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Your antibody works, but it will not express. Can that be fixed without losing function?

Yes — in most cases low titer is a property of the variable-domain sequence, not an immovable fact about the molecule, and it can be engineered out. Abwiz Bio rescues expression by using STEM™ to expand sequence diversity around your lead and then selecting the variants that keep parent binding while expressing far better. In one program this produced more than a 10-fold increase in yield with function retained (therapeutic patent filed). Our routine in-house transient titers run 71–91 mg/L. Send an amino-acid sequence — no new immunization is needed.

Why a functional antibody expresses badly

Poor titer almost never comes from the constant region. It comes from the variable domains: a VH/VL pair that folds inefficiently, an interface that pairs poorly, hydrophobic patches that push the molecule toward aggregation inside the secretory pathway, or sequence features that make the chain a poor substrate for folding and secretion. Antibodies discovered purely for binding are selected on one axis — affinity — so nothing in their history ever asked them to be easy to make.

That is why expression problems tend to appear late, after a lead has been chosen and a program has already committed to it. The molecule is right biologically and wrong industrially, and the usual options — change the host, change the vector, change the media — address everything except the actual cause.

How we rescue titer

We treat expression as a selectable property rather than a process-development problem.

• Diversity expansion. Using STEM™ (STage-Enhanced Maturation), we build variant libraries around your lead. CDR positions are designed from human antibody amino-acid usage, avoiding residues that are unfavourable at each position, using a local AlphaFold instance together with germline and structural bioinformatics.
• Selection with function held constant. Variants are panned against your antigen so that binding is never traded away. Clones that lose the parent specificity simply do not survive the selection.
• Biophysical filters at every stage. Thermostability and polyreactivity filters run throughout, so the rescued clone is not merely higher-titer but better behaved.
• Soluble Fab screening before IgG. Fabs are screened in 96-well plates first, so we do not spend the expensive IgG stage on clones that will not carry.
• Titer confirmation. Surviving clones are converted to IgG and expressed side by side with the parent, so the comparison is measured under identical conditions rather than inferred.

The output is a sequence, not a process tweak, so the improvement is a property of the molecule rather than of one production run — which is what allows it to carry into your own manufacturing platform.

What the data looks like

Expression rescue is frequently run together with developability optimization, because the same STEM™ selection that recovers titer also removes aggregation, viscosity and sequence liabilities. If your lead needs affinity as well, the diversity built for rescue can be selected for both at once.

You receive

• Expression titer data for rescued clones measured side by side with the parent under identical conditions
• Parent-equivalent function data (ELISA; BLI kinetics optional after IgG purification)
• Full VH/VL sequences for every delivered clone
• Recombinant IgG
• No downstream royalties, and stage-gated approval before each next step

When this service is the right one

Expression rescue is the right service when the molecule is biologically correct and the bottleneck is manufacturing: a lead that titers too low to supply toxicology or clinical material, a diagnostic antibody that cannot be produced economically at scale, or a humanized construct whose yield fell after grafting. If your antibody expresses acceptably but aggregates, is viscous at high concentration, or carries sequence liabilities, start instead at developability optimization. If it expresses well and simply binds too weakly, start at affinity maturation.

Frequently asked questions

Do I need to re-immunize or re-discover the antibody?

No. Expression rescue starts from an amino-acid sequence. We build variant libraries around your existing VH/VL, so no animal work and no new discovery campaign is required.

How much expression improvement is realistic?

In one Abwiz Bio program the rescued clone expressed more than 10-fold better than the parent with function retained, and a therapeutic patent was filed on the result. The achievable gain depends on how far the parent sits from a well-folding sequence, which is why we express rescued clones side by side with the parent rather than quoting a fixed multiplier.

Will the rescued antibody still bind the same epitope with the same affinity?

Function is held constant by the selection itself: variants are panned against your antigen, so clones that lose parent specificity do not survive. Delivered clones are characterized by ELISA, with BLI kinetics available after IgG purification, so you can confirm parent-equivalent binding directly.

Does the improvement carry over to my own manufacturing host?

The deliverable is an engineered sequence rather than a process change, so the improvement is a property of the molecule rather than of our expression conditions. That is what allows it to carry into your own host and platform, though final titer in any given system still depends on that system, so we recommend confirming it there.

Can expression rescue be combined with other engineering?

Yes, and it usually is. The same STEM™ diversity can be selected simultaneously for developability, thermostability, affinity or cross-species reactivity, which is more efficient than running sequential single-property campaigns.

What does a project cost and how long does it take?

Every campaign is scoped individually against your sequence, target and success criteria, then quoted. Contact info@abwizbio.com with your VH/VL sequence and current titer for a scoped quote and timeline.