Perspectives in melanoma: meeting report from the "Melanoma Bridge" (December 5th-7th, 2019, Naples, Italy)

The melanoma treatment landscape changed in 2011 with the approval of the first anti-cytotoxic T-lymphocyte-associated protein (CTLA)-4 checkpoint inhibitor and of the first BRAF-targeted monoclonal antibody, both of which significantly improved overall survival (OS). Since then, improved understanding of the tumor microenvironment (TME) and tumor immune-evasion mechanisms has resulted in new approaches to targeting and harnessing the host immune response. The approval of new immune and targeted therapies has further improved outcomes for patients with advanced melanoma and other combination modalities are also being explored such as chemotherapy, radiotherapy, electrochemotherapy and surgery. In addition, different strategies of drugs administration including sequential or combination treatment are being tested. Approaches to overcome resistance and to potentiate the immune response are being developed. Increasing evidence emerges that tissue and blood-based biomarkers can predict the response to a therapy. The latest findings in melanoma research, including insights into the tumor microenvironment and new biomarkers, improved understanding of tumor immune response and resistance, novel approaches for combination strategies and the role of neoadjuvant and adjuvant therapy, were the focus of discussions at the Melanoma Bridge meeting (5-7 December, 2019, Naples, Italy), which are summarized in this report.

Dendritic Cells, the T-cell-inflamed Tumor Microenvironment, and Immunotherapy Treatment Response

The development of the most successful cancer immunotherapies in solid tumors, immune-checkpoint blockade, has focused on factors regulating T-cell activation. Until recently, the field has maintained a predominately T-cell centric view of immunotherapy, leaving aside the impact of innate immunity and especially myeloid cells. Dendritic cells (DC) are dominant partners of T cells, necessary for initiation of adaptive immune responses. Emerging evidence supports a broader role for DCs in tumors including the maintenance and support of effector functions during T-cell responses. This relationship is evidenced by the association of activated DCs with immune-checkpoint blockade responses and transcriptional analysis of responding tumors demonstrating the presence of type I IFN transcripts and DC relevant chemokines. T-cell-inflamed tumors preferentially respond to immunotherapies compared with non-T-cell-inflamed tumors and this model suggests a potentially modifiable spectrum of tumor microenvironmental immunity. Although host and commensal factors may limit the T-cell-inflamed phenotype, tumor cell intrinsic factors are gaining prominence as therapeutic targets. For example, tumor WNT/β-catenin signaling inhibits production of chemokine gradients and blocking DC recruitment to tumors. Conversely, mechanisms of innate immune nucleic acid sensing, normally operative during pathogen response, may enhance DC accumulation and make tumors more susceptible to cancer immunotherapy. Elucidating mechanisms whereby DCs infiltrate and become activated within tumors may provide new opportunities for therapeutic intervention. Conceptually, this would facilitate conversion of non-T-cell-inflamed to T-cell-inflamed states or overcome secondary resistance mechanisms in T-cell-inflamed tumors, expanding the proportion of patients who benefit from cancer immunotherapy.

Abstract IA24: Molecular correlates of T cell-inflamed and non-T cell-inflamed tumors

Analysis of the tumor microenvironment from patients with melanoma suggests a paradigm of two broad immunologic phenotypes characterized by the presence or absence of CD8 effector tumor-infiltrating lymphocytes (TIL) and other mediators of an adaptive immune response. Those with activated TIL are sometimes referred T cell-inflamed tumors and appear to be those associated with clinical benefit to cancer immunotherapy. T cell-inflamed tumors demonstrate high levels of gene transcripts associated with type II interferons as well as resistance mechanisms linked to interferon (IFN)-γ. This is in contrast with non-T cell-inflamed tumors, which have low TIL count and inflammatory signature. Further, the transcripts associated with CD8 and IFN-γ are correlated with the presence of type I IFN, suggesting that the major deficit in non-T cell-inflamed tumors may be lack of early signals of initial innate immune. The interaction of tumor and immune system is now considered a hallmark of cancer, given the growing importance of immune-checkpoint blocking immunotherapy. These treatments, mostly related to the programmed-death receptor 1 (PD1), are now standard of care in many tumor types. Multiple biomarkers may predict the activity of checkpoint immunotherapy but a biologic predict to effective cancer immunotherapy is an IFN-γ driven response and thus the T cell-inflamed tumor microenvironment. As such, this phenotype may be considered as an approximate surrogate of clinical benefit to study factors promoting or limiting the immune response against cancer.

One aspect impacting efficacy of cancer immunotherapy may be tumor microenvironment-intrinsic molecular biology. The first oncogene to be linked in tumor-intrinsic fashion to immune exclusion was β-catenin in melanoma. Activation of β-catenin eliminated chemokine gradients that attract dendritic cells, leading to resistance to checkpoint and adoptive cellular immunotherapy. This impact of β-catenin has further been confirmed across multiple tumors. Other molecular changes beyond β-catenin have additionally been identified to mediate immune evasion. For example, PTEN loss, STK11 mutation, or MYC activation appears to have this effect. It is not clear whether the immune suppression associated with these pathways comes from an individual molecular event or whether the phenotype is multifactorial and due to complex interactions via multiple pathways. Recognizing the T cell-inflamed phenotype as an approximation of clinical immunotherapy response, we investigated patterns on the molecular level that associate or are anti-correlated with the presence of this phenotype, assuming that they nominate therapeutic opportunities.

