with 0–1 prior tx was 47% (9/19; 1 CR, 8 PR) and 58% (11/19; 1 CR, 8 PR, 2 SD), respectively; for pts with ≥2 prior tx, ORR and DCR were 0% and 36% (4/11; all SD). At data cutoff, 9/9 responses were ongoing (range, 1+ to 372+ days). PFS and biomarker analyses are ongoing. TRAEs occurring in ≥10% of the 33 pts included fatigue and rash (36% each); and arthralgia, diarrhea, pruritus, and pyrexia (12% each). Grade ≥3 TRAEs occurred in 15% of pts (none in > 1 pt). Two pts discontinued due to TRAEs (grade 3 autoimmune hepatitis, n = 1; grade 3 aseptic meningitis/headache/nausea/vomiting/anxiety, n = 1). Conclusions: E + P was generally well tolerated and associated with encouraging response outcomes in advanced RCC pts with 0–1 prior line of tx. E + P represents a novel immunotherapeutic strategy. A phase 3 RCC study is planned. Clinical trial information: NCT02178722.

Identification of T-cell-inflamed gastric adenocarcinoma in The Cancer Genome Atlas (TCGA)

16

Background: Gastroesophageal adenocarcinoma (GEC) is a significant global health problem. KEYNOTE-012 demonstrated a 22% objective response rate in patients with PD-L1 expressing GEC that received pembrolizumab. A subset of patients (pts) tumors express a T cell “inflamed” (TCI) phenotype, which can be measured using an IFN-γ-based immune signature and may prove more predictive of clinical benefit. Using a 160 gene RNA-Seq immune expression profile, we sought to characterize the molecular environments of TCI versus non-TCI GEC patients in The Cancer Genome Atlas (TCGA). Methods: 395 GEC pts with primary tumors in TCGA were clustered into TCI, non-TCI, and intermediate subtypes using both unsupervised hierarchical and K-means clustering (k = 3). Molecular characteristics were categorized using data acquired via CbioPortal and the UCSC Xena repository. Only non-silent somatic mutations and copy number variations (CNVs) reaching GISTIC2 -2 or +2 thresholds were considered. Statistical comparisons were performed using chi-square, ANOVA, and t-test. Results: The TCI subtype contained patients from all TCGA-defined subtypes - EBV-associated (56%), MSI-high (16%), chromosomal unstable (6%), and genomically stable (27%). No significant differences were seen between TCI and non-TCI for tumor site or stage. Mutations in PTEN, PIK3CA, CDH1, and RHOA were more frequent in TCI patients. ERBB2, CCNE1, and KRAS CNVs were infrequent in TCI patients as were PDE4D deletions ( p< 0.05 ). TCI tumors had higher expression of both co-inhibitory (PD-1, PD-L1/L2, CD28/80, BTLA, LAG3) and co-stimulatory (CD137/40/27, OX40, GITR, ICOS) checkpoint molecules ( p< 10-7). Total mutation burden was no different between TCI and non-TCI pts when excluding MSI-high pts nor when assessing MSI-high alone. Conclusions: The IFN immune phenotype encompassed GEC patients from all TCGA subsets. Correlation of clinical outcome with checkpoint blockade is necessary to confirm these molecular associations and the independent predictive utility of this immune-profile stratification.

A phase II study of cediranib, an oral VEGF inhibitor, in previously untreated patients with metastatic or recurrent malignant melanoma

PURPOSE

A two stage multi-institution Phase II study was undertaken by the Princess Margaret Hospital Consortium to evaluate the efficacy and toxicity of oral cediranib, an inhibitor of vascular endothelial growth factor receptors 1 and 2, in patients with previously untreated advanced malignant melanoma.

PATIENTS AND METHODS

Between May 2006 and April 2008, 24 patients (median age 65 years) with advanced malignant melanoma were treated with oral cediranib. Cediranib was given on a continuous, oral once daily schedule of 45 mg, on a 28 day cycle.

