PAB6 Antibody
Description
HER2/HER3 Proximity-Driven Signaling
PAb6 induces HER2-HER3 proximity, triggering PI3K/Akt signaling and proliferation in HER2-positive breast cancer cells (e.g., SK-BR-3, BT-474). This contrasts with monospecific antibodies like trastuzumab or pertuzumab, which inhibit signaling .
Key Findings
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Proliferation Induction: PAb6 treatment increased proliferation in SK-BR-3 cells compared to control or monospecific antibody combinations .
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Signaling Activation:
Antibody Performance in Proliferation Assays
| Antibody | Cell Line | Effect on Proliferation | pAkt (24h) |
|---|---|---|---|
| PAb6 | SK-BR-3 | Increased proliferation | ↑ |
| TAb6 (Trastuzumab+Ab6) | SK-BR-3 | Increased proliferation | ↑ |
| Ab6 (Monospecific) | SK-BR-3 | Reduced proliferation | ↓ |
| Pertuzumab+Ab6 (Combo) | SK-BR-3 | Reduced proliferation | ↓ |
Data synthesized from comparative studies .
Internalization Kinetics
PAb6’s multivalent binding enhances HER3 internalization:
| Antibody | Entry into Early Endosomes | Lysosomal Localization |
|---|---|---|
| Ab6 | 15–60 minutes | Within 60 minutes |
| Ab6tet | <5 minutes | Rapid degradation |
| PAb6 | Persistent membrane retention | Minimal lysosomal uptake |
Internalization rates inferred from fluorescence microscopy .
Advantages
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Targeted Proximity: PAb6’s design forces HER2-HER3 interaction, bypassing ligand dependency .
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Half-Life: In vivo half-lives (~215 hours) suggest prolonged exposure potential .
Limitations
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Proliferation Risk: Induced PI3K/Akt signaling may counteract therapeutic goals in HER2+ cancers .
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Expression Yields: Lower production yields (2.5 mg/L for PAb6 vs. 8 mg/L for TAb6) pose scalability challenges .
Research Gaps and Future Directions
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Context-Dependent Efficacy: HER2/HER3 co-expression levels may influence PAb6’s pro-proliferative vs. inhibitory effects.
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Combination Therapies: Pairing PAb6 with inhibitors of PI3K/Akt (e.g., GDC-0941) could mitigate proliferative signaling.
Product Specs
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4
Target Background
Q&A
Here’s a structured FAQ collection for academic researchers studying the PAB6 antibody (referenced as PBD-C06 in literature), synthesized from peer-reviewed findings and technical reports:
What distinguishes PAB6’s mechanism of action from other anti-amyloid antibodies?
PAB6 targets pyroglutamate-3 Aβ (pGlu3-Aβ), a post-translationally modified Aβ species forming neurotoxic oligomers. Unlike pan-Aβ antibodies (e.g., aducanumab), PAB6 avoids binding unmodified Aβ monomers, preserving their physiological roles in synaptic regulation .
Methodological Insight:
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Validate specificity using ELISA with synthetic pGlu3-Aβ(3–42) peptides and amyloid plaque homogenates.
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Compare binding kinetics via surface plasmon resonance (SPR) against unmodified Aβ1–42 .
How should researchers design in vivo experiments to evaluate PAB6’s efficacy?
Experimental Design Table:
Include controls: IgG4 isotype (Fc-silenced) to isolate target-mediated effects .
What strategies mitigate immunogenicity risks in PAB6’s humanized framework?
PAB6’s de-immunization involved:
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Hotspot removal: Seven immunogenic residues in the humanized variable region were substituted while preserving paratope structure .
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Fc engineering: Retained FcγR binding for microglial phagocytosis but eliminated C1q binding to prevent complement activation .
Validation:
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Use T-cell epitope mapping (e.g., EpiMatrix) and measure anti-drug antibodies (ADA) in primate studies .
How do researchers resolve contradictions between in vitro and in vivo phagocytosis data?
Case Example:
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In vitro assays show PAB6 enhances microglial uptake of pE3-Aβ fibrils .
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In vivo, efficacy depends on blood-brain barrier penetration (~0.1% of serum levels) .
Resolution Protocol:
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Quantify brain antibody levels via mass spectrometry.
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Use two-photon imaging to track real-time phagocytosis in live models.
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Compare results across species (mice vs. non-human primates) .
What computational tools predict PAB6’s binding to mixed Aβ/pE3-Aβ aggregates?
Leverage molecular dynamics simulations:
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Model the N-terminal pGlu3 protrusion using cryo-EM structures of Aβ fibrils .
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Validate with competitive SPR against co-aggregated Aβ/pE3-Aβ(3–42) .
Data Contradiction Analysis
Conflict: PAB6 shows strong fibril binding in vitro but limited plaque clearance in vivo.
Resolution Framework:
