Some molecules refuse to be easy to study. In this case, the drug was highly charged, sticky, and extremely sensitive to proteolysis, and previous partner labs had already struggled with it; “they’ve never seen anything like this before!” Keeping the entire process, from method transfer, optimization, validation, and GLP (Good Laboratory Practices) in‑study sample analysis, within one CRO allowed the project in rat and NHP (Non-Human Primates) serum to move forward in a straight, controlled line instead of stopping and restarting at each handover.
Method development: getting a difficult molecule under control
The project began when the sponsor asked KCAS Bio to transfer existing PK (Pharmacokinetics) methods for rat and NHP serum, confirm their feasibility on our platforms, and optimize them where needed. As required by the sponsor’s specifications, the methods were implemented on the MSD Meso QuickPlex SQ120 platform. Early on, it was clear the molecule would need special handling to stay stable and to keep variability low. The team therefore adjusted day‑to‑day lab practices.
We implemented:
- Manipulations and dilutions on ice, to limit proteolysis
- LoBind tubes and low‑retention tips, to reduce nonspecific binding
- No vortexing, to avoid stressing and aggregating the molecule
- A standardized pipetting technique, to minimize operator‑to‑operator variability
For rat serum, the method arrived already well optimized. The work there focused mainly on clean method transfer and improving sensitivity compared with the original setup. In NHP serum, more re‑thinking was required. We used the robust rat protocol as a template and gradually tuned conditions to the NHP matrix. Because NHP serum showed less matrix interference than rat, we were able to reduce the MRD (Minimum Required Dilution) in NHP and gain sensitivity without introducing artifacts. In rat, where matrix effects were stronger, the MRD had to remain higher. With this, we have successfully developed two PK methods that require less than 15 µL of sample per time point, which is particularly valuable in rats where sample volume is often limited.
A key strategic decision was to switch both methods to frozen standards and QCs, while the original NHP method had used fresh standards. This change:
- Reduced variability
- Limited the consumption of rare matrix
- Aligned calibration curves with frozen study samples, avoiding bias from fresh–frozen shift
These adaptations paid off quickly. All standard and QC batches passed acceptance criteria during development, so there were no cycles of retest and delay. We could move forward with confidence and prepare large batches of standards and QCs for the validation phase and testing phases.
GLP validation: from fit-for-purpose to fully GLP-ready
With solid methods in hand, both rat and NHP PK assays moved into full validation for use in GLP in‑study sample analysis. The validation strategy was built on international expectations, including the ICH M10 guideline on bioanalytical method validation and study sample analysis. This ensured that the methods would not only perform well technically, but also stand up to regulatory review.
During validation, we evaluated:
- Calibration curve performance
- Accuracy and precision
- Selectivity and matrix effects
- Dilution linearity and potential hook effect
- Stability under realistic conditions: bench‑top, freeze–thaw cycles, and long‑term storage
Specificity was not assessed, as no related substances were known that could interfere with quantification in the rat or NHP matrices.
The outcome was straightforward: all validation parameters for both species met predefined acceptance criteria. At this point, both PK methods were fully validated and ready to support GLP in‑study sample analysis, without additional rework or major protocol changes.
GLP in-study sample analysis
The validated methods were then put to work in GLP toxicity studies in rat and NHP. The same GLP framework applied here as in validation, including national GLP requirements, the European directive on GLP, OECD principles for GLP and OECD principles for multisite studies, and ICH M10 recommendations for in-study sample analysis.
- Rat GLP toxicity study
- 1,000 samples analyzed
- Retests <3%
- ISR (Incurred Sample Reanalysis) pass rate >90%
- Conclusion: robust and accurate PK method under routine GLP conditions
- NHP GLP toxicity study
- 1,000 samples analyzed
- Retests <9%
- ISR pass rate >90%
- Conclusion: optimization of handling, matrix management, and MRD selection translated into strong, reliable routine performance across both species
Looking ahead: preparing for clinical sensitivity
With preclinical PK in rat and NHP successfully delivered, the next step is to build a method suitable for future clinical studies, where sensitivity requirements are even higher. To reach lower concentration ranges and handle more challenging scenarios, the team is considering advanced ultrasensitive platforms such as NULISATM or Simoa® HD-X Analyzer™. These technologies may help extend the dynamic range and support reliable measurement when expected concentrations are very low.
Why continuity with one CRO matters (From Transfer to Results)
This case nicely illustrates why keeping everything with one CRO, from method transfer through validation to GLP in‑study sample analysis, brings tangible benefits.
- Knowledge stays with the project. The same scientists who adjusted the pipetting technique or MRD during development are the ones interpreting ISR trends and troubleshooting during GLP analysis.
- Troubleshooting is quicker and more targeted. When something unexpected appears in QC performance or sample trends, the team can immediately link it back to what they learned earlier, instead of rediscovering the same issues at a new site.
- Handling is consistently gentle and appropriate for the molecule. For a highly proteolysis‑sensitive, sticky analyte, continuity in pre‑analytical handling (on ice, LoBind plastics, no vortexing) is just as critical as the analytical run conditions.
- Transitions become smooth instead of disruptive. Moving from development to validation to in‑study analysis becomes a continuous flow, rather than three separate mini‑projects with documentation gaps and differing interpretations. This made the entire process more efficient and time-saving.
In practice, choosing one CRO for method transfer, optimization, full validation, and GLP sample analysis is not just about convenience. It is a practical way to secure high‑quality PK data, reduce rework and delays, and give complex molecules the consistent, well‑understood environment they need, from the very first feasibility runs all the way through to final GLP reports.