Abstract
The act of nonmedical switching, defined as switching stable patients who are generally doing well with their current therapy from an originator biologic to its biosimilar, has been endorsed as a reasonable treatment strategy. The safety and efficacy of nonmedical switching have been evaluated in randomized controlled and real-world evidence studies, which have demonstrated that although many patients maintain treatment response after the switch, some patients experience therapy failure, resulting in therapy discontinuation. It has been postulated that the vast majority, if not all, of these treatment failures result from a "nocebo effect", defined as patients' negative expectations toward the therapy change. Reports suggest that the risk of a nocebo effect is higher following a mandated nonmedical switch. Although the nocebo effect is a well-recognized phenomenon in pain studies, evidence is limited in immune-mediated diseases primarily because it is difficult to quantify, especially retrospectively. In spite of this, numerous biosimilar studies in patients with immune-mediated diseases have concluded that nonmedical switching failures are due to a nocebo effect. The objective of this narrative review was to explore the reasons for nonmedical switch failure or discontinuation and the role of the nocebo effect among patients with inflammatory rheumatic and gastrointestinal diseases who switched from an originator biologic to its biosimilar.