99mTc-anti-TNF-α scintigraphy in the assessment of rheumatic disease activity

Bianca Gutfilen, Sergio Augusto Lopes de Souza Gianluca Valentini

1 Departamento de Radiologia, Laboratório de Marcação de Células e Moléculas (LMCM), Universidade Federal do Rio de Janeiro,Brazil

2 Advanced Center Oncology Macerata (ACOM), Località Cavallino, Montecosaro, Italy

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic and systemic disease that primarily attacks synovial joints, leads to articular destruction and functional disability. It can affect all ages,sexes, and races. RA is characterized by swelling, pain, and stiffness in joints, but it can also damage the heart, eyes,lungs, kidneys, and skin. Patients with RA experience progressive disability and an increased risk of death. Genetic,hormonal, and environmental factors have been reported to be related to RA.1

In RA, proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-1, and IL-17 play dominant pathological roles.2In the context of inflammatory diseases such as RA, T helper 1 (Th1) and Th17 subsets are well known to mediate inflammation. Furthermore, evidence exists that a defect in either the number or function of Tregs contributes to immune imbalance that culminates in RA.2

Efforts to discover new target therapies for RA have achieved considerable success. For instance, TNF-α inhibitors and B-cell-depleting therapies have benefited many RA patients.2However, these approaches are expensive and none of them reach long-term drug-free remission. Therefore, it is important to develop a new and more effective therapy for RA. Therefore, new effective therapeutic approaches for RA such as the use of mesenchymal stem cells(MSCs) have been considered.2

Psoriatic disease is an inflammatory condition that affects skin and joints, as well as other organs and tissues. Rheumatologists refer to it as psoriatic arthritis (PsA). Patients with PsA show a high prevalence of comorbidities and risk factors, in particular cardiovascular (CV) disease and metabolic syndrome (MetS). Other frequent comorbidities are hyperuricemia, gout, hepatic steatosis, and mood disorders; in addition, patients with PsA consume more tobacco and alcohol than healthy controls, with all its implications.3

Axial spondyloarthritis (axSpA) is an immune-mediated chronic inflammatory disease affecting predominantly the axial skeleton and to a lesser extent the peripheral skeleton,as well as extra-articular organs such as the skin, gut, and eyes. AxSpA is characterized by low back pain from chronic inflammation, which may progress to structural damage to sacroiliac joints and spine, with or without formation of syndesmophytes and ankylosis. The term axSpA includes non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS). The onset of axSpA is usually in the 3rdand 4thdecades. AxSpA is associated with significant loss of function, work disability, and impaired quality of life. Worldwide prevalence of axSpA ranges from 0.5%to 1.5% of the general population. Although patients with AS have worse functional impairment than those with nraxSpA, the clinical disease activity and response to therapy are similar among patients with both the conditions. Patients with axSpA have multiple comorbidities, prominently being myocardial infarction, stroke, osteoporosis, vertebral fractures, duodenal ulcers, and hypertension, as compared to the general population. These comorbidities contribute to the increased morbidity as well as mortality.4

With better knowledge about the natural history of the disease, early diagnosis during the non-radiographic stage has been made possible by using guidance from the Assessment of SpondyloArthritis International Society(ASAS) classification criteria. With advances in the understanding of immunopathogenesis of the disease, new therapeutic agents targeting the inflammatory cytokines and/or their receptors have been developed to treat axSpA. Early diagnosis and treatment of patients with shorter disease duration is associated with improvement of disease activity,function and inflammatory lesions on the MRI, whereas those with longer disease duration are less likely to attain ASAS partial remission. This reinforces the need for early diagnosis and effective treatment to avoid morbidity from symptoms and late consequences of untreated inflammation,and to improve health related quality of life in patients with axSpA. The data on the effect of therapy on radiographic progression are less clear.4

