Winters, Jeffrey L.

2565 Background: Mesothelin (MSLN) is overexpressed in mesothelioma and other solid tumors making it the focus of multiple targeted therapies, including antibody drug conjugates (ADCs), T cell receptor (TCR) fusion constructs, and chimeric antigen receptor T-cell (CAR-T) products. However, the clinical efficacy of these treatments remains limited. We hypothesize that soluble MSLN (sMSLN) in the plasma binds to MSLN-targeted therapies before reaching the tumor. Our study aimed to evaluate the effects of sMSLN on a MSLN-targeting antibody, anetumab, and explore methods to reduce sMSLN. Methods: Exploratory analysis in NCT03126630: sMSLN testing was performed on blood samples from participants enrolled in NCT03126630 at the Molecular Targets Core Lab, National Cancer Institute. The median was used to categorize high and low levels of sMSLN. Survival was estimated with the Kaplan-Meier method and compared between groups with the log rank test. Anetumab immunoprecipitation: Anetumab was covalently coupled to Dynabeads at 5 µg per mg of beads to immunoprecipitate MSLN from two plasma samples. Assays were performed in duplicate. Therapeutics plasma exchange (TPE):Whole blood samples were collected before and after one plasma volume of TPE with albumin as the replacement fluid in patients undergoing routine TPE for various medical conditions, such as autoimmune diseases and hyperviscosity syndromes. Plasma levels of sMSLN were measured with an ELISA assay in matched pre- and post-TPE plasma samples. Results: We obtained sMSLN levels from 40 patients enrolled in NCT03126630. For patients treated with both anetumab ravtansine and pembrolizumab, median progression free survival (PFS) was shorter in the high sMSLN group (5 months) vs the low sMSLN group (12 months). For patients treated with pembrolizumab alone, PFS was similar for patients with high and low sMSLN (4 vs 3.4 months). Anetumab significantly reduced the concentration of sMSLN in plasma samples as detected by MSLN ELISA (p<0.05), demonstrating that sMSLN can bind to and sequester anetumab. Next, we evaluated TPE as a mechanism to reduce sMSLN. We obtained pre- and post-TPE plasma samples from 15 patients undergoing routine TPE for various medical conditions. TPE consistently reduced sMSLN (p<0.05) with an average decrease of 43.6% or 15.4 ng/mL. Conclusions: We found that high sMSLN levels are associated with shorter PFS for anetumab ravtansine, but not pembrolizumab. Additionally, anetumab binds to sMSLN in the plasma, which suggests that sMSLN can sequester anti-MSLN antibodies and may limit the efficacy of MSLN-targeted therapies. High levels of sMSLN could potentially be used as a biomarker to select which patients should not receive MSLN-targeting therapies. Furthermore, our results indicate that sMSLN reduction is feasible with TPE. Decreasing sMSLN could restore the activity of MSLN-targeted therapies.

Abstract Purpose We describe the case of a 22-year-old male who developed thyroid storm necessitating therapeutic plasma exchange (TPE). The patient’s past medical history was complicated by epilepsy, for which he took lacosamide. Little evidence was available to guide lacosamide dosing during TPE. Because of an exacerbation of the patient’s underlying epilepsy in the context of the thyroid storm, we conducted therapeutic medication monitoring of lacosamide concentrations to guide management. Summary We arranged for measurement of the lacosamide concentration immediately before TPE (5.1 μg/mL) and 2.5 hours after the initial measurement (3.4 μg/mL) to determine the amount of lacosamide removed by TPE. Utilizing population pharmacokinetic parameters, we calculated the expected concentration and compared this to the measured concentration. The difference between these values was used to determine the percentage removed via TPE compared to the expected post-TPE concentration. We found that one TPE session removed an additional 20% of serum lacosamide. Conclusion TPE appeared to remove an additional 20% of lacosamide when compared to the expected post-TPE concentration.

