The potential for directly DNAinteracting mutagenesis by naloxegol and/or its S9 metabolites was examined in vitro in bacterial reverse mutation assays and in forward mutations in mammalian cells as well as in vivo in the mouse bone marrow micronucleus test. All assays were of acceptable design and quality, and were consistent with ICH S2A, ICHS2B, and relevant Organisation for Economic Co-operation and Development (OECD) test guidelines and test acceptance criteria. Naloxegol was not classically mutagenic or clastogenic in the mammalian cell forward mutation assay or in the mouse bone marrow micronucleus test.
No evidence of mutagenicity was observed in bacterial reverse-mutation assays when naloxegol was tested as the oxalate salt. However a clearly mutagenic and genotoxic degradant, glycidaldehyde, was present in a number of batches of free base naloxegol. Use of the naloxegol oxalate salt that has been stored in the solid state protects naloxegol from degradation and release of glycidaldehyde. Other genotoxic impurities are present in Movantik (see Impurities below).