SHR1 Antibody

What is SHR1 Antibody and what are its main variants studied in research?

SHR1 appears in several contexts in antibody research literature:

• SHR-1210: A novel anti-PD-1 monoclonal antibody evaluated in clinical trials for advanced solid tumors. Clinical data demonstrates promising antitumor activity with a manageable safety profile at multiple dosing levels (60mg, 200mg, and 400mg) .

• SHR-1906: A fully humanized monoclonal antibody targeting connective tissue growth factor, investigated for idiopathic pulmonary fibrosis. Phase I studies have tested doses ranging from 1.5 to 45 mg/kg with favorable tolerability .

• Anti-Shr antibodies: Human monoclonal antibodies (including TRL186 and TRL96) targeting the Shr surface receptor in Group A Streptococcus (GAS). These antibodies have demonstrated efficacy in both prophylactic and therapeutic infection models .

When designing experiments, researchers must clearly identify which specific SHR1 antibody is being investigated, as their targets and mechanisms differ substantially.

How do different SHR1 antibodies function in their respective experimental contexts?

Each SHR1 antibody variant functions through distinct biological mechanisms:

• Anti-Shr antibodies (e.g., TRL186): Function by interfering with iron acquisition pathways in Group A Streptococcus. TRL186 specifically impedes Shr binding to hemoglobin and inhibits bacterial growth on hemoglobin iron. It binds to the N-terminal region (NTR) of Shr protein, inhibiting hemoglobin binding in a dose-dependent manner with maximum inhibition of 43% at 2 μg/mL concentration .

• SHR-1210: Functions as a PD-1 inhibitor in cancer immunotherapy contexts. By blocking the interaction between PD-1 on T cells and its ligands, it enhances anti-tumor immune responses. Clinical studies have documented complete responses in gastric cancer and bladder carcinoma patients .

• SHR-1906: Targets connective tissue growth factor in fibrotic diseases. Pharmacokinetic studies show nonlinear behavior where peak concentration increases in a dose-proportional manner, while area under the concentration-time curve demonstrates greater than dose-proportional increases .

How are SHR1 antibodies isolated and characterized in laboratory settings?

The isolation and characterization of SHR1 antibodies involve sophisticated methodologies:

• Isolation techniques: For anti-Shr antibodies, researchers employed the CellSpot platform where memory B cells were stimulated to proliferate and differentiate into plasma cells. The secreted immunoglobulin footprints were then probed with fluorescent nanoparticles conjugated with target proteins (full-length Shr, NEAT1, NEAT2 domains) and counter-screening beads .

• Binding characterization: Multiple assays determine binding properties:

  • ELISA with recombinant proteins, domains, and peptides

  • Western blot analysis for protein detection

  • Flow cytometry for cell-surface binding

• Functional characterization: Methods include:

  • Inhibition of ligand binding (e.g., hemoglobin binding inhibition)

  • Effects on bacterial growth in limited-iron conditions

  • Phagocytosis assays with cultured immune cells

  • In vivo protection in animal infection models

• Pharmacokinetic characterization: For clinical-stage antibodies like SHR-1210 and SHR-1906, analysis of clearance rates, volume distribution, and half-life determination across multiple doses .

What methodologies have been validated for evaluating the efficacy of SHR1 antibodies?

Multiple complementary methodologies provide robust efficacy assessment:

• In vitro binding assays:

  • ELISA using purified target proteins (e.g., Shr-NTR coated plates with biotinylated hemoglobin)

  • Peptide library screening to map exact epitopes (overlapping 15-mers with 12 amino acid overlaps)

  • Competitive binding assays to measure inhibition of natural ligand interactions

• Functional assays:

  • For anti-Shr antibodies: Inhibition of hemoglobin binding measured as percentage reduction compared to controls

  • Cell-based killing assays: "Preincubation with TRL186 or TRL96 resulted in 35% and 44% reduction in GAS recovery following incubation with differentiated HL-60 cells"

