Unveiling the proteome-wide autoreactome enables enhanced evaluation of emerging CAR-T therapies in autoimmunity.

Given the global surge in autoimmune diseases, it is critical to evaluate emerging therapeutic interventions. Despite numerous new targeted immunomodulatory therapies, comprehensive approaches to apply and evaluate the effects of these treatments longitudinally are lacking. Here, we leveraged advances in programmable-phage immunoprecipitation (PhIP-Seq) methodology to explore the modulation, or lack thereof, of autoantibody profiles, proteome-wide, in both health and disease. Using a custom set of over 730,000 human derived peptides, we demonstrated that each individual, regardless of disease state, possesses a distinct and complex constellation of autoreactive antibodies. For each individual, the set of resulting autoreactivites constituted a unique immunological fingerprint, or "autoreactome," that was remarkably stable over years. Using the autoreactome as a primary output, we evaluated the relative effectiveness of various immunomodulatory therapies in altering autoantibody repertoires. We found that therapies targeting B-Cell Maturation Antigen (BCMA) profoundly altered an individual's autoreactome, while anti-CD19 and CD20 therapies had minimal effects. These data both confirm that the autoreactome is comprised of autoantibodies secreted by plasma cells, and strongly suggest that BCMA or other plasma cell targeting therapies may be highly effective in treating currently refractory autoantibody mediated diseases.

Long-term safety and efficacy of zilucoplan in patients with generalized myasthenia gravis: interim analysis of the RAISE-XT open-label extension study.

Background: Generalized myasthenia gravis (gMG) is a chronic, unpredictable disease associated with high treatment and disease burdens, with a need for more effective and well-tolerated treatments. Objectives: To evaluate the long-term safety, tolerability, and efficacy of zilucoplan in a mild-to-severe, acetylcholine receptor autoantibody-positive (AChR+) gMG population. Design: Ongoing, multicenter, phase III open-label extension (OLE) study. Methods: Eligible patients had completed a qualifying randomized, placebo-controlled phase II or phase III zilucoplan study and received daily, self-administered subcutaneous 0.3 mg/kg zilucoplan. The primary endpoint was incidence of treatment-emergent adverse events (TEAEs). Secondary efficacy endpoints included change from baseline in Myasthenia Gravis Activities of Daily Living (MG-ADL) score. Results: In total, 200 patients enrolled. At the cut-off date (8 September 2022), median (range) exposure to zilucoplan in RAISE-XT was 1.2 (0.11-4.45) years. Mean age at OLE baseline was 53.3 years. A total of 188 (94%) patients experienced a TEAE, with the most common being MG worsening (n = 52, 26%) and COVID-19 (n = 49, 25%). In patients who received zilucoplan 0.3 mg/kg in the parent study, further improvements in MG-ADL score continued through to Week 24 (least squares mean change [95% confidence interval] from double-blind baseline -6.06 [-7.09, -5.03]) and were sustained through to Week 60 (-6.04 [-7.21, -4.87]). In patients who switched from placebo in the parent study, rapid improvements in MG-ADL score were observed at the first week after switching to zilucoplan; further improvements were observed at Week 24, 12 weeks after switching (-6.46 [-8.19, -4.72]), and were sustained through to Week 60 (-6.51 [-8.37, -4.65]). Consistent results were observed in other efficacy endpoints. Conclusion: Zilucoplan demonstrated a favorable long-term safety profile, good tolerability, and sustained efficacy through to Week 60 with consistent benefits in a broad AChR+ gMG population. Additional long-term data will be available in future analyses. Trial registration: ClinicalTrials.gov identifier: NCT04225871 (https://clinicaltrials.gov/ct2/show/NCT04225871).

A Noncanonical CD56dimCD16dim/- NK Cell Subset Indicative of Prior Cytotoxic Activity Is Elevated in Patients with Autoantibody-Mediated Neurologic Diseases.

Neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein Ab disease, and autoimmune myasthenia gravis (MG) are autoantibody-mediated neurologic conditions where autoantibodies can induce Ab-dependent cellular cytotoxicity (ADCC), a NK cell-mediated effector function. However, whether ADCC is a pathogenic mechanism in patients with these conditions has not been confirmed. We sought to characterize circulatory NK cells using functional assays, phenotyping, and transcriptomics to elucidate their role in pathology. NK cells from NMOSD patients and MG patients with elevated disease burden exhibited reduced ADCC and CD56dimCD16hi NK cells, along with an elevated frequency of CD56dimCD16dim/- NK cells. We determined that ADCC induces a similar phenotypic shift in vitro. Bulk RNA sequencing distinguished the CD56dimCD16dim/- population from the canonical CD56dimCD16hi cytotoxic and CD56hiCD16- immunomodulatory subsets, as well as CD56hiCD16+ NK cells. Multiparameter immunophenotyping of NK cell markers, functional proteins, and receptors similarly showed that the CD56dimCD16dim/- subset exhibits a unique profile while still maintaining expression of characteristic NK markers CD56, CD94, and NKp44. Notably, expression of perforin and granzyme is reduced in comparison with CD56dimCD16hi NK cells. Moreover, they exhibit elevated trogocytosis capability, HLA-DR expression, and many chemokine receptors, including CCR7. In contrast with NMOSD and MG, myelin oligodendrocyte glycoprotein Ab disease NK cells did not exhibit functional, phenotypic, or transcriptomic perturbations. In summary, CD56dimCD16dim/- NK cells are a distinct peripheral blood immune cell population in humans elevated upon prior cytotoxic activity by the CD56dimCD16hi NK cell subset. The elevation of this subset in NMOSD and MG patients suggests prior ADCC activity.

Safety and Efficacy of Nipocalimab in Patients With Generalized Myasthenia Gravis: Results From the Randomized Phase 2 Vivacity-MG Study

BACKGROUND AND OBJECTIVES: To evaluate in a phase 2 study the safety and efficacy of IV nipocalimab, a fully human, antineonatal Fc receptor monoclonal antibody, in patients with generalized myasthenia gravis (gMG). METHODS: Patients with gMG with inadequate response to stable standard-of-care (SOC) therapy were randomized 1:1:1:1:1 to receive either IV placebo every 2 weeks (Q2W) or one of 4 IV nipocalimab treatments: 5 mg/kg once every 4 weeks (Q4W), 30 mg/kg Q4W, 60 mg/kg Q2W each for 8 weeks, or a 60 mg/kg single dose, in addition to their background SOC therapy. Infusions (placebo or nipocalimab) were Q2W in all groups to maintain blinding. The primary safety endpoint was incidence of treatment-emergent adverse events (TEAEs), including serious adverse events and adverse events of special interest. The primary efficacy endpoint was change from baseline to day 57 in Myasthenia Gravis-Activities of Daily Living (MG-ADL) total scores. Dose response of change at day 57 was analyzed with a linear trend test over the placebo, nipocalimab 5 mg/kg Q4W, nipocalimab 30 mg/kg Q4W, and nipocalimab 60 mg/kg Q2W groups. RESULTS: Sixty-eight patients (nipocalimab: n = 54; placebo, n = 14) were randomized; 64 patients (94.1%) were positive for antiacetylcholine receptor autoantibodies, and 4 patients (6%) were positive for antimuscle-specific tyrosine kinase autoantibodies. Fifty-seven patients (83.8%) completed treatment through day 57. The combined nipocalimab group compared with the placebo group demonstrated similar incidences of TEAEs (83.3% vs 78.6%, respectively) and infections (33.3% vs 21.4%, respectively). No deaths or discontinuations due to TEAEs and no TEAEs of special interest (grade ≥3 infection or hypoalbuminemia) were observed with nipocalimab treatment. A statistically significant dose response was observed for change from baseline in MG-ADL at day 57 (p = 0.031, test of linear trend). DISCUSSION: Nipocalimab was generally safe, well-tolerated, and showed evidence of dose-dependent reduction in MG-ADL scores at day 57 in this phase 2 study. These results support further evaluation of nipocalimab for the treatment of gMG. TRIAL REGISTRATION INFORMATION: Clinical Trials Registration: NCT03772587; first submitted December 10, 2018; EudraCT Number: 2018-002247-28; first submitted November 30, 2018; date of first patient dosed April 10, 2019. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients with gMG, nipocalimab was well-tolerated, and it did not significantly improve MG-ADL at any individual dose but demonstrated a significant dose response for improved MG-ADL across doses.

