Targeting DNA Damage Response Deficiency in Thoracic Cancers.

Thoracic cancers comprise non-small cell lung cancers (NSCLCs), small cell lung cancers (SCLCs) and malignant pleural mesotheliomas (MPM). Collectively, they account for the highest rate of death from malignancy worldwide. Genomic instability is a universal feature of cancer, which fuels mutations and tumour evolution. Deficiencies in DNA damage response (DDR) genes amplify genomic instability. Homologous recombination deficiency (HRD), resulting from BRCA1/BRCA2 inactivation, is exploited for therapeutic synthetic lethality with poly-ADP ribose polymerase (PARP) inhibitors in breast and ovarian cancers, as well as in prostate and pancreatic cancers. However, DDR deficiency and its therapeutic implications are less well established in thoracic cancers. Emerging evidence suggests that a subset of thoracic cancers may harbour DDR deficiency and may, thus, be effectively targeted with DDR agents. Here, we review the current evidence surrounding DDR in thoracic cancers and discuss the challenges and promise for achieving clinical benefit with such therapeutics.

Leveraging the pleural space for anticancer therapies in pleural mesothelioma.

Most patients with pleural mesothelioma (PM) present with symptomatic pleural effusion. In some patients, PM is only detectable on the pleural surfaces, providing a strong rationale for intrapleural anticancer therapy. In modern prospective studies involving expert radiological staging and specialist multidisciplinary teams, the population incidence of stage I PM (an approximate surrogate of pleura-only PM) is higher than in historical retrospective series. In this Viewpoint, we advocate for the expansion of intrapleural trials to serve these patients, given the paucity of data supporting licensed systemic therapies in this setting and the uncertainties involved in surgical therapy. We begin by reviewing the unique anatomical and physiological features of the PM-bearing pleural space, before critically appraising the evidence for systemic therapies in stage I PM and previous intrapleural PM trials. We conclude with a summary of key challenges and potential solutions, including optimal trial designs, repurposing of indwelling pleural catheters, and new technologies.

Pegargiminase Plus First-Line Chemotherapy in Patients With Nonepithelioid Pleural Mesothelioma: The ATOMIC-Meso Randomized Clinical Trial.

Importance: Arginine deprivation using ADI-PEG20 (pegargiminase) combined with chemotherapy is untested in a randomized study among patients with cancer. ATOMIC-Meso (ADI-PEG20 Targeting of Malignancies Induces Cytotoxicity-Mesothelioma) is a pivotal trial comparing standard first-line chemotherapy plus pegargiminase or placebo in patients with nonepithelioid pleural mesothelioma. Objective: To determine the effect of pegargiminase-based chemotherapy on survival in nonepithelioid pleural mesothelioma, an arginine-auxotrophic tumor. Design, Setting, and Participants: This was a phase 2-3, double-blind randomized clinical trial conducted at 43 centers in 5 countries that included patients with chemotherapy-naive nonepithelioid pleural mesothelioma from August 1, 2017, to August 15, 2021, with at least 12 months' follow-up. Final follow-up was on August 15, 2022. Data analysis was performed from March 2018 to June 2023. Intervention: Patients were randomly assigned (1:1) to receive weekly intramuscular pegargiminase (36.8 mg/m2) or placebo. All patients received intravenous pemetrexed (500 mg/m2) and platinum (75-mg/m2 cisplatin or carboplatin area under the curve 5) chemotherapy every 3 weeks up to 6 cycles. Pegargiminase or placebo was continued until progression, toxicity, or 24 months. Main Outcomes and Measures: The primary end point was overall survival, and secondary end points were progression-free survival and safety. Response rate by blinded independent central review was assessed in the phase 2 portion only. Results: Among 249 randomized patients (mean [SD] age, 69.5 [7.9] years; 43 female individuals [17.3%] and 206 male individuals [82.7%]), all were included in the analysis. The median overall survival was 9.3 months (95% CI, 7.9-11.8 months) with pegargiminase-chemotherapy as compared with 7.7 months (95% CI, 6.1-9.5 months) with placebo-chemotherapy (hazard ratio [HR] for death, 0.71; 95% CI, 0.55-0.93; P = .02). The median progression-free survival was 6.2 months (95% CI, 5.8-7.4 months) with pegargiminase-chemotherapy as compared with 5.6 months (95% CI, 4.1-5.9 months) with placebo-chemotherapy (HR, 0.65; 95% CI, 0.46-0.90; P = .02). Grade 3 to 4 adverse events with pegargiminase occurred in 36 patients (28.8%) and with placebo in 21 patients (16.9%); drug hypersensitivity and skin reactions occurred in the experimental arm in 3 patients (2.4%) and 2 patients (1.6%), respectively, and none in the placebo arm. Rates of poststudy treatments were comparable in both arms (57 patients [45.6%] with pegargiminase vs 58 patients [46.8%] with placebo). Conclusions and Relevance: In this randomized clinical trial of arginine depletion with pegargiminase plus chemotherapy, survival was extended beyond standard chemotherapy with a favorable safety profile in patients with nonepithelioid pleural mesothelioma. Pegargiminase-based chemotherapy as a novel antimetabolite strategy for mesothelioma validates wider clinical testing in oncology. Trial Registration: ClinicalTrials.gov Identifier: NCT02709512.

Gene fusions during the early evolution of mesothelioma correlate with impaired DNA repair and Hippo pathways.

Malignant pleural mesothelioma (MPM), a rare cancer a long latency period (up to 40 years) between asbestos exposure and disease presentation. The mechanisms coupling asbestos to recurrent somatic alterations are poorly defined. Gene fusions arising through genomic instability may create novel drivers during early MPM evolution. We explored the gene fusions that occurred early in the evolutionary history of the tumor. We conducted multiregional whole exome sequencing (WES) of 106 samples from 20 patients undergoing pleurectomy decortication and identified 24 clonal nonrecurrent gene fusions, three of which were novel (FMO9P-OR2W5, GBA3, and SP9). The number of early gene fusion events detected varied from zero to eight per tumor, and presence of gene fusions was associated with clonal losses involving the Hippo pathway genes and homologous recombination DNA repair genes. Fusions involved known tumor suppressors BAP1, MTAP, and LRP1B, and a clonal oncogenic fusion involving CACNA1D-ERC2, PARD3B-NT5DC2, and STAB2-NT5DC2 fusions were also identified as clonal fusions. Gene fusions events occur early during MPM evolution. Individual fusions are rare as no recurrent truncal fusions event were found. This suggests the importance of early disruption of these pathways in generating genomic rearrangements resulting in potentially oncogenic gene fusions.

Family Matters: Germline Testing in Thoracic Cancers.

Most thoracic cancers arise via a series of stepwise somatic alterations driven by a well-defined carcinogen (ie, tobacco or asbestos for lung cancer and mesothelioma, respectively). A small proportion can emerge on a background of pathogenic germline variants (PGVs), which have the property of heritability. In general, PGVs may be initially suspected on the basis of the presence of specific clinical features. Such gene × environment interactions significantly increase the risk of developing lung cancer (1.5- to 3.2-fold). PGVs have been discovered involving the actionable driver oncogene, epidermal growth factor receptor (EGFR), with an EGFR T790M PGV rate of 0.3%-0.9% in the nonsquamous non-small-cell lung cancer subtype. Its appearance during routine somatic DNA sequencing in those patients who have not had a previous tyrosine kinase inhibitor should raise suspicion. In patients with sporadic mesothelioma, BAP1 is the most frequently mutated tumor driver, with a PGV rate between 2.8% and 8%, associated with a favorable prognosis. BAP1 PGVs accelerate mesothelioma tumorigenesis after asbestos exposure in preclinical models and may be partly predicted by clinical criteria. At present, routine germline genetic testing for thoracic cancers is not a standard practice. Expert genetic counseling is, therefore, required for patients who carry a PGV. Ongoing studies aim to better understand the natural history of patients harboring PGVs to underpin future cancer prevention, precise counseling, and cancer management with the goal of improving the quality and length of life.

The evolution of non-small cell lung cancer metastases in TRACERx.

