Multiple Onychopapillomas and BAP1 Tumor Predisposition Syndrome

Importance

BRCA1-associated protein (BAP1) tumor predisposition syndrome (TPDS) is a cancer genodermatosis associated with high risk of uveal and cutaneous melanoma, basal cell carcinoma, and multiple internal malignant neoplasms, including mesothelioma and renal cell carcinoma. Early detection of the syndrome is important for cancer surveillance and genetic counseling of family members who are at risk.

Objective

To determine the prevalence of nail abnormalities in individuals with pathogenic germline variants in BAP1.

Design, Setting, and Participants

In this prospective cohort study, individuals who were known carriers of pathogenic BAP1 germline variants were consecutively enrolled between October 10, 2023, and March 15, 2024. Dermatologic evaluation for nail abnormalities was performed, including a history of nail abnormalities and associated symptoms, physical examination, medical photography, and nail biopsy for histopathology. This was a single-center study conducted at the National Institutes of Health Clinical Center.

Main Outcomes and Measures

Primary outcomes were the prevalence and spectrum of nail changes and histopathologic characterization.

Results

Among 47 participants (30 female [63.8%]; mean [SD] age, 46.4 [15.1] years) ranging in age from 13 to 72 years from 35 families, nail abnormalities were detected in 41 patients (87.2%) and included leukonychia, splinter hemorrhage, onychoschizia, and distal nail hyperkeratosis. Clinical findings consistent with onychopapilloma were detected in 39 patients (83.0%), including 35 of 40 individuals aged 30 years or older (87.5%). Nail bed biopsy was performed in 5 patients and was consistent with onychopapilloma. Polydactylous involvement with onychopapillomas was detected in nearly all patients who had nail involvement (38 of 39 patients [97.4%]).

Conclusions and Relevance

This study found that BAP1 TPDS was associated with a high rate of nail abnormalities consistent with onychopapillomas in adult carriers of the disease. Findings suggest that this novel cutaneous sign may facilitate detection of the syndrome in family members who are at risk and patients with cancers associated with BAP1 given that multiple onychopapillomas are uncommon in the general population and may be a distinct clue to the presence of a pathogenic germline variant in the BAP1 gene.

Tumor resistance to anti-mesothelin CAR-T cells caused by binding to shed mesothelin is overcome by targeting a juxtamembrane epitope

Despite many clinical trials, CAR-T cells are not yet approved for human solid tumor therapy. One popular target is mesothelin (MSLN) which is highly expressed on the surface of about 30% of cancers including mesothelioma and cancers of the ovary, pancreas, and lung. MSLN is shed by proteases that cleave near the C terminus, leaving a short peptide attached to the cell. Most anti-MSLN antibodies bind to shed MSLN, which can prevent their binding to target cells. To overcome this limitation, we developed an antibody (15B6) that binds next to the membrane at the protease-sensitive region, does not bind to shed MSLN, and makes CAR-T cells that have much higher anti-tumor activity than a CAR-T that binds to shed MSLN. We have now humanized the Fv (h15B6), so the CAR-T can be used to treat patients and show that h15B6 CAR-T produces complete regressions in a hard-to-treat pancreatic cancer patient derived xenograft model, whereas CAR-T targeting a shed epitope (SS1) have no anti-tumor activity. In these pancreatic cancers, the h15B6 CAR-T replicates and replaces the cancer cells, whereas there are no CAR-T cells in the tumors receiving SS1 CAR-T. To determine the mechanism accounting for high activity, we used an OVCAR-8 intraperitoneal model to show that poorly active SS1-CAR-T cells are bound to shed MSLN, whereas highly active h15B6 CAR-T do not contain bound MSLN enabling them to bind to and kill cancer cells.

NAV-003, a bispecific antibody targeting a unique mesothelin epitope and CD3ε with improved cytotoxicity against humoral immunosuppressed tumors

Mesothelin (MSLN) is a cell surface protein overexpressed in a number of cancer types. Several antibody- and cellular-based MSLN targeting agents have been tested in clinical trials where their therapeutic efficacy has been moderate at best. Previous studies using antibody and Chimeric Antigen Receptor-T cells (CAR-T) strategies have shown the importance of particular MSLN epitopes for optimal therapeutic response, while other studies have found that certain MSLN-positive tumors can produce proteins that can bind to subsets of IgG1-type antibodies and suppress their immune effector activities. In an attempt to develop an improved anti-MSLN targeting agent, we engineered a humanized divalent anti-MSLN/anti-CD3ε bispecific antibody that avoids suppressive factors, can target a MSLN epitope proximal to the tumor cell surface, and is capable of effectively binding, activating, and redirecting T cells to the surface of MSLN-positive tumor cells. NAV-003 has shown significantly improved tumor cell killing against lines producing immunosuppressive proteins in vitro and in vivo. Moreover, NAV-003 demonstrated good tolerability in mice and efficacy against patient-derived mesothelioma xenografts co-engrafted with human peripheral blood mononuclear cells. Together these data support the potential for NAV-003 clinical development and human proof-of-concept studies in patients with MSLN-expressing cancers.

Mesothelin-targeting T cell receptor fusion construct cell therapy in refractory solid tumors: phase 1/2 trial interim results

The T cell receptor fusion construct (TRuC) gavocabtagene autoleucel (gavo-cel) consists of single-domain anti-mesothelin antibody that integrates into the endogenous T cell receptor (TCR) and engages the signaling capacity of the entire TCR upon mesothelin binding. Here we describe phase 1 results from an ongoing phase1/2 trial of gavo-cel in patients with treatment-refractory mesothelin-expressing solid tumors. The primary objectives were to evaluate safety and determine the recommended phase 2 dose (RP2D). Secondary objectives included efficacy. Thirty-two patients received gavo-cel at increasing doses either as a single agent (n = 3) or after lymphodepletion (LD, n = 29). Dose-limiting toxicities of grade 3 pneumonitis and grade 5 bronchioalveolar hemorrhage were noted. The RP2D was determined as 1 × 108 cells per m2 after LD. Grade 3 or higher pneumonitis was seen in 16% of all patients and in none at the RP2D; grade 3 or higher cytokine release syndrome occurred in 25% of all patients and in 15% at the RP2D. In 30 evaluable patients, the overall response rate and disease control rate were 20% (13% confirmed) and 77%, respectively, and the 6-month overall survival rate was 70%. Gavo-cel warrants further study in patients with mesothelin-expressing cancers given its encouraging anti-tumor activity, but it may have a narrow therapeutic window. ClinicalTrials.gov identifier: NCT03907852 .

Abstract 1786: Mesothelin-targeting, nanobody-based CAR T cells effectively target solid tumors in fully immunocompetent hosts

Nanobody-based chimeric antigen receptor (CAR) T cells are currently being tested in early phase clinical trials against blood and solid tumor antigens. Owing to the low molecular weight, increased stability, and low immunogenicity of nanobodies, nanobody-based CAR T cells are an attractive alternative to antibody-based CAR T cells for improving in vivo persistence and overcoming loss of antigen in solid tumors. However, no such agent has been described that can target mesothelin, a tumor antigen that is highly expressed in mesotheliomas, pancreatic, ovarian, and lung carcinomas. Here, a novel nanobody-based CAR T cell that targets both mouse and human mesothelin was created and evaluated in a pre-clinical model of lung adenocarcinoma that encompasses a fully functional murine immune system. To obtain the nanobody, a selection of camel-derived nanobodies were screened for human mesothelin binding using phage panning. Binding of the lead candidate to mouse mesothelin was confirmed using flow cytometry. The antigen binding variable region of the nanobody was incorporated into a second-generation CAR backbone and the sequence was optimized for expression in the mouse host. To generate the nanobody-based CAR T cells, CD3 T cells were isolated from the spleens of naïve mice and transduced using a lentiviral vector. Following expansion, the functionality of the CAR T cells was assessed in cytotoxicity assays and by monitoring the subcutaneous tumor growth rate of the mouse-derived lung adenocarcinoma cell line 344SQ (mouse mesothelin positive) in 129S2/SvPasCrl syngeneic female mice. Murine CAR T cells demonstrated antigen specificity by selectively targeting tumor cells expressing mesothelin in co-culture assays. When mice were treated with a single dose of 10 million CAR T cells, there was a threefold reduction in tumor size one-week post-treatment (n = 6) with complete responses observed approximately two weeks post-treatment in 83% of the treated mice (n = 5/6). Complete responses were maintained for at least two months after treatment in those mice. Collectively, this demonstrates that the nanobody-based CAR T cells can effectively target established subcutaneous tumors even after a single dose and without the need to manipulate the immune system of the host to enhance persistence. This study constitutes a first attempt to establish an immunocompetent pre-clinical model for the study of mesothelin-targeting, nanobody-based CAR T cells in unprimed hosts. This model will facilitate the study of the dynamic changes occurring in the tumor microenvironment following nanobody-based CAR T cell therapy while also providing valuable insight into the tumor resistance mechanisms and methods to overcome them.

