Case Study: Titer Correlation analysis

Goal: To evaluate the correlation between the harvested cell culture fluid (HCCF) protein mass and activity durations in the recovery train

High level summary

• Batch by Batch analysis was performed for all downstream activities to evaluate the correlation between the HCCF mass and recovery durations
• 2 of the 16 activities reflected a positive correlation with increasing titer, far fewer than expected by process development SMEs
• Analysis guided efforts to more fully understand operational considerations for facility design, rather than just titer-dependent analysis.

The Brief

Over the past decade, titer increases in the biopharmaceutical manufacturing industry have shifted focus towards purification operations that have become increasingly unable to process the large quantity of protein mass produced. Purification main operation times are typically assumed to be directly related with the protein mass of the cell culture fluid (HCCF mass): the higher the mass, the longer operations should take. However these assumptions were not being seen by operating facilities. Bioproduction Group's brief was to investigate this correlation using historical data obtained from facility data historians.

How We Did It

Bioproduction Group's approach was to carry out a detailed analysis on all the main and supporting operations that were directly or indirectly related to downstream processing of the harvested cell culture fluid. "One should never decide without having supporting data;" comments Principal David Zhang "there might be correlation between two things that seems completely unrelated; but might have an underlying correlation due to reasons buried under operational details."

Historical data collected on every unit operation and batch over the last 3 years was examined to match protein mass at that production stage with times for that operation. By looking at multiple products with different titers, Bio-G was also able to determine whether the variability between products was due to titer variability or process variability.

Results

Analysis performed by Bioproduction Group showed that almost no activities in the downstream processing train reflect a positive correlation between HCCF mass and downstream activity durations. In fact, high inherent process variability was far more significant in determining the time of an operation than the HCCF mass itself.

The graph above shows a typical relationship between protein mass and the durations of two of the main operations in downstream. The natural variability of the processes dominates the overall variability of the activity durations, and therefore the majority of the downstream activities do not show a statistically significant correlation with the input protein mass.

There was only one activity, that showed statistically significant correlation; even in this case, the operational variability was more important in determining overall activity durations and therefore final run rates. Bioproduction Group found the reason for this was that operational decisions and physical constraints of the facility limit the actual activity durations.

The analysis guided the process development engineers of a large biopharmaceutical manufacturer to change their approach when designing processes for the higher titer new molecular entities in the pipeline.