Metastatic disease is responsible for the majority of cancer-related deaths1. We report the longitudinal evolutionary analysis of 126 non-small cell lung cancer (NSCLC) tumours from 421 prospectively recruited patients in TRACERx who developed metastatic disease, compared with a control cohort of 144 non-metastatic tumours. In 25% of cases, metastases diverged early, before the last clonal sweep in the primary tumour, and early divergence was enriched for patients who were smokers at the time of initial diagnosis. Simulations suggested that early metastatic divergence more frequently occurred at smaller tumour diameters (less than 8 mm). Single-region primary tumour sampling resulted in 83% of late divergence cases being misclassified as early, highlighting the importance of extensive primary tumour sampling. Polyclonal dissemination, which was associated with extrathoracic disease recurrence, was found in 32% of cases. Primary lymph node disease contributed to metastatic relapse in less than 20% of cases, representing a hallmark of metastatic potential rather than a route to subsequent recurrences/disease progression. Metastasis-seeding subclones exhibited subclonal expansions within primary tumours, probably reflecting positive selection. Our findings highlight the importance of selection in metastatic clone evolution within untreated primary tumours, the distinction between monoclonal versus polyclonal seeding in dictating site of recurrence, the limitations of current radiological screening approaches for early diverging tumours and the need to develop strategies to target metastasis-seeding subclones before relapse.

The evolution of lung cancer and impact of subclonal selection in TRACERx.

Lung cancer is the leading cause of cancer-associated mortality worldwide1. Here we analysed 1,644 tumour regions sampled at surgery or during follow-up from the first 421 patients with non-small cell lung cancer prospectively enrolled into the TRACERx study. This project aims to decipher lung cancer evolution and address the primary study endpoint: determining the relationship between intratumour heterogeneity and clinical outcome. In lung adenocarcinoma, mutations in 22 out of 40 common cancer genes were under significant subclonal selection, including classical tumour initiators such as TP53 and KRAS. We defined evolutionary dependencies between drivers, mutational processes and whole genome doubling (WGD) events. Despite patients having a history of smoking, 8% of lung adenocarcinomas lacked evidence of tobacco-induced mutagenesis. These tumours also had similar detection rates for EGFR mutations and for RET, ROS1, ALK and MET oncogenic isoforms compared with tumours in never-smokers, which suggests that they have a similar aetiology and pathogenesis. Large subclonal expansions were associated with positive subclonal selection. Patients with tumours harbouring recent subclonal expansions, on the terminus of a phylogenetic branch, had significantly shorter disease-free survival. Subclonal WGD was detected in 19% of tumours, and 10% of tumours harboured multiple subclonal WGDs in parallel. Subclonal, but not truncal, WGD was associated with shorter disease-free survival. Copy number heterogeneity was associated with extrathoracic relapse within 1 year after surgery. These data demonstrate the importance of clonal expansion, WGD and copy number instability in determining the timing and patterns of relapse in non-small cell lung cancer and provide a comprehensive clinical cancer evolutionary data resource.

Cytoreductive surgery with hyperthermic intrathoracic chemotherapy for malignant pleural mesothelioma: a systematic review.

INTRODUCTION: Cytoreductive surgery has been used a part of multimodality treatment in patients with malignant pleural mesothelioma (MPM). The residual microscopic disease that remains will lead to disease progression in the majority of patients. Delivery of hyperthermic intrathoracic chemotherapy at the time of surgery has been used to address this microscopic disease, however it's effect and place in the multimodality treatment sphere is unknown. The aim of this systematic review was to assess the effect of surgery and hyperthermic intrathoracic chemotherapy in patients with MPM on overall survival and disease-free interval. METHODS: Ovid MEDLINE, Embase, Web of Science and the Cochrane Database of Systematic Reviews were searched from database inception through to June 2021. Studies reporting overall survival and/or disease-free interval in patients with MPM undergoing cytoreductive surgery with hyperthermic intrathoracic chemotherapy were considered. Study quality was assessed using the Newcastle-Ottawa Scale. A narrative review was performed. RESULTS: Fifteen studies were eligible for inclusion comprising 598 patients. Surgery with hyperthermic intrathoracic chemotherapy was associated with a median overall survival and disease-free interval ranging from 11 to 75 months and 7.2 to 57 months, respectively. These appeared to be superior to patients not receiving hyperthermic intrathoracic chemotherapy (overall survival: 5-36 months and disease-free interval: 12.1-21 months). A higher dose of hyperthermic intrathoracic chemotherapy was associated with an improvement in overall survival compared with a lower dose: 18-31 months versus 6-18 months, respectively. The most common morbidity was atrial fibrillation followed by renal complications. CONCLUSION: Surgery with hyperthermic intrathoracic chemotherapy offers a safe and effective therapy with an improvement in disease-free interval and overall survival, particularly when hyperthermic intrathoracic chemotherapy is administered at a higher dose. PROSPERO REGISTRATION NUMBER: CRD42019129002.