RESULTS

Of the 17 patients evaluable for response, there was stable disease in 8 patients, and progressive disease in 9 patients, with no objective responses seen. Only 2 patients had stable disease >/= 6 months, thus the study was terminated at the end of stage 1 accrual. The overall median survival was 9.9 months, and the median time to progression was 3.5 months. The most frequent non-hematologic adverse events were hypertension (78%), fatigue (69%), diarrhea (69%) and anorexia and nausea (each 57%).

CONCLUSIONS

Although 2 patients had stable disease at 6 months, the short median time to progression and lack of any objective responses indicate that single agent cediranib at this dose and schedule is not sufficiently active to warrant study continuation.

Abstract IA09: Molecular mechanisms controlling the T cell-inflamed tumor microenvironment: Implications for therapy

Two major categories of melanoma metastases have been observed based on gene expression profiling and confirmatory technologies. One subgroup of patients has T cell-inflamed phenotype that includes expression of chemokines, T cell markers, and a type I IFN gene signature. In contrast, the other major subset lacks this phenotype and these tumors show a behavior of immune “exclusion”. The optimal immunotherapeutic intervention may be distinct for these two general subsets. The T cell-inflamed tumor microenvironment subset contains the highest expression of negative regulatory factors, including PD-L1, IDO, and FoxP3+ Tregs, and evidence for T cell-intrinsic anergy has also emerged. In addition, the mechanism of induction of these inhibitory mechanisms has been elucidated—PD-L1 and IDO are induced by IFN-γ, and Tregs are largely recruited by chemokines such as CCL22, produced by activated CD8+ effector T cells. Preclinical experiments have confirmed a critical role for all 4 of these mechanisms in limiting anti-tumor T cell efficacy in vivo, giving a mechanism base for translation back into the clinic. These include anti-PD-1/PD-L1 mAbs, IDO inhibitors, and approaches to deplete CD25+ Tregs and/or reverse anergy. The presence of multiple inhibitory mechanisms in the same tumor microenvironment argues that combination therapies may be advantageous to overcome compensatory effects. Preclinical data indicated synergy between anti-CTLA-4 +/- anti-PD-L1 +/- IDO inhibition. The mechanism of synergy is striking, as it correlates with a marked improvement of IL-2 production and proliferation of tumor-infiltrating CD8+ T cells. Clinical translation of these combination immunotherapies is promising and ongoing. In contrast to the T cell-inflamed melanomas, a new paradigm may be needed to promote de novo inflammation in cases of the non-T cell-infiltrated tumor microenvironment. Recent work has indicated that successful innate immune sensing of tumors involves the STING pathway and type I IFN production. Therefore, STING agonists are being developed to promote effective innate immune activation and generation of an adaptive immune response. Molecular mechanisms that explain the presence or absence of a T cell-inflamed tumor microenvironment in patients are being elucidated, which is opening up new concepts for therapies that may overcome immune exclusion and render patients responsive to immunotherapies.

Citation Format: Thomas Gajewski. Molecular mechanisms controlling the T cell-inflamed tumor microenvironment: Implications for therapy. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr IA09.

Inhibition of the STING pathway by the AIM2 inflammasome (INM2P.352)

Tumor-derived DNA triggers the host STING pathway and the subsequent production of IFN-β by antigen-presenting cells, facilitating adaptive immunity against tumors. But cytosolic DNA also activates the AIM2 inflammasome, raising the question of functional impact of this pathway. We found that after DNA stimulation, macrophages or dendritic cells deficient in AIM2, ASC or caspase-1 produce substantially higher IFN-β. This observation suggests possible negative regulation of the STING pathway by the AIM2 inflammasome. We found no evidence for differential delivery of DNA into the cells, increased cell death triggered by activation of the inflammasome, or release of an inhibitory soluble factor. However, biochemical analysis revealed that the AIM2 inflammasome inhibits the early steps of STING pathway activation. Aggregation of STING and phosphorylation of TBK1 and IRF3 were highly enhanced in AIM2 inflammmasome-deficient cells. In addition, pre-treatment with a caspase-1 inhibitor increased the activation of TBK1/IRF3, suggesting that assembly and activation of the inflammasome complex is necessary for the inhibition of the STING pathway. Our data suggest the active AIM2 inflammasome inhibits the STING pathway at or upstream from STING. This crosstalk may have potential consequences for anti-tumor immunity which should be explored in vivo.