1757O Early reduction in ctDNA, regardless of best RECIST response, is associated with overall survival (OS) on tebentafusp in previously treated metastatic uveal melanoma (mUM) patients

Liquid Biopsy Response Evaluation Criteria in Solid Tumors (LB-RECIST)

Current evaluation of treatment response in solid tumors depends on dynamic changes in tumor diameters as measured by imaging. However, these changes can only be detected when there are enough macroscopic changes in tumor volume, which limits the usability of radiological response criteria in evaluating earlier stages of disease response and necessitates much time to lapse for gross changes to be notable. One promising approach is to incorporate dynamic changes in circulating tumor DNA (ctDNA), which occur early in the course of therapy and can predict tumor responses weeks before gross size changes manifest. However, several issues need to be addressed before recommending the implementation of ctDNA response criteria in daily clinical practice such as clinical, biological, and regulatory challenges and, most importantly, the need to standardize/harmonize detection methods and ways to define ctDNA response and/or progression for precision oncology. Herein, we review the use of liquid biopsy (LB) to evaluate response in solid tumors and propose a plan toward standardization of LB-RECIST.

PRAME Expression: A Target for Cancer Immunotherapy and a Prognostic Factor in Uveal Melanoma

Purpose

Uveal melanoma (UM) is a rare disease with a high mortality, and new therapeutic options are being investigated. Preferentially Expressed Antigen in Melanoma (PRAME) is a cancer testis antigen, expressed in the testis, but also in cancers, including uveal melanoma. PRAME is considered a target for immune therapy in several cancers, and PRAME-specific T cell clones have been shown to kill UM cells.

Methods

We studied the literature on PRAME expression in hematological and solid malignancies, including UM, and its role as a target for immunotherapy. The distribution of tumor features was compared between PRAME-high and PRAME-low UM in a 64-patient cohort from the Leiden University Medical Center (LUMC) and in the Cancer Genome Atlas (TCGA) cohort of 80 cases and differential gene expression analysis was performed in the LUMC cohort.

Results

PRAME is expressed in many malignancies, it is frequently associated with a negative prognosis, and can be the target of T cell receptor (TCR)-transduced T cells, a promising treatment option with high avidity and safety. In UM, PRAME is expressed in 26% to 45% of cases and is correlated with a worse prognosis. In the LUMC and the TCGA cohorts, high PRAME expression was associated with larger diameter, higher Tumor-Node-Metastasis (TNM) stage, more frequent gain of chromosome 8q, and an inflammatory phenotype.

Conclusions

We confirm that PRAME is associated with poor prognosis in UM and has a strong connection with extra copies of 8q. We show that PRAME-specific immunotherapy in an adjuvant setting is promising in treatment of malignancies, including UM.

Detection of metastases using circulating tumour DNA in uveal melanoma

BACKGROUND

Approximately 50% of uveal melanoma (UM) patients will develop metastatic disease depending on the genetic features of the primary tumour. Patients need 3-12 monthly scans, depending on their prognosis, which is costly and often non-specific. Circulating tumour DNA (ctDNA) quantification could serve as a test to detect and monitor patients for early signs of metastasis and therapeutic response.

METHODS

We assessed ctDNA as a biomarker in three distinct UM cohorts using droplet-digital PCR: (A) a retrospective analysis of primary UM patients to predict metastases; (B) a prospective analysis of UM patients after resolution of their primary tumour for early detection of metastases; and (C) monitoring treatment response in metastatic UM patients.

RESULTS

Cohort A: ctDNA levels were not associated with the development of metastases. Cohort B: ctDNA was detected in 17/25 (68%) with radiological diagnosis of metastases. ctDNA was the strongest predictor of overall survival in a multivariate analysis (HR = 15.8, 95% CI 1.7-151.2, p = 0.017). Cohort C: ctDNA monitoring of patients undergoing immunotherapy revealed a reduction in the levels of ctDNA in patients with combination immunotherapy.

CONCLUSIONS

Our proof-of-concept study shows the biomarker feasibility potential of ctDNA monitoring in for the clinical management of uveal melanoma patients.

Circulating Tumor DNA as a Prognostic Factor in Patients With Resectable Hepatic Metastases of Uveal Melanoma

OBJECTIVE

We report here the results of a prospective study of circulating tumor DNA (ctDNA) detection in patients undergoing uveal melanoma (UM) liver metastases resection (NCT02849145).

BACKGROUND

In UM patients, the liver is the most common and often only site of metastases. Local treatments of liver metastases, such as surgical resection, have a likely benefit in selected patients.

METHODS

Upon enrollment, metastatic UM patients eligible for curative liver surgery had plasma samples collected before and after surgery. GNAQ / GNA11 mutations were identified in archived tumor tissue and used to quantify ctDNA by droplet digital polymerase chain reaction which was then associated with the patient's surgical outcomes.

