MAUI, HAWAII – A variant in the human leukocyte antigen gene – DQA1*05 – almost doubled the risk of antibodies forming against tumor necrosis factor (TNF) inhibitors in Crohn’s disease patients, irrespective of concomitant immunomodulator use, according to a report in Gastroenterology.
“Pretreatment genetic testing for HLA-DQA1*05 may help personalize the choice of anti-TNF and the need for combination therapy,” concluded investigators led by Aleksejs Sazonovs, of the Wellcome Sanger Institute in Hinxton, England.
The same variant increases the risk of celiac disease, and it is included in commercial celiac genotyping assays. The allele is carried by about 40% of Europeans.
“This is turning into a hot topic; people are talking about it, [and it’s] blowing up on Twitter,” said Edward Loftus, MD, a professor and consultant in the division of gastroenterology and hepatology at the Mayo Clinic in Rochester, Minn. “It turns out this is really a significant predictor of immunogenicity. Whatever your risk of developing antibodies, it’s going to double if you have this HLA marker, and it’s common.
M. Alexander Otto/MDedge News
Dr. Edward Loftus
“I think we are going to start [stratifying] our decision on combination [or] monotherapy based on this,” added Dr. Loftus, speaking at the Gastroenterology Updates, IBD, Liver Disease Conference. “I would argue that, if your patient has this marker, it would be criminal to give that patient infliximab monotherapy.”
The finding also begs the question of whether to bypass anti-TNFs altogether if a patient has the marker, Dr. Loftus noted, and just use ustekinumab, vedolizumab, or another agent.
Checking for celiac disease in inflammatory bowel disease isn’t unusual and involves the same gene variant, he added, so payer coverage shouldn’t be much of a problem.
The investigators ran a genome-wide association study on 1,418 biologic-naive Crohn’s patients starting infliximab or adalimumab therapy. Patients were in their 30s, on average, with a disease duration of about 3 years; there were about equal numbers of men and women.
A total of 44% of patients developed antidrug antibodies within a year. Overall, the rate of immunogenicity – defined as an antidrug antibody titer of at least 10 AU/mL – was nearly doubled in HLA-DQA1*05 carriers (hazard ratio, 1.90; 95% confidence interval, 1.60-2.25).
The association was consistent for patients treated with adalimumab (HR, 1.89; 95% CI, 1.32-2.70) or infliximab (HR, 1.92; 95% CI, 1.57-2.33) and for patients treated with anti-TNF therapy alone (HR, 1.75; 95% CI, 1.37-2.22) or in combination with an immunomodulator, usually azathioprine (HR, 2.01; 95% CI, 1.57-2.58).
The highest rates of immunogenicity, 92% at 1 year, were in HLA-DQA1*05 carriers on infliximab monotherapy. The lowest rates, 10% at 1 year, were in adalimumab patients on combination therapy who didn’t carry the variant. HLA-DQA1*05 was also associated with lower drug persistence rates.
The specific alleles HLA-DQA1*05:01 and HLA-DQA1*05:05 mediated most of the risk.
The study authors advised that “all patients treated with an anti-TNF should be prescribed an immunomodulator to lower the risk of immunogenicity.” Among HLA-DQA1*05 carriers “in whom immunomodulators are contraindicated or not tolerated, clinicians might advise against the use of anti-TNF drugs, particularly infliximab.”
In contrast, “patients who do not carry HLA-DQA1*05 might be given the choice between adalimumab or infliximab combination therapy,” the investigators said. “Patients without the risk allele and a history of adverse drug reactions to thiopurines and/or methotrexate, or who are at high risk of opportunistic infections, might be spared the additional risks of combination therapy and treated with adalimumab monotherapy.”
The mechanism for the association is unknown, the authors said.
The work was funded by the British Society of Gastroenterology, AbbVie, Merck, Pfizer, and others. The authors disclosed numerous ties to those or other pharmaceutical companies. Two authors were employees of AbbVie, marketer of the branded adalimumab Humira.
SOURCE: Sazonovs A et al. Gastroenterology. 2020 Jan;158(1):189-99.