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Quality control is the backbone of cell and gene therapies.
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Removing Roadblocks in Cell and Gene Therapy Quality Control

Droplet digital PCR (ddPCR) technology provides unmatched quality control for cell and gene therapies

Marwan Alsarraj, MS

Marwan Alsarraj is the biopharma segment manager at Bio-Rad. He has been at the forefront of developing, marketing, and commercializing technologies for the past 15 years in the life science...

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Published:Nov 07, 2022
|Updated:Oct 28, 2022
|4 min read
Photo portrait of Marwan Alsarraj
Marwan Alsarraj is the biopharma segment manager at Bio-Rad. He has been at the forefront of developing, marketing, and commercializing technologies for the past 15 years in the life science research industry. Marwan obtained his MS in biology at the University of Texas, El Paso.

Powerful gene-editing technologies such as CRISPR-Cas9 have transformed the human genome from an untouchable sacred text into a therapeutic vessel. Personalized medicine, a field that promises treatments tailored to an individual's genetic profile, is finally stepping into its own with the explosion of cell and gene therapy. These powerful treatments are revolutionizing both the clinic and the lab, and the industry is expected to exceed $36 billion USD by 2027.

Personalized medicine in cell and gene therapy takes two forms. In cell therapy, such as CAR-T therapy, cells are administered as a treatment after targeted genetic modification to increase their therapeutic potency. The second form is gene therapy, where the DNA within cells is edited directly without removal and reintroduction. Both approaches walk a razor’s edge between therapeutic and toxic effects, making quality control testing of these novel treatments of paramount importance.

Quality control is the backbone of cell and gene therapies

Ensuring individuals receive the correct dosage of a cell or gene therapy is critical for clinical success. Robust quality control metrics are essential for quantifying the precise genetic dosage of a treatment, ensuring patient safety. The foundation of therapeutic trust in the biopharma industry is rooted in robust quality control procedures that require extreme precision and accuracy.

Beyond biological potency, cell and gene therapy quality control systems must identify potential contaminants. Unlike traditional chemical-based therapies, which can be produced, tested, and stored in large scalable batches, cell and gene therapies often require individual production. This is an absolute win for personalized medicine, but individual production requires individual quality control, which can throttle the transition into the clinic.

While many developers turn to qRT-PCR for quality control testing, this method requires standard curves in each run, introducing biases and inconsistencies and making it impossible to achieve absolute quantification. Here, we explore Droplet digital PCR (ddPCR) technology as an alternative method that provides unmatched rigor and consistency in quality control for cell and gene therapies.

Droplet digital PCR provides individual precision to PCR technology

Through the power of sample portioning, ddPCR technology achieves absolute precision and unparalleled accuracy. To do this, ddPCR assays start with a nucleic acid sample that is partitioned into 20,000 discrete droplets. This partitioning leads to an average of one copy of the donor DNA template per droplet. Then, individual PCR reactions take place within each discrete droplet. Positive droplets containing the target DNA will produce a fluorescent signal during PCR cycling. Taken together, this system produces absolute quantification without a standard curve, generating results quickly and efficiently with unparalleled precision.

An excellent example of ddPCR assays in action in cell and gene therapy is the one-step quantification method published by Clarner et al. in 2021. Researchers simultaneously quantified the transfer of genetic material and changes in expression using ddPCR technology. As proof of principle, they quantified transgene expression and potency in vitro and in nonhuman primates. Specifically, the authors noted that ddPCR workflows enabled powerful precision, reduced variability, and simplified workflows for their team.

In another example relevant to cell and gene therapy, ddPCR can dramatically reduce the time required to detect impurities. Mycoplasma is a common contaminant that can take up to four weeks to detect using traditional testing methods. On the other hand, ddPCR assays can detect low-level contaminants such as Mycoplasma in a single day. The revolutionary pace of ddPCR technology is matched with its industry-leading sensitivity. In a head-to-head test, ddPCR assays identified contaminants undetectable by qPCR. The speed and precision of ddPCR technology is streamlining quality control testing for cell and gene therapies, allowing scientists to focus on what they do best­—the science.

Benefits of ddPCR technology: rigor, cost savings, and more

The ingenious partition system of ddPCR technology generates unparalleled precision, and simplified workflows, and removes PCR bias. These factors result in reduced timelines and highly accurate quality control detection, lowering costs across the board.

First, ddPCR reduces one of the most significant costs in biopharma production: labor. 

Highly skilled workers are expensive, and their time should be spent executing complex valuable experiments rather than running standard quality control assays. Luckily, ddPCR technology is relatively simple to operate and automate, freeing up these skilled team members for more intricate tasks. ddPCR instruments are also versatile, with the ability to detect numerous targets. Therefore, ddPCR technology can help automate and streamline multiple avenues of quality control, from contaminant detection to potency quantification.

ddPCR technology is easily scalable from scientific discovery to commercial deployment. Unfortunately, the transition required to scale up to clinical production is a common bottleneck in cell and gene therapy. To make novel, first-in-class treatments widely accessible, researchers need high-throughput quality control solutions such as ddPCR technology. And while small-scale inefficient qPCR assays may work for the development phase of a therapeutic, changing quality control methods after commercialization can lead to regulatory roadblocks. Therefore, cell and gene therapy developers must start with the endpoint in mind—using the most sensitive and specific quality control protocols. Using ddPCR technology from the outset allows developers to move products swiftly into the clinic without regulatory hiccups.

A new age of cell and gene therapy quality control

From potency quantification to contaminant detection, ddPCR assays are positioned to bring cell and gene therapy quality control testing into a new age. As the cell and gene therapy space continues to expand, it is critical to standardize therapy production with the most rigorous and efficient quality control systems to safeguard patients. Powered by ddPCR technology, cell and gene therapies can now transform the clinical landscape.