Subcutaneous batoclimab in generalized myasthenia gravis: Results from a Phase 2a trial with an open-label extension.

OBJECTIVES: To assess the safety, tolerability, and key pharmacodynamic effects of subcutaneous batoclimab, a fully human anti-neonatal Fc receptor monoclonal antibody, in patients with generalized myasthenia gravis and anti-acetylcholine receptor antibodies. METHODS: A Phase 2a, proof-of-concept, randomized, double-blind, placebo-controlled trial is described. Eligible patients were randomized (1:1:1) to receive once-weekly subcutaneous injections of batoclimab 340 mg, batoclimab 680 mg, or matching placebo for 6 weeks. Subsequently, all patients could enter an open-label extension study where they received batoclimab 340 mg once every 2 weeks for 6 weeks. Primary endpoints were safety, tolerability, and change from baseline in total immunoglobulin G, immunoglobulin G subclasses, and anti-acetylcholine receptor antibodies at 6 weeks post-baseline. Secondary endpoints included changes from baseline to 6 weeks post-baseline for Myasthenia Gravis Activities of Daily Living, Quantitative Myasthenia Gravis, Myasthenia Gravis Composite, and revised 15-item Myasthenia Gravis Quality of Life scores. RESULTS: Seventeen patients were randomized to batoclimab 680 mg (n = 6), batoclimab 340 mg (n = 5), or placebo (n = 6). Batoclimab was associated with significantly greater reductions in total immunoglobulin G and anti-acetylcholine receptor antibodies from baseline to 6 weeks post-baseline than placebo. Reductions in immunoglobulin G subclasses were generally consistent with total immunoglobulin G. While clinical measures showed directionally favorable improvements over time, the study was not powered to draw conclusions about therapeutic efficacy. No safety issues were identified. INTERPRETATION: The safety profile, pharmacodynamics, and preliminary clinical benefits observed in this study support further investigation of subcutaneous batoclimab injections as a potential patient-administered therapy for seropositive generalized myasthenia gravis.

Remission of severe myasthenia gravis after autologous stem cell transplantation.

OBJECTIVE: Myasthenia gravis (MG) is an autoantibody-mediated neuromuscular junction disorder involving the acetylcholine receptors on the motor endplate. The safety and response to high-dose chemotherapy (HDIT) and autologous hematopoietic cell transplantation (HCT) were assessed in a patient with severe refractory MG. METHODS: As part of a pilot study of HDIT/HCT for patients with treatment-resistant autoimmune neurological disorders, a patient with severe refractory MG underwent treatment. After mobilization of hematopoietic stem cells with rituximab, prednisone, and G-CSF, the patient had HDIT consisting of carmustine, etoposide, cytarabine, melphalan, and rabbit antithymocyte globulin, followed by autologous HCT. The effect of treatment on the autoantibody to the acetylcholine receptor (AChR) was assessed. RESULTS: The patient had been diagnosed with AChR antibody-positive MG 14 years before HDIT/HCT and had failed thymectomy, therapeutic plasma exchange, and multiple immunomodulatory agents. The Myasthenia Gravis Foundation of America (MGFA) clinical classification was IVb before HDIT/HCT. She tolerated HDIT/HCT well and started to improve clinically within days of treatment. At both 1 and 2 years after HDIT/HCT, patients remained symptom-free. After HDIT/HCT, AChR-binding autoantibodies persisted, and the relative frequency of immune cell subtypes shifted. INTERPRETATION: HDIT/HCT induced a complete response of disease activity in a patient with severe refractory MG. This response may suggest that a cell-mediated etiology may be a significant contributing factor in refractory MG cases. A phase 2 clinical trial is warranted to establish if HDIT/HCT can be an effective therapy for severe refractory MG and to gain a further understanding of disease pathogenesis.

