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Dissociative bioorthogonal reactions allow for chemically controlling the release of bioactive agents and reporter probes. Here we describe 3-isocyanopropyl substituents as masking groups that can be effectively removed in biological systems. 3-Isocyanopropyl derivatives react with tetrazines to afford 3-oxopropyl groups that eliminate diverse functionalities. The study shows that the reaction is rapid and can liberate phenols and amines near-quantitatively under physiological conditions. The reaction is compatible with living organisms as demonstrated by the release of a resorufin fluorophore and a mexiletine drug in zebrafish embryos implanted with tetrazine-modified beads. The combined benefits of synthetic ease, rapid kinetics, diversity of leaving groups, high release yields, and structural compactness, make 3-isocyanopropyl derivatives attractive chemical caging moieties for uses in chemical biology and drug delivery.

Leflunomide has been reported as an alternative therapy in sarcoidosis. However, the published data are limited.We performed a retrospective chart review of the tolerance and effects of leflunomide therapy in patients with sarcoidosis.76 patients were included. The most common reasons for initiation were progression of disease or failure of other immunomodulator therapy. Side-effects attributable to leflunomide were noted in 34% of subjects, prompting discontinuation in 17%. The lungs were a target of therapy in 33 (44%) and extrapulmonary organs were a target in 45 (59%). The mean¡SD change in forced vital capacity in the 6 months prior to leflunomide was -0.1¡0.3 L, and it was +0.09¡0.3 L in the following 6 months (p50.01). For extrapulmonary target organ response, 51% had a good response and 32% a partial response. The median corticosteroid dose at initiation was 10 mg (interquartile range 5-20) mg at baseline, and 0 (0-10) mg at the 6-month follow-up (p,0.001).Leflunomide is a viable alternative agent for pulmonary and extrapulmonary sarcoidosis. Leflunomide appears to facilitate reduction of steroid dose and can be considered as monotherapy or as add-on therapy in cases of progressive disease.

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Bioorthogonal reactions that proceed readily under physiological conditions without interference from biomolecules have found widespread application in the life sciences. Complementary to the bioorthogonal reactions that ligate two molecules, reactions that release a molecule or cleave a linker are increasingly attracting interest. Such dissociative bioorthogonal reactions have a broad spectrum of uses, for example, in controlling bio‐macromolecule activity, in drug delivery, and in diagnostic assays. This review article summarizes the developed bioorthogonal reactions linked to a release step, outlines representative areas of the applications of such reactions, and discusses aspects that require further improvement.