Leon Tian, Director of US Project Management, ProBio, walked through the cell line development, high-concentration formulation, and purification workflow, delivering a bispecific antibody tox batch from a single selected clone in 4 to 5 months.
Speed is always a top priority in biologic CMC development — but most of the time, speed trades against quality or regulatory confidence. What I want to show today is that this trade-off is not necessary.”
ProBio’s client brought a demanding brief: a bispecific antibody project requiring a high-concentration formulation of approximately 120 mg/mL, produced from a single selected clone, with a tox batch delivered in 4 to 5 months. Tian called it a “mission impossible” scenario, then spent the session methodically explaining how ProBio’s platform addresses each part of that challenge.
Why High-Concentration Formulations
Since 1998, approximately one-third of FDA-approved therapeutic antibodies have used high-concentration formulations, with around 70% administered via subcutaneous (SC) injection. Tian cited the benefits as patient self-administration, reduced clinical burden, lower drug substance (DS) volume, and reduced manufacturing and logistics costs. He also flagged intravitreal injections as a specialist application, where volume constraints of 50 µL or less make high-concentration formulations a practical necessity. ProBio’s platform reaches up to 150 mg/mL and covers multiple modalities, including monoclonal antibodies (mAbs), bispecific antibodies (BsAbs), trispecific antibodies (TsAbs), and Fc fusion proteins.
The Formulation Workflow
Tian described a staged screening process that moves from pH and buffer screening through solubility, excipient, and surfactant evaluation, progressively narrowing candidates before advancing to viscosity reducer screening, freeze-drying process development, and formulation verification. The funnel begins with 12 or fewer candidates at the initial excipient screening stage and closes to three or fewer candidates before high-concentration testing. Analytical tools used across the process include nanodifferential scanning fluorimetry (nanoDSF), differential scanning calorimetry (DSC), dynamic light scattering (DLS), and freeze-drying microscopy (FDM). The session included a case study where the final formulation was 140 mg/mL in histidine buffer with sucrose, proline, and PS80, verified at 40°C for four weeks.
A significant technical challenge at high concentration is pH drift during ultrafiltration and diafiltration (UF/DF). Tian explained that increased viscosity above 140 mg/mL generates pressure challenges, while the buffer exchange process produces pH shifts of up to 0.3 units. ProBio’s solution combines a reformulated buffering strategy with flux adjustments at buffer change points and post-exchange pH correction.
BsAb Process Development and Timeline
“Most CDMOs claim they can deliver tox materials in four months, but most achieve that with a mixed pool or mixed clones. Then you need a comparability study to show your tox material is comparable to your final GMP material. Our client wanted to avoid that risk entirely, which is why we used a single clone.”
The ExpressCMC timeline targets tox drug substance (DS) in 4 months and GMP drug product (DP) in 9 months, enabled by the proprietary ProMax vector. Its two elements, TiterLift and SteadyHold, deliver titers of approximately 6 g/L for mAbs and 9 g/L for BsAbs, with titer drop below 30% over 60 or more population doublings without selective pressure.
“Over 50% of our projects are these kinds of challenge molecules — bispecifics, high concentration, complex formats. We’ve accumulated a lot of hands-on experience, and from that we’ve built a toolbox to quickly identify problems, find the root cause, and avoid the same issue happening again.”