• In vivo efficacy models:

  • Survival studies in infection models: "TRL186 prophylactic administration increased mice survival from 68% (mock) to 100%"

  • Therapeutic administration models: "When administered 4 hours post-challenge... mice that received TRL186 had a 73% survival rate [compared to 27% in controls]"

• Clinical endpoints for SHR-1210 and SHR-1906:

  • Safety profiles across dose ranges

  • Pharmacokinetic parameters including half-life determination

  • Response rates (complete and partial responses for SHR-1210)

How does epitope specificity affect the functional outcomes of different SHR1 antibody variants?

The search results provide a compelling example of how epitope specificity directly determines functional outcomes:

In anti-Shr antibody research, two antibodies with distinct binding specificities demonstrated dramatically different efficacy profiles:

• TRL186 (binds to NTR domain): Provided 100% survival in prophylactic studies

• TRL96 (binds to NEAT1 domain): Showed no protection compared to control group

Despite both antibodies demonstrating similar in vitro phagocytic killing activity (35% vs. 44% reduction in bacterial recovery), only TRL186 impeded hemoglobin binding and bacterial growth on hemoglobin iron.

This exemplifies how targeting a functional domain (NTR) involved in nutrient acquisition produces superior outcomes compared to targeting non-functional domains, despite similar binding to the target organism. The researchers concluded: "Interference with iron acquisition is central for TRL186 efficacy against GAS" .

What challenges exist in transitioning SHR1 antibodies from preclinical to clinical applications?

Several challenges emerge when advancing SHR1 antibodies to clinical settings:

• Immunogenicity concerns: For SHR-1906, "Anti-drug antibodies were detected in nine of 54 participants (16.7%)" , indicating potential immunogenicity that could affect long-term efficacy and safety.

• Nonlinear pharmacokinetics: SHR-1906 exhibited nonlinear PK where "peak concentration increased in a dose-proportional manner, whereas the area under the concentration-time curve showed a greater than dose-proportional increase" . This complexity complicates dose selection and prediction of drug exposure.

• Variable half-life: The half-life of SHR-1210 was documented as "2.94 d, 5.61 d and 11.0 d for 3 dose levels" , revealing significant dose-dependency that must be accounted for in dosing regimens.

• In vitro to in vivo translation gaps: For anti-Shr antibodies, both TRL186 and TRL96 "promoted killing by phagocytes in vitro, but prophylactic administration of only TRL186 increased mice survival" , highlighting that in vitro efficacy doesn't always predict in vivo outcomes.

How should researchers interpret contradictory results between different assays measuring SHR1 antibody activity?

When encountering contradictory results across different assay systems, researchers should:

• Consider biological relevance hierarchy: In the anti-Shr antibody research, in vivo protection outcomes superseded in vitro phagocytosis results. Both TRL186 and TRL96 promoted similar levels of phagocytic killing (35% vs. 44%), yet only TRL186 conferred protection in animal models .

• Investigate mechanistic differences: The researchers resolved the apparent contradiction by determining that "TRL186 but not TRL96 also impeded Shr binding to hemoglobin and GAS growth on hemoglobin iron" . This mechanistic difference explained the superior in vivo performance despite similar phagocytosis enhancement.

• Evaluate assay limitations: Some assays may lack sensitivity to detect biologically meaningful differences or may introduce artificial conditions that don't reflect in vivo complexity.

• Perform comprehensive characterization: Multiple assays examining different aspects of antibody function (binding, inhibition of natural ligand interactions, cellular effects, in vivo protection) provide a more complete understanding than any single assay.

• Examine dose-response relationships: Different concentration requirements across assays may reveal important pharmacodynamic properties.

What control conditions should be implemented when conducting SHR1 antibody binding studies?

Based on published SHR1 antibody research, robust experimental designs should include:

• Isotype controls: The anti-Shr study employed "TRL308, a human mAb to respiratory syncytial virus" as a control antibody to establish background binding levels .

