An ultra scale-down method to investigate monoclonal antibody processing during tangential flow filtration using ultrafiltration membranes.

The availability of material for experimental studies is a key constraint in the development of full-scale bioprocesses. This is especially true for the later stages in a bioprocess sequence such as purification and formulation, where the product is at a relatively high concentration and traditional scale-down models can require significant volumes. Using a combination of critical flow regime analysis, bioprocess modelling, and experimentation, ultra scale-down (USD) methods can yield bioprocess information using only millilitre quantities before embarking on highly demanding full-scale studies. In this study the performance of a pilot-scale tangential flow filtration (TFF) system based on a membrane flat-sheet cassette using pumped flow was predicted by devising an USD device comprising a stirred cell using a rotating disc. The USD device operates with just 2.1 cm2 of membrane area and, for example, just 1.7 mL of feed for diafiltration studies. The novel features of the design involve optimisation of the disc location and the membrane configuration to yield an approximately uniform shear rate. This is characterised using computational fluid dynamics for a defined layer above the membrane surface. A pilot-scale TFF device operating at ~500-fold larger feed volume and membrane area was characterised in terms of the shear rate derived from flow rate-pressure drop relationships for the cassette. Good agreement was achieved between the USD and TFF devices for the flux and resistance values at equivalent average shear rates for a monoclonal antibody diafiltration stage.

High throughput chromatography strategies for potential use in the formal process characterization of a monoclonal antibody.

High throughput experimental strategies are central to the rapid optimization of biologics purification processes. In this work, we extend common high throughput technologies towards the characterization of a multi-column chromatography process for a monoclonal antibody (mAb). Scale-down strategies were first evaluated by comparing breakthrough, retention, and performance (yields and clearance of aggregates and host cell protein) across miniature and lab scale columns. The process operating space was then evaluated using several integrated formats, with batch experimentation to define process testing ranges, miniature columns to evaluate the operating space, and comparison to traditional scale columns to establish scale-up correlations and verify the determined operating space. When compared to an independent characterization study at traditional lab column scale, the high throughput approach identified the same control parameters and similar process sensitivity. Importantly, the high throughput approach significantly decreased time and material needs while improving prediction robustness. Miniature columns and manufacturing scale centerpoint data comparisons support the validity of this approach, making the high throughput strategy an attractive and appropriate scale-down tool for the formal characterization of biotherapeutic processes in the future if regulatory acceptance of the miniature column data can be achieved. Biotechnol. Bioeng. 2016;113: 1273-1283. © 2015 Wiley Periodicals, Inc.

Streamlining process characterization efforts using the high throughput ambr® crossflow system for ultrafiltration and diafiltration processing of monoclonal antibodies.

Commercial process development for biopharmaceuticals often involves process characterization (PC) studies to gain process knowledge and understanding in preparation for process validation. One common approach to conduct PC activities is by using design-of-experiment, which can help determine the impact process parameter deviations may have on product quality attributes. Qualified scale-down systems are typically used to conduct these studies. For an ultrafiltration/diafiltration (UF/DF) application, however, a traditional scale-down still requires hundreds of milliliters of material per run and can only conduct one experiment at a time. This poses a challenge in resources as there could be 20+ experiments required for a typical UF/DF PC study. One solution to circumvent this is the use of high-throughput systems, which enable parallel experimentation by only using a fraction of the resources. Sartorius Stedim Biotech has recently commercialized the ambr® crossflow high-throughput system to meet this need. In this study, the performance of this system during a monoclonal antibody UF/DF step was first compared with a pilot- and a manufacturing-scale tangential flow filtration (TFF) system at a single operating condition. Due to material limitations, it was then compared to only the pilot-scale TFF system across wider ranges of transmembrane pressure; crossflow rate; and diafiltration concentration in a PC study. Permeate flux, aggregate content, process yield, pH/conductivity traces, retentate concentration, axial pressure drop, and turbidity values were measured at both scales. A good agreement was attained across scales, further supporting its potential use as a scale-down system.

High throughput screening of ultrafiltration and diafiltration processing of monoclonal antibodies via the ambr® crossflow system.