Pharmaceutical proteins with therapeutic application (anti-TNF) have been developed, which have positively impacted the quality of life and the course of various autoimmune diseases including RA.5The safety and efficacy of these biotherapeutic products could be affected by unwanted immune responses which are more common with this type of drug given their protein nature. Immune activation could affect both the safety and effectiveness of the product. This immunogenic response may vary between irrelevant events and serious side effects such as autoimmune reactions or the creation of anti-drug antibodies (ADAb) that are linked to loss of effectiveness for some drugs.5

The experimental models used during the research stages for monoclonal antibodies cannot completely predict this immunotoxic potential since they are in vitro experiments,models in vivo with animal species or studies in small groups of human beings.5Given the above, one of the most relevant objectives for pharmaco-vigilance of biotechnological drugs must be the identification and active search for unknown immunogenic reactions to these pharmaceutical products(Enbrel®and Etanar®). Bearing in mind the potential variations in immune responses to therapeutic proteins based on the genotype of each population group, it is not completely appropriate to extrapolate from the results of immunogenic studies of one population group to another or from one drug to another. The above is especially important in the midst of the current debate after the patent expiration for drugs of this nature which has led to the development and marketing of follow-on biological drugs also called biosimilars. These monoclonal antibodies and fusion proteins are among the more highly developed products of “biotech” origin and currently hold an important place in therapy for immunebased diseases. One group of these molecules, those targeting TNF-α, are of particular interest due to their frequency of use in different autoimmune diseases, i.e., RA. However,development of antibodies against anti-TNF-α drugs, as well as the subsequent loss of the drug effectiveness is known to occur. This presents a major problem in designing therapies to treat these types of diseases.5

TNF-α antagonists, which include Infliximab and Adalimumab, are widely used for treatment of various chronic inflammatory or autoimmune diseases, e.g., RA, Crohn’s disease, AS and PsA.6However, some patients develop anti-therapeutic antibodies (ATAs) which alter the pharmacokinetics and in some instances neutralize the biological effects of these therapeutics, impacting on clinical outcome.Approximately 10-30% of patients fail to respond to anti-TNF-α therapy and up to 60% of patients who responded initially fail to respond to treatment over time and require either dose-escalation or a switch to an alternative therapeutic to maintain a clinical response.6The presence of ATA is thought to be responsible, at least in some patients, for the loss of clinical response.6

The aim of this study is to detect disease’s activity in order to institute anti-TNF-α therapy at the exact moment,avoiding unnecessarily high cost treatments.

SUBJECTS AND METHODS

Study design

This open-label, case analysis, single-center prospective phase I/II clinical trial has been performed at the Department of Radiology of the Federal University of Rio de Janeiro,Brazil. Twelve patients with RA were included. Clinical examination of patients’ hands, wrists, skin and joints were performed on the same day as the99mTc-anti-TNF-α scintigraphy and by the same rheumatologist throughout the study in order to standardize examinations. MRI was performed at an interval of ＜ 48 hours following scintigraphy. Two patients with PsA were evaluated according to Classification Criteria for Psoriatic Arthritis (CASPAR).7For eight patients with AS, besides clinical evaluation,the Bath Ankylosing Spondylitis Disease Activity Score(BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) were used.8Radiographic changes assessed by Bath Ankylosing Spondylitis Radiology Index (BASRI)were also used.9

Ethical approval

This work was approved by Brazilian National Ethics Committee (CONEP - 711/2008) and was registered at ClinicalTrials.gov (identifier: NCT02134613). All procedures were performed in accordance with the ethical standards of the Institutional and/or National Committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Participants

Twelve patients meeting the ACR 1987 criteria for RA,aged ＞18 years, with active disease as defined by 28-joint DAS (DAS-28 ＞ 3.2); two patients according to the CASPAR criteria for PsA, eight AS patients according to the Ankylosing Spondylitis Disease Activity Score and three healthy volunteers were enrolled in this study. All RA patients were positive for Rheumatoid Factor (RF)and two had used anti-TNF-α drugs 5 years ago. The PsA patients were negative for RF. All AS patients were negative for RF and positive for Human Leukocyte Antigen B-27(HLA-B27). Exclusion criteria were pregnancy, lactation,active infection, concomitant severe disease, or a history of drug allergy.

