MAT Methods
There are currently two commercialised MAT methods available in the market – distinguished based on the type of cell source they employ. However, only the one using cryopreserved, pooled PBMCs is accepted as an endotoxin and non-endotoxin assay by the European Pharmacoepeia.
Available MAT methods
Method classification
There are currently two different types of MAT kit available on the market: (i) the cryopreserved pooled PBMC MAT and (ii) the Mono-Mac 6.
Method differentiators
Among others, the primary differentiator between these kits is the cell source they make use of. The Mono-Mac 6 (MM6) employs the Monocytic Continuous Cell Line based on blood derived from an acute monocytic leukemia patient. The cryopreserved pooled PBMC MAT makes use of monocytes derived from whole blood of healthy donors in the US that are then pooled and cryopreserved to maintain their fresh complexion.
Cryopreserved, pooled PBMC analysis
Legal feasibility
The EP clearly underlines cryopreserved, pooled PBMCs as an appropriate cell source for the detection of both bacterial endotoxins and non-endotoxin pyrogens. As a result, the MAT based on cryopreserved, pooled PBMCs is sufficient as a stand alone pyrogenicity assay for batch release or as a risk assessment (replacing RPT) where BET is used.
Suitability to EP compliant release testing
Cryopreserved, pooled PBMC are made from multiple donors with different genetic backgrounds. EP recommends a minimum of 4 and preferably 8 for batch release testing which is possible based on the offerings of the vendor chosen by producers.
Mono-Mac 6 analysis
Legal feasibility
On the feasibility of MM6 as a pyrogenicity assay the EP (2.6.8.) concludes:
Monocytic cell lines are appropriate for the detection of bacterial endotoxins but have limited use for the detection of non-endotoxin pyrogens.
The MM6’s unsuitability for non-endotoxin detection means similar risk assessments to those required for BET would need to be employed wherever it’s used. In other words, the use of MM6 would require the use of cryopreserved pooled MAT in tandem – unnecessarily increasing pyrogen testing costs.
Suitability to EP compliant release testing
The MM6 cell line is made from a single donor and represents a single genetic background, which is in contradiction with the EPs accepted practices for batch release testing. Specifically, EP regulators required the use of pooled donors with varied genetic backgrounds where MAT is used for release testing.