INTRODUCTION:Diffuse pleural mesothelioma (DPM) is a lethal malignancy with no approved therapies directly targeting tumor cells. Based on reports that EGFR and MET are frequently expressed in DPM, we sought to systematically assess their co-expression and determine the preclinical activity of amivantamab, a bispecific antibody that targets EGFR and MET. METHODS:We evaluated EGFR and MET expression in patient cohorts and cell lines using transcriptomic analysis, immunohistochemistry, and biochemical assays. The mechanistic actions of amivantamab, including receptor internalization, signaling blockade, and immune-mediated cytotoxicity, were assessed using in vitro co-culture systems with peripheral blood mononuclear cells and natural killer (NK) cells. In vivo efficacy was evaluated in mesothelioma patient-derived xenograft models using immunodeficient mice reconstituted with human NK cells. RESULTS:Transcriptomic and single-cell RNA-sequencing analyses of DPM patient cohorts revealed frequent co-expression of EGFR and MET, predominantly in malignant cells. Immunohistochemical analyses confirmed EGFR and MET protein expression across mesothelioma histologic subtypes. In vitro, amivantamab preferentially bound to DPM cells, inhibited ligand-induced EGFR and MET signaling, and promoted receptor internalization. Co-culture experiments demonstrated that amivantamab induced dose-dependent cytotoxicity through NK cell-mediated antibody-dependent cellular cytotoxicity. In multiple mesothelioma patient-derived xenograft models, the combination of amivantamab and NK cells significantly reduced tumor growth without overt toxicity. CONCLUSIONS:Amivantamab demonstrates robust preclinical antitumor activity in mesothelioma, primarily through innate immune-mediated cytotoxicity associated with EGFR and MET engagement. These findings support the clinical evaluation of bispecific EGFR/MET-targeting antibodies in mesothelioma.

Cell surface mesothelin (MSLN) can be solubilized and released into the systemic circulation. The resulting soluble MSLN (sMSLN) may interfere with therapies targeting surface MSLN. We investigated the effects of sMSLN on anetumab, an antibody-based therapy against MSLN, anetumab ravtansine, an antibody drug conjugate, and mechanisms to decrease sMSLN. Whole blood samples were collected before and after one plasma volume of therapeutic plasma exchange (TPE). sMSLN levels were measured with ELISA assays in matched pre- and post-TPE plasma samples, and anetumab-immunoprecipitated samples. We also used protease inhibitors (PIs) as a mechanism to stabilize surface MSLN, then evaluated the cytotoxic effects of anetumab ravtansine. Our findings indicate that sMSLN sequesters and may impair the efficacy of this anti-MSLN antibody based on results showing that anetumab decreases the concentration of MSLN in plasma (p < 0.05) and reduced cytotoxicity of anetumab ravtansine in the presence of recombinant MSLN in cell lines, a surrogate for sMSLN. TPE consistently reduced sMSLN (p < 0.05) with an average decrease of 43.6% (15.4 ng/mL). Surface MSLN stabilization was inconsistently observed with PIs. Overall, sMSLN could represent a predictive biomarker for MSLN directed therapies. TPE may be more reliable than PIs to reduce sMSLN and ultimately restore sensitivity to these therapies in patients with high sMSLN.

PURPOSE BRAF and MEK inhibitors are standard treatments in histiocytic disorders, such as Erdheim-Chester disease (ECD). Some patients lack MAPK-pathway alterations, making these treatments less effective. METHODS We describe three patients with histiocytic disorders who have novel non-MAPK pathway alterations. These alterations were studied through genomic and in silico analyses when applicable, then treated with off-label medications rationally selected on the basis of genomic alterations. RESULTS Patient 1 had rapidly progressive ECD involving the CNS. A CSF1R in-frame deletion (p.S560_P566del) was identified, and in silico modeling predicted a gain-of-function mutation. This alteration was targeted with pexidartinib, which led to a clinical complete response (CR) within 2 months, and a partial response (PR) on imaging after 3 months. After 15 months, the disease became resistant to pexidartinib and transformed to histiocytic sarcoma. Patient 2 has skin-only involvement of a xanthogranuloma disorder. A KIF5B-FGFR1 fusion was identified on RNA sequencing and targeted with pemigatinib. At 24 months of follow-up, she remains in a clinical PR. Patient 3 has ECD involving the bone marrow, gastrointestinal tract, and subcutaneous tissues. A MEF2C-FLT3 fusion was identified and targeted with sorafenib. He achieved a clinical CR and radiographic PR within 3 months, which has continued for 30 months. CONCLUSION We report three patients with histiocytic disorders harboring novel alterations who had sustained responses to off-label kinase inhibitors specific to their histiocytic disorder. Pathogenic variants outside of the MAPK pathway, including variants of unknown significant, may be targeted with readily available small molecules.