Recruitment

Twenty-three consecutive outpatients with rheumatic diseases, without any exclusion criteria, that accepted to participate in this study were enrolled. Healthy volunteers were recruited via advertisement.

Scintigraphy

Following clinical evaluation, patients underwent99mTcanti-TNF-α scintigraphy 15 minutes and 2 hours after administration of the radiopharmaceutical agent prepared in our lab. Planar and single-photon emission computed tomography (SPECT) images were acquired (Millennium gamma camera; GE Healthcare). Images were considered positive when either the skin or the joints were captured by the test, i.e., had99mTc-anti-TNF-α uptake.

MRI

MRI of hands or wrists was acquired at an interval of no more than 7 days after scintigraphy in order to compare the two imaging methods. Axial and coronal cohorts were obtained in T1-weighted spin echo (repetition time/echo time/thickness: 600-700 ms/15 ms/3 mm) before and after intravenous contrast 0.1 mmol/kg body weight gadolinium(gadoteric acid; Dotarem, Guerbert, France). A 224 × 256 matrix was used and the field of view was 140 mm. We also used the short tau inversion recovery (STIR) sequence on axial and coronal plans (repetition time/echo time /inversion time/thickness: 4,000-3,250 ms/53 ms/150 ms/3 mm).MRI of the hands or wrists was performed (1.5 T Magnetom Avanto MRI; Siemens) in the T1 and T2 weighted sequences with fat suppression in the coronal and axial planes, and in T1 with fat suppression in the coronal and axial planes and after administration of gadolinium.

RESULTS

Tolerance of participants

99mTc-anti-TNF-α administration was well tolerated without any side effects in all patients. No uptake of the radiopharmaceuticals was observed in the joints or skin of the healthy volunteers.

RA

All 12 patients with RA were female, with a median age of 57 years, and DAS-28 ＞ 4.02,99mTc-anti-TNF-α scintigraphy results corresponded to MRI in all cases. There was99mTc-anti-TNF-α uptake in 3 knees, 3 feet, 7 hands, 1 elbow,10 wrists and 2 ankles. The presence of synovitis, joint swelling, tenosynovitis and bone edema in MRI was considered the gold standard for the presence of inflammation.

PsA

Two PsA patients were male, with a median age of 54 years and a diagnosis of psoriasis vulgaris for more than 10 years.The99mTc-anti-TNF-α scintigraphy results corresponded to MRI in both cases.

AS

In eight AS patients, six were male and two were female,with a median age of 49 years, and a BASDAI ranging from 4.5 to 10.0. The99mTc-anti-TNF-α scintigraphy results corresponded to MRI in six cases (2 positives and 4 negatives for active disease) but they did not correspond to MRI in two cases (1 false negative and 1 false positive).All three patients with mechanical lombalgia were negative for active disease in both scintigraphy and MRI.

DISCUSSION

Our group of research has developed a novel approach to label a fully human monoclonal anti-TNF-α antibody (Adalimumab, Abbott, IL, USA) with99mTc, with high labeling efficiency (95%). This technique has shown great success in evaluating disease activity in patients with RA, PsA and AS.It provides an important clinical tool for planning therapy and precisely monitoring the disease. We have compared the scintigraphic results with those from MRI, laboratorial findings and clinical examination. Moreover, to the best of our knowledge, we are the first group of research that has shown the presence of anti-TNF-α in skin through images.