To investigate correlates of the T cell-inflamed or non-T cell-inflamed tumor microenvironments we downloaded gene expression, somatic mutation, and clinical data for 31 solid tumors from The Cancer Genome Atlas. A total of 9,555 tumor samples and 742 normal samples were initially downloaded. After excluding the three tumor types, 9,244 tumors and 683 matched normal were included in the analysis. Using a defined T-cell inflamed gene expression signature consisting of 160 genes (“concordant gene list,” described previously), the tumor samples were categorized into three groups: non-T-cell inflamed, T-cell inflamed, and intermediate following previous protocols. In brief, a quantitative scoring system was developed to categorize tumors into three groups: non-T cell-inflamed, T cell-inflamed, and intermediate, based on the expression profile of the T cell-inflamed gene expression signature. First, gene expression values were converted to a score Si = μi ± βiσi (i = 1,2, … n), where μ and σ represent the mean and standard deviation (sd) of the i th gene’s expression across all samples, respectively. n is the total number of genes. β represents the distance between the i th gene’s expression in a sample and its mean in the unit of sd (equivalent to a z-score). Within each individual cancer, the non-T cell-inflamed group was contrasted against the T cell-inflamed tumor groups and differentially expressed genes (DEGs) were identified by Linear Models for Microarray and RNA-Seq Data (limma) voom algorithm with precision weights (v3.38.3). Pathways significantly altered by the DEGs were detected by IPA® (QIAGEN Inc., Germany) with the curated Ingenuity Knowledge Base (accessed November 2015). Upstream transcriptional regulators and their change of direction were predicted by the cumulative effect of target molecules (encoded by DEGs) up or downregulated under condition implemented in IPA® causal network analysis. Somatic mutations were annotated by Oncotator and Annovar (release date April 16, 2018) and silent mutations were removed. The total tumor mutational burden (TMB) was calculated as the total number of predicted protein-changing mutations (referred to as NSSMs, non-synonymous somatic mutations), including non-synonymous/stoploss/stopgain small nucleotide variants (SNVs), frameshift/non-frameshift small insertions and deletions (indels), and variants that affect the splicing site. The relative enrichment of 64 stroma and immune cell types in tumor microenvironment was estimated by xCell (v1.1.0) from the bulk-tissue RNAseq data. Level 3 Clinical Proteomic Tumor Analysis Consortium (CPTAC) high-throughput mass spec antibody-level protein abundance data (release date January 28, 2016) produced by Georgetown University were downloaded from CPTAC Data Portal (https://cptac-data-portal.georgetown.edu/cptacPublic) (accessed December 08, 2018). Protein level was estimated using median-centered normalized values from the data files with gene annotation.

We observed multiple correlations between somatic mutation profiles and gene expression patterns (manifest via pathway analysis) that associated with either the T cell-inflamed or non-T cell-inflamed tumor types. We note that candidate cancer oncogenes or tumor suppressors are sporadically enriched in select tumor types. Additionally, somatic mutations in oncogenic signaling pathways are enriched in non-T cell-inflamed tumors of individual cancer types. Further, somatic mutations in oncogenic signaling pathways can be shared in non-T cell-inflamed tumors across cancer types. We went on to observe that activation of transcriptional programs correlates with the non-T cell-inflamed tumor microenvironment across cancer types and that integration of somatic mutations and transcriptional programs forms an interweaving network of resistance mechanisms. Finally, using available drug databases we note that gene-drug interaction analysis nominates drugs specific to molecular targets in non-T cell-inflamed and T cell-inflamed tumors.

In summary, we observe that molecular correlates of T cell-inflamed versus non-inflamed tumors can nominate and therapeutic targets of high priority for clinical investigation and next-generation clinical trials across cancer types.

Citation Format: Riyue Bao, Jason J. Luke. Molecular correlates of T cell-inflamed and non-T cell-inflamed tumors [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr IA24.

Abstract B04: Molecular correlates of the non-T cell-inflamed tumor microenvironment in head and neck squamous cell carcinoma

Background: Immunotherapy confers clinical benefit in head and neck squamous cell carcinoma (HNSCC); however, only a fraction of patients respond. The non-T cell-inflamed tumor microenvironment is associated with lack of response, and tumor-intrinsic molecular signaling pathways may be critical drivers of immune exclusion. Therefore, understanding correlations between T-cell inflammation and mutated or activated oncogenic pathways may inform combination immunotherapy approaches.

Methods: RNAseq, somatic mutations, and clinical data were downloaded from The Cancer Genome Atlas (TCGA) database for 484 HNSCC patients (88 HPV-positive, 396 HPV-negative). Gene expression was used to segregate tumors into non-T cell-inflamed, T cell-inflamed, or intermediate groups and genes more frequently mutated in non-T cell-inflamed versus inflamed (or vice versa) were identified. Differentially expressed genes (DEGs) between the two groups were detected by limma voom with precision weights. Pathway activation was identified by Ingenuity Pathway Analysis® (IPA). Association between molecular markers and patients’ overall survival (OS) was tested using Cox proportional-hazards regression models.

