Clinical Follow-up of Anti-Carbamylated Antibody Status in Rheumatoid Arthritis Patients at 6, 12 and 18 Months
Conditions: RheumatoId Arthritis
Sponsor: Universidad Autonoma de Nuevo Leon

ID: RE16-00001     Clinical Follow-up of Anti-Carbamylated  
    NCT02958319  
Antibody Status in Rheumatoid Arthritis  
 
Date of the document: November 25th, 2021 
  
Clinical follow-up of Anti-Carbamylated Antibody Status in Rheumatoid 
Arthritis patients at 6, 12 and 18 months  
  
Concept  
Patients with rheumatoid arthritis with positive antibodies against carbamylated proteins  
(anti-CarP) have a more severe clinical course  
Background  
The immune based pathophysiology of rheumatoid arthritis is one of the most studied. We 
already know that the citrullinated peptide antigen inducing antibody formation and subsequent 
[LVG1] anti-cyclic citrullinated peptide (anti-CCP). In some patients this can explain the clinical 
manifestations. However it is also apparent in some groups of patients with rheumatoid arthritis 
who do not have anti-CCP antibodies. It is possible that there is the presence of a variety of 
antigens exposed during the disease, and perhaps different clinical presentations associated with 
each of them.  
The use of anti-CCP has been included in the classification criteria of rheumatoid arthritis 
developed by the American College of Rheumatology in 2010 and generated the presence of two 
sub-groups of patients with rheumatoid arthritis, the positive and negative for anti-CCP. It is very 
important to study the presence of anti-CCP antibodies in rheumatoid arthritis patients because 
they influence the clinical behavior and response to treatment. In very early or undifferentiated 
arthritis, the presence of anti-CCP antibodies can predict the presence of erosions in the course of 
the disease. On the other hand, patients with anti-CCP tend to have better responses to treatment 
with methotrexate.  
Initially it was thought that the obvious pathophysiological link between rheumatoid 
arthritis and citrullinated peptides leading to formation of antibodies was the apparent cause of 
the clinical manifestations, but soon it was demonstrated that there were groups of patients with 
clinical manifestations of rheumatoid arthritis that did not have anti-CCP antibodies so its genesis 
was not explained by citrullination. Then it is plausible to find a diversity of antigens exposed 
during the illness and perhaps different clinical presentations associated with each one or its 
combinations. So, some studies are attempting to show other possible antigens involved in 
rheumatoid arthritis and one of them uses homocitrulline as an antigenic basis to rheumatoid 
arthritis pathophysiology. The carbamylation or homocitrullination is a posttranslational 

modification of proteins that occurs when the amino acid lysine reacts with cyanate in a non-
enzyme-mediated process generating homocitrulline. Mydel, Bokarewa and cols. demonstrated 
that immunization of mice with homocitrulline- and citrulline-containing peptides leads to 
development of erosive arthritis following intra-articular injection of homocitrulline-containing 
peptides and proposed that homocitrulline induced activation of T cells is a key mechanism in the 
pathogenesis of autoimmune arthritis as it serves as an initial triggering event for neo-epitope 
recognition of citrulline containing peptides. Recently It has been shown that rheumatoid arthritis 
patients have homocitrullinated proteins in their joints which can trigger an inflammatory 
response with formation of antibodies against homocitrulline.  
Shi et al. showed in a study of 571 rheumatoid arthritis patients and 350 healthy subjects 
the following statements:  
● 
Anti-CarP antibodies are different from anti-cyclic citrullinated peptide and they do not 
cross-react.  
● 
The Anti-CarP antibodies are present in sera of patients with rheumatoid arthritis.  
● 
Anti-CarP antibodies are found in sera of patients without anti-CCP.  
● 
The Anti-CarP antibodies are associated with increased progression to radiographic 
damage.  
Thus, anti-CarP antibodies are a promising new serological marker for anti-CCP negative 
Rheumatoid Arthritis and are associated with a more severe clinical course.  
Hypothesis  
Patients with rheumatoid arthritis with positive antibodies against carbamylated proteins 
(anti-CarP) have a more severe clinical course and elevated cardiovascular risk. 
Design  
It is a parallel study for clinical follow-up, observational.  
Description of Subject Population(s)  
● Patients older than 18 years old, both genders, with rheumatoid arthritis diagnosis 
according to ACR EULAR 2010 classification that accepted and signed informed consent 
that were seen at the Rheumatology Clinic in Hospital Universitario “Dr. José Eleuterio 
González”, Monterrey, NL. México.   
● Exclusion: Chronic kidney disease and pregnant patients  
Assessment Tools and Procedures  
● DAS-28 VSG  
● Lipid profile  
Length of Study in Months  

