CSU1 Antibody

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Description

Introduction to Barzolvolimab (CSU1 Antibody)

Barzolvolimab is a humanized IgG1 monoclonal antibody that selectively inhibits the KIT receptor tyrosine kinase, a critical regulator of mast cell survival and activation . As a first-in-class mast cell-depleting therapy, it targets the root cause of CSU by reducing mast cell populations responsible for histamine release and chronic inflammation .

Structure and Mechanism of Action

Phase 2 Trial Outcomes (NCT04882757)

  • Population: 320 CSU patients refractory to H1-antihistamines (45% omalizumab-resistant).

  • Dosing: 150 mg or 300 mg subcutaneous injections.

  • Week 12 Results:

    • 71% achieved complete response (UAS7=0) vs 12% placebo (p<0.001).

    • DLQI scores improved by 82% (mean baseline 14.2 → 2.6).

  • Week 52 Durability:

    • 68% maintained UAS7=0 without rescue medications .

Phase 3 EMBARQ-CSU Program

ParameterEMBARQ-CSU1/2 Design
Sample Size915 patients globally
Dosing Arms150 mg Q4W vs 300 mg Q8W vs placebo
Primary EndpointUAS7 reduction at Week 12
Key InclusionUAS7≥16 despite H1-antihistamines
Secondary OutcomesDLQI, ISS7, HSS7, anaphylaxis rates

Mast Cell Depletion Metrics

  • Skin Biopsies: 92% reduction in mast cell density at Week 12 (p<0.0001).

  • Serum Tryptase: Sustained decrease from baseline 8.4 μg/L to 3.1 μg/L (Week 52).

Quality of Life Impact

MetricImprovement RateTimeframe
DLQI ≤1 (no QoL impact)82%Week 52
UCT ≥12 (well-controlled)79%Week 24
Work Productivity Loss87% reductionWeek 12

Comparative Efficacy vs Existing Therapies

TherapyMechanismComplete Response RateQoL Normalization
OmalizumabAnti-IgE38% (Week 24) 61%
BarzolvolimabAnti-KIT71% (Week 52) 82%
LigelizumabAnti-IgE (high-affinity)51% (Week 12) 68%

Future Directions

  • Regulatory Status: Phase 3 completion expected Q4 2026 .

  • Combination Potential: Synergy studies ongoing with anti-IgE biologics .

  • Extended Indications: Phase 2 trials active for chronic inducible urticaria (ColdU, SD) .

Product Specs

Buffer
Preservative: 0.03% Proclin 300
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4
Form
Liquid
Lead Time
Made-to-order (14-16 weeks)
Synonyms
CSU1 antibody; At1g61620 antibody; T25B24.3E3 ubiquitin-protein ligase CSU1 antibody; EC 2.3.2.27 antibody; Protein COP1 SUPPRESSOR 1 antibody; RING-type E3 ubiquitin transferase CSU1 antibody
Target Names
CSU1
Uniprot No.

Target Background

Function
CSU1 is a RING-finger E3 ubiquitin-protein ligase that plays a crucial role in maintaining COP1 homeostasis in darkness. It negatively regulates COP1 protein accumulation by targeting COP1 for ubiquitination and subsequent proteasomal degradation in dark-grown seedlings. Additionally, CSU1 negatively regulates the accumulation of SPA1 protein in the dark.
Database Links

KEGG: ath:AT1G61620

STRING: 3702.AT1G61620.1

UniGene: At.58060

Protein Families
NOSIP family
Subcellular Location
Nucleus. Nucleus speckle.

Q&A

What is the current global utilization pattern of omalizumab for CSU treatment?

According to worldwide survey data from allergists and immunologists, 82% prescribe omalizumab for CSU patients, with higher usage rates among younger practitioners. The primary barriers to prescription include cost (63%) and restricted formulary access (24%). When making treatment decisions, clinicians prioritize drug safety (63%) and potential adverse events (47%) as the most significant factors .

Methodologically, researchers should consider these barriers when designing clinical studies, particularly when comparing omalizumab to emerging therapies. Multi-center international studies should account for regional variations in healthcare systems that may influence omalizumab accessibility.

What assessment tools should researchers use to measure antibody efficacy in CSU clinical trials?

Several validated assessment tools are commonly employed in CSU research:

Assessment ToolUsage RatePrimary Function
UAS7 (Urticaria Activity Score over 7 days)55%Measures disease activity
UCT (Urticaria Control Test)29%Assesses disease control
CU-QoL (Chronic Urticaria Quality of Life)25%Evaluates impact on quality of life
OASIS-DValidated in studiesData extraction from electronic records

These standardized measures should be incorporated into study designs to ensure consistent outcome assessment. The OASIS-D rating system has demonstrated superiority in accurately assessing demographic and outcome data compared to self-reported patient information .

What comorbidities should be documented in CSU antibody research protocols?

Research indicates that certain comorbidities are frequently associated with CSU and may influence antibody treatment outcomes:

  • Autoimmune thyroid disease (62% of patients)

  • Thyroid abnormality (43% of patients)

  • Allergic rhinitis (35% of patients)

When designing research protocols, these comorbidities should be systematically documented and considered as potential stratification variables, particularly since thyroid autoimmunity correlates with treatment response to antibody therapies.

How can serum biomarkers be integrated into research protocols to predict response to antibody therapy in CSU?