Citation Format: Chaido Stathopoulou, Jessica Hong, Mitchell Ho, Raffit Hassan. Mesothelin-targeting, nanobody-based CAR T cells effectively target solid tumors in fully immunocompetent hosts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1786.

Abstract 5666: NAV-003, a full-length IgG1 bispecific antibody targeting a unique mesothelin epitope and CD3 to improve cytotoxicity against humoral immunosuppressed tumors

Mesothelin (MSLN) is a cell surface protein over-expressed in a number of cancer types. Several antibody- and cellular-based MSLN targeting agents have been tested in clinical trials where their therapeutic efficacy has been moderate at best. Previous studies using antibody and CAR-T based agents have shown the importance of particular MSLN epitopes for optimal therapeutic response, while other studies have found certain MSLN-positive tumors can produce proteins that can bind to subsets of IgG1-type antibodies and suppress their immune-effector activities. In an attempt to develop a more optimized anti-MSLN targeting agent, we engineered a humanized divalent anti-MSLN/anti-CD3ε bispecific antibody called NAV-003 that targets a MSLN epitope proximal to the tumor cell surface and an anti-CD3ε single-chain antibody capable of effectively binding, activating and directing T-cells to the surface of MSLN-bound tumor cells. NAV-003 has shown significantly improved tumor cell killing against lines producing immunosuppressive proteins in vitro and in vivo. Moreover, NAV-003 demonstrated good tolerability and efficacy against patient-derived mesothelioma xenograft models co-engrafted with human peripheral blood mononuclear cells. Together these data support the potential for NAV-003 clinical development and human proof-of-concept studies in patients with MSLN-expressing cancers.

Citation Format: Luigi Grasso, Qun Jiang, Raffit Hassan, Nicholas C. Nicolaides, J. Bradford Kline. NAV-003, a full-length IgG1 bispecific antibody targeting a unique mesothelin epitope and CD3 to improve cytotoxicity against humoral immunosuppressed tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5666.

Genomic and transcriptomic analyses identify a prognostic gene signature and predict response to therapy in pleural and peritoneal mesothelioma

Malignant mesothelioma is an aggressive cancer with limited treatment options and poor prognosis. A better understanding of mesothelioma genomics and transcriptomics could advance therapies. Here, we present a mesothelioma cohort of 122 patients along with their germline and tumor whole-exome and tumor RNA sequencing data as well as phenotypic and drug response information. We identify a 48-gene prognostic signature that is highly predictive of mesothelioma patient survival, including CCNB1, the expression of which is highly predictive of patient survival on its own. In addition, we analyze the transcriptomics data to study the tumor immune microenvironment and identify synthetic-lethality-based signatures predictive of response to therapy. This germline and somatic whole-exome sequencing as well as transcriptomics data from the same patient are a valuable resource to address important biological questions, including prognostic biomarkers and determinants of treatment response in mesothelioma.

CD70 and PD-L1 (CD274) co-expression predicts poor clinical outcomes in patients with pleural mesothelioma

Diffuse pleural mesothelioma (PM) is a highly aggressive tumour typically associated with short survival. Recently, the effectiveness of first-line immune checkpoint inhibitors in patients with unresectable PM was reported. CD70-CD27 signalling plays a co-stimulatory role in promoting T cell expansion and differentiation through the nuclear factor κB (NF-κB) pathway. Conversely, the PD-L1 (CD274)-PD-1 (PDCD1) pathway is crucial for the modulation of immune responses in normal conditions. Nevertheless, pathological activation of both the CD70-CD27 and PD-L1-PD-1 pathways by aberrantly expressed CD70 and PD-L1 participates in the immune evasion of tumour cells. In this study, 171 well-characterised PMs including epithelioid (n = 144), biphasic (n = 15), and sarcomatoid (n = 12) histotypes were evaluated immunohistochemically for CD70, PD-L1, and immune cell markers such as CD3, CD4, CD8, CD56, PD-1, FOXP3, CD68, and CD163. Eight percent (14/171) of mesotheliomas simultaneously expressed CD70 and PD-L1 on the tumour cell membrane. PMs co-expressing CD70 and PD-L1 contained significantly higher numbers of CD8+ (p = 0.0016), FOXP3+ (p = 0.00075), and CD163+ (p = 0.0011) immune cells within their microenvironments. Overall survival was significantly decreased in the cohort of patients with PM co-expressing CD70 and PD-L1 (p < 0.0001). In vitro experiments revealed that PD-L1 and CD70 additively enhanced the motility and invasiveness of PM cells. In contrast, PM cell proliferation was suppressed by PD-L1. PD-L1 enhanced mesenchymal phenotypes such as N-cadherin up-regulation. Collectively, these findings suggest that CD70 and PD-L1 both enhance the malignant phenotypes of PM and diminish anti-tumour immune responses. Based on our observations, combination therapy targeting these signalling pathways might be useful in patients with PM.

Systemic immune changes accompany combination treatment with immunotoxin LMB-100 and nab-paclitaxel

LMB-100 is a novel immune-conjugate (immunotoxin) that targets mesothelin. A phase 1/2 clinical trial was conducted (NCT02810418) with primary objectives assessing the safety and efficacy of LMB-100 ± nab-paclitaxel. Participant blood samples were analyzed for changes in serum cytokines and circulating immune cell subsets associated with response or toxicity. On Arm A, participants (n = 20) received standard 30-minute LMB-100 infusion with nab-paclitaxel. Although clinical efficacy was observed, the combination caused intolerable capillary leak syndrome (CLS), a major toxicity of unclear etiology that affects many immunotoxin drugs. Participants developing CLS experienced rapid elevations in IFNγ and IL-8 compared to those without significant CLS, along with midcycle increases in Ki-67- CD4 T cells that were CD38, HLA-DR, or TIM3 positive. Additionally, a strong increase in activated CD4 and CD8 T cells and a concurrent decrease in Tregs were seen in the single Arm A patient achieving a partial response. In Arm B, administration of single agent LMB-100 to participants (n = 20) as a long infusion given over 24-48 h was investigated based on pre-clinical data that this format could reduce CLS. An optimal dose and schedule of long infusion LMB-100 were identified, but no clinical efficacy was observed even in patients receiving LMB-100 in combination with nab-paclitaxel. Despite this, both Arm A and B participants experienced increases in specific subsets of proliferating CD4 and CD8 T cells following Cycle 1 treatment. In summary, LMB-100 treatment causes systemic immune activation. Inflammatory and immune changes that accompany drug associated CLS were characterized for the first time.

Structures of Cancer Antigen Mesothelin and Its Complexes with Therapeutic Antibodies

The tumor-associated antigen mesothelin is expressed at high levels on the cell surface of many human cancers, while its expression in normal tissues is limited. The binding of mesothelin to the tumor-associated cancer antigen 125 (CA-125) can lead to heterotypic cell adhesion and tumor metastasis within the pleural and peritoneal cavities. Immunotherapeutic strategies targeting mesothelin are being intensively investigated. Here, we report the crystal structures of mesothelin that reveal a compact, right-handed solenoid consisting of 24 short helices and connecting loops. These helices form a 9-layered spiral coil that resembles ARM/HEAT family proteins. Glycan attachments have been identified in the structure for all three predicted N-glycosylation sites and confirmed with samples from cell culture and patient ascites. The structures of full-length mesothelin and its complex with the Fab of MORAb-009 reveal the interaction of the antibody with the complete epitope, which has not been previously reported. The N-terminal half of mesothelin is conformationally rigid, suitable for eliciting specific antibodies, whereas its C-terminal portion is more flexible. The structure of the C-terminal shedding-resistant fragment of mesothelin complexed with a monoclonal antibody 15B6 displays an extended linear epitope and helps explain the protection afforded by the antibody for the shedding sites.

Abstract 5567: hYP218 CAR-T cells targeting a membrane-proximal epitope of mesothelin are highly effective against mesothelin expressing cancers

Background and Hypothesis: Mesothelin is an attractive target for CAR-T cell therapy since it is highly expressed in many solid tumors but has limited expression on normal human tissues. However, anti-mesothelin CAR-T cells have shown limited efficacy in patients. Since most antibodies to mesothelin bind the membrane distal epitopes we generated antibodies that bind mesothelin in a membrane-proximal region. We hypothesize that CAR-T cells recognizing a membrane proximal epitope on mesothelin will be more efficacious.

Study Design: We developed CAR-T cells targeting a membrane-distal (SS1CAR-T) and a membrane-proximal epitope (hYP218 CAR-T) of mesothelin. Using mesothelin-expressing cancer cell lines, anti-tumor efficacy of CAR-T cells was assessed in vitro by measuring direct killing of tumor cells by the CAR-T cells and quantifying cytokine-release by the CAR-T cells. In vivo anti-tumor efficacy of CAR-T was determined in NSG mice using three different solid tumor models of high-mesothelin expression: ovarian cancer (OVCAR-8), pancreatic cancer (KLM-1), and mesothelioma patient-derived xenograft (NCI-Meso63). Blood and tumor infiltration of CAR-T cells in vivo was determined via flow cytometry analysis.

