Precision at Speed: Molecular Assays for Safer Cell Therapies

As cell and gene therapy technologies advance, molecular assays have become essential for ensuring both speed and safety in product release. At C3i, these assays are designed with a single objective: to deliver rapid, validated data that regulators and clinicians can trust.

The mycoplasma assay exemplifies this balance. Traditional compendial methods require a 28-day culture period to confirm sterility. C3i’s real-time PCR assay achieves equivalent sensitivity and specificity in just one day. Running on the QuantStudio 5 platform, the method detects over 200 mycoplasma species using TaqMan chemistry and Ct value analysis. Its workflow has been adapted to accommodate cellular therapy products, ensuring comparability with USP <63> and EP 2.6.7 guidelines, an innovation that directly accelerates patient access to treatment.

Safety testing continues with vector copy number (VCN) quantification. Because integrating viral vectors can pose oncogenic risks at high copy levels, precise measurement is critical. C3i’s qPCR assay targets both the vector and a housekeeping gene. The ongoing development of a digital PCR version will enable absolute quantification without the need of standard curves, thereby further improving assay robustness.

C3i also performs replication-competent virus testing (RCR/RCL) to verify that the unwanted recombination events did not occur, ensuring product safety. These qPCR assays monitor viral particle genes and housekeeping genes under strict system-suitability criteria, ensuring that each drug product is free from replication-competent contaminants before release.

For gene-edited therapies, sequencing provides an additional layer of confidence. Sanger sequencing on the SeqStudio platform confirms the accuracy and efficiency of editing. In addition, next-generation sequencing (NGS) on the Ion Chef and S5 systems enables deep profiling of TCR beta receptors, allowing for the monitoring of immune reconstitution over time.

Across all these methods, one principle drives C3i’s approach: data integrity. Every platform operates in accordance with 21 CFR Part 11 compliance, featuring audit trails, and secure signatures. The result is a molecular testing pipeline that unites speed, accuracy, and complete regulatory alignment, transforming complex analytics into actionable, inspection-ready data.

This article is drawn from material presented during the webinar “Cellular Therapy Product Release Testing within a GMP context“, presented on October 16th 2025, by C3i’s experts Ann Brasey (Principal Scientist), Pauline Cassart (QC Technical Supervisor), and Ludovic Durrieu (QC Operations Manager).