Monitor antidrug antibodies for their impact on drug clearance to maximize treatment outcomes in rheumatology patients treated with biologics, Niels Vande Casteele, PharmD, PhD, said in a virtual presentation at the annual Perspectives in Rheumatic Diseases held by Global Academy for Medical Education.

Dr. Niels Vande Casteele, University of California, San Diego

Dr. Niels Vande Casteele

Antidrug antibodies (ADAb) are associated with impaired drug efficacy and safety, he noted. Furthermore, he indicated that when ADAb bind to the drug, they can either block the activity of the drug directly and/or may cause the formation of complexes, leading to accelerated drug clearance and reduced drug exposure.

Dr. Vande Casteele, assistant professor in the department of medicine at the University of California, San Diego, outlined factors that contribute to immunogenicity, which occurs when the body reacts to neoantigens, or when there is a breakdown in immune tolerance, he said.

Genetics can play a key role in the risk for immunogenicity, as can the route of administration, dose, treatment duration, and concomitant diseases or medications, he explained.

In addition, product-related factors including sequence variation, glycosylation, host cells, contaminants and processing impurities, formulation, and handling and storage issues can impact immunogenicity, he noted.

For example, Dr. Vande Casteele cited a study in which the proportion of infliximab-treated patients with positive ADAbs was substantially higher among those receiving the drug intravenously, compared with those receiving it subcutaneously. As for treatment dosing, data on patients treated with infliximab have shown that maintenance therapy is associated with lower rates of immunogenicity, compared to episodic therapy, he said.

In terms of genetics, Dr. Vande Casteele cited a study published in January in Gastroenterology showing the presence of the HLA-DQA1*05 allele, carried by approximately 40% of the European population, significantly increased the rate of immunogenicity to infliximab and adalimumab in patients with Crohn’s disease (hazard ratio, 1.90).

Therapeutic drug monitoring and overcoming immunogenicity

Dr. Vande Casteele also reviewed how to measure ADAbs. “Antidrug antibody units and concentrations can differ across assays,” he said.

In clinical practice, “the majority of patients at the time of secondary loss of response will present with low drug exposure, and that is when you measure antidrug antibodies,” he said.

In rheumatology patients, the presence of ADAbs against anti–tumor necrosis factor monoclonal antibodies conveys a risk for treatment discontinuation, as well as “a risk of development of hypersensitivity reactions in all immune-mediated inflammatory diseases,” Dr. Vande Casteele said.

However, “the combined use of anti–tumor necrosis factor monoclonal antibodies and disease-modifying antirheumatic drugs reduces the development of antibodies and subsequent risks,” he noted.

For therapeutic drug monitoring in patients with a secondary loss of response, “first, look at the trough concentration,” Dr. Vande Casteele said. “If it is optimal, then ADAbs are probably inconsequential.” If the trough is low or undetectable, examine ADAbs, he added. To manage ADAbs, data support the use of drug dose escalation in some cases. However, “you may be able to overcome the antidrug antibodies in some patients with dose escalation, but this is not always a cost-effective strategy in the long term,” and some patients fail a drug despite adequate drug concentration, which may mean they are failing the mechanism, and not because of pharmacokinetic-related issues, he said.

Dr. Vande Casteele cited a post hoc analysis of the TAXIT trial, published in Gastroenterology. It was the first prospective study to look at proactive therapeutic drug monitoring in patients with inflammatory bowel diseases treated with maintenance infliximab. This post hoc analysis showed that ADAbs were overcome with dose escalation in nearly 50% of patients in the lowest two ADAb quartiles at the start of the trial, and although ADAb were masked by dose escalation in the highest two quartiles, measurement with a drug-sensitive assay showed that ADAb never disappeared, he said.

Another strategy to try to overcome immunogenicity is to add an immunomodulator, Dr. Vande Casteele said. He cited a recent study published in Rheumatology showing that the effect of methotrexate was mediated through immunogenicity for immunogenic compounds such as adalimumab.

Importantly, there is a risk for immunogenicity across agents, he noted. “Patients who are antibody positive to the prior anti-TNF are at a higher risk of developing antibodies to subsequent anti-TNFs.”

Dr. Vande Casteele reported receiving research grants from R-Biopharm; grants and personal fees from Takeda and UCB; and personal fees from Alimentiv (formerly Robarts Clinical Trials), Celltrion, and Prometheus. Global Academy for Medical Education and this news organization are owned by the same parent company.