Case Studies
Featured Case Studies
Achieving Picomolar Affinity from a Nanomolar Lead
Therapeutic mAb • Oncology Target • Human IgG
Challenge
A client’s lead therapeutic antibody showed promising target specificity but insufficient binding affinity (5 nM KD) for the desired clinical application. Previous optimization attempts using CDR walking had yielded only modest 2-3× improvements.
STEM™ Approach
We applied all three stages of our STEM™ platform. Stage A1 generated single-CDR variant libraries (>1010 diversity per CDR), followed by Stage A2 combining light and heavy chain pools under stringent selection. Stage B combined the best variants with strict stability and polyreactivity counter-selections at each stage.
Results
The top engineered candidate achieved >1,300-fold improvement to 4 pM KD, validated by surface plasmon resonance (SPR). The final clone retained full target specificity and was patented for therapeutic use.
Project Details
- Starting Affinity: 5 nM KD
- Final Affinity: 4 pM KD
- Stages: A1 → A2 → B (Full STEM™)
- Species: Humanized
- Validation: SPR (Biacore)
- Timeline: ~5 months
- Outcome: Therapeutic patent filed
Rescuing a Poorly-Expressing Therapeutic Lead
Therapeutic mAb • Cell-Surface Target • Human IgG
Challenge
A client antibody showed excellent functional activity in cell-based assays but critically poor expression yield, creating a manufacturability bottleneck that threatened the program’s clinical viability.
STEM™ Approach
Using only cells natively expressing the target antigen, STEM™ selected for clones retaining function while improving expression. Libraries were transiently heated to remove unstable clones, then subtracted on polyspecificity reagents before positive selection on antigen-expressing cells. Filter stringency was increased at each stage.
Results
Engineered clones showed >10-fold improved expression with equivalent functional activity in cell assays. Stability and polyreactivity profiles were significantly improved. A therapeutic patent was filed on the final candidates.
Project Details
- Goal: Improve expression
- Selection: Cell-based panning
- Filters: Thermostability + polyreactivity
- Expression Gain: >10-fold
- Function: Maintained
- Outcome: Patent filed
Engineering pH-Dependent Binding for Enhanced Recycling
Biobetter Program • Anti-Cytokine Target • Human IgG
Challenge
A program required antibodies with strong target binding at physiological pH 7.4 but rapid release at endosomal pH 5.8, enabling efficient antibody recycling for enhanced potency and extended half-life. The parent antibody showed negligible pH sensitivity.
STEM™ Approach
All three stages of STEM™ were performed with dual-pH selection: high affinity binding at pH 7.4 combined with release screening at pH 5.8. Libraries were designed to introduce pH-sensitive histidine substitutions at key CDR positions while maintaining overall structural integrity.
Results
While the parent antibodies showed negligible pH sensitivity, the STEM™-engineered clones achieved rapid dissociation under mildly acidic conditions while retaining high-affinity binding at physiological pH — enabling efficient endosomal recycling for improved therapeutic potency.
Project Details
- Goal: Engineer pH sensitivity
- Mechanism: Endosome recycling
- Selection pH: 7.4 / 5.8
- Stages: Full STEM™ (A1→A2→B)
- Validation: BLI (Octet)
- Outcome: Biobetter candidates advanced
Avidity Engineering for Optimal Functional Activity
Fab Engineering • Multi-Format Screening • Affinity Range
Challenge
For certain therapeutic formats — such as single-chain TCRs, CARs, or agonistic/antagonistic antibodies — extremely high affinity binding may not be optimal. This project required generating a panel of variants with precisely tuned on-rates and off-rates to identify the ideal binding kinetics for maximal functional activity.
STEM™ Approach
In Stage A1, single-CDR variant libraries were selected under mild conditions to remove non-productive clones. The Stage A2 combined library was then subjected to multiple selection conditions including all combinations of fast/slow on-rates and off-rates. Candidates were screened by both monovalent ELISA (true affinity) and bivalent pseudo-IgG ELISA (avidity).
Results
A panel of engineered clones with a broad range of binding affinities was successfully generated. Both high-affinity and weakly-binding, high-avidity variants were obtained, enabling identification of the optimal kinetic profile for the intended therapeutic application.
Project Details
- Goal: Kinetic tuning panel
- Format: Fab-based engineering
- Selection: Multi-condition panning
- Screening: Monovalent + bivalent ELISA
- Outcome: Kinetic variants for functional screening
Peer-Reviewed Publications
Our STEM™ platform results have been validated in peer-reviewed journals including Cell Reports, Antibody Therapeutics, and the Journal of Biological Chemistry. Our published work on engineering broadly-neutralizing therapeutic antibodies demonstrates the platform’s ability to iteratively improve both affinity and breadth of activity across rapidly evolving targets.
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