Rabbit Pyrogen Test alternative: The Monocyte Activation Test (MAT)
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The Ph. Eur. Commission has engaged in a path to completely replace the Rabbit Pyrogen Test with MAT by 2026.
Parenteral products are mandated by the European Pharmacopoeia to be free of either endotoxins or pyrogens more broadly. A pyrogen test is often specifically favoured by Ph. Eur. where there is an established risk of non-endotoxin pyrogen contamination during the product's manufacturing process or where the product's very nature makes Bacterial Endotoxin testing (BET) unsuitable (e.g. intrinsic pyrogenicity of product or where interfering factors between product and BET are insurmountable).
For over 100 years, the Rabbit Pyrogen Test (RPT) has been the gold standard test for pyrogens.
However, the Ph. Eur. has mandated the transition towards in-vitro alternatives in accordance with the 3Rs principles of Replacement, Reduction and Refinement of in-vivo testing. Having added the Monocyte-activation test (2.6.30.) general chapter in 2009, as of June 2021 the Ph. Eur. has committed to a five year plan to see the rabbit pyrogen test completely replaced. The General Chapter on the Rabbit pyrogen test (2.6.8.) clearly states:
“... In accordance with the provisions of the European Convention for the Protection of Vertebrate Animals used for Experimental and Other Scientific Purposes, tests must be carried out in such a way as to use the minimum number of animals and to cause the least pain, suffering, distress, or lasting harm. Wherever possible and after product specific validation, the [rabbit] pyrogen test is replaced by the monocyte-activation test.”
The Monocyte Activation Test will replace the Rabbit Pyrogen Test as —
(1) In-vitro pyrogen test batch release assay
There are currently 59 Ph. Eur. texts including those for human vaccines, blood products, antibiotics and radio-pharmaceuticals that employ the Rabbit Pyrogen Test as a batch release assay which will need to be replaced by the Monocyte Activation Test.
(2) Non-endotoxin pyrogen risk assessment assay
The Rabbit Pyrogen test was previously been used as a means to assess the risk of non-endotoxin pyrogenic contamination in manufacturing processes where BET was employed as the stand-alone release assay. Here too, MAT will be employed as the in-vitro replacement by 2026.
Ways to get started replacing the Rabbit Pyrogen Test with MAT
a. Buy a Monocyte Activation Test kit
Request a quote through our website and we'll reach out to you to walk you through pricing, feasibility study planning, all necessary equipment, kit manuals and organise either online or in-house training where needed.
b. Outsource testing to MAT experts
MAT BioTech has a global network of GMP certified MAT CROs that have the experience to carry-out feasibility studies, product-specific validation and routine testing. Using these services can be a great way to investigate replacing RPT with MAT without investing heavily internally.
How does the Monocyte Activation Test method work, broadly?
Unlike the Rabbit Pyrogen Test, the Monocyte Activation test uses human blood to simulate a human's immunological response to a parenteral product's endotoxin and non-endotoxin pyrogenic contamination. MAT is carried out as follows:
(i) Incubation of parenteral
The parenteral product is incubated with you MAT kit's peripheral blood mononuclear cells.
(ii) Monocyte activation
The product preparation is then left overnight, during which the TLRs of the monocytes will in turn recognise the presence of any potential endotoxins and non-endotoxins which will then launch the human immune system response. Cytokine release is then stimulated.
(iii) Detection/quantification of cytokines
A human IL-6 ELISA is carried-out the next morning as means of detection and quantification of the concentration of cytokines released.
Making use of the LPS standard curve, the concentration of cytokines measured in the product preparation is then converted into Endotoxin Equivalent units/ml.
What international regulatory bodies say about MAT as a Rabbit Pyrogen Test replacement
The US Food and Drug Association (FDA) & US Pharmacopeia (USP)
FDA "Guidance For Industry – Pyrogen and
Endotoxins testing: Questions and Answers" 2012:
the use of Monocyte Activation Test is
pointed out as an alternative to the Rabbit Pyrogen Test but must be validated according to USP <1225>;
USP <151> Pyrogen Test mentions that "A
validated, equivalent in vitro pyrogen or bacterial
endotoxin test (e.g. MAT ) may be used in place of the in vivo Rabbit Pyrogen Test, where appropriate".
The European Pharmacopoeia (Ph. Eur.)
Ph. Eur. 2.6.8 Pyrogens: Recommendations to use MAT (2.6.30) as a replacement to Rabbit Pyrogen Test wherever possible;
Ph. Eur. 2.6.30 Monocyte Activation Test: "The monocyte Activation Test (MAT) is primarily intended to be used as a replacement for the Rabbit Pyrogen Test."
Ph. Eur. 5.1.10: "The Monocyte Activation Test (2.6.30) is a suitable method to use to rule out the presence of non-endotoxin pyrogens in substances or products"
The Indian Pharmacopoeia Commission (IPC)
As of July 1st 2018, the Monocyte Activation Test has been included in the Indian Pharmacopoeia's 8th edition as viable alternative to the Rabbit Pyrogen Test.
Japanese Pharmacopoeia (JP)
JP XVII edition: the validation of alternative methods like MAT are possible (as replacement of Rabbit Pyrogen Test, for example) if the alternative method gives better accuracy and precision.
International Conference on Harmonisation “recommends that the analytical procedures described in the official pharmacopeial texts, European Pharmacopoeia (Ph. Eur.): 2.6.14. Bacterial Endotoxins, Japanese Pharmacopoeia (JP): 4.01 Bacterial Endotoxins Test, and United States Pharmacopeia (USP) General Chapter <85> Bacterial Endotoxins Test, can be used as interchangeable in the ICH regions.
Comparing the rabbit pyrogen test (RPT) and monocyte activation test (MAT)
Beyond a solely regulatory impetus to protect animal welfare, the phenomenon of organisations transitioning away from the Rabbit Pyrogen test (RPT) has already been steadily occurring since the early 2000’s. This primarily owes to the rabbit pyrogen test’s low sensitivity, non-human specificity and the solely qualitative results it can promise. Further, the Rabbit Pyrogen Test (RPT) lacks a positive control, is widely considered to be unrobust as stress to rabbits has been found to influence results, and perhaps most saliently, the Rabbit Pyrogen Test is limited in the types of products it can effectively test. For example, the Rabbit Pyrogen Test cannot be employed in detecting pyrogens in chemotherapeutics, immunosuppressive agents, nor can it be used to test human cellular preparations such as plasmas or stem cells.
Unlike the Rabbit Pyrogen Test, the CTL-MAT Monocyte Activation Test kit offered by MAT BioTech reflects the specifically human reaction to pyrogens and thus better predicts the pyrogenic activity in humans than the Rabbit Pyrogen Test does. Moreover, while the Rabbit Pyrogen Test has a relatively high limit of detection (EU/ml) when compared to BETs on the market, the CTL-MAT Monocyte Activation Test kit in fact has the very lowest limit of detection (0.004 EU/ml) when compared to any other assay – whether LAL, rFC or Rabbit Pyrogen Test – on the market. As previously mentioned, the Rabbit Pyrogen Test is limited in the different types of medicinal products or devices that it can test while the Monocyte Activation Test is efficacious in testing every type of product.
Rabbit Pyrogen Test (RPT) vs. Monocyte Activation Test (MAT)
Monocyte Activation Test (MAT)
Sensitivity (Limit of Detection)
Ph. Eur. perspective
Detectable pyrogenic contaminations
Endotoxins (from Gram-negative bacteria)
Yeasts & Molds
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