Journal Article Persistent Tumor Mutational Burden (pTMB) May Predict Response to Immune Checkpoint Inhibitors Get access Katherine E R Smith, Katherine E R Smith Department of Oncology, Mayo Clinic, Rochester, MN, United States Address correspondence to this author at: Department of Oncology, 200 1st St SW, Rochester, MN 55905, United States. Email smith.katherine3@mayo.edu. Search for other works by this author on: Oxford Academic Google Scholar Svetomir N Markovic Svetomir N Markovic Department of Oncology, Mayo Clinic, Rochester, MN, United States Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 70, Issue 1, January 2024, Pages 25–26, https://doi.org/10.1093/clinchem/hvad128 Published: 04 January 2024 Article history Received: 17 March 2023 Accepted: 12 April 2023 Published: 04 January 2024

PURPOSE:The mesothelin-targeting antibody-drug conjugate anetumab ravtansine was evaluated in combination with the programmed cell death-1 (PD-1) inhibitor pembrolizumab based on the common expression of mesothelin and reports of activity in mesothelioma. PATIENTS AND METHODS:A phase 1 safety run-in of the combination of anetumab ravtansine (6.5 mg/kg iv q3weeks) and pembrolizumab (200 mg, IV q3weeks) was conducted, followed by a phase 2 randomization to the combination or pembrolizumab alone at medical centers across the United States and Canada in the National Cancer Institute's Experimental Therapeutics Clinical Trials Network. Patients with pleural mesothelioma that expressed mesothelin and had previously received platinum-based therapy were eligible. RESULTS:In phase 1 (n = 12) only one dose limiting toxicity was observed and the rules for dose reduction were not met. In phase 2, there was no difference in the confirmed response rates between the combination group (n = 18, 2 partial responses [PR], 11 %) and the pembrolizumab group (n = 17, 1 PR, 6 %; z = -0.5523, p = 0.29116). The median PFS was 12.2 months (95 % CI 5.1-not evaluable [NE]) for the combination, and 3.9 months for pembrolizumab (95 % CI 2.1-NE)(HR=0.55, p = 0.20). Patients with high baseline levels of soluble mesothelin who received anetumab ravtansine had a median PFS of 5 months. CONCLUSIONS:The numeric difference in PFS between treatment groups was not statistically significant, likely related to a smaller than planned sample size. High levels of soluble mesothelin should potentially be considered to select against the use of mesothelin-targeting therapies in development that are neutralized by soluble mesothelin.

Oncologic viruses (OV) can induce tumor death through both direct oncolysis and immune-mediated destruction. Our study investigates the use of a novel OV with a Vesicular Stomatitis Virus (VSV) vector modified to express interferon-beta (IFN-b) and Tyrosinase Related Protein 1 (TYRP1) (VSV-IFNb-TYRP1). VSV is an attractive vector since humans are not naturally infected with VSV; thus, pre-existing immunity is minimal. IFN-b leads to increased T-cell responses and tumor cell apoptosis, while TYRP1, a melanocyte differentiation antigen, increases immunogenicity of the therapy. We conducted a Phase 1 clinical trial with a 3+3 design in patients with metastatic uveal melanoma. VSV-IFNb-TYRP1 was injected into a liver metastasis under image guidance, then administered on the same day as a single intravenous (IV) infusion. IV doses started at dose level (DL) 1 1 × 1010 TCID50, then escalated to DL2 3 × 10 10, DL3 1 × 1011, and DL4 3 × 1011. The dose delivered intratumorally (IT) varied based on the IV dose. The primary endpoints were safety and maximum tolerated dose (MTD). Efficacy was a secondary endpoint. Correlative studies focused on understanding viral pharmacokinetics (PK) and immunological responses induced by VSV-IFNb-TYRP1 therapy. Twelve patients with previously treated metastatic uveal melanoma were enrolled. Median follow up was 19.1 months. Four DLs were evaluated with one patient at DL4 experiencing dose limiting toxicities (DLTs), including decreased platelet count (grade 3), increased aspartate aminotransferase (AST), and cytokine release syndrome (CRS). Non-DLTs at DL4 were fatigue, fever, CRS, hematological toxicities (decreased platelets and lymphocytes), and AST elevation. Four patients had stable disease (SD) and 8 had progressive disease (PD) as their best response. ELIspot data show that three of the four patients with response to TYRP1 also had a response to gp100, suggesting possible epitope spreading. These four patients received immune checkpoint inhibitor treatment as the next line of therapy, which led to clinical benefit for two patients. Our study evaluated VSV-IFNb-TYRP1 administered via IT and IV routes in a previously treated population of metastatic uveal melanoma patients and found no major safety events. Although there were no clear objective responses to VSV-IFNb-TYRP1, dose-dependent immunogenicity to melanoma antigens was seen. While OV response alone is not sufficient for clinical benefit, the evidence of epitope spreading is encouraging. Future studies of VSV-IFNb-TYRP1 will evaluate combinations with other therapies. Citation Format: Katherine E. Smith, Adam Weisbrod, Carrie Strand, Jacob Allerd, Jose S. Pulido, Alysha Newsom, Lianwen Zhang, Nandakumar Packiriswamy, Heather Montane, Lisa Kottschade, Anastasios Dimou, Yiyi Yan, Markovic Svetomir, Kah Whye Peng, Richard G. Vile, Matthew S. Block, Roxana S. Dronca. Phase I trial of vesicular stomatitis virus expressing human interferon beta and tyrosinase related protein 1 (VSV-IFNb-TYRP1) in metastatic ocular melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT207.