Results: Upon co-culture with tumor cells with high mesothelin expression (A431-H9, OVCAR-8, KLM-1, H226, NCI-Meso63, NCI-Meso29), hYP218 CAR-T cells killed cancer cells more efficiently than SS1 CAR-T cells, with a 2-4-fold lower ET50 value (Effector to Target ratio for 50% killing of tumor cells). Additionally, compared to SS1 CAR-T cells, hYP218 CAR-T cells secreted significantly higher level of cytokines (IL-2, TNFα, IFNγ) in a co-culture with tumor cells. In three solid tumor models, single treatment of tumor-bearing mice with hYP218 CAR-T cells lead to improved tumor response and survival compared to SS1 CAR-T, with complete regression of OVCAR-8 and NCI-Meso63 tumors. Compared to SS1 CAR-T cells, higher hYP218 CAR-T cell infiltration was detected both in the blood and tumors isolated from hYP218 CAR-T treated mice seven days post-treatment.

Conclusion: We demonstrate that hYP218 CAR-T cells targeting a membrane-proximal epitope of mesothelin are more potent than similar CAR-T cells targeting a membrane distal epitope. Increased accumulation of hYP218 CAR-T cells in the tumor may explain their increased efficacy. These results support its clinical development to treat patients with mesothelin expressing cancers.

Citation Format: Sakshi Tomar, Jingli Zhang, Nan Li, Ira Pastan, Mitchell Ho, Raffit Hassan. hYP218 CAR-T cells targeting a membrane-proximal epitope of mesothelin are highly effective against mesothelin expressing cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5567.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of lung cancer and mesothelioma

Immunotherapy has transformed lung cancer care in recent years. In addition to providing durable responses and prolonged survival outcomes for a subset of patients with heavily pretreated non-small cell lung cancer (NSCLC), immune checkpoint inhibitors (ICIs)— either as monotherapy or in combination with other ICIs or chemotherapy—have demonstrated benefits in first-line therapy for advanced disease, the neoadjuvant and adjuvant settings, as well as in additional thoracic malignancies such as small-cell lung cancer (SCLC) and mesothelioma. Challenging questions remain, however, on topics including therapy selection, appropriate biomarker-based identification of patients who may derive benefit, the use of immunotherapy in special populations such as people with autoimmune disorders, and toxicity management. Patient and caregiver education and support for quality of life (QOL) is also important to attain maximal benefit with immunotherapy. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). This CPG represents an update to SITC’s 2018 publication on immunotherapy for the treatment of NSCLC, and is expanded to include recommendations on SCLC and mesothelioma. The Expert Panel drew on the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for lung cancer and mesothelioma, including diagnostic testing, treatment planning, immune-related adverse events, and patient QOL considerations. The evidence- and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers using immunotherapy to treat patients with lung cancer or mesothelioma.

Highly active CAR T cells that bind to a juxtamembrane region of mesothelin and are not blocked by shed mesothelin

SignificanceMesothelin (MSLN) is a cell-surface protein that is a popular target for antibody-based therapies. We have identified shed MSLN as a major obstacle to successful antibody therapies and prepared a monoclonal antibody that inhibits shedding and makes very active CAR T cells whose activity is not blocked by shed MSLN and merits further preclinical development.

Development of highly effective anti-mesothelin hYP218 Chimeric Antigen Receptor T cells with increased tumor infiltration and persistence for treating solid tumors

Mesothelin targeting CAR T cells have limited activity in patients. In this study, we sought to determine if efficacy of anti-mesothelin CAR T cells is dependent on the mesothelin epitopes that are recognized by them. To do so, we developed hYP218 (against membrane-proximal epitope) and SS1 (against membrane-distal epitope) CAR T cells. Their efficacy was assessed in vitro using mesothelin positive tumor cell lines and in vivo in NSG mice with mesothelin expressing ovarian cancer (OVCAR-8), pancreatic cancer (KLM-1) and mesothelioma patient-derived (NCI-Meso63) tumor xenografts. Persistence and tumor infiltration of CAR T cells was determined using flow cytometry. hYP218 CAR T cells killed cancer cells more efficiently than SS1 CAR T cells, with 2-4-fold lower ET50 value (Effector to Target ratio for 50% killing of tumor cells). In mice with established tumors, single intravenous administration of hYP218 CAR T cells lead to improved tumor response and survival compared to SS1 CAR T cells, with complete regression of OVCAR-8 and NCI-Meso63 tumors. Compared to SS1 CAR T cells, there was increased peripheral blood expansion, persistence, and tumor infiltration of hYP218 CAR T cells in the KLM-1 tumor model. Persistence of hYP218 CAR T cells in treated mice led to anti-tumor immunity when rechallenged with KLM-1 tumor cells. Our results demonstrate that hYP218 CAR T cells, targeting mesothelin epitope close to cell membrane, are very effective against mesothelin positive tumors and are associated with increased persistence and tumor infiltration. These results support its clinical development to treat patients with mesothelin expressing cancers.

Anetumab ravtansine versus vinorelbine in patients with relapsed, mesothelin-positive malignant pleural mesothelioma (ARCS-M): a randomised, open-label phase 2 trial

BACKGROUND

Few treatment options exist for second-line treatment of malignant pleural mesothelioma. We aimed to assess the antibody-drug conjugate anetumab ravtansine versus vinorelbine in patients with unresectable locally advanced or metastatic disease overexpressing mesothelin who had progressed on first-line platinum-pemetrexed chemotherapy with or without bevacizumab.

METHODS

In this phase 2, randomised, open-label study, done at 76 hospitals in 14 countries, we enrolled adults (aged ≥18 years) with unresectable locally advanced or metastatic malignant pleural mesothelioma, an Eastern Cooperative Oncology Group performance status of 0-1, and who had progressed on first-line platinum-pemetrexed chemotherapy with or without bevacizumab. Participants were prospectively screened for mesothelin overexpression (defined as 2+ or 3+ mesothelin membrane staining intensity on at least 30% of viable tumour cells by immunohistochemistry) and were randomly assigned (2:1), using an interactive voice and web response system provided by the sponsor, to receive intravenous anetumab ravtansine (6·5 mg/kg on day 1 of each 21-day cycle) or intravenous vinorelbine (30 mg/m2 once every week) until progression, toxicity, or death. The primary endpoint was progression-free survival according to blinded central radiology review, assessed in the intention-to-treat population, with safety assessed in all participants who received any study treatment. This study is registered with ClinicalTrials.gov, NCT02610140, and is now completed.

FINDINGS

Between Dec 3, 2015, and May 31, 2017, 589 patients were enrolled and 248 mesothelin-overexpressing patients were randomly allocated to the two treatment groups (166 patients were randomly assigned to receive anetumab ravtansine and 82 patients were randomly assigned to receive vinorelbine). 105 (63%) of 166 patients treated with anetumab ravtansine (median follow-up 4·0 months [IQR 1·4-5·5]) versus 43 (52%) of 82 patients treated with vinorelbine (3·9 months [1·4-5·4]) had disease progression or died (median progression-free survival 4·3 months [95% CI 4·1-5·2] vs 4·5 months [4·1-5·8]; hazard ratio 1·22 [0·85-1·74]; log-rank p=0·86). The most common grade 3 or worse adverse events were neutropenia (one [1%] of 163 patients for anetumab ravtansine vs 28 [39%] of 72 patients for vinorelbine), pneumonia (seven [4%] vs five [7%]), neutrophil count decrease (two [1%] vs 12 [17%]), and dyspnoea (nine [6%] vs three [4%]). Serious drug-related treatment-emergent adverse events occurred in 12 (7%) patients treated with anetumab ravtansine and 11 (15%) patients treated with vinorelbine. Ten (6%) treatment-emergent deaths occurred with anetumab ravtansine: pneumonia (three [2%]), dyspnoea (two [1%]), sepsis (two [1%]), atrial fibrillation (one [1%]), physical deterioration (one [1%]), hepatic failure (one [1%]), mesothelioma (one [1%]), and renal failure (one [1%]; one patient had 3 events). One (1%) treatment-emergent death occurred in the vinorelbine group (pneumonia).

INTERPRETATION

Anetumab ravtansine showed a manageable safety profile and was not superior to vinorelbine. Further studies are needed to define active treatments in relapsed mesothelin-expressing malignant pleural mesothelioma.

FUNDING

Bayer Healthcare Pharmaceuticals.

Meningiomas in Patients With Malignant Pleural Mesothelioma Harboring Germline BAP1 Mutations

BAP1 is a tumor suppressor gene implicated in DNA repair and cell growth. Individuals with germline BAP1 mutations are at a significantly increased risk for developing many different cancers including malignant mesothelioma, uveal melanomas, cutaneous melanomas and renal clear cell carcinomas. Meningiomas with absent BAP1 expression have been reported to be more aggressive and present often with rhabdoid features. Here, we report the co-occurrence of pleural mesotheliomas and meningiomas in patients with germline BAP1 mutations. We describe the cancer history, family pedigrees, clinical management, and outcomes of four BAP1 germline mutation carrier families with a history of malignant mesothelioma and meningioma.

