Immunotherapy for mesothelioma: Moving beyond single immune check point inhibition

Meta-Analysis on the Combination of Chemotherapy With Programmed Death-Ligand 1 and Programmed Cell Death Protein 1 Blockade as First-Line Treatment for Unresectable Pleural Mesothelioma

INTRODUCTION

Dual immune checkpoint blockers regimen represents a standard first-line therapy in unresectable pleural mesothelioma (PM). Novel combination strategies, including immune checkpoint blockers and antiangiogenic drugs, are currently under investigation in this setting. We aimed to assess the efficacy of the chemoimmunotherapy combination by reference to literature evidence.

METHODS

A systematic review and meta-analysis of trials with first-line platinum-based chemotherapy associated with programmed death-ligand 1 and programmed cell death protein 1 agent in unresectable PM. We estimated the weighted summary proportion of disease response, along with the landmark probability of survival outcomes.

RESULTS

A total of 349 patients with unresectable PM from four trials (DREAM, PrE0505, JME-001, and IND.227) were included, 79% (n = 274) with epithelioid and 21% (n = 75) with nonepithelioid histologic type. In aggregate, the objective response rate was 59.2% (95% confidence interval [CI]: 50.3%-67.9%) and disease control rate was 92.2% (95% CI: 89.2%-94.8%). Comparing epithelioid versus nonepithelioid tumors, the objective response rate was 64.5% versus 46.4%, (p < 0.001) and the disease control rate was 92.3% versus 80.0%, (p = 0.043), with an OR of 2.56 (95% CI: 1.51-4.32) for disease response and of 3.37 (95% CI: 0.99-11.47) for disease control. The aggregated estimated probability of progression-free survival was 63% (95% CI: 53%-71%) at 6 months and 25% (95% CI: 21%-31%) at 12 months, whereas the 6-, 12- and 24-month overall survival rates were 88% (95% CI: 81%-93%), 71% (95% CI: 61%-79%) and 39% (95% CI: 34%-45%), respectively.

CONCLUSIONS

According to our analysis, first-line chemoimmunotherapy holds promise as a new treatment approach for PM, exhibiting encouraging survival outcomes and an enhanced response rate, including for the epithelioid subtype. Ongoing studies are necessary to establish its precise placement within the treatment algorithm.

ATG5 as biomarker for early detection of malignant mesothelioma

OBJECTIVES

Malignant pleural mesothelioma (MPM) is an aggressive disease with grim prognosis due to lack of effective treatment options. Disease prediction in association with early diagnosis may both contribute to improved MPM survival. Inflammation and autophagy are two processes associated with asbestos-induced transformation. We evaluated the level of two autophagic factors ATG5 and HMGB1, microRNAs (miRNAs) such as miR-126 and miR-222, and the specific biomarker of MPM, soluble mesothelin related proteins (Mesothelin) in asbestos-exposed individuals, MPM patients, and healthy subjects. The performance of these markers in detecting MPM was investigated in pre-diagnostic samples of asbestos-subjects who developed MPM during the follow-up and compared for the three groups.

RESULTS

The ATG5 best distinguished the asbestos-exposed subjects with and without MPM, while miR-126 and Mesothelin were found as a significant prognostic biomarker for MPM. ATG5 has been identified as an asbestos-related biomarker that can help to detect MPM with high sensitivity and specificity in pre-diagnostic samples for up to two years before diagnosis. To utilize this approach practically, higher number of cases has to be tested in order to give the combination of the two markers sufficient statistical power. Performance of the biomarkers should be confirmed by testing their combination in an independent cohort with pre-diagnostic samples.

Benefits and Challenges of Inhibiting EZH2 in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer that is mainly associated with prior exposure to asbestos fibers. Despite being a rare cancer, its global rate is increasing and the prognosis remains extremely poor. Over the last two decades, despite the constant research of new therapeutic options, the combination chemotherapy with cisplatin and pemetrexed has remained the only first-line therapy for MPM. The recent approval of immune checkpoint blockade (ICB)-based immunotherapy has opened new promising avenues of research. However, MPM is still a fatal cancer with no effective treatments. Enhancer of zeste homolog 2 (EZH2) is a histone methyl transferase that exerts pro-oncogenic and immunomodulatory activities in a variety of tumors. Accordingly, a growing number of studies indicate that EZH2 is also an oncogenic driver in MPM, but its effects on tumor microenvironments are still largely unexplored. This review describes the state-of-the-art of EZH2 in MPM biology and discusses its potential use both as a diagnostic and therapeutic target. We highlight current gaps of knowledge, the filling of which will likely favor the entry of EZH2 inhibitors within the treatment options for MPM patients.

Isolated BAP1 Genomic Alteration in Malignant Pleural Mesothelioma Predicts Distinct Immunogenicity with Implications for Immunotherapeutic Response

Malignant pleural mesothelioma (MPM), an aggressive cancer of the mesothelial cells lining the pleural cavity, lacks effective treatments. Multiple somatic mutations and copy number losses in tumor suppressor genes (TSGs) BAP1, CDKN2A/B, and NF2 are frequently associated with MPM. The impact of single versus multiple genomic alterations of TSG on MPM biology, the immune tumor microenvironment, clinical outcomes, and treatment responses are unknown. Tumors with genomic alterations in BAP1 alone were associated with a longer overall patient survival rate compared to tumors with CDKN2A/B and/or NF2 alterations with or without BAP1 and formed a distinct immunogenic subtype with altered transcription factor and pathway activity patterns. CDKN2A/B genomic alterations consistently contributed to an adverse clinical outcome. Since the genomic alterations of only BAP1 was associated with the PD-1 therapy response signature and higher LAG3 and VISTA gene expression, it might be a candidate marker for immune checkpoint blockade therapy. Our results on the impact of TSG genotypes on MPM and the correlations between TSG alterations and molecular pathways provide a foundation for developing individualized MPM therapies.