Study to Evaluate the Efficacy and Safety of Plitidepsin in Adults With Post-COVID-19 Condition (PCC)

Plitidepsin, a marine-derived cyclic depsipeptide that inhibits SARS-CoV-2 replication at nanomolar concentrations by targeting the host protein eukaryotic translation elongation factor 1A, could be a suitable candidate treatment for "Long COVID" because of a triple mechanism of action; a) it has demonstrated potent anti-SARS-CoV-2 in vitro activity, (b) it has a systemic anti-inflammatory effect, detailed in the text below, and (c) has an anti-herpes antiviral effect, which could provide additional therapeutic benefits to prevent herpesvirus reactivation seen in Long-COVID. An interim analysis will be conducted upon reaching 30% and 50% of recruitment (patients treated with at least one dose and 28 days (+/- 2 days) of FUP)). The first interim analysis will focus exclusively on safety assessment, based on adverse events reported to date. The second interim analysis (50%) will evaluate safety and futility. A blinded safety report will be prepared, summarizing adverse events, and submitted to the Data Safety Monitoring Board (DSMB) for review and to determine whether to continue, modify, or terminate the study