Since Antibody-drug Conjugates (ADC) are already approved for the treatment of relapsed Hodgkin’s lymphoma, HER2-positive metastatic breast cancer and B cell lymphoma, among others, high expectations are placed on this class of bioconjugates. Indeed, more than 100 different ADCs have been studied for various applications by 2022, presumably with several more to follow. [1][2]

Due to their composition, however, advanced risk management is necessary during ADC manufacturing, processing and transport. With a monoclonal antibody, a cytotoxic payload and a linker being their three main constituents, individual characteristics and risks of these three components have to be considered. In particular, but not limited to, cytotoxic payloads present unique challenges and pose considerable risks at multiple levels. Therefore, end-to-end solutions for bioconjugation processing are playing an increasing role in ADC processing and the task to cope with these challenges and provide a safe way to make the unique advantages of antibody-drug conjugates more accessible.

Risks when dealing with ADCs
As already anticipated, the risks associated with the handling of antibody-drug conjugates are manifold and are related to their three main components: a highly toxic drug substance, bound to a monoclonal antibody with a chemical linker. Within their therapeutic application, ADCs target specific cancer cells and release their cytotoxic substance to induce cell death.

However, the components themselves as well as their combination requires elaborate pharmaceutical processes with regard to potential risks for staff, the environment and patient.

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Risks for staff and the environment
HPAPIs – highly potent active pharmaceutical ingredients – used in the production of antibody-drug conjugates have the major advantage of being extremely effective, with only minute doses necessary to achieve enormous effects. They are able to damage cellular structures and can be used in the targeted treatment of various types of cancer by being linked to monoclonal antibodies.

However, it is their highly toxic nature that makes the processing of HPAPIs a challenging endeavor. Manufacturing sites have to establish effective and fail-safe security measures in order for staff and the environment to be protected from exposure. These preventive measures have to eliminate the risk of skin contact, but also of inhalation, as these substances have an occupational exposure limit (OEL) of 10 μg/m3 or below. This makes even small amounts of HPAPIs extremely dangerous to employees, which is why staff has to be protected from any direct contact – be it with HPAPIs in a solid or solute state. [3]

Product safety
ADCs are not only highly effective and dangerous if mishandled, but also extremely vulnerable. Their chemical structure needs to be prevented from damage, which could result in ineffectiveness of the bioconjugate and subsequent risks or delays in a patient’s therapy.

Aseptic fluid management is vital in order to avoid cross-contamination and bioburden. Additionally, the processed monoclonal antibodies are temperature-sensitive, making it necessary to establish streamlined cold-chain management along the manufacture and transport of ADCs.

Critical steps in ADC processing
In the production of ADCs, equally hazardous and sensitive substances are processed. The process consists of several coordinated steps, each of which takes into account the safety requirements for personnel and the environment, but also the fragile structure of antibody-drug conjugates.

Critical steps within this process include fluid management of ADCs, freezing processes, as well as their subsequent storage and shipping.

Fluid management of ADCs
In the production of antibody-drug conjugates, both monoclonal antibodies and cytotoxic payload are usually processed in a liquid state (in a solution with other components). Therefore, fluid management solutions are required that both protect the sensitive nature of the monoclonal antibodies and staff from being exposed to highly potent active pharmaceutical ingredients.

Additionally, it is important to prevent contamination of the individual components of ADCs and, of course, of the resulting bioconjugates. To meet these requirements, special processes and equipment are needed for aseptic fluid management, e.g. sterile tubings, filters, and packaging.

Sterilization of the components of an aseptic fluid management process is usually performed via gamma irradiation or autoclaving. However, this process can be outsourced if pre-sterilized equipment based on single-use technologies are used, saving both costs and energy at the manufacturing site. [4]

Freezing Antibody-Drug Conjugates
Both monoclonal antibodies and the resulting ADCs are not stable at room temperature and would lose viability before doing their job. Additionally, repeated freeze and thaw processes can also affect the quality of ADCs. Therefore, measures have to be taken to store different volume sizes of ADCs in an adequate manner. [5]

In order to maintain their structural qualities, advanced cold chain management of ADCs  including controlled freeze and thaw processes is necessary. These processes, however, demand for more elaborate equipment, such as specialized freeze/thaw units or ultra-cold temperature freezers. These machines have to be cGMP compliant and meet high security standards as well as regulatory requirements. An additional focus has to be put on scalability, as the implementation of cold chain management solutions means a considerable investment for manufacturers.