AbstractAABB hosted the Blood Center Executive Summit on 20 October 2019 during the AABB Annual Meeting in San Antonio, Texas. The session was sponsored by the Commonwealth Transfusion Foundation, a nonprofit, private foundation whose mission is to inspire and champion research and education that optimizes clinical outcomes in transfusion medicine and ensures a safe and sustainable blood supply for the United States. The Summit focused on the intersection of blood centers and plasma centers. Presenters and attendees explored existing and needed data, regulatory requirements, risks and benefits of different donor models, and future direction of the plasma community and blood centers. The Summit also identified priority issues that warrant further investigation and provide opportunities to drive progress. Introductory remarks provided context for the Summit presentations. Debra BenAvram, FASAE, CAE, Chief Executive Officer, AABB (Bethesda, Maryland), noted that during the past year, she and other AABB staff have had many discussions with blood center executives on key issues and challenges. In these talks, many executives requested that AABB provide programming specifically for this member segment. The Summit is a direct result of those requests, and the AABB supports a fruitful discussion as well as important and actionable next steps. Kevin Belanger, DHS, MS, MT(ASCP)SBB, President and Chief Executive Officer of the Shepeard Community Blood Center (Evans, Georgia), observed that he and his colleagues have seen a decrease in the donor base and, at the same time, an increase in plasma centers. He also noted that the resulting discussions about competition and donor compensation have been muted. The Summit provides a forum for a broad, open discussion that can be the start of something important. As chair of the Summit planning committee, he thanked both panelists and audience members for participating. Bob Carden, Chief Executive Officer of the Commonwealth Transfusion Foundation (Richmond, Virginia), who moderated the Summit, joined BenAvram and Belanger in welcoming participants to the day's presentations. He emphasized the need for data and noted that one outcome of the day would be a list of potential research projects that could be pursued and considered for funding.

Abstract Background Bevacizumab is commonly used to manage cerebral edema associated with brain tumors. However, its long half-life poses challenges for patients requiring urgent surgery due to wound complications. We present a case of utilizing therapeutic plasma exchange (TPE) to remove bevacizumab in a patient with recurrent glioblastoma requiring urgent surgery. Methods A 58-year-old male with recurrent glioblastoma, IDH-wildtype, presented with clinical and radiographic concern for ventriculitis requiring urgent wound washout only 4 days after his last bevacizumab infusion. TPE was performed for 3 sessions after surgery using a centrifugation-based cell separator. Replacement fluids included normal serum albumin, normal saline, and fresh frozen plasma. Bevacizumab levels were quantified using an enzyme-linked immunoabsorbent assay before and after each TPE session. Results TPE effectively removed bevacizumab, enabling safe surgery without new complications. Plasma bevacizumab levels decreased from 1087.63 to 145.35 ng/mL (13.4% of original) by the end of the last TPE session. This decline is consistent with nearly 3 half-lives, which compares favorably to the expected timeline of natural decline given the 21-day half-life. Conclusions We report a complex clinical scenario of a patient requiring urgent wound washout 4 days after last bevacizumab infusion for CNS infection. Surgery was successfully performed without new complications with use of TPE to remove bevacizumab immediately following surgery. This case highlights the feasibility of this approach, which may be utilized effectively in patients requiring surgery after having recently received bevacizumab.

AbstractBackgroundIdiopathic inflammatory myopathies (IIMs) encompass many rheumatologic diseases characterized by inflammatory muscle disease, typically unified by proximal muscle weakness. A subset of patients with IIM present with interstitial lung disease (ILD) with identifiable antibodies such as in anti‐synthetase syndrome (AS) with antibodies to aminoacyl‐tRNA synthetases, and clinically amyopathic dermatomyositis (CADM) with anti‐melanoma differentiation‐associated protein 5 (MDA5). Recent case reports demonstrate response to therapeutic plasma exchange (TPE) or column filtration plasmapheresis in IIM with ILD resistant to medical management. We present our experience with eight patients with IIM with ILD undergoing TPE at a large US‐based hospital system.Patient characteristicsEight patients with IIM with ILD were treated with TPE over the last 10 years. The therapy consisted of 5‐7 one plasma volume exchanges every other day to daily. Seven of eight patients had identifiable antibodies.ResultsFollowing completion of TPE, seven of eight demonstrated improvement in pulmonary function despite lack of improvement of pulmonary function with standard therapy.ConclusionIn antibody‐mediated, treatment refractory IIM with ILD, TPE may be a viable intervention. This is a disease for which the role of apheresis is evolving.Clinical trial registrationNot application.