BAP1 loss induces mitotic defects in mesothelioma cells through BRCA1-dependent and independent mechanisms.

The tumour suppressor BRCA1-associated protein 1 (BAP1) is the most frequently mutated cancer gene in mesothelioma. Here we report novel functions for BAP1 in mitotic progression highlighting the relationship between BAP1 and control of genome stability in mesothelioma cells with therapeutic implications. Depletion of BAP1 protein induced proteasome-mediated degradation of BRCA1 in mesothelioma cells while loss of BAP1 correlated with BRCA1 loss in mesothelioma patient tumour samples. BAP1 loss also led to mitotic defects that phenocopied the loss of BRCA1 including spindle assembly checkpoint failure, centrosome amplification and chromosome segregation errors. However, loss of BAP1 also led to additional mitotic changes that were not observed upon BRCA1 loss, including an increase in spindle length and enhanced growth of astral microtubules. Intriguingly, these consequences could be explained by loss of expression of the KIF18A and KIF18B kinesin motors that occurred upon depletion of BAP1 but not BRCA1, as spindle and astral microtubule defects were rescued by re-expression of KIF18A and KIF18B, respectively. We therefore propose that BAP1 inactivation causes mitotic defects through BRCA1-dependent and independent mechanisms revealing novel routes by which mesothelioma cells lacking BAP1 may acquire genome instability and exhibit altered responses to microtubule-targeted agents.

Corrigendum: CDKN2A determines mesothelioma cell fate to EZH2 inhibition.

[This corrects the article DOI: 10.3389/fonc.2021.678447.].

Olaparib maintenance versus placebo monotherapy in patients with advanced non-small cell lung cancer (PIN): A multicentre, randomised, controlled, phase 2 trial.