Introduction: Immune-related adverse events (irAEs) due to immune checkpoint inhibitors can have complicated clinical courses. We comprehensively evaluated the timing, trajectory, and incidence of both single and multiple irAEs for NSCLC treated with atezolizumab. Methods: Data were pooled from 2457 patients who participated in the IMpower130, IMpower132, and IMpower150 clinical trials investigating the use of atezolizumab in metastatic NSCLC as part of a chemoimmunotherapy regimen. Longitudinal irAE data with landmark analysis, time-to-onset, changes in grading severity, and occurrence of multiple events were summarized. Results: In general, 1557 patients were treated with atezolizumab and 900 patients were in the control groups. Median follow-up was 32.3 and 23.5 months, respectively. In the atezolizumab group, 753 patients (48.4%) experienced at least one irAE. In the control group, 289 patients (32.1%) experienced at least one nonimmune adverse event that was attributed to an irAE. In the atezolizumab group, the most common irAEs were rash, hepatitis, and hypothyroidism. Furthermore, 13% of the patients experienced two irAEs and 4% experienced three irAEs. Within 5 months of treatment, the cumulative incidence for any irAE was 39.2%. Median time-to-onset varied from 1 to 10 months based on the specific irAE. Grade 1 to 2 irAEs increased in severity for 33% of the patients. Conclusions: We identified dynamic clinical patterns for irAEs in patients treated with atezolizumab, including variations in time-to-onset, incidence of multiple irAEs, and frequency of irAEs increasing in severity. These results can guide clinical management and future reporting of adverse events to enable comprehensive longitudinal analyses.

Introduction Metastatic uveal melanoma (MUM) has a poor prognosis and treatment options are limited. These patients do not typically experience durable responses to immune checkpoint inhibitors (ICIs). Oncolytic viruses (OV) represent a novel approach to immunotherapy for patients with MUM. Methods We developed an OV with a Vesicular Stomatitis Virus (VSV) vector modified to express interferon-beta (IFN-β) and Tyrosinase Related Protein 1 (TYRP1) (VSV-IFNβ-TYRP1), and conducted a Phase 1 clinical trial with a 3 + 3 design in patients with MUM. VSV-IFNβ-TYRP1 was injected into a liver metastasis, then administered on the same day as a single intravenous (IV) infusion. The primary objective was safety. Efficacy was a secondary objective. Results 12 patients with previously treated MUM were enrolled. Median follow up was 19.1 months. 4 dose levels (DLs) were evaluated. One patient at DL4 experienced dose limiting toxicities (DLTs), including decreased platelet count (grade 3), increased aspartate aminotransferase (AST), and cytokine release syndrome (CRS). 4 patients had stable disease (SD) and 8 patients had progressive disease (PD). Interferon gamma (IFNγ) ELIspot data showed that more patients developed a T cell response to virus encoded TYRP1 at higher DLs, and a subset of patients also had a response to other melanoma antigens, including gp100, suggesting epitope spreading. 3 of the patients who responded to additional melanoma antigens were next treated with ICIs, and 2 of these patients experienced durable responses. Discussion Our study found that VSV-IFNβ -TYRP1 can be safely administered via intratumoral (IT) and IV routes in a previously treated population of patients with MUM. Although there were no clear objective radiographic responses to VSV-IFNβ-TYRP1, dose-dependent immunogenicity to TYRP1 and other melanoma antigens was seen.

Background: Biomarkers have the potential to provide clinical guidance, but there is limited data for biomarkers in metastatic hormone sensitive prostate cancer (mHSPC). Methods: We performed a retrospective multicenter review from Winship Cancer Institute at Emory University and Georgia Cancer Center for Excellence at Grady Memorial Hospital (2014-2020) in the United States of America (USA). We collected demographics, disease characteristics, and laboratory data, including complete blood counts (CBC) at the start of upfront therapy. We evaluated overall survival (OS) and progression-free survival (PFS) associated with baseline lab values. Results: 165 patients were included with a median follow-up time of 33.5 months (mo). 105 (63.6%) had Gleason scores of 8-10 and 108 (65.9%) were classified as high-volume disease. 92 patients received upfront docetaxel (55.8%) and 73 received upfront abiraterone (44.2%). Univariate analyses (UVA) and multivariable analyses (MVA) identified worse clinical outcomes (CO) associated with elevated basophils and basophil-to-lymphocyte ratio (BLR). Based on MVA, elevated basophils (defined as >= 0.1, optimal cut) were associated with a hazard ratio (HR) of 3.51 (95% CI 1.65- 7.43, P 0.001) for OS and HR of 1.88 (95% CI 1.05-3.38, P 0.034) for PFS. Our MVA also found that BLR >= 0.0142 was associated with HR 2.11 (95% CI 1.09- 4.10, P 0.028) for OS; however, PFS was not statistically significant. Conclusion: We conclude that elevated baseline basophils and BLR are associated with worse clinical outcomes in mHSPC. Although results require further validation, BLR is a potential prognostic biomarker. (c) 2022 Elsevier Inc. All rights reserved.

Small-cell lung cancer is an aggressive malignancy with poor clinical outcomes, especially for patients diagnosed with extensive stage disease. Historically, platinum-based chemotherapy was the standard of care, which provided an overall survival of 9–11 months.1 Since the 1980s, many attempts were made to improve upon the platinum-doublet without success until 2018, when the addition of immunotherapy to chemotherapy increased overall survival in two large, randomised clinical trials.2–3 The first trial, IMpower133,2 tested the addition of the PD-L1 inhibitor atezolizumab to platinum-based chemotherapy, which improved median overall survival from 10·3 months (95% CI 9·3–11·3) to 12·3 months (10·8–15·9; hazard ratio [HR] 0·70 [95% CI 0·54–0·91]).

52 Background: The landscape of mCSPC treatment changed with the addition of ABA and DOC. The prevalence of AA pts in the trials that led to these approvals was < 10%. We characterized the clinical outcomes (CO) of a cohort of AA pts treated with these agents. Methods: We retrospectively reviewed 51 AA pts with mCSPC treated with ABA or DOC at Grady Memorial Hospital from 2015-2018. The CO included median overall survival (mOS), progression-free survival (mPFS) and PSA response (PSAr) as defined by a ≥ 50% drop in PSA over the 1st 12 weeks of treatment. Cox proportional hazard model and Kaplan-Meier method were used for association with OS and PFS and logistic regression model for PSAr. Results: Median age was 63 years, 64% were grade group 5 and 67% had an ECOG status of 0-1. 82% had high volume disease per CHAARTED; 51% did per LATITUDE. 21 pts received ABA; 30 received DOC. The groups (ABA vs DOC) were balanced except for high volume disease per LATITUDE (28.6 vs. 66.7%) and lymph node metastases (66.7 vs. 96.7%). The DOC cohort received a mean of 5.2 cycles. Median follow-up was 10.3 months (mos). The overall mOS was 37.8 mos, mPFS was 10.3 mos, and PSAr was 89.6%. CO trended toward favoring ABA over DOC but did not differ significantly with a 12-month OS of 100% vs. 81.7% and PFS of 53.7% vs. 35.4%, respectively. Albumin and hemoglobin at baseline were associated with CO (Table). Conclusions: We present the first real world efficacy of ABA and DOC in a cohort of AA pts with mCSPC and found similar outcomes between the two groups. These findings warrant a larger study for validation.[Table: see text]