A systematic approach to biomarker evaluation in CSU research should include:

  • Baseline measurement of multiple biomarkers:

    • IgG anti-thyroid peroxidase (TPO) antibodies

    • Total IgE levels

    • Basophil histamine release assay (BHRA/CU Index)

    • C-reactive protein

    • Absolute eosinophil count

  • Analysis of predictive value:
    Research indicates that high IgG anti-TPO levels significantly predict poor response to omalizumab. In one study, among patients with no response to omalizumab and high CU Index levels, 66.67% had high IgG anti-TPO levels, compared to only 11.11% in the responsive group (OR, 0.06 [95% CI, 0.01 to 0.69]; P = .0236) .

  • Methodological considerations:

    • Laboratory standardization is critical as interlaboratory reporting measurements can vary

    • Consider both absolute values and established clinical thresholds

    • Account for potential interactions between biomarkers

What experimental approaches enable design of antibodies with customized binding specificity for CSU research?

Current methodologies for designing antibodies with specific binding profiles involve:

  • Phage display experiments with antibody libraries

    • Libraries based on naïve human V domains with strategic variation in complementary determining regions (CDRs)

    • Selection against specific ligands or combinations of ligands

    • High-throughput sequencing to closely monitor antibody library composition

  • Biophysics-informed computational modeling

    • Identification of distinct binding modes associated with specific ligands

    • Energy function optimization for either cross-specificity (binding to multiple targets) or high specificity (binding to single target)

    • Prediction and generation of antibody variants beyond those observed experimentally

  • Experimental validation

    • Testing computationally designed antibodies with predefined binding profiles

    • Verification of specific or cross-specific binding properties

These approaches overcome limitations of traditional selection methods, offering greater control over specificity profiles and enabling the discrimination of chemically similar ligands.

How should dose optimization studies be designed for partial or non-responders to antibody therapy in CSU?

Based on current clinical practice, two main approaches to dose optimization for partial or non-responders should be investigated:

  • Frequency adjustment: 34% of clinicians prefer increasing administration frequency to every 2 weeks

  • Dose escalation: 18% of clinicians prefer increasing the dose to 600 mg every 4 weeks

Research protocols should include:

  • Clear definitions of complete response, partial response, and non-response

  • Standardized assessment timepoints

  • Measurement of both objective symptoms and quality of life metrics

  • Biomarker assessment before and during treatment adjustment

These considerations are particularly important given that only 22% of clinicians report 80-100% of their patients achieve complete response to standard omalizumab dosing .

How can researchers address the heterogeneity of CSU phenotypes in antibody treatment studies?

The heterogeneity of CSU presents significant methodological challenges. Researchers should:

  • Implement comprehensive phenotyping:

    • Document urticaria vs. angioedema predominant phenotypes

    • Assess autoimmune markers including TPO antibodies

    • Measure total IgE and other relevant biomarkers

    • Record comorbidities, particularly thyroid disease

  • Stratify analysis based on:

    • Biomarker profiles (e.g., high vs. low IgG anti-TPO)

    • Clinical phenotypes

    • Comorbidity patterns

    • Prior treatment response

  • Consider using combination biomarker approaches:
    Studies suggest that combining biomarkers may increase specificity for predicting treatment response. For example, the combination of high CU Index levels with high IgG anti-TPO significantly predicted non-response to omalizumab .

What methodological approaches can differentiate binding modes in antibody design for CSU-related targets?

Advanced techniques to identify and differentiate binding modes include:

  • Biophysics-informed modeling approaches:

    • Association of distinct binding modes with specific ligands

    • Mathematical optimization of energy functions for desired binding profiles

    • Disentanglement of modes associated with chemically similar ligands

  • Experimental validation through:

    • Independent selections against different ligand combinations

    • Testing of model-generated antibody variants not present in initial libraries

    • Verification of specificity profiles using standardized binding assays

  • Analysis of functional consequences:

    • Assessment of antibody-mediated effects on target cells

    • Evaluation of functional outcomes beyond binding affinity

    • Correlation of binding modes with clinical outcomes

How should biomarkers be incorporated into clinical decision algorithms for antibody therapies in CSU?

Based on current evidence, researchers should develop and validate clinical algorithms that:

  • Incorporate IgG anti-TPO levels as a primary decision factor:

    • High levels predict poor response to omalizumab

    • Patients with elevated levels may benefit from alternative therapies

  • Evaluate combinations of biomarkers:

    • IgG anti-TPO with CU Index

    • Ratios of IgG anti-TPO to total IgE

    • Combinations with other inflammatory markers

  • Validate prediction models through:

    • Prospective, multi-center studies

    • Standardized laboratory measurements

    • Clear definitions of treatment response

These algorithms could significantly improve treatment selection and reduce the time to effective therapy for CSU patients.

What novel approaches can improve antibody specificity for CSU-related targets?

Innovative methodologies to enhance antibody specificity include:

  • Integration of experimental and computational approaches:

    • High-throughput sequencing combined with biophysics-informed modeling

    • Identification of binding modes associated with specific ligands

    • Optimization of sequences for desired specificity profiles

  • Design of antibodies with customized cross-reactivity:

    • Joint minimization of energy functions for desired ligands

    • Maximization of functions for undesired ligands

    • Generation of sequences optimized for specific binding profiles

  • Mitigation of experimental artifacts:

    • Control for selection biases in phage display experiments

    • Account for potential contamination from unintended ligands

    • Validate specificity through multiple independent assays

These approaches offer promising avenues for developing next-generation antibody therapies for CSU with improved specificity and efficacy.

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