A UF/DF step before Protein A. Which statement is NOT correct?

Question

BlackTom AI · Accepted Answer

Protein A capture is typically the first chromatographic capture step after clarification in monoclonal antibody (mAb) downstream processing, not preceded routinely by UF/DF. Relevant concepts: typical mAb process flows (clarification → Protein A capture → low‑pH viral inactivation → polishing → UF/DF formulation), dynamic binding capacity (DBC) of Protein A resins, and reasons to insert UF/DF (concentration, buffer exchange, removal of interfering components).

Step‑by‑step reasoning:
1. Standard practice: clarified harvest (cell culture supernatant) is directly loaded onto Protein A because Protein A offers very high selectivity and tolerates typical harvest conditions. UF/DF prior to Protein A is not a routine, general step.
2. Situations where pre‑Protein A UF/DF is applied: if the harvest volume is extremely large relative to column throughput or titers are very low, concentrating the feed via UF can reduce load volume and improve productivity. Similarly, if DBC is unacceptable due to interfering components or high aggregate/particulate content, UF/DF or other pre‑treatments can be used to make capture feasible.
3. Therefore the statement “UF/DF can be included before Protein A when DBCs are unacceptable” is correct — it is a valid special‑case justification. The statement “UF/DF is an optional upstream step to improve feasibility/productivity” is also correct — it’s conditional and not universal. “UF/DF can be included before Protein A when titers are low” is likewise correct — concentration helps when titers/loads are limiting.

Why the flagged option is NOT correct:
“UF/DF is generally included before Protein A in modern mAb processes” is false because the general, common sequence uses Protein A as the primary capture immediately after clarification; pre‑Protein A UF/DF is the exception, applied only for specific process constraints. Thus this option is the incorrect statement.

Conclusion: The correct NOT‑correct choice is “UF/DF is generally included before Protein A in modern mAb processes,” which matches the provided answer.

A UF/DF step before Protein A. Which statement is NOT correct?Single choice

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