As the biopharmaceutical industry moves toward high concentration of monoclonal antibody drug substance, additional development is required early on when material is still limited. A key constraint is the availability of predictive high-throughput low-volume filtration screening systems for bioprocess development. This particularly impacts final stages such as ultrafiltration/diafiltration steps where traditional scale-down systems need hundreds of milliliters of material per run. Recently, the ambr® crossflow system has been commercialized by Sartorius Stedim Biotech (SSB) to meet this need. It enables parallel high throughput experimentation by only using a fraction of typical material requirements. Critical parameters for predictive filtration systems include loading, mean transmembrane pressure (Δ P¯TMP ), and crossflow rate (QF ). While axial pressure drop (ΔPaxial ) across the cartridge is a function of these parameters, it plays a key role and similar values should result across scales. The ambr® crossflow system is first presented describing typical screening experiments. Its performance is then compared to a traditional pilot-scale tangential flow filtration (TFF) at defined conditions. The original ambr® crossflow (CF) cartridge underperformed resulting in ~20x lower ΔPaxial than the pilot-scale TFF flat-sheet cassette. With an objective to improve the scalability of the system, efforts were made to understand this scale difference. The ambr® CF cartridge was successfully modified by restricting the flow of the feed channel, and thus increasing its ΔPaxial . Additional studies across a range of loading (100-823 gm-2 ); Δ P¯TMP (12-18 psi); and QF (4-8 L/min/m2 ) were conducted in both scales. Comparable flux and aggregate levels were achieved.

Prediction of lab and manufacturing scale chromatography performance using mini-columns and mechanistic modeling.

Chromatography is a cornerstone of biologics downstream purification processes, and there is an ever increasing demand for improved speed and efficiency in process development. Scale-down models are used in process development to optimize operating conditions and study process robustness while expending as little time and material as possible. The advent of automated liquid handling systems and miniature columns has taken the efficiency of process development to another level by allowing up to eight column runs in parallel with column volumes under 1 ml. As expected, results between these miniature columns and typical lab/manufacturing scale columns can deviate due to scale dependent and/or configuration dependent differences. Regulatory guidelines do not require an exact match in scale-down and large scale data, but do require that small scale models account for scale effects, be representative of the commercial process, and be scientifically justified. Therefore, it is important to gain insight into what causes differences between scales and account for them during development. Mechanistic models can be used to understand the physics of the process (fluid flow, mass transfer, etc.) as a function of scale, and provide explanation for deviations that may be observed. We have used mechanistic modeling to study the factors leading to differences in pool sizes observed between scales, and to make predictions on lab scale pool sizes from miniature column data. Results indicate that changes in mass transfer parameters, specifically axial dispersion, between scales leads to the observed differences in pool size. Additionally, we have studied the effect of system differences between automated liquid handling systems and conventional preparative chromatography systems on elution pool volume. This work provides new insight into the fundamental differences observed between scales and overcomes the challenge of enabling the use of miniature column chromatography as a scale-down model for process characterization.

A practical strategy for using miniature chromatography columns in a standardized high-throughput workflow for purification development of monoclonal antibodies.

The emergence of monoclonal antibody (mAb) therapies has created a need for faster and more efficient bioprocess development strategies in order to meet timeline and material demands. In this work, a high-throughput process development (HTPD) strategy implementing several high-throughput chromatography purification techniques is described. Namely, batch incubations are used to scout feasible operating conditions, miniature columns are then used to determine separation of impurities, and, finally, a limited number of lab scale columns are tested to confirm the conditions identified using high-throughput techniques and to provide a path toward large scale processing. This multistep approach builds upon previous HTPD work by combining, in a unique sequential fashion, the flexibility and throughput of batch incubations with the increased separation characteristics for the packed bed format of miniature columns. Additionally, in order to assess the applicability of using miniature columns in this workflow, transport considerations were compared with traditional lab scale columns, and performances were mapped for the two techniques. The high-throughput strategy was utilized to determine optimal operating conditions with two different types of resins for a difficult separation of a mAb monomer from aggregates. Other more detailed prediction models are cited, but the intent of this work was to use high-throughput strategies as a general guide for scaling and assessing operating space rather than as a precise model to exactly predict performance.