Results: 132 (27%) and 183 (38%) tumors were categorized into the non-T cell-inflamed and inflamed group, respectively, with the rest intermediate. Survival analysis revealed that among age, sex, tumor grade, and HPV status, age was the strongest prognostic factor (p=0.003), with older patients showing a decreased 5-year survival. The absence of a T cell-inflamed signature was significantly associated with poorer prognosis within patients ≤65 years of age (p=0.03, HR=1.18) and remained significant after adjusting for covariates such as HPV status. This association was not observed in older patients. Comparison of somatic mutational profiles between the non-T cell-inflamed and inflamed groups identified top mutated genes enriched (TP53, COL11A1, NSD1) and depleted (CASP8) in noninflamed relative to inflamed (FDR-corrected p<0.05). Comparing gene expression profiles of non-T cell-inflamed to inflamed patient groups identified 4092 DEGs (FDR-corrected p<0.05, fold change ≥1.5 or ≤-1.5). Utilizing these DEGs as downstream target molecules in IPA causal network analysis, activation of MYC, SOX2, NFE2L2, and CTNNB1 transcriptional programs correlated with the non-T cell-inflamed tumor microenvironment (z-score ≥2.0, p<0.05). Of note, NFE2L2 (nuclear factor erythroid-2-related factor 2; NRF2) has been described as a context-dependent regulator of innate immune responses and modulator of checkpoint inhibitor response in murine models.

Conclusions: A discrete list of oncogenes, some with known targeted therapies, associates with immune exclusion, suggesting rational immunotherapy combinations to overcome non-T cell-inflamed tumors in HNSCC.

Citation Format: Riyue Bao, Jason J. Luke. Molecular correlates of the non-T cell-inflamed tumor microenvironment in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B04.

PD-1 Blockade in Chinese versus Western Patients with Melanoma

In this trial of programmed cell death-1 (PD-1) blockade with toripalimab in previously treated Chinese patients with melanoma, unique histologic and molecular features may explain why the objective response rate is lower than those defined in Western populations. This work suggests future avenues for investigating mechanisms of melanoma formation and resistance to PD-1 blockade.See related article by Tang et al., p. 4250.

A phase Ia/Ib dose-escalation study of intravenously administered SB 11285 alone and in combination with nivolumab in patients with advanced solid tumors

TPS3162

Background: Activation of the Stimulator of Interferon Genes (STING) pathway in immune cells in the tumor microenvironment (TME) and tumor cells results in the induction of innate and adaptive immunity and subsequent activation of cytotoxic T cells and NK cells for durable anti-tumor responses. SB 11285 is a novel agonist of the STING pathway leading to the activation of tumor-resident APCs and priming of tumor antigen specific CD8+ T cells. In our preclinical studies using multiple tumor-derived cell lines, SB 11285 has been observed to cause the induction of cytokines, such as INF-b, INF- a, TNFa and others consistent with engagement of the STING target, as well as tumor cell death by STING-mediated apoptosis. SB 11285 reduced tumor volumes in multiple rodent tumor models when administered intravenously, intraperitoneally or intratumorally as monotherapy or in combination with checkpoint inhibitors such as anti-CTLA-4 or anti-PD-1 antibody. Systemic administration could additionally facilitate trafficking of newly activated CD8+T cells from periphery into the tumor site. Methods: This open-label, multicenter phase 1a/1b clinical trial (NCT04096638) aims to enroll approximately 110 patients in the dose escalation (Part 1) and expansion cohorts (Part 2). Part 1 of the trial is a dose escalation study with IV SB 11285 monotherapy followed by combination with the checkpoint inhibitor nivolumab. Part 1 Dose Escalation of the study will evaluate ascending doses of intravenously administered SB 11285 with respect to dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), recommended phase 2 dose (RP2D) and the pharmacokinetic (PK)/pharmacodynamic profile as monotherapy and in combination with nivolumab. SB 11285, with a starting dose of 0.3μg/kg, will be administered as monotherapy weekly on Days 1, 8, 15, and 22 of repeated 28-day cycles in escalating doses and in combination with nivolumab administered on Q4W schedule. Part 2 Expansion Cohorts of the study will explore initial signs of efficacy in pre-specified tumor types (such as Melanoma, Head and Neck squamous cell carcinoma) using the recommended phase 2 dose (RP2D) of SB 11285 in combination with nivolumab. In addition, the biological effects of SB 11285 will be evaluated by changes in immune cell types and activation state, serum cytokines, and gene expression patterns indicative of activation of the immune compartment. The trial is being conducted at multiple sites in the U.S . Clinical trial information: NCT04096638 .