The most promising approach in freezing and thawing ADCs is plate freezing based on single-use technologies. Filled in sterile single-use bioprocess containers, ADCs are brought to ultra-cold temperatures with fully controllable and rapid freezing rates. Fast freezing has the advantage of a reduced risk for cryoconcentration compared to slow freezing, and is therefore a favorable approach in freezing ADCs. [6][7]

Comparison: Effects of fast and controlled vs. slow and uncontrolled freezing (click on the image to enlarge).

Safe transport of ADCs
Another challenge is the safe transport of ADCs. Not only must they be protected from temperature fluctuations during ultra-cold storage – leakages must be avoided at all costs. Product loss does not only result in high costs, but also exposes personnel to toxic substances.

To eliminate these risks, protective measures must be taken, such as the use of protective shells that enclose the filled single-use bags. Additionally, high-performance freezers are required that are both cost and space efficient, delivering constant temperature levels during storing and shipping.

Closed systems to avoid safety impacts
As illustrated in the previous sections, there are several challenges to overcome in the safe handling of ADCs. Nevertheless, their success so far and the high expectations that oncology puts in this new class of biopharmaceuticals justify the effort to develop adequate solutions.

RoSS® Shell from Single Use Support, protecting single-use bioprocess containers. Photo courtesy: 2023 Single Use Support GmbH.

One approach to overcoming these challenges is the implementation of processes enabling closed systems in ADC manufacturing and logistics. With seamless transitions between single processing steps and an advanced level of automation, manual intervention by staff is reduced to an absolute minimum. Considering the complexity of each of these steps, an additional focus on risk management is essential.

Furthermore, ADCs themselves have to be protected from damaging environmental impacts, such as mechanical stress or variations in temperature. Leakage and breakage are critical on two levels: On one hand, this leads to significant security problems. In addition, the loss of products causes financial stress and time delays.

Closed fluid management systems and the implementation of accurate hardware solutions are a chance to optimize risk management in dealing with ADC, which is essential for the research, industrial and healthcare sectors to fully take advantage of these drug products.

[1] Zhao P, Zhang Y, Li W, Jeanty C, Xiang G, Dong Y. Recent advances of antibody drug conjugates for clinical applications. Acta Pharm Sin B. 2020 Sep;10(9):1589-1600. doi: 10.1016/j.apsb.2020.04.012. Epub 2020 Apr 24. PMID: 33088681; PMCID: PMC7564033.
[2] Fu, Z., Li, S., Han, S. et al. Antibody drug conjugate: the “biological missile” for targeted cancer therapy. Sig Transduct Target Ther 7, 93 (2022).
[3] Hensgen MI, Stump B. Safe handling of cytotoxic compounds in a biopharmaceutical environment. Methods Mol Biol. 2013;1045:133-43. doi: 10.1007/978-1-62703-541-5_8. PMID: 23913145.
[4] Marciniak, M. Process safety in fluid management of ADCs. Single Use Support. Online. Last accesses on June 17, 2023
[5] Källsten M, Hartmann R, Kovac L, Lehmann F, Lind SB, Bergquist J. Investigating the Impact of Sample Preparation on Mass Spectrometry-Based Drug-To-Antibody Ratio Determination for Cysteine- and Lysine-Linked Antibody-Drug Conjugates. Antibodies (Basel). 2020 Sep 8;9(3):46. doi: 10.3390/antib9030046. PMID: 32911603; PMCID: PMC7551423.
[6] Minatovicz B. et al. Freeze-concentration of solutes during bulk freezing and its impact on protein stability. Journal of Drug Delivery Science and Technology. 58 (2020). 101703. doi: 10.1016/j.jddst.2020.101703.
[7] Kirchmair, J. Controlled freezing of ADCs. Single Use Support. 2022. Online. Last accesses on June 17, 2023.


Corresponding Author E-mail: Brian Moloney

Key terms: ADC, Advanced Risk management, Aseptic fluid management, Freezing, occupational exposure limit, process enabling closed systems, single-use technology, SUT
Published In: ADC Review| Journal of Antibody-drug Conjugates


How to cite:
Brian Moloney 1 How Process Enabling Closed Systems Offer Maximum Safety in ADC Manufacturing – J. ADC. April 10, 2023. DOI: 10.14229/jadc.2023.06.19.001.

1 Single Use Support

Last Editorial Review: June 16, 2023

Creative Commons License

Article History:

  • Original Manuscript Received May 29, 2023
  • Review results received May 9, 2022
  • Manuscript accepted for publication June  19, 2023

Featured image by BlitzKrieg1982, licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

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