● 18  
Primary Endpoints  
● Clinical activity measured by DAS28-VSG in patients with rheumatoid arthritis according to 
antibodies against carbamylated proteins (anti-CarP) status at 6, 12 and 18 months  
Secondary Endpoints  
● Number and accumulative dose of DMARDs according to antibodies against carbamylated 
proteins (anti-CarP) status at 6, 12 and 18 months  
● Cardiovascular risk according to antibodies against carbamylated proteins (anti-CarP) 
status at 6, 12 and 18 months  
Clinical Information  
● Total number of subjects 262  
● Number of subjects for each treatment arm 131  
● Study Duration Per Patient (in Months) 18  
Primary Objective  
The primary objective of this study in adult subject with RA is as follows:  
1. To explore the clinical differences in activity indexes (DAS28-VSG) at 6, 12 and 18 months of 
follow up according the anti-CarP status  
Study Secondary Objective(s)  
● To investigate the remission rate (DAS28-VSG) according the anti-CarP status 
● To compare the percentage of subjects with DAS28-VSG LDA at 6, 12 and 18 months 
according the anti-CarP status  
● To compare the accumulative dose of prednisone between groups according the anti-CarP 
status  
● To compare the number and doses of DMARD´s used to treat RA between groups 
according the ant CarP status  
Study Design   
● Prospective, Non-Randomized, Open Label  
● Inception Cohort Study  
Study Primary Efficacy Endpoints  
The primary efficacy endpoints is as follows:  

● The percentage of subjects who meet DAS28-VSG < 2.6 at 6, 12 and 18 months in the Anti 
CarP+ve arm compared Anti CarP-ve arm  
Study Secondary Efficacy Endpoints  
The secondary efficacy endpoints are as follows:  
● Percentage of subjects with DAS28-VSG LDA at 6, 12 and 18 months at 6, 12 and 18 
months in the Anti CarP+ve arm compared Anti CarP-ve arm  
● Median of the cumulative dose of prednisone at 18 months at 6, 12 and 18 months in the 
Anti CarP+ve arm compared Anti CarP-ve arm  
● Mean of the number and doses of DMARD´s used to treat RA at enrollment at 6, 12 and  
18 months in the Anti CarP+ve arm compared Anti CarP-ve arm  
● Cardiovascular risk according to anti-CarP status  
Study Sample Size Calculation  
A total of 262 subjects will be followed in this study. According the pilot study were we found a 12 
month remission rate in the Anti CarP+ve of 33% arm compared Anti CarP-ve arm of 50%, with a 
difference of 17% in remission rate at 12 month follow-up. We need 131 patients per group. A 2 
group continuity corrected chi square test with a 2-sided significance level (alpha) of 0.05 was 
used to compare sample size and a 0.2 (beta) to power.  
Study References  
.- Jing Shi,Rachel Knevel, et.al. Autoantibodies recognizing carbamylated proteins are present in 
sera of patients with rheumatoid arthritis and predict joint damage.PNAS, October 18, 2011 | vol.  
108 | no. 42  
Jing Shi,Rachel Knevel, et.al. Autoantibodies recognizing carbamylated proteins are present in sera 
of patients with rheumatoid arthritis and predict joint damage. Supporting information 10.1073/ 
pnas. 1114465108  
van Venrooij, W. J. et al. Anti-CCP antibodies: the past, the present and the future Nat. Rev. 
Rheumatol. 7, 391&ndash;398 (2011)  
Turunen S, Koivula MK, Risteli L, Risteli J. Anticitrulline antibodies can be caused by 
homocitrullinecontaining proteins in rabbits. Arthritis Rheum. 2010;62:3345&ndash;3352  
Mydel P, et al. Carbamylation-dependent activation of T cells: A novel mechanism in the 
pathogenesis of autoimmune arthritis. J Immunol. 2010;184:6882&ndash;6890.  
Wang Z, et al. Protein carbamylation links inflammation, smoking, uremia and atherogenesis. Nat 
Med. 2007;13:1176&ndash;1184.