A phase I, first-in-human, open-label, dose-escalation study of MGD013, a bispecific DART molecule binding PD-1 and LAG-3, in patients with unresectable or metastatic neoplasms

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Background: MGD013 is an investigational, first-in-class, Fc-bearing bispecific tetravalent DART molecule designed to bind PD-1 and LAG-3 and sustain/restore the function of exhausted T cells. MGD013 demonstrates ligand blocking properties consistent with anti-PD-1 and anti-LAG-3 benchmark molecules, and improves T cell responses beyond that observed with benchmark or component antibodies alone or in combination. Methods: This study characterizes the safety, tolerability, dose-limiting toxicities, maximum tolerated dose (MTD), PK/PD, and antitumor activity of MGD013 in patients (pts) with advanced solid and hematologic malignancies. Sequential single-pt cohorts were treated with escalating flat doses of MGD013 (1-1200 mg IV every 2 weeks), followed by a 3+3 design. Tumor-specific expansion cohorts are being treated at the recommended Phase 2 dose of 600 mg. Results: At data-cutoff, 50 pts (46% checkpoint-experienced) were treated in Dose Escalation, and 157 pts (32% checkpoint-experienced) in Cohort Expansion. No MTD was defined. Treatment-related adverse events (TRAEs) occurred in 146/207 (70.5%) pts, most commonly fatigue (19%) and nausea (11%). The rate of Grade ≥ 3 TRAEs was 23.2%. Immune-related AEs were consistent with events observed with anti-PD-1 antibodies. Mean half-life was 11 days; peripheral blood flow cytometry analyses confirmed full and sustained on-target binding during treatment at doses ≥ 120 mg. Among 41 response-evaluable [RE] dose escalation pts, 3 confirmed partial responses [cPRs] (triple negative breast cancer [TNBC], mesothelioma, gastric cancer) per RECIST 1.1 were observed, while 21 pts had stable disease [SD]. Among select expansion cohorts, PRs have been observed in epithelial ovarian cancer (n=2; both cPRs, and 7 with SD among 15 RE pts) and TNBC (n=2; 1 cPR, 1 unconfirmed PR [uPR], and 5 with SD among 14 RE pts). In a cohort of pts with HER2+ tumors treated with MGD013 in combination with margetuximab (investigational anti-HER-2 antibody), 3 PRs have been observed (breast [n=2], colorectal [n=1]; 1 cPR, 2 uPRs) and 2 pts with SD among 6 RE pts. Objective responses have been observed in several pts after prior anti-PD-1 therapy. Investigations into potential correlative biomarkers including LAG-3 and PD-1 are ongoing. Conclusions: MGD013, a novel molecule designed to coordinately block PD-1 and LAG-3, has demonstrated an acceptable safety profile and encouraging early evidence of anti-tumor activity. Clinical trial information: NCT03219268 .

Response criteria for intratumoral immunotherapy in solid tumors: ItRECIST

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Background: The approval of intratumoral (IT) immunotherapy for metastatic melanoma and the active development of numerous novel IT drugs have created a need for standardized evaluation of response to this unique treatment strategy. The Response Evaluation Criteria in Solid Tumors (RECIST) is not suitable for assessing responses separately for injected and noninjected tumors. Building on RECIST concepts, we propose an IT immunotherapy RECIST (itRECIST) to capture data and assess local and systemic responses in a standardized fashion for clinical trials involving IT immunotherapies. Methods: itRECIST will address the unique needs of IT immunotherapy trials but, where possible, aligns with RECIST 1.1 and iRECIST. It does not dictate which lesions to inject but provides guidelines for collecting data and assessing response as treatment evolves. Results: itRECIST enables overall response assessment, separate response assessments in injected and noninjected lesions, and continued assessment following modifications of therapy at initial progression. At baseline, lesions are classified into 4 categories: target injected, target noninjected, nontarget injected, and nontarget noninjected. After baseline, lesions can be reclassified from noninjected to injected if the investigator decides to change the lesions to inject, but target and nontarget designations never change. Overall response at each assessment is based on target lesion response (injected and noninjected), nontarget lesion response, and absence/appearance of new lesions. Noninjected lesion response is determined by comparing tumor burden with baseline and nadir values. Injected lesion assessment is based on visit-to-visit changes in the lesions injected during treatment and on a combined assessment once the patient is off treatment. A new response category is defined to capture progression that would be “confirmed” per iRECIST even though injected lesions are responding and therapy continues. Multiple examples have been created to aid in training and adoption. Conclusions: itRECIST is an important step toward a standardized method of response assessment for this promising and evolving therapeutic modality. The proposed guidelines can be adopted into trial protocols and routine clinical practice without the need for complex additional assessments by treating physicians. Until there is evidence to support wider use, itRECIST is intended only to support standardized collection of data and to facilitate exploratory analysis. Authors G.V.G. and A.D.K. contributed equally to this work.

