Fc Engineering Overview
The Human IgG1 (LS: M428L/N434S) Fc variant introduces two synergistic CH3 domain mutations designed to optimize the Fc-FcRn interaction surface. This modification significantly increases FcRn affinity at acidic pH, improving endosomal recycling and extending serum half-life while maintaining neutral FcγR and C1q binding profiles.
Functional Profile
| Property | Effect |
|---|---|
| FcγRIIIa binding | Neutral |
| ADCC | Neutral |
| CDC | Neutral |
| FcRn binding | Increased ↑↑ |
| Serum half-life | Extended ↑↑ |
| Effector potency | Normal |
Mechanism of Action
The LS Fc variant introduces two synergistic CH3-domain mutations—M428L and N434S—that optimize the Fc–FcRn interaction surface. M428L improves hydrophobic packing at the FcRn interface, while N434S refines hydrogen bonding and steric geometry for enhanced FcRn engagement. Together, these mutations significantly increase FcRn affinity at acidic pH, improving endosomal recycling and extending serum half-life without altering FcγR or C1q interactions.
Phenotypic Effects
- Increased FcRn binding.
- Extended serum half-life.
- Preserved ADCC and CDC.
- Maintains normal effector function profile.
- Ideal for long-acting therapeutic antibodies.
Applications
- Long-acting IgG1 therapeutics.
- Antibodies requiring reduced dosing frequency.
- Fc-fusion proteins needing improved exposure.
- PK optimization studies.
- Biologics where effector function must remain unchanged.
Plasmid Map & Feature Annotation
Insert Structure: VH – CH1 – hinge – CH2 – CH3(M428L/N434S)
- VH: Variable heavy domain
- CH1: Constant heavy 1
- Hinge: Native IgG1 hinge
- CH2: Native IgG1 CH2
- CH3(M428L/N434S): FcRn-enhancing mutations
Fusion BioLabs FcRn / PK-Modulated Family Comparison Matrix
| Variant | Mechanism | Strength (PK Extension) | Primary Application & Notes |
|---|---|---|---|
| human IgG1 (WT) Wild-Type |
Native FcRn binding | ★★☆☆☆ | Baseline Control. Standard physiological baseline (~21-day half-life in humans). |
| human IgG1 (N434A) N434A |
Single-point FcRn-enhanced | ★★★☆☆ | Single-point mutation providing a moderate 1.5–2× PK boost with low immunogenicity risk and easy manufacturing integration. |
| human IgG1 (LA) M428L / N434A |
FcRn-enhanced | ★★★★☆ | Strong PK Extension. Dual mutation combining M428L and N434A; enhances acidic FcRn binding with minimal neutral binding. |
| human IgG1 (LS) M428L / N434S |
FcRn-enhanced | ★★★★★ | This Product. Very Strong PK Extension. Extends human serum half-life up to 3–5× (>70–90 days; e.g., tixagevimab / cilgavimab). |
| human IgG1 (YTE) M252Y / S254T / T256E |
FcRn-enhanced | ★★★★★ | Benchmark PK Extension. Industry-standard benchmark delivering ~3–4× PK boost in humans (e.g., nirsevimab / Beyfortus®). |
| human IgG1 (QL) T250Q / M428L |
FcRn-enhanced | ★★★★☆ | Moderate-to-Strong PK Extension. Increases acidic FcRn affinity with favorable intellectual property freedom to operate. |
| human IgG1 (YTE + KF) M252Y/S254T/T256E + H433K/N434F |
Hyper-FcRn-enhanced / FcRn Blocker | ★★★★★ | FcRn Antagonist / Autoimmune Control. Binds tightly across pH 6.0 and 7.4 to block FcRn recycling and clear endogenous IgGs. |
| human IgG1 (V308P) V308P |
Controlled/Accelerated Clearance | ★★☆☆☆ | Tunable Fast-Clearance Variant. Modulates FcRn dissociation kinetics to yield accelerated clearance (2–5-day half-life); ideal for ADCs and immuno-PET imaging to limit non-target toxicity. |
| human IgG1 (I253A) I253A |
FcRn-null / Abrogated | ★☆☆☆☆ | Ultra-Fast Clearance Control. Complete knockout of the core FcRn binding triad; rapidly cleared within hours. |
Storage & Handling
- Store plasmid at −20°C.
- Avoid repeated freeze–thaw cycles.
- Use sterile technique.
- Suitable for transient or stable mammalian expression.
References
- Zalevsky J et al. Enhanced antibody half-life improves in vivo activity. Nat Biotechnol. 2010;28:157–159.