Background Patients with metastatic melanoma rely on PD-(L)1 immunotherapy, but only one-third of patients experience treatment response and all initial responders eventually develop resistance. Tumour-derived extracellular vesicles expressing Programmed death ligand 1 (evPD-L1) and soluble Programmed death ligand 1 (sPD-L1) in peripheral blood of patients with melanoma limit PD-(L)1 immunotherapy and correlate with poor survival. Therapeutic plasma exchange (TPE) removes immunosuppressive evPD-L1 and sPD-L1. We hypothesise that TPE may rescue and restore antimelanoma immunity. Methods In this two-arm study, 60 patients with metastatic melanoma progressing on checkpoint inhibition will be accrued. All patients will undergo radiotherapy on days 1–5 (at least one measurable lesion will not be irradiated) and ongoing checkpoint inhibition on day 8 and every 2–3 weeks per standard of care. Patients with baseline sPD-L1 level of ≥1.7 ng/mL and adequate clinical capacity will be enrolled in the TPE intervention arm and will undergo TPE on days 5–7, in addition to standard of care radiotherapy and immunotherapy. Other patients will remain in the standard of care arm. The primary endpoint of the study is to evaluate safety. Secondary endpoints include kinetics of sPD-L1 and evPD-L1 and clinical response by RECIST (Response Evaluation Criteria in Solid Tumors) criteria. Study registered at ClinicalTrials.gov ( NCT04581382 ). Ethics and dissemination This trial has been approved by the Mayo Clinic Institutional Review Board. It will assess the safety and feasibility of TPE in improving outcomes for PD-(L)1 inhibitor immunotherapy in melanoma. Data will be maintained on a secure database with deidentified patient information. Data will be shared on publication in a peer-reviewed journal without the aid of professional writers. If successful, this trial will lay the ground for phase II studies that will include cancer treated with PD-(L)1 inhibitors which may benefit from TPE such as renal, bladder and lung cancers. Trial registration number NCT04581382 .

AbstractEculizumab is effective for complement-mediated thrombotic microangiopathy (CM-TMA), also known as atypical hemolytic uremic syndrome. Although lifelong therapy had been suggested, discontinuation does not universally lead to relapse. Comprehensive data evaluating risk factors for recurrence following discontinuation are limited. Our aim was to systematically review available literature assessing the role of complement genetic variants in this setting. Reports on CM-TMA and eculizumab withdrawal published before 1 January 2021, were included. Key reasons for patient exclusion were no follow-up after drug withdrawal and patients lacking complement genetic testing. Two-hundred eighty patients from 40 publications were included. Median age was 28 years, and 25 patients had a known history of renal transplant. Complement genetic variants were identified in 60%, most commonly in CFH (n = 59) and MCP/CD46 (n = 38). Of patients with a complement gene variant, 51.3% had ≥1 likely pathogenic/pathogenic variant whereas the remaining had variants of uncertain significance (VUS). Overall relapse rate after therapy discontinuation was 29.6%. Relapse rate was highest among patients with CFH variants and MCP/CD46 variants in canonical splice regions. VUS (P &lt; .001) and likely pathogenic/pathogenic variants (P &lt; .001) were associated with increased relapse. Presence of a renal allograft (P = .009); decreasing age (P = .029); and detection of variants in CFH (P &lt; .001), MCP/CD46 (P &lt; .001), or C3 (P &lt; .001) were all independently associated with relapse after eculizumab discontinuation. Eculizumab discontinuation is appropriate in specific patients with CM-TMA. Caution should be exerted when attempting such a strategy in patients with high risk of recurrence, including a subgroup of patients with MCP/CD46 variants.

AbstractBackgroundChimeric antigen receptor T (CAR‐T) cell successes have encouraged continued clinical study. Apheresis collection of starting material for CAR‐T cell therapy product manufacturing is critical but described approaches suggest variability and clinical guidelines are currently lacking. The goal of this study was to gather and assess variability in apheresis collection descriptions in publicly available CAR T‐cell therapy clinical trials.Study designWe searched clinicaltrials.gov (a publicly available clinical trial database) for “chimeric antigen receptor T cells” on July 01, 2020 and studies accessed July 30, 2020‐August 15, 2020. Data collected included date posted, study characteristics, apheresis mentions (number, location, and context), laboratory parameters and transfusion allowances. Apheresis context was analyzed using a qualitative inductive approach of grounded theory method with open coding. Text was classified into 37 context codes, grouped into 12 categories, and then consolidated into patient, procedure, product, and miscellaneous themes.ResultsApheresis was mentioned 1044 times in 322 (51.9%) of 621 total studies. Laboratory parameters mentioned included white blood cells (100 studies), absolute neutrophil count (220 studies), absolute lymphocyte count (102 studies), CD3+ cell (38 studies), hemoglobin (233 studies, 54 studies specified transfusion allowance), and platelet (269 studies, 48 studies specified transfusion allowance).ConclusionsApheresis collection of CAR‐T cell products is not well‐defined in clinical study descriptions and the context is inconsistent. Laboratory parameters useful for apheresis collection are variably present and do not consistently align with current practices. Further exploration, and clinical guideline development will encourage alignment of apheresis collections for CAR‐T cell products.