Initial report of treatment of uveal melanoma with hepatic metastases with yttrium90 internal radiation followed by ipilimumab and nivolumab

10025

Background: Hepatic metastases from uveal melanoma have no established therapy, with a median survival of only 6-12 months. To date therapy with checkpoint inhibitors has yielded minimal results. To take advantage of possible synergy between radiation and immunotherapy we treated patients with yttrium90 internal radiation followed by immunotherapy. Methods: Patients received yttrium90 (Sir-Spheres) via hepatic artery infusion in two treatments, one to each lobe 3-4 weeks apart, followed in 3-6 weeks by ipilimumab and nivolumab for 4 doses, then nivolumab maintenance. Results: We are presenting interim results because of the excessive toxicity seen when these FDA-approved modalities were used in sequence with the FDA-approved dosages. Initially dosing of yttrium90 (Y90) followed the package insert “BSA method” but after 8 patients we had 5 cases of grade 3-4 hepatic toxicity; in 4 cases the toxicity was observed after just the Y90. One case of cirrhosis occurred in a patient whose liver received 40-45Gy; her cirrhosis was felt most likely due to the Y90. Y90 dosing was then reduced to limit dosage to normal liver to 35Gy, and none of the next 5 patients have had more than grade 2 hepatic toxicity. Dosage to the normal liver is approximated by the MIRD formula: Actual delivered liver dose [Gy] = 50 * Administered activity [GBq] * (1 – Lung shunt fraction) / kg of treated liver. If calculated dose was > 35GY, dosage in GBq is reduced proportionally. Toxicity in the first 5 patients to receive immunotherapy included one grade 4, two grade 3 and two grade 2 hepatic toxicities, and only 3 of the 5 patients received more than one dose of ipilimumab. We then reduced dosing of ipilimumab from 3mg/kg x 4 to 1mg/kg x 4 because of this excessive autoimmune toxicity. Of 13 patients, 10 received both Y90 and immunotherapy, and 3 had responses (1 CR, 2 PR) with 3 patients stable > 5months. Median progression-free survival for all patients is 27 weeks and median overall survival is greater than 48 weeks. Treatment with Y90 produced an over 50% fall in peripheral blood lymphocytes which was reversed in most patients by the immunotherapy. Conclusions: With dose modifications this therapy appears feasible and objective tumor responses were seen. Sequential therapy with Y90 and immunotherapy appears tolerable if radiation to normal liver is limited to 35Gy and ipilimumab dose is 1mg/kg. Clinical trial information: NCT02913417.

Significant antitumor activity for low-dose ipilimumab (IPI) with pembrolizumab (PEMBRO) immediately following progression on PD1 Ab in melanoma (MEL) in a phase II trial

10004

Background: Combination PD1 + CTLA4 antibodies (Abs) shows greater response rate (RR) versus PD1 Ab alone in MEL, but RR after initial PD1 Ab progression awaits robust investigation. CTLA4 Ab alone after PD1 Ab progression has a historical RR of 13%. We report final results of the first prospective clinical trial evaluating IPI 1mg/kg + PEMBRO immediately following progression on PD1 Ab (NCT02743819). Methods: Patients (pts) with advanced MEL, no prior CTLA4 Ab for metastatic disease, and who had progressed on PD1 Ab as immediately prior therapy (or non-CTLA4 Ab combination) were eligible. Pts received PEMBRO 200 mg + IPI 1 mg/kg Q3W for 4 doses, then PEMBRO alone for up to two years. The primary endpoint was RR by irRECIST. After 35 pts, the study met its primary endpoint with 10/22 evaluable pts achieving a response. The trial was expanded to enroll a total of 70 pts in open-label accrual to further describe the RR for this regimen in an exploratory fashion. The data analysis cutoff was January 30, 2020. Results: 67/70 accrued patients were evaluable for treatment response. Prior treatments included 60 on PD1 Ab alone and 10 on PD1 Ab-based combinations. Of these, 10 pts had progressed in the adjuvant setting. Median length of treatment on prior PD1 Ab was 4.8 months. Response assessments included 4 CR, 17 PR and 16 SD for a RR of 31% (21/67) in evaluable pts, and 30% (21/70) in all enrolled pts. 4 pts with a PR and 6 with SD had unconfirmed responses making the irRECIST response rate 25% (17/67) and 24% (17/70) among evaluable and enrolled pts, respectively. Median progression free survival (PFS) was 4.7 mo (95% CI: 2.8-8.3) and PFS at six months was 45% (95% CI: 33%-57%). 15/70 (21%) pts experienced ≥ grade 3-4 drug-related AEs, the most common being diarrhea, rash and transaminase elevation. PD-L1 positive vs negative status from historical tumor specimens did not associate with RR. Conclusions: This is the largest prospective study of IPI 1mg/kg + PEMBRO, demonstrating significant antitumor activity and tolerability in MEL post-PD1 Ab. Clinical trial information: NCT02743819.

Inhibition of the Wnt/β-catenin pathway enhances antitumor immunity in ovarian cancer

Background:

The Wnt/β-catenin pathway is linked to tumorigenesis in a variety of tumors and promotes T cell exclusion and resistance to checkpoint inhibitors. We sought to determine whether a small molecule inhibitor of this pathway, WNT974, would impair tumor growth, affect gene expression patterns, and improve the immune response in human and murine ovarian cancer models.

Methods:

Human ovarian cancer cells were treated with WNT974 in vitro. RNAseq libraries were constructed and differences in gene expression patterns between responders and nonresponders were compared to The Cancer Genome Atlas (TCGA). Mice with subcutaneous or intraperitoneal ID8 ovarian cancer tumors were treated with WNT974, paclitaxel, combination, or control. Tumor growth and survival were measured. Flow cytometry and β-TCR repertoire analysis were used to determine the immune response.