Plasmapheresis Versus Intravenous Immunoglobulin in Patients With Autoimmune Neuromuscular and Neuro-immunological Conditions.

OBJECTIVES: Plasmapheresis (PLEX) and intravenous immunoglobulin (IVIg) are commonly used to treat autoimmune neuromuscular disorders, including myasthenia gravis, acute inflammatory demyelinating polyradiculoneuropathy, chronic inflammatory demyelinating polyradiculoneuropathy, and other autoimmune neurological disorders. The side effect profiles of these therapies vary, and concern has been raised regarding the safety of PLEX in the elderly population. In this study, we have examined the pattern of PLEX and IVIg use for autoimmune neurological disorders at a single facility and in a national database, focusing on the complications in elderly patients. METHODS: We performed a retrospective chart review of adult patients at our institution receiving PLEX or IVIg for any autoimmune neuromuscular or neuro-immunological disease. Next, we analyzed the National Inpatient Sample database to confirm the trend in IVIg and PLEX use from 2012 to 2018 for a set of neuromuscular and neuro-immunological primary diagnoses. RESULTS: IVIg was overall favored over PLEX. The adverse effects were similar among elderly patients (age ≥65 years) compared with younger patients (<65 years) in our institution, even after adequate matching of patients based on age, sex, and medical history. We examined the National Inpatient Sample dataset and noted increasingly higher frequency of IVIg use, consistent with the findings from our institution or facility. CONCLUSIONS: Both PLEX and IVIg are safe therapeutic choices in adult patients with autoimmune neuromuscular disorders and other neuro-immunological diseases and can be safely administered in the appropriate clinical setting.

Individual myasthenia gravis autoantibody clones can efficiently mediate multiple mechanisms of pathology.

Serum autoantibodies targeting the nicotinic acetylcholine receptor (AChR) in patients with autoimmune myasthenia gravis (MG) can mediate pathology via three distinct molecular mechanisms: complement activation, receptor blockade, and antigenic modulation. However, it is unclear whether multi-pathogenicity is mediated by individual or multiple autoantibody clones. Using an unbiased B cell culture screening approach, we generated a library of 11 human-derived AChR-specific recombinant monoclonal autoantibodies (mAb) and assessed their binding properties and pathogenic profiles using specialized cell-based assays. Five mAbs activated complement, three blocked α-bungarotoxin binding to the receptor, and seven induced antigenic modulation. Furthermore, two clonally related mAbs derived from one patient were each highly efficient at more than one of these mechanisms, demonstrating that pathogenic mechanisms are not mutually exclusive at the monoclonal level. Using novel Jurkat cell lines that individually express each monomeric AChR subunit (α2ßδε), these two mAbs with multi-pathogenic capacity were determined to exclusively bind the α-subunit of AChR, demonstrating an association between mAb specificity and pathogenic capacity. These findings provide new insight into the immunopathology of MG, demonstrating that single autoreactive clones can efficiently mediate multiple modes of pathology. Current therapeutic approaches targeting only one autoantibody-mediated pathogenic mechanism may be evaded by autoantibodies with multifaceted capacity.

The Plasma Cell Infiltrate Populating the Muscle Tissue of Patients with Inclusion Body Myositis Features Distinct B Cell Receptor Repertoire Properties.

