Rheumatoid factor titers, but not Fc fragments, may be strongly associated with drug survival of anti-TNF agents in patients with rheumatoid arthritis

OBJECTIVE

To investigate the effects of both the Fc fragment in tumor necrosis factor (TNF) inhibitors and rheumatoid factor (RF) titers on treatment survival, disease activity, and laboratory parameters in patients with rheumatoid arthritis (RA).

METHODS

In this retrospective cohort study, patients with RA who had started any anti-TNF therapy between January 2017 and March 2020 and who had stayed on this treatment for at least six months were included. The data of the patients were compared separately according to continuation or discontinuation of treatment and the presence or absence of Fc portion in the structure of anti-TNFs. Patients who were taking certolizumab pegol (CZP) without the Fc fragment were placed in the "without Fc group" (wo/Fc), while patients who were taking other drugs (adalimumab, etanercept, golimumab, and infliximab) were placed in the "with Fc group" (w/Fc).

RESULTS

Among the 221 RA patients whose data were available, 52 patients met the inclusion criteria and were included in the study. There was a significant difference in the DAS28-CRP score between wo/Fc group and w/Fc group in the third month of treatment (p=0.012). However, this difference did not persist at the sixth month of treatment (p=0.384). According to the cox-regression results, RF titers were determined to have a significant impact on the drug survival of anti-TNF agents when adjustments were made for the effects of other candidate predictors (Hazard ratio: 1.007 (1.002-1.012), p=0.009).

CONCLUSION

Our results suggest that compared to the Fc fragment, RF titers were the more important risk factor in survival of anti-TNF drugs.

Camelid VHHs Fused to Human Fc Fragments Provide Long Term Protection Against Botulinum Neurotoxin A in Mice

The bacterium Clostridium botulinum is the causative agent of botulism-a severe intoxication caused by botulinum neurotoxin (BoNT) and characterized by damage to the nervous system. In an effort to develop novel C. botulinum immunotherapeutics, camelid single-domain antibodies (sdAbs, VHHs, or nanobodies) could be used due to their unique structure and characteristics. In this study, VHHs were produced using phage display technology. A total of 15 different monoclonal VHHs were selected based on their comlementarity-determining region 3 (CDR3) sequences. Different toxin lethal dose (LD50) challenges with each selected phage clone were conducted in vivo to check their neutralizing potency. We demonstrated that modification of neutralizing VHHs with a human immunoglobulin G (IgG)1 Fc (fragment crystallizable) fragment (fusionbody, VHH-Fc) significantly increased the circulation time in the blood (up to 14 days). At the same time, VHH-Fc showed the protective activity 1000 times higher than monomeric form when challenged with 5 LD50. Moreover, VHH-Fcs remained protective even 14 days after antibody administration. These results indicate that this VHH-Fc could be used as an effective long term antitoxin protection against botulinum type A.