Results:

Gene expression profiling revealed distinct signatures in responders and nonresponders, which strongly correlated with T cell infiltration patterns in the TCGA analysis of ovarian cancer. WNT974 inhibited tumor growth, prevented ascites formation, and prolonged survival in mouse models. WNT974 increased the ratio of CD8⁺ T cells to T regulatory cells (Tregs) in tumors and enhanced the effector functions of infiltrating CD4⁺ and CD8⁺ T cells. Treatment also decreased the expression of inhibitory receptors on CD8⁺ T cells. Combining WNT974 with paclitaxel further reduced tumor growth, prolonged survival, and expanded the T cell repertoire.

Conclusions:

These findings suggest that inhibiting the Wnt/β-catenin pathway may have a potent immunomodulatory effect in the treatment of ovarian cancer, particularly when combined with paclitaxel.

Tumor neoantigenicity assessment with CSiN score incorporates clonality and immunogenicity to predict immunotherapy outcomes

Lack of responsiveness to checkpoint inhibitors is a central problem in the modern era of cancer immunotherapy. Tumor neoantigens are critical targets of the host antitumor immune response, and their presence correlates with the efficacy of immunotherapy treatment. Many studies involving assessment of tumor neoantigens principally focus on total neoantigen load, which simplistically treats all neoantigens equally. Neoantigen load has been linked with treatment response and prognosis in some studies but not others. We developed a Cauchy-Schwarz index of Neoantigens (CSiN) score to better account for the degree of concentration of immunogenic neoantigens in truncal mutations. Unlike total neoantigen load determinations, CSiN incorporates the effect of both clonality and MHC binding affinity of neoantigens when characterizing tumor neoantigen profiles. By analyzing the clinical responses in 501 treated patients with cancer (with most receiving checkpoint inhibitors) and the overall survival of 1978 patients with cancer at baseline, we showed that CSiN scores predict treatment response to checkpoint inhibitors and prognosis in patients with melanoma, lung cancer, and kidney cancer. CSiN score substantially outperformed prior genetics-based prediction methods of responsiveness and fills an important gap in research involving assessment of tumor neoantigen burden.

Genomic Profiling of Metastatic Uveal Melanoma and Clinical Results of a Phase I Study of the Protein Kinase C Inhibitor AEB071

Up to 50% of patients with uveal melanoma (UM) develop metastatic disease, for which there is no effective systemic treatment. This study aimed to evaluate the safety and efficacy of the orally available protein kinase C inhibitor, AEB071, in patients with metastatic UM, and to perform genomic profiling of metastatic tumor samples, with the aim to propose combination therapies. Patients with metastatic UM (n = 153) were treated with AEB071 in a phase I, single-arm study. Patients received total daily doses of AEB071 ranging from 450 to 1,400 mg. First-cycle dose-limiting toxicities were observed in 13 patients (13%). These were most commonly gastrointestinal system toxicities and were dose related, occurring at doses ≥700 mg/day. Preliminary clinical activity was observed, with 3% of patients achieving a partial response and 50% with stable disease (median duration 15 weeks). High-depth, targeted next-generation DNA sequencing was performed on 89 metastatic tumor biopsy samples. Mutations previously identified in UM were observed, including mutations in GNAQ, GNA11, BAP1, SF3B1, PLCB4, and amplification of chromosome arm 8q. GNAQ/GNA11 mutations were observed at a similar frequency (93%) as previously reported, confirming a therapeutic window for inhibition of the downstream effector PKC in metastatic UM.In conclusion, the protein kinase C inhibitor AEB071 was well tolerated, and modest clinical activity was observed in metastatic UM. The genomic findings were consistent with previous reports in primary UM. Together, our data allow envisaging combination therapies of protein kinase C inhibitors with other compounds in metastatic UM.

STING pathway agonism as a cancer therapeutic

The fact that a subset of human cancers showed evidence for a spontaneous adaptive immune response as reflected by the T cell-inflamed tumor microenvironment phenotype led to the search for candidate innate immune pathways that might be driving such endogenous responses. Preclinical studies indicated a major role for the host STING pathway, a cytosolic DNA sensing pathway, as a proximal event required for optimal type I interferon production, dendritic cell activation, and priming of CD8⁺ T cells against tumor-associated antigens. STING agonists are therefore being developed as a novel cancer therapeutic, and a greater understanding of STING pathway regulation is leading to a broadened list of candidate immune regulatory targets. Early phase clinical trials of intratumoral STING agonists are already showing promise, alone and in combination with checkpoint blockade. Further advancement will derive from a deeper understanding of STING pathway biology as well as mechanisms of response vs resistance in individual cancer patients.

KEYNOTE-716: Phase III study of adjuvant pembrolizumab versus placebo in resected high-risk stage II melanoma

Patients with high-risk stage II melanoma are at significant risk for recurrence after surgical resection. Adjuvant treatment options to lower the risk for distant metastases are limited. Although adjuvant IFN-α2b is associated with improved relapse-free survival in patients with high-risk melanoma, toxicity and limited overall survival benefits limit its use. Adjuvant treatment with the PD-1 inhibitor pembrolizumab significantly improved recurrence-free survival, compared with placebo, in patients with resected stage III melanoma in the Phase III KEYNOTE-054 trial; efficacy in patients with stage II disease has not been established. This article describes the design and rationale of KEYNOTE-716 (NCT03553836), a two-part, randomized, placebo-controlled, multicenter Phase III study of adjuvant pembrolizumab in patients with surgically resected high-risk stage II melanoma. Clinical trial registry & ID: ClinicalTrials.gov, NCT03553836.