Inclusion body myositis (IBM) is an autoimmune and degenerative disorder of skeletal muscle. The B cell infiltrates in IBM muscle tissue are predominantly fully differentiated Ab-secreting plasma cells, with scarce naive or memory B cells. The role of this infiltrate in the disease pathology is not well understood. To better define the humoral response in IBM, we used adaptive immune receptor repertoire sequencing, of human-derived specimens, to generate large BCR repertoire libraries from IBM muscle biopsies and compared them to those generated from dermatomyositis, polymyositis, and circulating CD27+ memory B cells, derived from healthy controls and Ab-secreting cells collected following vaccination. The repertoire properties of the IBM infiltrate included the following: clones that equaled or exceeded the highly clonal vaccine-associated Ab-secreting cell repertoire in size; reduced somatic mutation selection pressure in the CDRs and framework regions; and usage of class-switched IgG and IgA isotypes, with a minor population of IgM-expressing cells. The IBM IgM-expressing population revealed unique features, including an elevated somatic mutation frequency and distinct CDR3 physicochemical properties. These findings demonstrate that some of IBM muscle BCR repertoire characteristics are distinct from dermatomyositis and polymyositis and circulating Ag-experienced subsets, suggesting that it may form through selection by disease-specific Ags.

Addressing Outcome Measure Variability in Myasthenia Gravis Clinical Trials.

An increasing number of clinical trials are enrolling patients with myasthenia gravis (MG). A lack of standardization in the performance of outcome measures leads to confusion among site research teams and is a source of variability in clinical trial data. MGNet, the NIH-supported Rare Disease Clinical Research Network for MG, views standardization of MG outcome measures as a critical need. To address this issue, a group of experts summarized key outcome measures used in MG clinical trials and a symposium was convened to address issues contributing to outcome measure variability. Consensus recommendations resulted in changes to outcome measure instructions and, in some cases, modifications to specific instruments. Recommended changes were posted for public commentary before finalization. Changes to the MG-Activities of Daily Living, MG-Quality of Life-15r, and MG-Impairment Index were limited to adding details to the administration instructions. Recommendations for proper positioning of participants and how to score items that could not be performed because of non-MG reasons were provided for the MG Composite. The Quantitative MG (QMG) score required the most attention, and changes were made both to the instructions and the performance of certain items resulting in the QMG-Revised. The Postintervention Status was believed to have a limited role in clinical trials, except for the concept of minimal manifestation status. As a next step, training materials and revised source documents, which will be freely available to study teams, will be created and posted on the MGNet website. Further studies are needed to validate changes made to the QMG-Revised.

MOGAD patient autoantibodies induce complement, phagocytosis, and cellular cytotoxicity.

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an inflammatory demyelinating CNS condition characterized by the presence of MOG autoantibodies. We sought to investigate whether human MOG autoantibodies are capable of mediating damage to MOG-expressing cells through multiple mechanisms. We developed high-throughput assays to measure complement activity (CA), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and antibody-dependent cellular cytotoxicity (ADCC) of live MOG-expressing cells. MOGAD patient sera effectively mediate all of these effector functions. Our collective analyses reveal that (a) cytotoxicity is not incumbent on MOG autoantibody quantity alone; (b) engagement of effector functions by MOGAD patient serum is bimodal, with some sera exhibiting cytotoxic capacity while others did not; (c) the magnitude of CDC and ADCP is elevated closer to relapse, while MOG-IgG binding is not; and (d) all IgG subclasses can damage MOG-expressing cells. Histopathology from a representative MOGAD case revealed congruence between lesion histology and serum CDC and ADCP, and we identified NK cells, mediators of ADCC, in the cerebrospinal fluid of relapsing patients with MOGAD. Thus, MOGAD-derived autoantibodies are cytotoxic to MOG-expressing cells through multiple mechanisms, and assays quantifying CDC and ADCP may prove to be effective tools for predicting risk of future relapses.

Clinicoserological insights into patients with immune checkpoint inhibitor-induced myasthenia gravis.

To compare the immunopathology of immune checkpoint inhibitor-induced myasthenia gravis (ICI-MG) and idiopathic MG, we profiled the respective AChR autoantibody pathogenic properties. Of three ICI-MG patients with AChR autoantibodies, only one showed complement activation and modulation/blocking potency, resembling idiopathic MG. In contrast, AChR autoantibody-mediated effector functions were not detected in the other two patients, questioning the role of their AChR autoantibodies as key mediators of pathology. The contrasting properties of AChR autoantibodies in these cases challenge the accuracy of serological testing in establishing definite ICI-MG diagnoses and underscore the importance of a thorough clinical assessment when evaluating ICI-related adverse events.