Phase 2 Study of Olaparib in Malignant Mesothelioma and Correlation of Efficacy With Germline or Somatic Mutations in BAP1 Gene

Introduction

PARP inhibition may enhance antitumor responses in BAP1-associated mesothelioma by inducing synthetic lethality.

Methods

A single-center, nonrandomized, phase 2 trial was conducted, in which patients with refractory mesothelioma were given olaparib 300 mg twice daily in a 21-day cycle until disease progression or intolerable toxicity. The primary objective was to determine the objective response rate on the basis of somatic or germline mutation status of DNA repair genes. The secondary objectives were to assess safety and tolerability and to determine progression-free survival (PFS) and overall survival (OS). Whole-exome sequencing was performed on blood and tumor.

Results

A total of 23 previously treated patients with pleural and peritoneal mesothelioma were enrolled and treated (germline BAP1, n = 4; germline MRE11A, n = 1; somatic BAP1, n = 8 mutations). There was one (4%) partial response, 18 (78%) with stable disease at 6 weeks, and four (17%) with progressive disease. The median overall PFS and OS were 3.6 months (95% confidence interval [CI]: 2.7–4.2 mo) and 8.7 months (95% CI: 4.7 mo–not estimable), respectively. The median PFS of germline BAP1 mutants (n = 4) was 2.3 months (95% CI: 1.3–3.6 mo) versus 4.1 months (95% CI: 2.7–5.5 mo) for wild-type (n = 19; p = 0.019). The median OS was 4.6 months (95% CI: 3.1–4.9 mo) for germline BAP1 mutation versus 9.6 months (95% CI: 5.5 mo–not estimable) in no germline mutation (p = 0.0040). Olaparib was safe with no new safety concerns.

Conclusions

Olaparib has limited activity in previously treated mesothelioma including patients with BAP1 mutations. Germline BAP1 mutations were associated with decreased PFS and OS.

Modifications to Hepatopancreatobiliary surgical services during COVID-19 partial lockdown in a hospital in northern Malaysia

Maintaining hepatopancreatobiliary (HPB) services during the initial phase of a pandemic in a state referral hospital for COVID-19 presents a few challenges, especially when a nationwide, government-issued partial lockdown is in enforcement. We describe the adaptations to our practice to maintain the services whilst ensuring safety of patients and staff, by postponing non-urgent clinic cases, grouping our staff to two mutually exclusive teams that work on alternate shifts and selecting HPB operative cases according to the modified Risk Urgency Decision Matrix.

Abstract CT105: Preliminary safety and efficacy of gavocabtagene autoleucel (gavo-cel, TC-210), a T cell receptor fusion construct (TRuC™), in patients with treatment refractory mesothelin overexpressing solid tumors

Background: Mesothelin overexpression is present in over 80,000 patients/year with either malignant mesothelioma (MPM), ovarian cancer, cholangiocarcinoma, or non-small cell lung cancer (NSCLC) in the U.S. alone. We are testing a novel genetically engineered anti-mesothelin TRuC™ T cell therapy called gavo-cel (TC-210) in a Phase 1 study in treatment refractory patients with any of the four aforementioned cancers (NCT03907852).

Methods: Gavo-cel was engineered by transducing T cells with a lentiviral vector encoding for an anti-mesothelin llama-derived single domain antibody fused to the CD3epsilon subunit using a flexible glycine serine sequence. Upon translation, gavo-cel TRuCs integrate and reprogram intact TCR complexes to recognize tumor surface mesothelin in an HLA-independent manner. Eligibility criteria required demonstration of mesothelin overexpression on tumors (≥50% of tumor cells expressing 2+ or 3+ staining by IHC) at a central laboratory. Gavo-cel dose escalation proceeded following a modified 3+3 schema. TC-210 expansion and serum cytokine levels were serially measured.

Results: Seven patients (6 MPM, 1 ovarian) received a single gavo-cel intravenous infusion at the initial dose of 5x107/m2 either alone (dose level [DL] 0, n=1) or following lymphodepletion (LD) (DL1, n=6) with fludarabine (30mg/m2/day x4) and cyclophosphamide (600mg/m2/day x3). The median age was 69 years (range, 36-84) and the median number of prior therapies was 5 (range, 2-9). Four patients had received ≥4 lines of therapy, including immune checkpoint inhibitors (n=5), the anti-mesothelin ADC anetumab ravtansine (n=1), and anti-mesothelin mRNA CAR-T (n=1). Four patients required bridging therapy. No on-target/off-tumor toxicities or neurotoxicity events of any grade were observed. Grade (gr) ≥3 treatment emergent AEs occurred in 2 (29%) patients with MPM treated at DL1: 1 with gr3 CRS, and 1 with gr3 CRS, gr3 pneumonitis and gr5 fungal sepsis (unrelated to gavo-cel). CRS and pneumonitis events resolved with tocilizumab and corticosteroids. Grade 3 pneumonitis was considered a DLT, resulting in DL1 cohort expansion to 6 patients. At data cut-off date (November 8, 2020), 6 patients have been followed for &gt;3 months, including 4 followed through month 6. The disease control rate was 100%. All patients experienced target lesion regression by CT: median 61% (range, 5-75%). Three (43%) patients (2 with mesothelioma and 1 with ovarian cancer) had a partial response by RECIST v1.1 criteria, including 1 achieving a complete metabolic response. After a median follow-up of 6.5 months, the median OS at 6 months was (86%). The addition of LD increased TC-210 peak expansion and persistence, with cells being detected up to 30 days post infusion in peripheral blood.

Conclusion: Intravenous systemic administration of gavo-cel was generally safe and resulted in three of seven patients having objective partial response. Dose escalation is ongoing at 1x108/m2. Updated clinical and translational data will be presented.

Citation Format: David S. Hong, Melissa Johnson, Janos L. Tanyi, Lauren MacMullen, Robert Tighe, Lizzy Jalbert, Viera P. Muzithras, Kevin Zikaras, Alfonso Quintas Cardama, Raffit Hassan. Preliminary safety and efficacy of gavocabtagene autoleucel (gavo-cel, TC-210), a T cell receptor fusion construct (TRuC™), in patients with treatment refractory mesothelin overexpressing solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT105.

Abstract 667: Genomic and transcriptomic profiling of malignant mesothelioma patients identifies gene signatures predictive of survival and response to immuno and chemotherapy

Background

Malignant mesothelioma (MM) is an aggressive cancer with limited treatment options and poor prognosis. Malignant pleural mesothelioma comprises 80% of the cases and has worse outcome than malignant peritoneal mesothelioma. An in-depth knowledge of genetic, transcriptomic and immunogenic events involved in MM is critical for successful development of prognostics and therapeutic modalities.

Methods

We performed whole-exome sequencing of germline and tumors of 122 patients with pleural (n=59), peritoneal (n=61) and tunica vaginalis (n=2) mesothelioma, and RNA-sequencing of 100 tumors to identify pathogenic variants, somatic mutational signatures, and prognostic gene expression signatures, predictive of patient survival and tumor response to therapies. We validated our findings using the TCGA and Bueno et al. mesothelioma datasets.

Results

The important findings from this study include:

a) Key somatic mutational signatures are associated with DNA repair pathways and BRCA1 associated protein-1 (BAP1) is the most commonly mutated gene (~13% with germline mutation).

b) We identified a set of 48 genes, a “mesothelioma prognostic signature”, whose high expression level is associated with poor survival (Cox regression, FDR &lt; 0.1). These genes are enriched for genes related to cell cycle and DNA repair. This signature is highly predictive of patient survival in two other independent, pleural mesothelioma cohorts: TCGA (Hazard ratio (HR) = 2.6, P = 6.94e-10) and Bueno et al. mesothelioma dataset (HR = 1.49, P = 4.34e-07), after controlling for age and gender.

c) Among the 48 genes, the expression of CCNB1 is highly predictive of patient survival suggesting its important role in MM, possibly via its involvement in the CDK1-CCNB1-CCNF complex (HR = 2.54, P = 1.89e-08 for TCGA; HR = 1.40, P = 1.65e-05 for Bueno et al. dataset).

d) Using a synthetic lethality (SL) based precision-oncology computational framework for analyzing the patients' transcriptomic data, we were able to accurately predict response to an anti-PD1 immune checkpoint inhibitor and combination therapies with pemetrexed (chemotherapy) in mesothelioma patients. The SL profiles successfully predicted the overall patient-response observed across targeted, immuno- and chemotherapies in 11 independent mesothelioma clinical trials (Spearman's ρ = 0.64, P = 0.0348). This is the first analysis shown to successfully predict overall patient-response for various treatments within a cancer type.

Conclusions

By analyzing the tumor genomic and transcriptomics data of a large cohort of MM patients, we identify gene expression prognostic markers predictive of patient survival and response to therapy, both as independent signatures and via their SL interactions. These findings lay a basis for the future development of personalized therapy approaches for mesothelioma patients.

