An anti-tumor necrosis factor (TNF) monoclonal chimeric antibody, Infliximab, is used to treat a variety of immune mediated diseases including inflammatory bowel diseases (IBD). Anti-drug antibody (ADA) formation in mice increases with infliximab dose given and the blood concentration of infliximab-TNF complexes, according to a study published in Gastroenterology. Based on human studies, investigators were able to propose that these findings indicate the importance of optimizing infliximab dosage to a level that achieves efficacy without activating an immune response against the infliximab-TNF complex.

The efficacy of the monoclonal antibody infliximab can decrease in patients who develop ADAs. The current study was designed to investigate features of the immune system, infliximab antibodies, and the drug’s complex with TNF to see how these factors may contribute to the rise of ADAs. Female C57BL/6 mice (6-8 weeks; 17-20 g) obtained from Harlen were acclimatized for at least 1 week prior to experimentation, and were then given injections of recombinant human TNF and infliximab or infliximab F(ab’)2 fragments.

Every 2 to 3 days for 2 weeks, and then weekly thereafter for up to 6 weeks, blood samples were collected, and ADAs and infliximab-TNF complexes were measured with ELISA. Blood samples and intestinal biopsies were taken from patients undergoing endoscopy who had been given infliximab for inflammatory bowel diseases, and infliximab-TNF complexes were measured with ELISA. Mass cytometry was used to detect infliximab-specific plasma cells in patient tissue samples, and activation of innate immune cells in healthy donor peripheral blood-mononuclear cells (PBMC) incubated with infliximab or infliximab–TNF complexes were studied. Endocytosis was blocked with the inhibitor PitStop2, toll like receptors (TLR) were blocked with antibodies, and real-time PCR and ELISAs were used to measure cytokine expression. Confocal microscopy was used to measure infliximab and infliximab–TNF complexes uptake by THP-1 cells.

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In each dosing group, 4 to 5 mice were injected with infliximab at baseline and blood was drawn at intervals. In the mice, ADA formation was strongly predicted by injected infliximab dose (AUC, 0.922; 95% CI, 0.861-0.983; P <.0001), with high-dose infliximab (>0.002 mg/g [x/30]) being 90.6 times more likely to produce ADA formation compared with low dose (<0.002 mg/g) (OR, 90.6; 95% CI, 22.47-365.45; P <.0001). Levels of infliximab-TNF complex strongly predicted ADA formation (AUC, 0.944; 95% CI, 0.851-1.000; P =.003) and high ADA levels (AUC, 0.933; 95% CI, 0.831-1.000; =.001). Intestinal tissues, but not blood samples, from human patients contained infliximab-specific plasma cells and infliximab-TNF complexes. Compared with control PBMC, incubation of PBMC with infliximab–TNF complexes led to a 4.74-fold increase in interleukin 1beta (IL1B) mRNA level (P =.005), increased secretion of IL1B protein, and a 2.69-fold increase in TNF mRNA expression (P =.013). Infliximab only reduced expression of IL1B and TNF, and although TLR2 and TLR4 antibodies did not block increases in TNF or IL1B expression, endocytosis was required, and THP-1 cells endocytosed higher infliximab-TNF complex levels than infliximab only.

Limitations of this study included the use of a murine model raising the concern that the mouse antigen recognition for this antigen differs from the human response, as well as the origin from which infliximab-specific plasma cells were derived could not be determined. Nevertheless, study investigators concluded “that infliximab–TNF complexes, formed as a result of intestinal tissue stoichiometry, trigger ADA formation at least in part due to innate immune activation triggered by enhanced antigen uptake relative to infliximab only. Taken together, this data may add insight into variable ADA formation and suggests potential new means to reduce immunogenicity by manipulating drug doses. Further prospective research is needed to validate such possibility.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Bar-Yoseph H, Pressman S, Blatt A, et al. Infliximab-tumor necrosis factor complexes elicit formation of anti-drug antibodies [published online August 8, 2019]. Gastroenterology. doi: 10.1053/j.gastro.2019.08.009