Randomized Double-Blind Placebo-Controlled Trial of the Corticosteroid-Sparing Effects of Immunoglobulin in Myasthenia Gravis.

BACKGROUND AND OBJECTIVES: Myasthenia gravis (MG) is an autoimmune disease characterized by dysfunction at the neuromuscular junction. Treatment frequently includes corticosteroids (CSs) and IV immunoglobulin (IVIG). This study was conducted to determine whether immune globulin (human), 10% caprylate/chromatography purified (IGIV-C) could facilitate CS dose reduction in CS-dependent patients with MG. METHODS: In this randomized double-blind placebo-controlled trial, CS-dependent patients with MG (Myasthenia Gravis Foundation of America Class II-Iva; AChR+) received a loading dose of 2 g/kg IGIV-C over 2 days (maximum 80 g/d) or placebo at week 0 (baseline). Maintenance doses (1 g/kg IGIV-C or placebo) were administered every 3 weeks through week 36. Tapering of CS was initiated at week 9 and continued through week 36 unless the patient worsened (quantitative MG score ≥4 points from baseline). CS doses were increased (based on the current CS dose) in patients who worsened. Patients were withdrawn if worsening failed to improve within 6 weeks or if a second CS increase was required. The primary efficacy end point (at week 39) was a ≥50% reduction in CS dose. Secondary and safety end points were assessed throughout the study and follow-up (weeks 42 and 45). The study results and full protocol are available at clinicaltrials.gov/ct2/show/NCT02473965. RESULTS: The primary end point (≥50% reduction in CS dose) showed no significant difference between the IGIV-C treatment (60.0% of patients) and placebo (63.3%). There were no significant differences for secondary end points. Safety data indicated that IGIV-C was well tolerated. DISCUSSION: In this study, IGIV-C was not more effective than placebo in reducing daily CS dose. These results suggest that the effects of IGIV-C and CS are not synergistic and may be mechanistically different. TRIAL REGISTRATION INFORMATION: The trial was registered on clinicaltrialsregister.eu (EudraCT #: 2013-005099-17) and clinicaltrials.gov (identifier NCT02473965). CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that IVIG infusions in adult patients with MG do not increase the percentage of patients achieving a ≥50% reduction in corticosteroid dose compared with placebo.

Unveiling the autoreactome: Proteome-wide immunological fingerprints reveal the promise of plasma cell depleting therapy.

The prevalence and burden of autoimmune and autoantibody mediated disease is increasing worldwide, yet most disease etiologies remain unclear. Despite numerous new targeted immunomodulatory therapies, comprehensive approaches to apply and evaluate the effects of these treatments longitudinally are lacking. Here, we leverage advances in programmable-phage immunoprecipitation (PhIP-Seq) methodology to explore the modulation, or lack thereof, of proteome-wide autoantibody profiles in both health and disease. We demonstrate that each individual, regardless of disease state, possesses a distinct set of autoreactivities constituting a unique immunological fingerprint, or "autoreactome", that is remarkably stable over years. In addition to uncovering important new biology, the autoreactome can be used to better evaluate the relative effectiveness of various therapies in altering autoantibody repertoires. We find that therapies targeting B-Cell Maturation Antigen (BCMA) profoundly alter an individual's autoreactome, while anti-CD19 and CD-20 therapies have minimal effects, strongly suggesting a rationale for BCMA or other plasma cell targeted therapies in autoantibody mediated diseases.

Myasthenia Gravis in the Setting of Immune Checkpoint Inhibitor Therapy: Practical Considerations and Opinion-Based Approach to Acute Management.