Citation Format: Nishanth Ulhas Nair, Qun Jiang, Jun S. Wei, Vikram A. Misra, Betsy Morrow, Leandro C. Hermida, Joo Sang Lee, Idrees Mian, Jingli Zhang, Manjistha Sengupta, Javed Khan, Eytan Ruppin, Raffit Hassan. Genomic and transcriptomic profiling of malignant mesothelioma patients identifies gene signatures predictive of survival and response to immuno and chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 667.

Enhanced efficacy of mesothelin-targeted immunotoxin LMB-100 and anti-PD-1 antibody in patients with mesothelioma and mouse tumor models

LMB-100 is an immunotoxin targeting the cell surface protein mesothelin, which is highly expressed in many cancers including mesothelioma. Having observed that patients receiving pembrolizumab off protocol after LMB-100 treatment had increased tumor responses; we characterized these responses and developed animal models to study whether LMB-100 made tumors more responsive to antibodies blocking programmed cell death protein 1 (PD-1). The overall objective tumor response in the 10 patients who received PD-1 inhibitor (pembrolizumab, 9; nivolumab, 1) after progression on LMB-100 was 40%, and the median overall survival was 11.9 months. Of the seven evaluable patients, four had objective tumor responses, including one complete response and three partial responses, and the overall survival for these patients was 39.0+, 27.7, 32.6+, and 13.8 months. When stratified with regard to programmed death ligand 1 (PD-L1) expression, four of five patients with tumor PD-L1 expression had objective tumor response. Patients with positive tumor PD-L1 expression also had increased progression-free survival (11.3 versus 2.1 months, P = 0.0018) compared with those lacking PD-L1 expression. There was no statistically significant difference in overall survival (27.7 versus 6.8 months, P = 0.1). LMB-100 caused a systemic inflammatory response and recruitment of CD8⁺ T cells in patients' tumors. The enhanced antitumor effects with LMB-100 plus anti-PD-1 antibody were also observed in a human peripheral blood mononuclear cell-engrafted mesothelioma mouse model and a human mesothelin-expressing syngeneic lung adenocarcinoma mouse model. LMB-100 plus pembrolizumab is now being evaluated in a prospective clinical trial for patients with mesothelioma.

POS1276 LONG TERM OUTCOME OF MULTIPLE ULTRASOUND GUIDED SUPRASCAPULAR NERVE BLOCK IN TREATMENT OF FROZEN SHOULDER IN DIABETIC PATIENTS

Background:

Frozen shoulder is prevalent among diabetic patients, and usually has aggressive course, with more tendency to be bilateral and resistant to treatment. Suprascapular nerve block (SSNB) is used with increasing frequency by anesthetists and rheumatologists in the management of frozen shoulder. We previously introduced a protocol of nine injections for SSNB with better short term outcome than single SSNB injection (1). Long term outcome of SSNB in management of frozen shoulder is still not detected.

Objectives:

To evaluate the long term effect of multiple (nine) ultrasound guided supra-scapular nerve block in treatment of diabetic frozen shoulder.

Methods:

A retrospective cohort study followed up 40 diabetic patients who received a course of ultrasound guided multiple supra-scapular nerve block (9 injections) on 2014. In this study we retrospectively assessed the patients from previously recorded data at a mean duration of 6 years after completing the 9 injection course SSNB clinically by measuring the shoulder active range of motion (using a goniometer in three planes: abduction, internal, and external rotation). Visual analogue scale and Functional assessment by shoulder pain and disability index (SPADI).

Results:

Thirty four patients (85% of original cohort) completed the long term follow up.

The patients were 19 (55.9%) females, 60.6 y mean age, and the mean of disease duration was 85.6 months. The majority of patients (33 patients 97.05%) continues improvement and gained within normal complete range of motions in all directions and excellent grades of shoulder function (Table 1).

Table 1.Clinical ParametersAt base lineAt 4 monthsLast follow up at (72months±4)**P valueSPADI pain score (100)(68.8 ± 0.5)a(10.3 ± 7.4)b(0.9±1.9)c0.00*SPADI disability score (100)(69.2 ± 7.7)a(6.25 ± 2.25)b(0.4±0.8)c0.00*SPADI total (100)(69.1 ± 8.5)a(8.15 ± 5.4)b(1.1±0.9)c0.00*Patient global assessment (100)(90.2 ± 8.2)a(8.2 ± 4.2)b(0.4±2.1)c0.00*Night pain (100)(55.4±10.2)a(10.3 ± 4.9)b(2.3±1.1)c0.00*Abduction (180°)(77.5 ± 4.7)a(170.3 ± 10.3)b(174.2±6.2)b0.00*External rotation (100 °)(46 ± 12.6)a(80.1 ± 10.2)b(86.4±10.3)b0.00*Internal rotation (70 °)(34.5 ± 2.4)a(55.4 ± 10.1)b(60.2±9.5)b0.00*

* P <0.05 there was a statistical significant difference

•A,b,c--- the alphabet of different symbols ---means a significant statistical difference between groups

SPADI: shoulder pain and disability index

Conclusion:

The multiple injection courses for supra-scapular nerve block has an excellent long term efficacy as treatment of diabetic frozen shoulder. This method should be the treatment of choice in patients of diabetic frozen shoulder who do not respond to physiotherapy.

References:

[1]Mortada, M. A., Ezzeldin, N., Abbas, S. F., Ammar, H. A. & Salama, N. A. Multiple versus single ultrasound guided suprascapular nerve block in treatment of frozen shoulder in diabetic patients. J. Back Musculoskelet. Rehabil. 30, 537–542 (2017).

Disclosure of Interests:

None declared

Phase I study of mesothelin-targeted immunotoxin LMB-100 in combination with tofacitinib in patients with advanced pancreatobiliary cancer

3051

Background: LMB-100 recombinant immunotoxin consists of a mesothelin-binding Fab for targeting a modified Pseudomonas exotoxin A payload to tumors. Previous clinical trials demonstrated that almost all patients formed anti-drug-antibodies (ADAs) to LMB-100 that made administration beyond cycle 2 ineffective. Tofacitinib is an oral JAK inhibitor that prevented formation of ADAs against a closely related immunotoxin in pre-clinical studies. The primary objective of the dose escalation cohort was assessment of safety and tolerability of LMB-100 given with tofacitinib to patients with mesothelin-expressing solid tumors. The primary objective of the expansion cohort was to determine whether co-administration of tofacitinib delays formation of neutralizing LMB-100 ADAs. Methods: Patients (n = 13) with pancreatic adenocarcinoma and other mesothelin-expressing solid tumors (n = 3; cholangiocarcinoma, appendix, cystadenocarcinoma) were treated for up to 3 cycles with LMB-100 as a 30-minute infusion on days 4, 6, and 8 at two dose levels (100 and 140 mcg/kg) and co-treated with oral tofacitinib for the first 10 days of the cycle (10 mg BID). Results: Dose level 1 of LMB-100 was started at 100 mcg/kg one dose level below the single agent MTD. Dose escalation to 140 mcg/kg (dose level 2) resulted in DLTs in 2 of the 3 patients treated: grade 3 cardiac toxicity and grade 4 hyponatremia, both attributed to capillary leak syndrome. Ultimately, 7 patients were treated at dose level 1 without DLTs and 100 mcg/kg was chosen as the LMB-100 dose for the expansion cohort. The last of 6 patients treated in the expansion cohort developed grade 4 pericardial effusion leading to early closure of the study for toxicity. No objective responses were seen. Of the 8 patients who received two cycles of treatment at MTD, 4 met prespecified criteria for ADA prevention, and 2 patients who went on to receive cycle 3 had detectable LMB-100 plasma drug levels after administration. Conclusions: LMB-100 was unable to be co-administered safely with tofacitinib. ADA formation was prevented in 2 patients through 3 cycles, a rare occurrence. Clinical trial information: NCT04034238.

In Vitro and In Vivo Comparison of 3,2-HOPO Versus Deferoxamine-Based Chelation of Zirconium-89 to the Antimesothelin Antibody Anetumab

Introduction: [²²⁷Th]Th-3,2-HOPO-MSLN-mAb, a mesothelin (MSLN)-targeted thorium-227 therapeutic conjugate, is currently in phase I clinical trial; however, direct PET imaging using this conjugate is technically challenging. Thus, using the same MSLN antibody, we synthesized 3,2-HOPO and deferoxamine (DFO)-based zirconium-89 antibody conjugates, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb, respectively, and compared them in vitro and in vivo.

Methods: [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb were evaluated in vitro to determine binding affinity and immunoreactivity in HT29-MSLN and PDX (NCI-Meso16, NCI-Meso21) cells. For both the zirconium-89 conjugates, in vivo studies (biodistribution/imaging) were performed at days 1, 3, and 6, from which tissue uptake was determined.

Results: Both the conjugates demonstrated a low nanomolar binding affinity for MSLN and >95% immunoreactivity. In all the three tumor types, biodistribution of [⁸⁹Zr]Zr-DFO-MSLN-mAb resulted in higher tumor uptake(15.88-28-33%ID/g) at all time points compared with [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb(7–13.07%ID/g). [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb femur uptake was always higher than [⁸⁹Zr]Zr-DFO-MSLN-mAb, and imaging results concurred with the biodistribution studies.

