CAR-T cell therapy, a revolutionary technology that uses genetic engineering to modify a patient’s own immune cells to precisely attack cancer, has been hailed as a major breakthrough in cancer treatment. However, many are unaware that the cleanliness requirements for manufacturing these “living drugs” are extremely stringent—core production areas must meet ISO Class 5 (100) cleanliness standards and rely on ultra-high efficiency air filters (ULPA).
What is CAR-T Therapy?
Unlike traditional chemical drugs or antibody drugs, CAR-T cells are “living drugs.” They originate from the white blood cells of a patient or donor, undergo a series of complex processes in the laboratory, including separation, genetic modification, and in vitro expansion, before being reinfused into the patient.
This fundamental attribute determines the unique nature of its production process: cell products cannot undergo “terminal sterilization” like traditional pharmaceuticals after final filling through high temperatures, radiation, or filtration.
Any microbial contamination introduced during the production process—whether bacteria, fungi, or viruses—will be directly mixed into the final product and injected into the patient along with the cells. This can lead to serious infections, cell product failure, and even endanger the patient’s life. Therefore, “process control,” rather than “final gatekeeping,” has become the only way to ensure the safety of CAR-T therapy. Ensuring absolute cleanliness of the production environment becomes the first and most important line of defense.
ISO Class 5 Cleanliness
To create a sterile environment for non-sterilizable cell products, international standards classify cleanrooms into multiple levels, with ISO Class 5 (corresponding to the US Federal Standard Class 100) being the core environmental standard for high-risk aseptic operations.
This level imposes extremely stringent limits on the number of airborne particles. Specifically, under static testing conditions, the number of particles ≥0.5 micrometers per cubic meter of air cannot exceed 3,520, while particles ≥5 micrometers are strictly limited to less than 29 per cubic meter.
In the field of cell therapy, this level of cleanliness is typically achieved in two ways: first, by constructing an entire ISO 5 cleanroom; and second, by using equipment such as biosafety cabinets or isolators to create a localized, but more controllable, ISO 5 operating space within a relatively low-level background environment (such as ISO 7 or ISO 8).
ULPA Filters: A More Extreme Guardian Than HEPA
To create and maintain an ISO 5 clean environment, the air filtration system is crucial. End-point filtration typically uses high-efficiency particulate air (HEPA) filters, with ULPA filters representing the highest level of choice.
The choice of ULPA over conventional HEPA filters is based on the specific risks inherent in CAR-T production. Many bacteria, viruses, and even smaller aerosol particles are exactly in the 0.1-0.3 micrometer range or smaller.
ULPA filters, with their higher filtration efficiency, create an insurmountable barrier against these submicron-sized biological contaminants. For example, in gene modification steps involving viral vector manipulation, ULPA effectively prevents potential aerosol diffusion, protecting both products and personnel.
The CAR-T Industry’s Higher Demands for Clean Environments
With technological advancements, the requirements for clean environments have become more stringent than basic standards, in pursuit of ultimate quality and safety:
- More Precise Parameter Control:To prevent temperature and humidity fluctuations from affecting cell state, some leading stem cell or CAR-T laboratories control temperature and humidity fluctuations within ±0.5℃ and ±3% relative humidity, far exceeding conventional standards.
- Control of Harmful Gases: Focus is placed on potentially toxic chemicals such as total volatile organic compounds (TVOCs) that may be released from building materials or equipment, keeping them at extremely low levels (e.g., ≤50µg/m³).
- Automation and Closed-Loop Systems:To fundamentally reduce human intervention and contamination risks, the industry is vigorously promoting production automation. Closed-loop automated processing systems can complete many steps within an ISO 7 level environment, reducing reliance on the highest-level cleanroom area and improving efficiency and scalability while maintaining quality.
Simultaneously, the overall sealing performance of the cleanroom needs to be validated. Continuous environmental monitoring, including online particulate and microbial monitoring, is essential to demonstrating that the clean environment consistently meets standards and ensuring the safety of every batch of “living drugs.”
As a bag of CAR-T cells, prepared through rigorous purification processes, slowly flows into a patient’s bloodstream, the fibers of the ULPA filter in the Stuttgart laboratory are capturing the last trace of potentially present nanoscale dust. Trenntech continues to develop high-standard ULPA filters to protect cell purity, ensuring that promising cell therapies can safely and reliably reach every patient in need.