Roadmap for the accelerated development and clinical translation of fluorescent tracers using adalimumab-680LT

Introduction: Monoclonal antibodies, such as adalimumab, are effective treatment strategies in a wide range of diseases, however, these therapies are costly and do not benefit all patients. Currently, information on drug distribution at the target site is limited. Fluorescent guided imaging using fluorescent labelled antibodies can help elucidate the pharmacokinetics and pharmacodynamics of these drugs, enabling personalized medicine. However, tracer development is a time-consuming process. An accelerated process for the development and clinical translation of fluorescent tracers can be used, by building on experience obtained in the development of other fluorescent labelled tracers and the introduction of lab runs. A roadmap of this accelerated process is illustrated with the development of adalimumab-680LT.

Methods: The full development cycle of new fluorescent tracers consists of four phases: (1) feasibility testing, (2) lab development, (3) lab runs and (4) technology transfer (figure 1). The first development phase entails feasibility experiments in the lab, in which size exclusion high performance liquid chromatography (SE-HPLC) is used to demonstrate if fluorescent labelling is feasible. During the second phase, lab development, additional small-scale experiments are performed and other required analysis methods are developed, such as an antibody specific binding affinity assay. As soon as all analytical methods are functional, lab runs can be started. The implementation of these small-scale tracer batches in a non-sterile environment enables a quick transition from lab experiments to the collection of initial stability results. More long-term stability data is collected after the technology transfer, the first production of a batch in a cleanroom environment on the intended clinical scale. This confirms suitability of the production process and the set specifications and acceptance limits. Together, all obtained data is used to write an IMPD on the newly developed tracer.

Results: Previously developed tracers all use similar conjugation conditions, such as the label ratio, conjugation incubation time and used buffers. For the accelerated development, these conditions were also tested initially for feasibility experiments with adalimumab-680LT and were found satisfactory. No major changes to the chromatograms indicated that the antibody was suitable for conjugation with IRDye 680LT. After development of an indirect ELISA-assay, two lab runs were started to collect initial stability data. Based on experience with previously developed tracers, technology transfer was started once 3-month stability of adalimumab-680LT at 2-8 °C was demonstrated. This transfer was successful and a full-scale batch adalimumab-680LT was produced, which subsequently entered a long-term stability study. After one month of stability testing, enough stability data was collected with both lab runs and technology transfer to complete the IMPD, enabling submission to the ethical committee and the start of clinical translation.

Conclusions: By using previously obtained knowledge on fluorescent labelling and labelling conditions, and introducing lab runs to collect additional stability data, the development and clinical translation of adalimumab-680LT was strongly accelerated. The described roadmap is applicable to the development of other antibody-based fluorescent tracers as well, enabling a time reduction of months up to a year to transition from lab experiments to the production of a tracer suitable for human use.

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