Background: Impaired double strand DNA repair by homologous repair deficiency (HRD) leads to sensitivity to poly ADP ribose polymerase (PARP) inhibition. Poly-ADP ribose polymerase (PARP) inhibitors target HRD to induce synthetic lethality and are used routinely in the treatment of BRCA1 mutated ovarian cancer in the platinum-sensitive maintenance setting. A subset of non-small cell lung cancers (NSCLCs) harbour impaired DNA double strand break repair. We therefore hypothesised that patients with metastatic non-small cell lung cancer exhibiting partial responses to platinum doublet-based chemotherapy, might enrich for impaired HRD, rendering these tumours more sensitive to inhibition of PARP inhibition by olaparib. Methods: The Olaparib Maintenance versus Placebo Monotherapy in Patients with Advanced Non-Small Cell Lung Cancer trial (PIN) was a multicentre double-blind placebo controlled randomised phase II screening trial. This study was conducted at 23 investigative hospital sites in the UK. Patients had advanced (stage IIIB/IV) squamous (Sq) or non-squamous (NSq) NSCLC, and had to be chemo-naive, European Cooperative Oncology Group (ECOG) performance status 0-1. Prior immunotherapy with a PD1 or PDL1 inhibitor was allowed. Patients could be registered for PIN prior to (stage 1), or after (stage 2) initiation of induction chemotherapy. If any tumour shrinkage was observed (any shrinkage of RECIST target lesions), following a minimum of 3 cycles of platinum doublet chemotherapy, patients were randomised 1:1 using a centralised online system, to either olaparib (300 mg twice daily by mouth in 21-day cycles) or placebo, which was continued until disease progression, or unacceptable toxicity. Intention to treat (ITT) analyses of the primary endpoint included all randomised participants. Per protocol (PP) safety analysis included all participants who received at least one dose of study drug. Primary endpoint was progression-free survival (PFS), with a one-sided p-value of 0.2 to demonstrate statistical significance. Hazard ratios (HR) for PFS were both unadjusted and adjusted for the randomisation balancing factors (smoking status and histology). The trial was registered with ClinicalTrials.gov (NCT01788332) and EudraCT (2012-003383-51). Findings: A total of 940 patients were assessed for stage 1 eligibility of whom 263 were registered between Feb 24, 2014 and Nov 7, 2017. 194 patients were excluded prior to stage 2 (no tumour shrinkage or unevaluable) and 70 were randomised; 32 (46%) to Olaparib and 38 (54%) to placebo. 4% (3/70) of patients randomised had a CR and 96% (67/70) had a PR (or other evidence of tumour response/mixed stable) during induction therapy. A total of 36 patients were registered in stage 2 only, i.e., post induction therapy. Intention to treat (ITT) unadjusted analysis showed a PFS hazard ratio (HR) of 0.83 (one-sided 80% CI upper limit 1.03, one-sided unadjusted log rank test p-value=0.23). ITT Cox-adjusted model showed a HR 0.73 (one-sided 80% CI upper limit 0.91, one sided p-value 0.11). Adverse events were reported in 31/32 subjects (97%) in the olaparib arm and 38/38 (100%) in the placebo group. The most commonly reported adverse events in the olaparib group were fatigue (20/31; 65%), nausea (17/31; 55%), anaemia (15/31; 48%) and dyspnea (13/31; 42%). In the placebo group the most common adverse events were fatigue (25/38; 66%), coughing (22/38; 58%), dyspnea (15/38; 39%) and nausea (11/38; 29%). There were no treatment-related deaths. Interpretation: PFS was longer in the olaparib arm, but this did not reach statistical significance. When the PFS HR was adjusted for smoking status and histology, a significant difference at the one-sided 0.2 level was observed, suggesting that tumour control may be achieved for chemosensitive NSCLC treated with PARP monotherapy. We speculate that this signal may be driven by a molecular subgroup harbouring HRD. Funding: This study was funded between AstraZeneca CRUK, National Cancer Research Institute, and Cancer Research UK Feasibility Study Committee.

Immunotherapy approaches for malignant pleural mesothelioma.

Over the past decade, immune-checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer. In mesothelioma, a rare cancer with a dismal prognosis generally caused by exposure to asbestos, treatment with single or dual ICIs results in robust improvements in overall survival over previous standard-of-care therapies, both in the first-line and relapsed disease settings. Predictive biological features that underpin response to ICIs remain poorly understood; however, insights into the immune microenvironment and genomic landscape of mesothelioma as well as into their association with response or acquired resistance to ICIs are emerging. Several studies of rational combinations involving ICIs with either another ICI or a different agent are ongoing, with emerging evidence of synergistic antitumour activity. Non-ICI-based immunotherapies, such as peptide-based vaccines and mesothelin-targeted chimeric antigen receptor T cells, have demonstrated promising efficacy. Moreover, results from pivotal trials of dendritic cell vaccines and viral cytokine delivery, among others, are eagerly awaited. In this Review, we comprehensively summarize the key steps in the development of immunotherapies for mesothelioma, focusing on strategies that have led to randomized clinical evaluation and emerging predictors of response. We then forecast the future treatment opportunities that could arise from ongoing research.

Active symptom control with or without oral vinorelbine in patients with relapsed malignant pleural mesothelioma (VIM): A randomised, phase 2 trial.