RESULTS

Forty-seven patients were included. Liver surgery was associated with a major increase of cell-free circulating DNA levels, with a peak 2 days after surgery (∼20-fold). Among 40 evaluable patients, 14 (35%) had detectable ctDNA before surgery, with a median allelic frequency of 1.1%. These patients experienced statistically shorter relapse-free survival (RFS) versus patients with no detectable ctDNA before surgery (median RFS: 5.5 vs 12.2 months; hazard ratio=2.23, 95% CI: 1.06-4.69, P =0.04), and had a numerically shorter overall survival (OS) (median OS: 27.0 vs 42.3 months). ctDNA positivity at postsurgery time points was also associated with RFS and OS.

CONCLUSIONS

This study is the first to report ctDNA detection rate and prognostic impact in UM patients eligible for surgical resection of their liver metastases. If confirmed by further studies in this setting, this noninvasive biomarker could inform treatment decisions in UM patients with liver metastases.

Tebentafusp: a first-in-class treatment for metastatic uveal melanoma

Tebentafusp is a first-in-class immunotherapy agent that comprises an engineered T-cell receptor targeting a gp100 epitope presented by human leukocyte antigen-A*02:01 cells, fused to an anti-CD3 single-chain variable fragment. Tebentafusp is both the first bispecific T-cell engager to show efficacy in the treatment of advanced solid cancer and the first anti-cancer treatment to demonstrate an overall survival benefit in patients with uveal melanoma (UM). This review article will focus on the clinical development of tebentafusp, the mechanism of action and resultant evolution of the management of advanced UM.

Changes in circulating tumor DNA and outcomes in solid tumors treated with immune checkpoint inhibitors: a systematic review

BACKGROUND

Quantification of circulating tumor DNA (ctDNA) levels is a reliable prognostic tool in several malignancies. Dynamic changes in ctDNA levels in response to treatment may also provide prognostic information. Here, we explore the value of changes in ctDNA levels in response to immune checkpoint inhibitors (ICIs).

METHODS

We searched MEDLINE (host: PubMed) for trials of ICIs in advanced solid tumors in which outcomes were reported based on change in ctDNA levels. ctDNA reduction was defined as reported in individual trials. Typically, this was either >50% reduction or a reduction to undetectable levels. We extracted HRs and related 95% CIs and/or p values comparing ctDNA reduction versus no reduction for progression-free survival (PFS) and/or overall survival (OS). Data were then pooled in a meta-analysis. Variation in effect size was examined using subgroup analyses.

RESULTS

Eighteen trials were included in the meta-analysis. ctDNA levels were detectable in all participants in all studies prior to initiation of ICIs. A reduction in ctDNA measured 6-16 weeks after starting treatment was associated with significantly better PFS (HR 0.20; 95% CI, 0.14 to 0.28; p<0.001). Similarly, OS was superior in patients with reduced ctDNA levels (HR 0.18; 95% CI, 0.12 to 0.26; p<0.001). The results were consistent across all disease sites, lines of treatment, magnitude of change (to undetectable vs >50% reduction) and whether treatment exposure comprised single or combination ICIs.

CONCLUSIONS

In advanced solid tumors, a reduction in ctDNA levels in response to ICIs is associated with substantial improvements in outcome. ctDNA change is an early response biomarker which may allow for de-escalation of cross-sectional imaging in patients receiving ICIs or support treatment de-escalation strategies.

Tebentafusp in the Treatment of Metastatic Uveal Melanoma: Patient Selection and Special Considerations

Uveal melanoma (UM) is a rare type of melanoma with distinct features from cutaneous melanoma, low response rates to immune checkpoint inhibition, and poor survival rates. Tebentafusp, a bispecific antibody engaging T cells with gp 100 on HLA-A*02:01, was recently approved by the FDA as the first drug of its class and the first treatment approved by the FDA to treat UM. In this review, we summarize the preclinical and clinical data on tebentafusp for UM. We additionally discuss patient selection and the relevant challenges. For the literature search, PubMed search and relevant articles presented at international conferences were used.

Review of bi-specific therapies in uveal melanoma

Uveal melanoma is a rare subtype of melanoma that once metastatic portends a poor prognosis. Likely due to the distinct differences in biology, metastatic potential, and immunologic profile as compared to cutaneous melanoma, uveal melanoma's response to immune checkpoint inhibition has been disappointing. Bi-specific fusion protein therapies (T cell engagers) are a novel strategy to forcibly bridge the immune system with a target on a cancer cell. This approach has been explored in a number of cancer types and has recently demonstrated success in uveal melanoma. Tebentafusp, a first in class ImmTAC (Immune-mobilizing monoclonal TCRs against cancer), has now shown an overall survival benefit when compared to investigator's choice. This review aims to summarize the experience with this first in class bi-specific T cell engager as well as highlight bi-specifics as a novel treatment strategy in uveal melanoma.