Conclusions: Even though the conjugates exhibited a high binding affinity for MSLN, [⁸⁹Zr]Zr-DFO-MSLN-mAb showed a higher tumor and lower femur uptake than [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb. Nevertheless, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb could be used to study organ distribution and lesion uptake with the caveat of detecting MSLN-positive bone lesions. Clinical trial (NCT03507452).

Malignant mesothelioma: Advances in immune checkpoint inhibitor and mesothelin-targeted therapies

Malignant mesothelioma is an aggressive cancer with a poor prognosis and limited treatment options. For many years, the only US Food and Drug Administration-approved first-line treatment for unresectable mesothelioma was pemetrexed plus cisplatin. However, the recent approval of nivolumab plus ipilimumab as frontline treatment for patients with pleural mesothelioma marks a significant milestone for the treatment of this disease. In this review, the authors describe recent advances in therapeutic strategies for the treatment of patients with advanced, unresectable mesothelioma, highlighting the emerging use of immunotherapy and mesothelin-targeted therapies for the management of malignant mesothelioma.

Emergency Laparotomy in a COVID-19 patient with acute abdomen

We describe here the first laparotomy involving a COVID-19 patient in Malaysia. A 60-year-old man screened positive for SARS-CoV-2 in March 2020 and developed acute abdomen in the ward in Hospital Sultanah Bahiyah, Kedah. He underwent laparotomy and cholecystectomy for gangrenous cholecystitis. All personnel adhered to infectious control precautions, donning full personal protective equipment (PPE) throughout the surgery. Post-operatively, due to raised septic parameters, he was carefully diagnosed with and treated empirically for superimposed bacterial sepsis instead of cytokine release syndrome, with confirmed blood culture of Klebsiella pneumoniae. Patient was discharged well later. None of the staff involved in his care developed COVID-19 infection.

Phase I study of mesothelin-targeted immunotoxin LMB-100 in combination with tofacitinib in persons with pancreatobiliary cancer or other mesothelin expressing solid tumors

TPS452

Background: LMB-100 recombinant immunotoxin consists of a mesothelin-binding Fab for targeting with a modified Pseudomonas exotoxin A payload. Formation of anti-drug antibodies (ADAs) is thought to contribute significantly to limited clinical efficacy of LMB-100 seen in prior clinical trials. Most patients develop clinically meaningful ADAs after 1-2 cycles of LMB-100, resulting in rapid neutralization of LMB-100 during subsequent cycles and undetectable plasma drug levels. Tofacitinib is an oral Janus Kinase-1 and -3 (JAK) inhibitor approved by the FDA for the treatment of rheumatoid arthritis and ulcerative colitis. Pre-clinical studies have shown that tofacitinib can prevent the formation of ADAs against recombinant immunotoxin (Onda et al. Journal of Immunology 2014), and that co-administration of tofacitinib with LMB-100 increases immunotoxin serum half- life in mice and anti-tumor efficacy (Simon et al. JCI Insight 2019). We hypothesize that co-administration of tofacitinib with LMB-100 will prevent or delay the formation of high titer ADAs to LMB-100, such that 2 effective cycles of immunotoxin can be administered to patients. Methods: This phase I clinical trial consists of a dose escalation phase using 3+3 design to determine the maximum tolerated dose (MTD) of LMB-100 that can be administered with tofacitinib in participants (n = 18 max) with mesothelin-expressing solid tumors, followed by a dose expansion phase at the MTD for participants (n = 15) with pancreatic adenocarcinoma or extrahepatic cholangiocarcinoma. The primary objective of the expansion phase is to determine whether co-administration of tofacitinib delays formation of neutralizing anti-LMB-100 ADAs for cycle 2 of treatment as measured by LMB-100 plasma drug levels. A positive outcome will be reached if percent of participants achieving threshold LMB-100 drug levels during cycle 2 increases from 50% to 80% (83.6% probability if >10 of 15 evaluable participants meet this milestone). Plasma drug levels during cycle 3 will also be analyzed as a secondary endpoint. Key inclusion criteria include adults with histologically confirmed previously treated solid tumor malignancies. Participants will receive tofacitinib 10 mg twice daily on days 1-10 and LMB-100 at 65, 100, or 140 mcg/kg on days 4, 6 and 8 of a 21-day cycle. The dose escalation phase has been completed and enrollment onto dose expansion phase is ongoing. Clinical trial information: NCT04034238.

UHRF1 Is a Novel Druggable Epigenetic Target in Malignant Pleural Mesothelioma

INTRODUCTION

Ubiquitin-like with plant homeodomain and ring finger domains 1 (UHRF1) encodes a master regulator of DNA methylation that has emerged as an epigenetic driver in human cancers. To date, no studies have evaluated UHRF1 expression in malignant pleural mesothelioma (MPM). This study was undertaken to explore the therapeutic potential of targeting UHRF1 in MPM.

METHODS

Microarray, real-time quantitative reverse transcription-polymerase chain reaction, immunoblot, and immunohistochemistry techniques were used to evaluate UHRF1 expression in normal mesothelial cells (NMCs) cultured with or without asbestos, MPM lines, normal pleura, and primary MPM specimens. The impact of UHRF1 expression on MPM patient survival was evaluated using two independent databases. RNA-sequencing, proliferation, invasion, and colony formation assays, and murine xenograft experiments were performed to evaluate gene expression and growth of MPM cells after biochemical or pharmacologic inhibition of UHRF1 expression.

RESULTS

UHRF1 expression was significantly higher in MPM lines and specimens relative to NMC and normal pleura. Asbestos induced UHRF1 expression in NMC. The overexpression of UHRF1 was associated with decreased overall survival in patients with MPM. UHRF1 knockdown reversed genomewide DNA hypomethylation, and inhibited proliferation, invasion, and clonogenicity of MPM cells, and growth of MPM xenografts. These effects were phenocopied by the repurposed chemotherapeutic agent, mithramycin. Biochemical or pharmacologic up-regulation of p53 significantly reduced UHRF1 expression in MPM cells. RNA-sequencing experiments exhibited the pleiotropic effects of UHRF1 down-regulation and identified novel, clinically relevant biomarkers of UHRF1 expression in MPM.

CONCLUSIONS

UHRF1 is an epigenetic driver in MPM. These findings support the efforts to target UHRF1 expression or activity for mesothelioma therapy.

Clinical implications of conventional cytogenetics, fluorescence in situ hybridization (FISH) and molecular testing in chronic myeloid leukaemia patients in the tyrosine kinase inhibitor era - A review

Chronic myeloid leukaemia (CML) provides an illustrative disease model for both molecular pathogenesis of cancer and rational drug therapy. Imatinib mesylate (IM), a BCR-ABL1 targeted tyrosine kinase inhibitor (TKI) drug, is the first line gold standard drug for CML treatment. Conventional cytogenetic analysis (CCA) can identify the standard and variant Philadelphia (Ph) chromosome, and any additional complex chromosome abnormalities at diagnosis as well as during treatment course. Fluorescence in situ hybridization (FISH) is especially important for cells of CML patients with inadequate or inferior quality metaphases or those with variant Ph translocations. CCA in conjunction with FISH can serve as powerful tools in all phases of CML including the diagnosis, prognosis, risk stratification and monitoring of cytogenetic responses to treatment. Molecular techniques such as reverse transcriptase-polymerase chain reaction (RT-PCR) is used for the detection of BCR-ABL1 transcripts at diagnosis whereas quantitative reverse transcriptase-polymerase chain reaction (qRTPCR) is used at the time of diagnosis as well as during TKI therapy for the quantitation of BCR-ABL1 transcripts to evaluate the molecular response and minimal residual disease (MRD). Despite the excellent treatment results obtained after the introduction of TKI drugs, especially Imatinib mesylate (IM), resistance to TKIs develops in approximately 35% - 40% of CML patients on TKI therapy. Since point mutations in BCR-ABL1 are a common cause of IM resistance, mutation analysis is important in IM resistant patients. Mutations are reliably detected by nested PCR amplification of the translocated ABL1 kinase domain followed by direct sequencing of the entire amplified kinase domain. The objective of this review is to highlight the importance of regular and timely CCA, FISH analysis and molecular testing in the diagnosis, prognosis, assessment of therapeutic efficacy, evaluation of MRD and in the detection of BCR-ABL1 kinase mutations which cause therapeutic resistance in adult CML patients.

AB0177 RHEUMATOID ARTHRITIS SAUDI DATABASE (RASD): A SINGLE CENTER EXPERIENCE

Background:

National Registries are essential to direct current practice and design appropriate management strategies1. Rheumatoid arthritis (RA) registries in the middle east and north Africa remain scarcely represented2.

Objectives:

Our objective is to describe the Saudi RA population and to compare the findings to internationally reported data.