Use of immune checkpoint inhibitors (ICI) is increasing in patients with oncologic disease. Three classes of checkpoint inhibitors exist: anti-PD1 (nivolumab, pembrolizumab), anti-CTLA4 (ipilimumab), and anti-PDL1 (atezolizumab, avelumab, durvalumab). ICI therapy has been used in multiple malignancies including renal cell cancer, non-small-cell lung cancer, and melanoma. These therapies have led to improved oncologic treatment and outcomes in patients but can lead to immune-related or inflammatory adverse effects. Neuromuscular system side effects, particularly at the neuromuscular junction, have been observed, including myasthenia gravis (MG). This narrative review serves to summarize key available information regarding myasthenia gravis in the setting of immune checkpoint inhibitor use including the molecular targets of checkpoint inhibitors, the clinical manifestations of MG in patients with checkpoint inhibitor therapy, and potential treatment options. Studies have shown that the use of checkpoint inhibitor therapy can trigger MG, and that patients with ICI-related MG can have more severe disease. Recognition and understanding of the range of neurologic complications, including neuromuscular disorders, which can be seen with ICI therapy is a critical step toward developing better treatment algorithms and improved clinical outcomes. Future investigations which include deep mechanistic studies to further our understanding of the immunopathologic triggers and predictive markers of ICI-related MG will be important to address the current knowledge gaps.

Reemergence of pathogenic, autoantibody-producing B cell clones in myasthenia gravis following B cell depletion therapy.

Myasthenia gravis (MG) is an autoantibody-mediated autoimmune disorder of the neuromuscular junction. A small subset of patients (<10%) with MG, have autoantibodies targeting muscle-specific tyrosine kinase (MuSK). MuSK MG patients respond well to CD20-mediated B cell depletion therapy (BCDT); most achieve complete stable remission. However, relapse often occurs. To further understand the immunomechanisms underlying relapse, we studied autoantibody-producing B cells over the course of BCDT. We developed a fluorescently labeled antigen to enrich for MuSK-specific B cells, which was validated with a novel Nalm6 cell line engineered to express a human MuSK-specific B cell receptor. B cells (≅ 2.6 million) from 12 different samples collected from nine MuSK MG patients were screened for MuSK specificity. We successfully isolated two MuSK-specific IgG4 subclass-expressing plasmablasts from two of these patients, who were experiencing a relapse after a BCDT-induced remission. Human recombinant MuSK mAbs were then generated to validate binding specificity and characterize their molecular properties. Both mAbs were strong MuSK binders, they recognized the Ig1-like domain of MuSK, and showed pathogenic capacity when tested in an acetylcholine receptor (AChR) clustering assay. The presence of persistent clonal relatives of these MuSK-specific B cell clones was investigated through B cell receptor repertoire tracing of 63,977 unique clones derived from longitudinal samples collected from these two patients. Clonal variants were detected at multiple timepoints spanning more than five years and reemerged after BCDT-mediated remission, predating disease relapse by several months. These findings demonstrate that a reservoir of rare pathogenic MuSK autoantibody-expressing B cell clones survive BCDT and reemerge into circulation prior to manifestation of clinical relapse. Overall, this study provides both a mechanistic understanding of MuSK MG relapse and a valuable candidate biomarker for relapse prediction.

A preliminary, prospective study of peripheral neuropathy and cognitive function in patients with breast cancer during taxane therapy.

Dramatic improvements in cancer survival have occurred in the last decade, but the quality of life for many survivors is compromised due to severe, long-lasting, and often irreversible side effects of chemotherapy. The neurological side effects, chemotherapy induced peripheral neuropathy (CIPN) and cancer related/induced cognitive impairment (CRCI/CICI), are under-recognized and can occur after chemotherapy, immunotherapy, or radiation. The cellular mechanisms underlying these neurological side effects are poorly understood and there are no effective treatments or preventions, other than reduction or termination of cancer therapy. In our preliminary prospective, non-interventional study to examine the side effects of chemotherapy in patients with breast cancer (NCT03872141), patients with breast cancer who received standard of care single agent weekly taxane-based chemotherapy were assessed at baseline, midpoint, and end of treatment for neurological and cognitive changes and for blood levels of potential protein biomarkers (n = 13). CIPN and CRCI both showed an increase in severity with accumulating taxane and these changes were compared to protein alternations over the course of treatment. Using peripheral blood collected from patients (n = 10) during chemotherapy and tested with an antibody array curated by the MD Anderson RPPA Core), we found that 19 proteins were increased, and 12 proteins decreased over 12 weeks of treatment. Among those downregulate were proteins known to be critical for neuronal viability and function including GRB2 (growth factor receptor-bound protein 2) and NCS1 (neuronal calcium sensor 1). Concurrently, proteins associated with apoptosis, including BAK1 (Bcl-1 homologous antagonist/killer), were upregulated. These results support the proposal that CIPN and CRCI increase with increasing taxane exposure, and identified several proteins that are altered with taxane exposure that could be implicated in their pathogenesis. In conclusion, our study provides evidence for progressive neurological changes and the rationale to investigate the molecular basis for these changes with the goal of target identification for mitigation of these neurological side effects.