• Genetic controls: Testing with knockout or mutant strains - "A Δshr mutant did not react with TRL186 or TRL96, establishing Shr specificity in vivo" .

• Domain deletion variants: "Binding to a series of NZ131 mutants with complete or various in-frame deletions in Shr" validated domain-specific binding .

• Protein controls: "Wells were coated with BSA, and uncoated wells served as controls" to account for non-specific binding in ELISA experiments .

• Concentration gradients: Using multiple antibody concentrations to establish dose-dependency: "Hemoglobin binding by NTR was inhibited in a dose-dependent manner by TRL186... maximum inhibition (43%) was achieved at 2 µg/mL concentration" .

• Placebo controls: In clinical studies of SHR-1906, placebo controls were essential for safety and efficacy comparisons .

How should dose-response studies be designed to accurately capture SHR1 antibody efficacy?

Effective dose-response studies should incorporate these design elements:

• Broad dose range selection:

  • For SHR-1210: "36 patients received intravenous SHR-1210 at 60 mg, 200 mg and 400 mg"

  • For SHR-1906: "Single ascending doses (1.5, 6, 12, 20, 30, and 45 mg/kg)"

  • For in vitro studies: Multiple concentrations spanning sub-effective to saturating levels

• Appropriate controls:

  • Placebo controls at each dose level

  • Isotype-matched antibody controls

  • Positive controls where available

• Multiple endpoint measurements:

  • Target binding/receptor occupancy

  • Functional activity (e.g., inhibition of ligand binding)

  • Pharmacokinetic parameters

  • Safety indicators

  • Clinical responses (for clinical studies)

• Time-course evaluations:

  • For SHR-1906: "Followed for 71 days"

  • Multiple timepoints based on expected pharmacokinetics

• Statistical considerations:

  • Sufficient sample size for statistical power

  • Appropriate statistical tests for the endpoints measured

  • Analysis of dose-proportionality and linearity

What techniques provide the most reliable data on SHR1 antibody receptor occupancy?

While receptor occupancy studies were mentioned for SHR-1210 ("receptor occupancy on circulating T lymphocytes was assessed for pharmacodynamics" ), specific methodological details were limited in the search results.

For researchers designing receptor occupancy studies with SHR antibodies, these validated techniques should be considered:

• Flow cytometry-based approaches:

  • Direct detection using labeled antibodies that compete for the same epitope

  • Pre- and post-dose blood sampling to measure receptor availability

  • Ex vivo saturation analysis with labeled antibodies

• Competitive binding assays:

  • Measuring displacement of labeled natural ligands

  • Dose-dependent competition curves

• Proximity-based detection:

  • FRET (Fluorescence Resonance Energy Transfer) for measuring antibody-receptor interactions

  • Time-resolved fluorescence for enhanced sensitivity

• Target modulation biomarkers:

  • Downstream signaling effects as indirect measures of receptor occupancy

  • Changes in gene expression profiles

What statistical approaches are most appropriate for analyzing dose-dependent effects of SHR1 antibodies?

While explicit statistical methodologies weren't detailed in the search results, standard approaches for antibody dose-response analysis include:

• Nonlinear regression modeling:

  • For inhibition studies like TRL186's effect on hemoglobin binding, where "maximum inhibition (43%) was achieved at 2 µg/mL concentration"

  • Determination of EC50/IC50 values and confidence intervals

  • Comparison of dose-response curves between antibody variants

• Pharmacokinetic parameter analysis:

  • For SHR-1210: Calculation and comparison of half-life values across doses (2.94, 5.61, and 11.0 days for the three dose levels)

  • For SHR-1906: Analysis of "geometric mean clearance (0.14-0.63 mL/h/kg), geometric mean volume of distribution at steady-state (47.4-75.5 mL/kg), and terminal elimination half-life (51.9-349 h)"

  • Assessment of dose-proportionality or non-linearity

• Survival analysis methods:

  • Kaplan-Meier survival curves for comparing treatment groups in animal models

  • Log-rank tests for statistical significance in survival differences

  • Hazard ratios to quantify protection effects

• Multiple comparison corrections:

  • Bonferroni, Tukey, or false discovery rate methods when comparing multiple dose groups

  • Accounting for multiple endpoints and timepoints in analysis

How can researchers effectively map critical epitopes for SHR1 antibody binding and function?

