Endotoxin testing for cell & gene therapy products

Some of the newest forms of drugs use whole cells or nucleic acid vectors to treat disease.?Both can present difficult matrices for endotoxin recovery due to binding between endotoxin and drug components.?BioMerieux has a tool (a kit comprising a plate and reagent set called ENDOLISA?) that utilizes a phage protein bound to a microtiter plate to remove endotoxin (these recombinant phage proteins are highly specific for endotoxin) from such a sample matrix so that it can be subsequently tested at a very low dilution (typically 1:5 or 1:10).?This is possible because after binding of the endotoxin, the sample is completely removed and washed away. ?Then the seemingly empty plate is overlain with recombinant factor C reagent and tested by the regular rFC fluorescent method.?

Several companies have already used this method to test drugs for release testing.?Validation data has shown good PPC recovery (80-120%) and shows good recovery of endotoxin spiked into the sample solution (80-100%).?This “hard spike” is necessary to show that if the endotoxin were there then it would be recoverable.?When using LAL testing the analyst is limited to trying various treatments to try and make the solution more amenable to recovering endotoxin and sometimes this is just not possible.?

Sometimes a user (performing validation) may not be aware of the necessity of a hard spike and alternatively the PPC that is spiked into the plate as a 10 microliter spike is much more easily recovered than the hard spike and does not really mimic endotoxin that has been thoroughly mixed in the drug sample matrix.?This extra sample-reagent interaction is where the deleterious binding occurs most.?

Thus validation is not just getting something to work, but rather scientifically proving that the endotoxin in a sample will truly be detected in an outgoing QC test sample.

More info is available here:

https://biomerieuxdirect.com/industry/c/ENDOLISA%C2%AE/p/609033 ??