Considering adjuvant therapy for stage II melanoma

Melanoma is among the few cancers that demonstrate an increasing incidence over time. Simultaneously, this trend has been marked by an epidemiologic shift to earlier stage at diagnosis. Before 2011, treatment options were limited for patients with metastatic disease, and the median overall survival was less than 1 year. Since then, the field of melanoma therapeutics has undergone major changes. The use of anti–CTLA‐4 and anti‐PD1 immune checkpoint inhibitors and combination BRAF/MEK inhibitors for patients with BRAF V600 mutations has significantly extended survival and allowed some patients to remain in durable disease remission off therapy. It has now been confirmed that these classes of agents have a benefit for patients with stage III melanoma after surgical resection, and anti‐PD1 and BRAF/MEK inhibitors are standards of care in this setting. Some patients with stage II disease (lymph node‐negative; American Joint Committee on Cancer stage IIB and IIC) have worse melanoma‐specific survival relative to some patients with stage III disease. Given these results, expanding the population of patients who are considered for adjuvant therapy to include those with stage II melanoma has become a priority, and randomized phase 3 clinical trials are underway. Moving into the future, the validation of patient risk‐stratification and treatment‐benefit prediction models will be important to improve the number needed to treat and limit exposure to toxicity in the large population of patients with early stage melanoma.

Adjuvant therapy has improved outcomes in patients with stage III melanoma and is being explored in those with stage II melanoma. Stage III data as well as risk‐stratification tools and clinical considerations for the lymph node‐negative population are reviewed.

BMI, irAE, and gene expression signatures associate with resistance to immune-checkpoint inhibition and outcomes in renal cell carcinoma

BACKGROUND

Clinical variables may correlate with lack of response to treatment (primary resistance) or clinical benefit in patients with clear cell renal cell carcinoma (ccRCC) treated with anti-programmed death 1/ligand one antibodies.

METHODS

In this multi-institutional collaboration, clinical characteristics of patients with primary resistance (defined as progression on initial computed tomography scan) were compared to patients with clinical benefit using Two sample t-test and Chi-square test (or Fisher's Exact test). The Kaplan-Meier method was used to estimate the distribution of progression-free survival (PFS) and overall survival (OS) in all patients and the subsets of patients with clinical benefit or primary resistance. Cox's regression model was used to evaluate the correlation between survival endpoints and variables of interest. To explore clinical factors in a larger, independent patient sample, The Cancer Genome Atlas (TCGA) was analyzed. RNAseq gene expression data as well as demographic and clinical information were downloaded for primary tumors of 517 patients included within TCGA-ccRCC.

RESULTS

Of 90 patients, 38 (42.2%) had primary resistance and 52 (57.8%) had clinical benefit. Compared with the cohort of patients with initial benefit, primary resistance was more likely to occur in patients with worse ECOG performance status (p = 0.03), earlier stage at diagnosis (p = 0.04), had no prior nephrectomy (p = 0.04) and no immune-related adverse events (irAE) (p = 0.02). In patients with primary resistance, improved OS was significantly correlated with lower International Metastatic RCC Database Consortium risk score (p = 0.02) and lower neutrophil:lymphocyte ratio (p = 0.04). In patients with clinical benefit, improved PFS was significantly associated with increased BMI (p = 0.007) and irAE occurrence (p = 0.02) while improved OS was significantly correlated with overweight BMI (BMI 25-30; p = 0.03) and no brain metastasis (p = 0.005). The cohort TCGA-ccRCC was examined for the correlations between gene expression patterns, clinical factors, and survival outcomes observing associations of T-cell inflammation and angiogenesis signatures with histologic grade, pathologic stage and OS.

CONCLUSIONS

Clinical characteristics including performance status, BMI and occurrence of an irAE associate with outcomes in patients with ccRCC treated with immunotherapy. The inverse association of angiogenesis gene signature with ccRCC histologic grade highlight opportunities for adjuvant combination VEGFR2 tyrosine kinase inhibitor and immune-checkpoint inhibition.

Adenosine 2A Receptor Blockade as an Immunotherapy for Treatment-Refractory Renal Cell Cancer

Adenosine mediates immunosuppression within the tumor microenvironment through triggering adenosine 2A receptors (A2AR) on immune cells. To determine whether this pathway could be targeted as an immunotherapy, we performed a phase I clinical trial with a small-molecule A2AR antagonist. We find that this molecule can safely block adenosine signaling in vivo. In a cohort of 68 patients with renal cell cancer (RCC), we also observe clinical responses alone and in combination with an anti-PD-L1 antibody, including subjects who had progressed on PD-1/PD-L1 inhibitors. Durable clinical benefit is associated with increased recruitment of CD8⁺ T cells into the tumor. Treatment can also broaden the circulating T-cell repertoire. Clinical responses are associated with an adenosine-regulated gene-expression signature in pretreatment tumor biopsies. A2AR signaling, therefore, represents a targetable immune checkpoint distinct from PD-1/PD-L1 that restricts antitumor immunity. SIGNIFICANCE: This first-in-human study of an A2AR antagonist for cancer treatment establishes the safety and feasibility of targeting this pathway by demonstrating antitumor activity with single-agent and anti-PD-L1 combination therapy in patients with refractory RCC. Responding patients possess an adenosine-regulated gene-expression signature in pretreatment tumor biopsies.See related commentary by Sitkovsky, p. 16.This article is highlighted in the In This Issue feature, p. 1.

