1. PBMC Complexity Paragraph
Original
Peripheral blood mononuclear cells contain T cells, B cells, NK cells, monocytes, and other immune populations. Cell surfaces are crowded with hundreds of proteins. A delivery binder that looks impressive on an engineered 293T cell can still bind the wrong population, show donor-to-donor variability, or behave unpredictably when moved into primary cells.
Revised
Peripheral blood mononuclear cells contain T cells, B cells, NK cells, monocytes, and other immune populations. Cell surfaces are crowded with hundreds of proteins. A delivery binder that looks impressive on an engineered 293T cell can still show unexpected binding patterns, donor-to-donor variability, or different behavior when moved into primary cells.
Reason
Avoid saying “wrong population” too broadly. CD3- cells may include biologically relevant CD8-expressing NK subsets.
2. PBMC Candidate Example
Original
In PBMC testing, the candidate showed unacceptable non-specific binding. Another potent candidate showed donor-dependent non-specificity and a kinetic profile that raised additional questions. These are not details you want to discover after a delivery platform has already been built around a single binder.
Revised
In PBMC testing, some candidates showed binding signals outside the expected CD3+ T-cell gate, while another potent candidate showed donor-dependent binding patterns and a kinetic profile that raised additional questions. These signals need careful interpretation, because the CD3- compartment includes other immune cell types, including NK cells, and subsets of human NK cells can express CD8. They should therefore be further resolved by additional phenotyping rather than automatically labeled as non-specific binding. These are not details you want to discover after a delivery platform has already been built around a single binder.
Reason
This is the most important correction. CD3- signal is not automatically non-specific binding.
3. Binder Selection Profile Paragraph
Original
That experience, together with what we have learned from supporting partner and customer programs, has shaped how we think about binder selection. EC50 matters, but it is only the first filter. For a delivery binder, the real question is not simply whether it binds, but how it behaves across the broader biological and engineering context that follows: PBMC specificity, donor-to-donor consistency, internalization behavior, binding kinetics, manufacturability, risk of unintended T cell activation in vitro, formatting compatibility, conjugation behavior, assay transferability, etc.
Revised
That experience, together with what we have learned from supporting partner and customer programs, has shaped how we think about binder selection. EC50 matters, but it is only the first filter. For a delivery binder, the real question is not simply whether it binds, but how it behaves across the broader biological and engineering context that follows: PBMC binding profile, resolution of CD3+ and CD3- immune cell compartments, donor-to-donor consistency, internalization behavior, binding kinetics, manufacturability, risk of unintended T cell activation in vitro, formatting compatibility, conjugation behavior, assay transferability, etc.
Reason
Replace the broad phrase “PBMC specificity” with a more precise phrase that includes CD3+ / CD3- compartment resolution.
4. Available Characterization Paragraph
Original
For the CD8 VHH candidates, available characterization may include EC50, SPR affinity / kinetic data for selected clones, human CD8 and cynomolgus CD8 binding data, PBMC validation, non-specific binding assessment, internalization-related readouts, expression yield, and in vitro T cell activation assessment.
Revised
For the CD8 VHH candidates, available characterization may include EC50, SPR affinity / kinetic data for selected clones, human CD8 and cynomolgus CD8 binding data, PBMC validation, CD3+ / CD3- immune compartment profiling, background or off-target binding assessment where applicable, internalization-related readouts, expression yield, and in vitro T cell activation assessment.
Reason
More accurate than “non-specific binding assessment” alone.
5. Internal Data Package Paragraph
Original
In our internal data package, selected CD8 VHH candidates show sub-nanomolar to low-nanomolar cell-based binding activity, low non-specific binding in PBMC testing, and no detectable T cell activation in the in vitro activation assay used in the program.
Revised
In our internal data package, selected CD8 VHH candidates show sub-nanomolar to low-nanomolar cell-based binding activity, favorable PBMC binding profiles in the assays used, and no detectable T cell activation in the in vitro activation assay used in the program. Signals outside the CD3+ T-cell gate are interpreted with appropriate immune phenotyping context rather than automatically treated as non-specific binding.
Reason
Avoid overclaiming “low non-specific binding” without clarifying how CD3- signals are interpreted.
6. New Note Before References
Add
A note on PBMC interpretation
In PBMC analysis, signals outside the CD3+ T-cell gate should be interpreted carefully. The CD3- compartment includes multiple immune cell populations, including NK cells, and some human NK cell subsets can express CD8. Therefore, such signals may require additional phenotyping with markers such as CD16, CD56, CD8α, and CD8β, and should not be automatically labeled as non-specific binding.
Reason
This makes the correction explicit and scientifically defensible.