Five years of anti-IL 5 for severe asthma: promising long-term efficacy, but sustained remission is rare

<bold>Background</bold> Since 2016, anti-Interleukin 5 (IL5) therapy has been available for patients suffering from severe T2-high asthma, yet little is known about long-term real-world efficacy and sustained remission. <bold>Methods</bold> All Danish adults initiating anti-IL5 for severe asthma during 2016-19 were included. A five-domain remission score (no exacerbations, no mOCS, FEV1 >80%pred, ACQ<1.5 and no switch to non-anti-IL5 biologics) was constructed and assessed annually. <bold>Results</bold> In all, 400 patients were included (median age 56, 49% female). At baseline, 27%, 71%, 32% and 26% fulfilled the individual domains of no exacerbations, no mOCS, FEV1 >80%pred and ACQ<1.5, respectively. Through year one to five, 1%, 4%, 6%, 12% and 15% were switched to a non-anti-IL5 biologic. When assessed as complete response (no exacerbations and no mOCS), the rate was stable at 65-72% throughout all five years. 96% of patients achieved at least one year of complete response, and 40% had sustained five-year complete response. Overall remission rate was stable at 20-24% throughout all five years. However, remission was found to be dynamic, with approximately one-third of patients in remission per annum changing remission state the following year. At least one year of remission was achieved by 34% of patients, yet only 2% achieved sustained five-year remission. The most common reasons for non-remission were FEV1<80%pred and ACQ>=1.5. <bold>Conclusions</bold> Across five years, patients who initially respond well to anti-IL5 experience substantial improvements across all domains, although remission was found to be dynamic with recurrent relapses. Sustained long-term remission is rare when applying current remission domains.