Methods:

This is a cross sectional, analytical study that was conducted at Doctor Soliman Fakeeh Hospital (DSFH). The study ran from December of 2014 and concluded in December of 2018 using a pool of 433 patients. Inclusion criteria included adults older than 18 years of age who fulfilled the 2010 American College of Rheumatology criteria for diagnosis of RA3. Data were collected from patients and entered in a specially designed program for this registry. They included main demographic details,, lag times to final disease diagnosis. Disease Activity Score-28-C Reactive Protein (DAS-28-CRP) was calculated on presentation and on subsequent visits with intervals ranging from three to six months between them. Multiple regression model was used to assess the predictors of disease activity. We charted the lines of medications given, including conventional and biologic disease modifying antirheumatic drugs (DMARDs), following treat to target strategies4.

Results:

Out of 430 patients, 76.68% were female, while only 23.32% were male and the mean age was found to be 49.26 years with SD±11.

At initial presentation, 45.5% had demonstrated active disease (moderate or high disease activity) based on DAS-28-CRP scores while 54.5% were in remission or low disease activity. Out of the total number of clinic visitors, 330 had regular follow ups for more than 1 year while 103 patients were either irregularly visiting the rheumatology clinic or had lost follow up. The remission rates after 1 year had increased to 79.7% (263 patients), while 9.7% (32 patients) had low disease activity and no patients had sustained high disease activity at the end of follow up. It was also found that the female gender, higher Health Assessment Questionnaire-Disability Index (HAQ-DI) and a longer lag1/lag2 period were associated with higher disease activity in our population. Biologic medications had been used by 129 patients (29.7%) while conventional DMARDs were given to 304 patients (70.3%).

Conclusion:

We described a population of RA patients in a single center in SA. We detected higher remission rates at one year of follow up. This could be attributed to many factors, including good referral systems and treat to target strategies with easier access to biologic medications.

References:

[1]Singh JA, Saag KG, Bridges SL Jr, Akl EA, Bannuru RR, Sullivan MC, Vaysbrot E, McNaughton C, Osani M, Shmerling RH, Curtis JR, Furst DE, Parks D, Kavanaugh A, O’Dell J, King C, Leong A, Matteson EL, Schousboe JT, Drevlow B, Ginsberg S, Grober J, St Clair EW, Tindall E, Miller AS, McAlindon T. 2015 American College of Rheumatology Guideline for the Treatment of Rheumatoid Arthritis.Arthritis Rheumatol.2016 Jan;68(1):1-26.

[2]Smolen, Josef S., et al. “EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2013 update.”Annals of the rheumatic diseases73.3 (2014): 492-509.

[3]Saag KG, Teng GG, Patkar NM, Anuntiyo J, Finney C, Curtis JR, et al. American College of Rheumatology 2008 recommendations for the use of nonbiologic and biologic disease-modifying antirheumatic drugs in rheumatoid arthritis.Arthritis Rheum2008;59: 762–84.

[4]Hussain W, Noorwali A, Janoudi N. From symptoms to diagnosis: an observational study of the journey of rheumatoid arthritis patients in Saudi Arabia.Oman Med J.2016;31(1):29.

Disclosure of Interests:

Rola Hassan Grant/research support from: Pfizer pharmaceuticals, Mohamed Cheikh Grant/research support from: Pfizer pharmaceuticals, Hani Almoallim Grant/research support from: Pfizer pharmaceuticals, Hanan Faruqui Grant/research support from: Pfizer pharmaceuticals, Reem AlQuraa Grant/research support from: Pfizer pharmaceuticals, Ayman Eissa Grant/research support from: Pfizer pharmaceuticals, Aous Alhazmi Grant/research support from: Pfizer pharmaceuticals, Nahid Janoudi Grant/research support from: Pfizer pharmaceuticals

Phase II study of olaparib in malignant mesothelioma (MM) to correlate efficacy with germline and somatic mutations in DNA repair genes

9054

Background: BRCA1 associated protein 1 ( BAP1), a nuclear deubiquitinase involved in DNA double-strand break repair is frequently mutated in MM. Because poly(ADP-ribose) polymerase inhibitors (PARPIs) induce synthetic lethality in BRCA1/2 mutant cancers, we sought to evaluate efficacy of olaparib in patients with MM and correlate it with pathogenic germline and somatic mutations in DNA repair genes. Methods: Phase II single-center study (NCT03531840) enrolled patients with advanced pleural or peritoneal mesothelioma who had progressed on prior therapies, age >18 years, ECOG performance status <1, adequate organ and bone marrow function. Olaparib 300mg was given twice daily orally in 3 week cycles until disease progression or toxicity. Efficacy was assessed by CT scan every 6 weeks using RECIST criteria. Whole exome sequencing (WES) was performed on blood and tumor samples to identify pathogenic germline and somatic mutations in DNA repair genes. Primary objective was to determine response rate based on germline or somatic mutation status of DNA repair genes. Results: Between July 2018 to May 2019, 23 patients were enrolled, 15 pleural and 8 peritoneal MM [14 male; median age 63 (range 41-75 years); median number of prior treatments 3 (range 1-5)]. Median olaparib cycles received was 4 (2-21). WES to identify pathogenic mutations in the germline and tumor was performed in 23 and 17 patients respectively. Four patients had germline BAP1, 1 germline MRE11A, and 5 had somatic BAP1 mutations. Of 22 evaluable patients, 1(4%) had partial response (PR), 17 (77%) had stable disease at 6 weeks and 4 (18%) had progressive disease. Patient with PR had a germline mutation in MRE11A. Median progression free survival (PFS) and overall survival (OS) for all patients was 3.4 months (95% CI: 2.7 – 4.8 months) and 8.1 months (95% CI: 4.5 months – not estimable) respectively. Median PFS of germline BAP1 mutant patients (n = 4) was 2.3 months (95% CI: 1.3 – 3.6 months) compared to 4.1 months (95% CI: 2.7 – 5.5 months) for BAP1wild type patients (n = 18;P = 0.026). Median OS was 4.6 months (95% CI: 3.1 – 4.9 months) for patients with germline BAP1 mutation versus not reached for those without germline BAP1 mutation (P = 0.0058). The most common side effects of olaparib were anemia (16%), lymphopenia (24%), nausea (14%), and increased creatinine (9%). Conclusions: Olaparib has limited anti-tumor activity in previously treated MM patients including those with germline or somatic BAP1 mutations. Presence of germline BAP1 mutations was associated with decreased PFS and OS. Clinical trial information: NCT03531840.

Feasibility and preliminary safety and efficacy of first-in-human intraperitoneal delivery of MCY-M11, anti-human-mesothelin CAR mRNA transfected into peripheral blood mononuclear cells, for ovarian cancer and malignant peritoneal mesothelioma

3014

Background: MCY-M11 is a mesothelin-targeting chimeric antigen receptor (CAR) therapy made by a non-viral, mRNA-based platform, for rapid ( < 1 day) CAR manufacturing. We are conducting a phase I dose escalation trial in ovarian cancer and malignant peritoneal mesothelioma (MPM) (NCT03608618). Methods: MCY-M11 are fresh, non-expanded, autologous peripheral blood mononuclear cells (PBMCs) transfected by flow electroporation with mRNA encoding a human anti-mesothelin CAR. Following a 3+3 design, patients are treated in dose level (DL) escalating cohorts (DL1 1.0 x 107, DL2 5.0 x 107, DL3 1.0 x 108, DL4 5.0 x 108 cells/dose), in one cycle of weekly x 3 doses, intraperitoneal (ip) without preconditioning chemotherapy. Results: By January 2020, CP-M11-101 study successfully completed DL1 and DL2 without safety concerns. Based on 11 patients treated in DL1, DL2 and DL3, ip infusion of MCY-M11 is safe and well tolerated. No infusion-related adverse events and no dose limiting toxicities (DLTs) have occurred. No neurotoxicity has been observed. Most reported treatment-related adverse events have been Grades 1-2 per NCI CTCAE. One patient in DL3 presented with G2 pericarditis, fever and transient neutropenia clinically assessed as related SAEs, that resolved without further complications. These events were assessed as on-target off-tumor effects and possibly G1 cytokine release syndrome (CRS). Two unrelated SAEs (G2 confusion in a patient in DL2; G3 enterocutaneous fistula in a patient in DL3) were reported. These 2 patients have been replaced as they did not complete the evaluation period (3 weekly infusions and the DLT 43 day follow up). There have been no treatment-related discontinuations or deaths. Three patients in DL2 showed stable disease (SD) by RECIST 1.1 at the end of the DLT period. Of them, 1 completed the study and did not participate in additional follow up, 1 remained in SD 6 months, and 1 remained in SD 2 months. In DL3, 1 patient remains in SD at 2 months, and evaluation is pending for the other 2 patients. Enrollment is ongoing. Conclusions: Feasibility of 1-day manufacturing of MCY-M11 for ip delivery is demonstrated. Treatment has been safe. Initial SD observed in DL2 and DL3 with one-cycle infusions is encouraging and supports exploration of additional strategies such as the addition of preconditioning chemotherapy and multiple cycles to increase efficacy. Clinical trial information: NCT03608618 .

