Spotlight on daclizumab: its potential in the treatment of multiple sclerosis

What Have Failed, Interrupted, and Withdrawn Antibody Therapies in Multiple Sclerosis Taught Us?

In the past two decades, monoclonal antibodies (mAbs) have revolutionized the treatment of multiple sclerosis (MS). However, a remarkable number of mAbs failed due to negative study results were withdrawn because of unexpected serious adverse events (SAEs) or due to studies being halted for other reasons. While trials with positive outcomes are usually published in prestigious journals, negative trials are merely published as abstracts or not at all. This review summarizes MS mAbs that have either failed in phase II-III trials, have been interrupted for various reasons, or withdrawn from the market since 2015. The main conclusions that can be drawn from these 'negative' experiences are as follows. mAbs that have been proven to be safe in other autoimmune conditions, will not have the same safety profile in MS due to immunopathogenetic differences in these diseases (e.g., daclizumab). Identification of SAEs in clinical trials is difficult highlighting the importance of phase IV studies. Memory B cells are central players in MS immunopathogenesis (e.g., tabalumab). The pathophysiological mechanisms of disease progression are independent of leukocyte 'outside-in' traffic which drives relapses in MS. Therefore, therapies for progressive MS must be able to sufficiently cross the blood-brain barrier. Sufficiently long trial duration and multicomponent outcome measures are important for clinical studies in progressive MS. The success of trials on remyelination-promoting therapies mainly depends on the sufficient high dose of mAb, the optimal readout for 'proof of concept', time of treatment initiation, and appropriate selection of patients. Failed strategies are highly important to better understand assumed immunopathophysiological mechanisms and optimizing future trial designs.

Daclizumab: Development, Clinical Trials, and Practical Aspects of Use in Multiple Sclerosis

Daclizumab is a humanized monoclonal antibody directed towards CD25, the alpha subunit of the high-affinity interleukin (IL)-2 receptor. Daclizumab exerts its effects via multiple mechanisms, including reduction of IL-2-mediated lymphocyte activation and upregulation of CD56-bright natural killer cells. Intravenous daclizumab (Zenapax™) was initially approved for prevention of rejection in renal transplant. In subsequent early testing, followed by larger-scale phase II and phase III trials, both intravenous and subcutaneous daclizumab have demonstrated clinical efficacy in the treatment of multiple sclerosis. The subcutaneous daclizumab prepared by high-yield process was utilized in the advanced phase II and phase III trials (SELECT and DECIDE). High-yield process daclizumab is now approved by the US Food and Drug Administration for relapsing-remitting multiple sclerosis, and is now formally termed daclizumab beta (DAC-beta; Zinbryta™). In this review, the early development of anti-IL-2 receptor alpha monoclonal antibodies and the properties of IL-2 and its receptor are discussed, and diverse mechanisms of action for daclizumab are presented. Results of the CHOICE, SELECT, and DECIDE clinical trials are discussed in detail. Adverse events observed in clinical trials included cutaneous reactions, liver enzyme elevations, infections, and autoimmune phenomena. DAC-beta is a monthly, patient-administered subcutaneous injection that requires enrollment in a safety monitoring (REMS) program for monthly liver function testing. Prescribers should be aware of the potential adverse events, as early recognition and management is important, particularly in cutaneous and hepatic reactions. Continued clinical experience with DAC-beta, including observations from the REMS program, will define its place in the armamentarium of immunotherapeutics for relapsing-remitting multiple sclerosis.