Secondary resistance to immunotherapy associated with β-catenin pathway activation or PTEN loss in metastatic melanoma

Background

While cancer immunotherapies including checkpoint blockade antibodies, adoptive T cell therapy, and even some vaccines have given rise to major clinical responses with durability in many cases, a subset of patients who initially respond subsequently develop secondary resistance to therapy. Tumor-intrinsic mechanisms of acquired immunotherapy resistance are incompletely understood.

Methods

Baseline and treatment-resistant tumors underwent molecular analysis via transcriptional profiling or genomic sequencing for oncogenic alterations and histologic analysis for T cell infiltration to investigate mechanisms contributing to T cell exclusion and acquired resistance to immunotherapy.

Results

We describe two patients with metastatic melanoma who initially showed a durable partial response to either a melanoma-peptide/interleukin-12 vaccine or combined anti-CTLA-4 + anti-PD-1 therapy, but subsequently developed new treatment-resistant metastases. In the first case, the recurrent tumor showed new robust tumor expression of β-catenin, whereas in the second case genomic sequencing revealed acquired PTEN loss. Both cases were associated with loss of T cell infiltration, and both pathways have been mechanistically linked to immune resistance preclinically.

Conclusion

Our results suggest that secondary resistance to immunotherapies can arise upon selection for new oncogenic variants that mediate T cell exclusion. To identify the spectrum of underlying mechanisms of therapeutic resistance, similar evaluation for the emergence of tumor-intrinsic alterations in resistant lesions should be done prospectively at the time of relapse in a range of additional patients developing secondary resistance.

Randomized Phase II Trial and Tumor Mutational Spectrum Analysis from Cabozantinib versus Chemotherapy in Metastatic Uveal Melanoma (Alliance A091201)

PURPOSE

The surface receptor MET is highly expressed on primary uveal melanoma; MET inhibitors demonstrated early clinical signals of efficacy in slowing uveal melanoma growth. The primary objective of our study was to compare the progression-free survival rate at 4 months (PFS4) of patients with uveal melanoma treated with cabozantinib or chemotherapy.

PATIENTS AND METHODS

Patients with metastatic uveal melanoma and RECIST measurable disease were randomized 2:1 to receive either cabozantinib (arm 1) versus temozolomide or dacarbazine (arm 2) with restaging imaging every two cycles. Cross-over from arm 2 to cabozantinib after progression was allowed (arm 2X). Available tumor specimens were analyzed by whole-exome sequencing (WES) and results were correlated with outcome.

RESULTS

Forty-six eligible patients were accrued with 31, 15, and 9 in arms 1, 2, and 2X, respectively. Median lines of prior therapy, including hepatic embolization, were two. Rates of PFS4 in arm 1 and arm 2 were 32.3% and 26.7% (P = 0.35), respectively, with median PFS time of 60 and 59 days (P = 0.964; HR = 0.99). Median overall survival (OS) was 6.4 months and 7.3 months (P = 0.580; HR = 1.21), respectively. Grade 3-4 Common Terminology Criteria for Adverse Events were present in 61.3%, 46.7%, and 37.5% in arms 1, 2, and 2X, respectively. WES demonstrated a mean tumor mutational burden of 1.53 mutations/Mb and did not separate OS ≤ or >1 year (P = 0.14). Known mutations were identified by WES and novel mutations were nominated.

CONCLUSIONS

MET/VEGFR blockade with cabozantinib demonstrated no improvement in PFS but an increase in toxicity relative to temozolomide/dacarbazine in metastatic uveal melanoma.

Tumor-reprogrammed resident T cells resist radiation to control tumors

Successful combinations of radiotherapy and immunotherapy depend on the presence of live T cells within the tumor; however, radiotherapy is believed to damage T cells. Here, based on longitudinal in vivo imaging and functional analysis, we report that a large proportion of T cells survive clinically relevant doses of radiation and show increased motility, and higher production of interferon gamma, compared with T cells from unirradiated tumors. Irradiated intratumoral T cells can mediate tumor control without newly-infiltrating T cells. Transcriptomic analysis suggests T cell reprogramming in the tumor microenvironment and similarities with tissue-resident memory T cells, which are more radio-resistant than circulating/lymphoid tissue T cells. TGFβ is a key upstream regulator of T cell reprogramming and contributes to intratumoral Tcell radio-resistance. These findings have implications for the design of radio-immunotherapy trials in that local irradiation is not inherently immunosuppressive, and irradiation of multiple tumors might optimize systemic effects of radiotherapy.