The clinical need for clustered AChR cell-based assay testing of seronegative MG.

Trial eligibility in myasthenia gravis (MG) remains largely dependent on a positive autoantibody serostatus. This significantly hinders seronegative MG (SNMG) patients from receiving potentially beneficial new treatments. In a subset of SNMG patients, acetylcholine receptor (AChR) autoantibodies are detectable by a clustered AChR cell-based assay (CBA). Of 99 SNMG patients from two academic U.S. centers, 18 (18.2%) tested positive by this assay. Autoantibody positivity was further validated in 17/18 patients. In a complementary experiment, circulating AChR-specific B cells were identified in a CBA-positive SNMG patient. These findings corroborate the clinical need for clustered AChR CBA testing when evaluating SNMG patients.

Heterogeneity of Acetylcholine Receptor Autoantibody-Mediated Complement Activity in Patients With Myasthenia Gravis.

BACKGROUND AND OBJECTIVES: Autoantibodies targeting the acetylcholine receptor (AChR), found in patients with myasthenia gravis (MG), mediate pathology through 3 mechanisms: complement-directed tissue damage, blocking of the acetylcholine binding site, and internalization of the AChR. Clinical assays, used to diagnose and monitor patients, measure only autoantibody binding. Consequently, they are limited in providing association with disease burden, understanding of mechanistic heterogeneity, and monitoring therapeutic response. The objective of this study was to develop a cell-based assay that measures AChR autoantibody-mediated complement membrane attack complex (MAC) formation. METHODS: An HEK293T cell line-modified using CRISPR/Cas9 genome editing to disrupt expression of the complement regulator genes (CD46, CD55, and CD59)-was used to measure AChR autoantibody-mediated MAC formation through flow cytometry. RESULTS: Serum samples (n = 155) from 96 clinically confirmed AChR MG patients, representing a wide range of disease burden and autoantibody titer, were tested along with 32 healthy donor (HD) samples. AChR autoantibodies were detected in 139 of the 155 (89.7%) MG samples through a cell-based assay. Of the 139 AChR-positive samples, autoantibody-mediated MAC formation was detected in 83 (59.7%), whereas MAC formation was undetectable in the HD group or AChR-positive samples with low autoantibody levels. MAC formation was positively associated with autoantibody binding in most patient samples; ratios (mean fluorescence intensity) of MAC formation to AChR autoantibody binding ranged between 0.27 and 48, with a median of 0.79 and an interquartile range of 0.43 (0.58-1.1). However, the distribution of ratios was asymmetric and included extreme values; 16 samples were beyond the 10-90 percentile, with high MAC to low AChR autoantibody binding ratio or the reverse. Correlation between MAC formation and clinical disease scores suggested a modest positive association (rho = 0.34, p = 0.0023), which included a subset of outliers that did not follow this pattern. MAC formation did not associate with exposure to immunotherapy, thymectomy, or MG subtypes defined by age-of-onset. DISCUSSION: A novel assay for evaluating AChR autoantibody-mediated complement activity was developed. A subset of patients that lacks association between MAC formation and autoantibody binding or disease burden was identified. The assay may provide a better understanding of the heterogeneous autoantibody molecular pathology and identify patients expected to benefit from complement inhibitor therapy.