Background: Currently, there is no US Food and Drug Administration approved therapy for patients with pleural mesothelioma who have relapsed following platinum-doublet based chemotherapy. Vinorelbine has demonstrated useful clinical activity in mesothelioma, however its efficacy has not been formally evaluated in a randomised setting. BRCA1 expression is required for vinorelbine induced apoptosis in preclinical models. Loss of expression may therefore correlate with vinorelbine resistance. Methods: In this randomised, phase 2 trial, patients were eligible if they met the following criteria: age ≥ 18 years, Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, histologically confirmed pleural mesothelioma, post platinum-based chemotherapy, and radiological evidence of disease progression. Consented patients were randomised 2:1 to either active symptom control with oral vinorelbine versus active symptom control (ASC) every 3 weeks until disease progression, unacceptable toxicity or withdrawal at an initial dose of 60 mg/m2 increasing to 80 mg/m2 post-cycle 1. Randomisation was stratified by histological subtype, white cell count, gender, ECOG performance status and best response during first-line therapy. The study was open label. The primary endpoint was progression-free survival (PFS), measured from randomisation to time of event (or censoring). Analyses were carried out according to intention-to-treat (ITT) principles. Recruitment and trial follow-up are complete. This trial is registered with ClinicalTrials.gov, number NCT02139904. Findings: Between June 1, 2016 and Oct 31, 2018, we performed a randomised phase 2 trial in 14 hospitals in the United Kingdom. 225 patients were screened for eligibility, of whom 154 were randomly assigned to receive either ASC + vinorelbine (n = 98) or ASC (n = 56). PFS was significantly longer for ASC+vinorelbine compared with ASC alone; 4.2 months (interquartile range (IQR) 2.2-8.0) versus 2.8 months (IQR 1.4-4.1) for ASC, giving an unadjusted hazard ratio (HR) of 0·60 (80% CI upper limit 0.7, one-sided unadjusted log rank test p = 0.002); adjusted HR 0.6 (80% CI upper limit 0.7, one-sided adjusted log rank test p < 0.001). BRCA1 did not predict resistance to ASC+vinorelbine. Neutropenia was the most common grades 3, 4 adverse events in the ASC +vinorelbine arm. Interpretation: Vinorelbine plus ASC confers clinical benefit to patients with relapsed pleural mesothelioma who have progressed following platinum-based doublet chemotherapy. Funding: This study was funded by Cancer Research UK (grant CRUK A15569).

Comprehensive genomic and tumour immune profiling reveals potential therapeutic targets in malignant pleural mesothelioma.

BACKGROUND: Malignant pleural mesothelioma (MPM) has a poor overall survival with few treatment options. Whole genome sequencing (WGS) combined with the immune features of MPM offers the prospect of identifying changes that could inform future clinical trials. METHODS: We analysed somatic mutations from 229 MPM samples, including previously published data and 58 samples that had undergone WGS within this study. This was combined with RNA-seq analysis to characterize the tumour immune environment. RESULTS: The comprehensive genome analysis identified 12 driver genes, including new candidate genes. Whole genome doubling was a frequent event that correlated with shorter survival. Mutational signature analysis revealed SBS5/40 were dominant in 93% of samples, and defects in homologous recombination repair were infrequent in our cohort. The tumour immune environment contained high M2 macrophage infiltrate linked with MMP2, MMP14, TGFB1 and CCL2 expression, representing an immune suppressive environment. The expression of TGFB1 was associated with overall survival. A small subset of samples (less than 10%) had a higher proportion of CD8 T cells and a high cytolytic score, suggesting a 'hot' immune environment independent of the somatic mutations. CONCLUSIONS: We propose accounting for genomic and immune microenvironment status may influence therapeutic planning in the future.

EZH2 inhibitor tazemetostat in patients with relapsed or refractory, BAP1-inactivated malignant pleural mesothelioma: a multicentre, open-label, phase 2 study.