New targeted and epigenetic therapeutic strategies for the treatment of uveal melanoma

Uveal melanoma (UM) is a rare, genetically bland ocular malignancy with excellent local treatment options, but no disease-specific therapies are approved for use in the metastatic setting by the Food and Drug Administration. Metastatic UM (mUM) confers a prognosis of ~15 months. Unlike cutaneous melanoma, UM is poorly responsive to checkpoint inhibitors and cytotoxic chemotherapy highlighting the importance of clarifying vulnerable disease-specific mechanisms, such as cell cycle or metabolic pathways necessary for tumor growth and survival. The elucidation of signaling pathways downstream of the frequently mutated GNA GTPase such as PKC/MAPK/ERK/MEK, PI3K/AKT, and YAP-Hippo have offered potential targets. Potentially druggable epigenetic targets due to BAP1-mutated UM have also been identified, including proteins involved with histone deacetylation and DNA splicing. This review describes the preclinical rationale for the development of targeted therapies and current strategies currently being studied in clinical trials or will be in the near future.

Tebentafusp for the treatment of HLA-A*02:01-positive adult patients with unresectable or metastatic uveal melanoma

INTRODUCTION

: Metastatic uveal melanoma is associated with poor prognosis and few treatment options. Tebentafusp recently became the first FDA-approved agent for metastatic uveal melanoma.

AREAS COVERED

In this review, we describe the mechanism of action of tebentafusp as well as preclinical data showing high tumor specificity of the drug. We also review promising early phase trials in which tebentafusp demonstrated activity in metastatic uveal melanoma patients with an acceptable toxicity profile that included cytokine-mediated, dermatologic-related, and liver-related adverse events. Finally, we summarize findings from a pivotal phase III randomized trial in which tebentafusp demonstrated significant improvement in overall survival in comparison with investigator choice therapy.

EXPERT OPINION

Tebentafusp has transformed the treatment paradigm for metastatic uveal melanoma and should be the preferred frontline agent for most HLA-A*0201 positive patients. However, patients with rapidly progressing disease or high tumor benefit may not derive the same benefit. Areas of future study should focus on its role in the adjuvant setting as well as strategies to improve efficacy of tebentafusp in the metastatic setting.

Circulating tumor DNA: Opportunities and challenges for pharmacometric approaches

To support further development of model-informed drug development approaches leveraging circulating tumor DNA (ctDNA), we performed an exploratory analysis of the relationships between treatment-induced changes to ctDNA levels, clinical response and tumor size dynamics in patients with cancer treated with checkpoint inhibitors and targeted therapies. This analysis highlights opportunities for pharmacometrics approaches such as for optimizing sampling design strategies. It also highlights challenges related to the nature of the data and associated variability overall emphasizing the importance of mechanistic modeling studies of the underlying biology of ctDNA processes such as shedding, release and clearance and their relationships with tumor size dynamic and treatment effects.

Gp-100 as a Novel Therapeutic Target in Uveal Melanoma

Simple Summary

Glycoprotein 100 (Gp-100) is a protein highly expressed in melanoma tissue that has recently been effectively targeted by tebentafusp, a first-in-class bispecific protein of the immune-mobilizing monoclonal T cell receptors against cancer (ImmTACs) family. Recently, a randomized phase III trial reported an overall survival benefit for tebentafusp in patients with untreated metastatic uveal melanoma.

Abstract

Uveal melanoma is a rare neoplasm with poor prognosis in the metastatic setting. Unlike cutaneous melanoma, treatment with kinase inhibitors or immune checkpoint inhibitors is not effective. Glycoprotein 100 (Gp-100) is a protein highly expressed in melanocytes and melanoma that has recently been effectively targeted by tebentafusp, a first-in-class bispecific protein of the immune-mobilizing monoclonal T cell receptors against cancer (ImmTACs) family. Tebentafusp targets tumor cells that express a peptide of Gp-100 presented by HLA*A0201, creating an immune synapse that kills targeted tumor cells. Recently, a randomized phase III trial reported an overall survival benefit for tebentafusp in patients with untreated metastatic uveal melanoma. The aim of this comprehensive review is to summarize evidence of Gp-100 as a therapeutic target in melanoma, and the preclinical and clinical development of tebentafusp as a novel therapeutic strategy for patients with uveal melanoma.

Genetic Landscape and Emerging Therapies in Uveal Melanoma

Despite successful treatment of primary uveal melanoma, up to 50% of patients will develop systemic metastasis. Metastatic disease portends a poor outcome, and no adjuvant or metastatic therapy has been FDA approved. The genetic landscape of uveal melanoma is unique, providing prognostic and potentially therapeutic insight. In this review, we discuss our current understanding of the molecular and cytogenetic mutations in uveal melanoma, and the importance of obtaining such information. Most of our knowledge is based on primary uveal melanoma and a better understanding of the mutational landscape in metastatic uveal melanoma is needed. Clinical trials targeting certain mutations such as GNAQ/GNA11, BAP1, and SF3B1 are ongoing and promising. We also discuss the role of liquid biopsies in uveal melanoma in this review.