Epitope mapping techniques revealed crucial insights into SHR1 antibodies' function. For comprehensive mapping:

• Domain-level mapping:

  • Use recombinant protein fragments representing distinct domains

  • For anti-Shr antibodies: "TRL186 binding site using ELISA with recombinant Shr proteins encompassing the full-length protein, NTR, NEAT1, or NEAT2"

  • Results showed "TRL186 generated a strong binding signal with the NTR fragment similar to intact Shr, whereas only background signals were recorded from wells containing NEAT1 or NEAT2"

• Fine epitope mapping:

  • Overlapping peptide libraries: "A library of overlapping peptides (15-mers with 12 overlapping amino acids) covering Shr-NTR"

  • Analysis revealed "Among 109 peptides covering the Shr-NTR region, only 2 peptides (numbers 33 and 34) exhibited significant reactivity with TRL186"

• Genetic validation:

  • Testing with gene deletion or mutation variants

  • "TRL186 did not bind to GAS expressing Shr mutants lacking the NTR, and TRL96 did not interact with strains expressing Shr variants without NEAT1 domain"

• Functional correlation:

  • Connect epitope binding to functional outcomes

  • For TRL186, binding to the NTR domain correlated with inhibition of hemoglobin binding and in vivo protection

• Computational analysis:

  • Structural modeling and docking simulations

  • Sequence conservation analysis across variants or species

How do pharmacokinetic profiles of different SHR1 antibodies compare across studies?

The search results reveal distinct pharmacokinetic profiles for SHR antibodies:

• SHR-1210 (anti-PD-1):

  • Dose-dependent half-life: "2.94 d, 5.61 d and 11.0 d for 3 dose levels (60mg, 200mg, 400mg), respectively"

  • Shows increasing half-life with higher doses, suggesting potential target-mediated clearance at lower concentrations

• SHR-1906 (anti-CTGF):

  • Broader pharmacokinetic characterization: "geometric mean clearance was 0.14-0.63 mL/h/kg, geometric mean volume of distribution at steady-state was 47.4-75.5 mL/kg, and terminal elimination half-life was 51.9-349 h"

  • Nonlinear pharmacokinetics: "peak concentration increased in a dose-proportional manner, whereas the area under the concentration-time curve showed a greater than dose-proportional increase"

  • Wider variability in half-life (approximately 2-14.5 days)

These differences highlight the unique pharmacokinetic properties of each antibody. Researchers must characterize the specific pharmacokinetic profile of each antibody rather than assuming similarities based on nomenclature.

What immunogenicity considerations arise in SHR1 antibody research?

Immunogenicity data was explicitly reported for SHR-1906:

• "Anti-drug antibodies of SHR-1906 were detected in nine of 54 participants (16.7%)"

This significant rate of anti-drug antibody development highlights important considerations for researchers:

• Monitoring protocols: Include regular anti-drug antibody testing in study designs

• Impact assessment: Evaluate whether anti-drug antibodies affect:

  • Pharmacokinetics (increased clearance)

  • Pharmacodynamics (neutralizing activity)

  • Safety (hypersensitivity reactions)

  • Efficacy outcomes (reduced clinical benefit)

• Antibody engineering: Consider humanization or de-immunization strategies for novel antibodies

• Individual variability: Analyze patient factors that might predict immunogenicity risk

• Long-term implications: Design studies with sufficient duration to capture delayed immunogenicity