BACKGROUND: Treatment options for malignant pleural mesothelioma are scarce. Tazemetostat, a selective oral enhancer of zeste homolog 2 (EZH2) inhibitor, has shown antitumour activity in several haematological cancers and solid tumours. We aimed to evaluate the anti-tumour activity and safety of tazemetostat in patients with measurable relapsed or refractory malignant pleural mesothelioma. METHODS: We conducted an open-label, single-arm phase 2 study at 16 hospitals in France, the UK, and the USA. Eligible patients were aged 18 years or older with malignant pleural mesothelioma of any histology that was relapsed or refractory after treatment with at least one pemetrexed-containing regimen, an Eastern Cooperative Oncology Group performance status of 0 or 1, and a life expectancy of greater than 3 months. In part 1 of the study, participants received oral tazemetostat 800 mg once on day 1 and then twice daily from day 2 onwards. In part 2, participants received oral tazemetostat 800 mg twice daily starting on day 1 of cycle 1, using a two-stage Green-Dahlberg design. Tazemetostat was administered in 21-day cycles for approximately 17 cycles. The primary endpoint of part 1 was the pharmacokinetics of tazemetostat and its metabolite at day 15 after administration of 800 mg tazemetostat, as measured by maximum serum concentration (Cmax), time to Cmax (Tmax), area under the concentration-time curve (AUC) to day 15 (AUC0-t), area under the curve from time 0 extrapolated to infinity (AUC0-∞), and the half-life (t1/2) of tazemetostat, assessed in all patients enrolled in part 1. The primary endpoint of part 2 was the disease control rate (the proportion of patients with a complete response, partial response, or stable disease) at week 12 in patients with malignant pleural mesothelioma per protocol with BAP1 inactivation determined by immunohistochemistry. The safety population included all the patients who had at least one post-dose safety assessment. This trial is now complete and is registered with ClinicalTrials.gov, NCT02860286. FINDINGS: Between July 29, 2016, and June 2, 2017, 74 patients were enrolled (13 in part 1 and 61 in part 2) and received tazemetostat, 73 (99%) of whom had BAP1-inactivated tumours. In part 1, following repeat dosing of tazemetostat at steady state, on day 15 of cycle 1, the mean Cmax was 829 ng/mL (coefficient of variation 56·3%), median Tmax was 2 h (range 1-4), mean AUC0-twas 3310 h·ng/mL (coefficient of variation 50·4%), mean AUC0-∞ was 3180 h·ng/mL (46·6%), and the geometric mean t1/2 was 3·1 h (13·9%). After a median follow-up of 35·9 weeks (IQR 20·6-85·9), the disease control rate in part 2 in patients with BAP1-inactivated malignant pleural mesothelioma was 54% (95% CI 42-67; 33 of 61 patients) at week 12. No patients had a confirmed complete response. Two patients had a confirmed partial response: one had an ongoing partial response with a duration of 18 weeks and the other had a duration of 42 weeks. The most common grade 3-4 treatment-emergent adverse events were hyperglycaemia (five [7%] patients), hyponatraemia (five [7%]), and anaemia (four [5%]); serious adverse events were reported in 25 (34%) of 74 patients. Five (7%) of 74 patients died while on study; no treatment-related deaths occurred. INTERPRETATION: Further refinement of biomarkers for tazemetostat activity in malignant pleural mesothelioma beyond BAP1 inactivation could help identify a subset of tumours that are most likely to derive prolonged benefit or shrinkage from this therapy. FUNDING: Epizyme.

Medical and Surgical Care of Patients With Mesothelioma and Their Relatives Carrying Germline BAP1 Mutations.

The most common malignancies that develop in carriers of BAP1 germline mutations include diffuse malignant mesothelioma, uveal and cutaneous melanoma, renal cell carcinoma, and less frequently, breast cancer, several types of skin carcinomas, and other tumor types. Mesotheliomas in these patients are significantly less aggressive, and patients require a multidisciplinary approach that involves genetic counseling, medical genetics, pathology, surgical, medical, and radiation oncology expertise. Some BAP1 carriers have asymptomatic mesothelioma that can be followed by close clinical observation without apparent adverse outcomes: they may survive many years without therapy. Others may grow aggressively but very often respond to therapy. Detecting BAP1 germline mutations has, therefore, substantial medical, social, and economic impact. Close monitoring of these patients and their relatives is expected to result in prolonged life expectancy, improved quality of life, and being cost-effective. The co-authors of this paper are those who have published the vast majority of cases of mesothelioma occurring in patients carrying inactivating germline BAP1 mutations and who have studied the families affected by the BAP1 cancer syndrome for many years. This paper reports our experience. It is intended to be a source of information for all physicians who care for patients carrying germline BAP1 mutations. We discuss the clinical presentation, diagnostic and treatment challenges, and our recommendations of how to best care for these patients and their family members, including the potential economic and psychosocial impact.