Major advances have been made in the diagnosis and management of rheumatic diseases in the last two decades,especially in RA. Clinicians are now aware of that patients do best if their disease is diagnosed early and effective disease-suppressing therapy is begun before permanent joint damage occurs. Hence, there is an increasing need to develop individualized treatment protocols at reasonable cost and with optimal therapeutic effect. Advanced imaging techniques are promising tools to assist in the early diagnosis and monitoring of therapy in various rheumatic diseases. Tools are required that can image the therapeutic target and sensitively trace changes in disease activity.Nuclear imaging techniques have the potential to fulfill these clinical needs.10-12

Usually the first tracers within nuclear medicine used to evaluate RA are bone tracers made of phosphonates,in particular99mTc-metilenediphosphonate. These tracers bind to osteoblastic activity in bone, and reveal an active response to inflammation within bone. However,99mTcmetilenediphosphonate does not allow differentiation between active joint inflammation and chronic joint damage,either due to RA or due to osteoarthritis. This fact was one of the reasons that raised the need to develop more specific agents for targeting arthritis.10-12

An interesting group of potential radiopharmaceuticals are the radiolabelled biologicals. One of the most promise group is the99mTc-anti-TNFα, which has been shown to accumulate in arthritic joints.10Our group has shown interesting results in a small group of RA patients using99mTcanti-TNF-α scintigraphy in which 198 joints of eight active RA patients were examined. Among these points, signs of inflammation were detected by MRI in 49 (24.7%) joints and by scintigraphy in 48 (24.2%) joints, with agreement between the two methods in 44 joints.13

The limited sensitivity of MRI for non-radiographic axSPA and AS (estimated at around 38-51%) makes it challenging to evaluate young patients with suspected early disorders who have normal pelvic radiographs and negative magnetic resonance findings relating to the sacroiliac joints.14,15

Different groups have been using99mTc-infliximab to assess the degree of TNF-α expression in different rheumatological diseases.16,1799mTc-anti-TNF-α scintigraphy may recognize the molecule involved in the inflammatory process and provide crucial information to help physicians to make decisions about which drugs to use based on biological evidence, and which are cost-effective and appropriate for the treatment of choice. It allows direct identification of the monoclonal antibody anti-TNF-α in the articular joints and skin, while ensuring that the drug has reached its therapeutic target. It also allows correlations to be made between the presence of the drug and clinical responses.15-18Recently, Souza et al. described 2 cases of PsA with99mTc-anti-TNF-α uptake and positive correlation with MRI.18

Scintigraphy scans have the advantage of shorter acquisition time than MRI. Scintigraphy scans provide images of the whole body within 15 minutes and MRI evaluation of both hands and wrists takes up 2 hours. But scintigraphy scans have several limitations, including poor quantification, low accuracy in evaluating the correlation between scatter and attenuation, and difficulty in achieving a standardized uptake value (as done in PET).11-14

Our team has performed a series of studies using99mTcanti-TNF-α to evaluate rheumatic diseases.13,15,18This study protocol for phase I/II clinical trials was designed to investigate the efficacy and safety of99mTc-anti-TNF-α scintigraphy in detection of disease activity. We have not been able to perform statistical analysis because only a small amount of patients have been enrolled in this study.More studies are ongoing. Outcomes from these studies will add reliable clinical data to creat biological therapy for active disease.

Author contributions

BG drafted the paper. BG, SALS and GV were responsible for literature retrieval and edited the paper. All authors read and approved the final version of this paper.

Conflicts of interest

None declared.

Research ethics

This work was approved by Brazilian National Ethics Committee(CONEP - 711/2008). All procedures were performed in accordance with the ethical standards of the Institutional and/or National Committee and with theDeclaration of Helsinki(1964) and its later amendments or comparable ethical standards.

Registration

This work was registered at ClinicalTrials.gov (identifier:NCT02134613) on April 28, 2014.

Declaration of participant consent

The authors certify that they have obtained all appropriate participant consent forms. In the forms, the participants have given their consent for their images and other clinical information to be reported in the journal. The participants understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Open access statement

This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

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A statement of “Publishing Agreement” has been signed by an authorized author on behalf of all authors prior to publication.

Plagiarism check

This paper has been checked twice with duplication-checking software iThenticate.

Peer review

A double-blind and stringent peer review process has been performed to ensure the integrity, quality and significance of this paper.

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