Phase I study of mesothelin-targeted immunotoxin LMB-100 given as a long infusion with or without nab-paclitaxel

3553

Background: LMB-100 recombinant immunotoxin consists of a mesothelin-binding Fab for targeting a modified Pseudomonas exotoxin A payload. Previous Phase 1 clinical testing of a 30-minute LMB-100 “short” infusion format identified a serum half-life of ~1 hour. Pre-clinical data suggested that extending infusion time could improve anti-tumor efficacy by increasing tumor cell duration of exposure to LMB-100. The primary objective of this study was to determine the safety and tolerability of administering LMB-100 in a long infusion format over 24-48 hours alone or with nab-paclitaxel chemotherapy in patients with mesothelin-expressing solid tumors. Methods: Patients (n = 15) with pancreatic adenocarcinoma and other mesothelin-expressing solid tumors (n = 3; mesothelioma, colon, and ampullary cancers) treated on 3 dose levels received long infusion of LMB-100 (65 or 100 mcg/kg/day) for 24 hour on Days 1 and 4 (n = 6) or 48 hour on Day 1 (n = 9) with or without a loading dose (40 mcg/kg over 30 minutes) for up to 2 cycles. In the second arm, patients (n = 5) with pancreatic adenocarcinoma were treated with LMB-100 over 24 hours on Day 1 concurrently with nab-paclitaxel (125 mg/m2) for up to 3 cycles. Results: DLT of proteinuria (grade 3) in one patient and acute kidney injury (grade 1) in one patient were observed amongst patients receiving 100 mcg/kg/day over 48 hours and 24 hours, respectively. No objective responses were seen but all patients receiving nab-paclitaxel had > 50% decrease in CA 19-9. Patients at all single agent dose levels (8 of 10 evaluable) developed high titer anti-drug antibodies (ADAs) against LMB-100. Those with ADAs (8 of 8) had undetectable cycle 2 peak plasma LMB-100 concentration. Development of high titer ADAs occurred more frequently with long infusion than seen previously with “short” infusion LMB-100. Most long infusion patients (19 of 20) developed increased serum IL-6 within 24 hours of LMB-100 infusion. However, the systemic inflammatory response to LMB-100 (as measured by increased serum CRP) which occurs in most “short” infusion patients was not observed. Conclusions: Long infusion format LMB-100 is generally well tolerated but immunogenicity limits treatment to 1 effective cycle. No anti-tumor efficacy of the single agent was observed. Clinical trial information: NCT02810418 .

18F-FDG PET Assessment of Malignant Pleural Mesothelioma: Total Lesion Volume and Total Lesion Glycolysis-The Central Role of Volume

Cancer survival is related to tumor volume. ¹⁸F-FDG PET measurement of tumor volume holds promise but is not yet a clinical tool. Measurements come in 2 forms: the first is total lesion volume (TLV) based on the number of voxels in the tumor, and the second is total lesion glycolysis (TLG), which is the TLV multiplied by the average SUL (i.e., SUV normalized for lean mass) of the tumor (SUL_average). In this study, we measured tumor volume in patients with malignant pleural mesothelioma (MPM). Methods: A threshold-based program in Interactive Data Language was developed to measure tumor volume in ¹⁸F-FDG PET images. Nineteen patients with MPM were studied before and after 2 cycles (6 wk) of chemoimmunotherapy. Measurements included TLV, TLG, the sum of the SULs in the tumor (SUL_total, a measure of total ¹⁸F-FDG uptake), and SUL_average Results: Baseline TLV ranged from 11 to 2,610 cm³ TLG ranged from 32 to 8,552 cm³ g/mL and correlated strongly with TLV. Although tumor volumes ranged over 3 orders of magnitude, SUL_average stayed within a narrow range of 2.4-5.3 units. Thus, TLV was the major component of TLG, whereas SUL_average was a minor component and was essentially constant. Further evaluation of SUL_average showed that in this cohort its 2 components, SUL_total and TLV, changed in parallel and were strongly correlated (r = 0.99, P < 0.01). Thus, whether the tumors were large or small, ¹⁸F-FDG uptake as measured by SUL_total was proportional to the TLV. Conclusion: TLG equals TLV multiplied by SUL_average, essentially TLV multiplied by a constant. Thus TLG, commonly considered a measure of metabolic activity in tumors, is also in this cohort a measure of tumor volume. The constancy of SUL_average is due to the fact that ¹⁸F-FDG uptake is proportional to tumor volume. Thus, in this study, ¹⁸F-FDG uptake was also a measure of volume.

Is Procalcitonin more superior to hs-CRP in the diagnosis of infection in diabetic foot ulcer?

INTRODUCTION

Procalcitonin (PCT) has recently emerged as a marker for diagnosing infection. This study aimed to compare the performance of PCT and other infection markers in diagnosing infected diabetic foot ulcer (IDFU).

MATERIALS AND METHODS

A total of 128 diabetic patients with foot ulcers were recruited and divided into two groups, consisting of 73 patients in the IDFU group and 55 in the non-infected diabetic foot ulcer (NIDFU). The severity of infection in IDFU patients was graded based on the Infectious Disease Society of America-International Working Group on the Diabetic Foot classification. Blood samples from all the patients were collected for measurement of PCT, high sensitivity C-reactive protein (hs-CRP) and white cell count (WBC). The area under the receiver operating curves (AUC) were then constructed and analysed.

RESULTS

PCT, hs-CRP and WBC levels were significantly higher in the IDFU group compared to NIDFU with hs-CRP demonstrated the highest AUC (0.91; p <0.001) followed by PCT (0.814; p < 0.001) and lastly WBC (0.775; p < 0.001). The best cut off value, sensitivity and specificity for the presence of infection in diabetic foot, were 3.47 mg/dL, 80% and 89% for hs-CRP, 0.11 ng/ml, 70% and 87% for PCT and 11.8x109/L, 60% and 90% for WBC. All the infection markers showed significant positive correlations with infection severity of DFU.

CONCLUSION

This study showed that hs-CRP is a more sensitive marker for diagnosing IDFU. Although PCT is useful in differentiating IDFU from NIDFU, the use of PCT is not necessary as it adds little value to the current practice.

First-in-Human, Multicenter, Phase I Dose-Escalation and Expansion Study of Anti-Mesothelin Antibody-Drug Conjugate Anetumab Ravtansine in Advanced or Metastatic Solid Tumors

PURPOSE

This phase I study, which to our knowledge is the first-in-human study of this kind, investigates the safety, tolerability, pharmacokinetics, and clinical activity of anetumab ravtansine, an antibody–drug conjugate of anti-mesothelin antibody linked to maytansinoid DM4, in patients with advanced, metastatic, or recurrent solid tumors known to express the tumor-differentiation antigen mesothelin.

PATIENTS AND METHODS

This phase I, open-label, multicenter, dose-escalation and dose-expansion study of anetumab ravtansine enrolled 148 adult patients with multiple solid tumor types. Ten dose-escalation cohorts of patients with advanced or metastatic solid tumors (0.15-7.5 mg/kg) received anetumab ravtansine once every 3 weeks, and 6 expansion cohorts of patients with advanced, recurrent ovarian cancer or malignant mesothelioma received anetumab ravtansine at the maximum tolerated dose once every 3 weeks, 1.8 mg/kg once per week, and 2.2 mg/kg once per week.

RESULTS

Forty-five patients were enrolled across the 10 dose-escalation cohorts. The maximum tolerated dose of anetumab ravtansine was 6.5 mg/kg once every 3 weeks or 2.2 mg/kg once per week. Thirty-two patients were enrolled in the 6.5 mg/kg once-every-3-weeks, 35 in the 1.8 mg/kg once-per-week, and 36 in the 2.2 mg/kg once-per-week expansion cohorts. The most common drug-related adverse events were fatigue, nausea, diarrhea, anorexia, vomiting, peripheral sensory neuropathy, and keratitis/keratopathy. There were no drug-related deaths. Anetumab ravtansine pharmacokinetics were dose proportional; the average half-life was 5.5 days. Among 148 patients with mesothelioma or ovarian, pancreatic, non–small-cell lung, and breast cancers, 1 had a complete response, 11 had partial responses, and 66 had stable disease. High levels of tumor mesothelin expression were detected in patients with clinical activity.

CONCLUSION

Anetumab ravtansine exhibited a manageable safety and favorable pharmacokinetic profile with encouraging preliminary antitumor activity in heavily pretreated patients with mesothelin-expressing solid tumors. The results allowed for the determination of recommended doses, schedules, and patient populations for anetumab ravtansine in phase II studies.

Emerging Treatments for Malignant Pleural Mesothelioma: Where Are We Heading?

Malignant pleural mesothelioma (MPM) is an uncommon but aggressive and treatment resistant neoplasm with low survival rates. In the last years we assisted to an exponential growth in the appreciation of mesothelioma pathobiology, leading several new treatments to be investigated both in the early stage of the disease and in the advanced setting. In particular, expectations are now high that immunotherapy will have a leading role in the next years. However, caution is required as results from phase II studies in MPM were often not replicated in larger, randomized, phase III trials. In this review, we describe the most promising emerging therapies for the treatment of MPM, discussing the biological rationale underlying their development as well as the issues surrounding clinical trial design and proper selection of patients for every treatment.