Evaluation of Plitidepsin Efficacy and Safety in Adults with Post COVID-19 Condition: A Phase 3 Randomized, Double-Blind, Placebo-Controlled Trial

The primary objective of this study is to compare **plitidepsin** 2.5 mg versus placebo in terms of improvement of functional status in patients with post COVID-19 condition (PCC). This is clinically relevant as it aims to address the persistent symptoms and functional impairments experienced by individuals recovering from COVID-19, potentially offering a therapeutic option to enhance recovery and quality of life.

Secondary objectives include:

• Comparing plitidepsin 2.5 mg versus placebo in terms of improvement of functional status in patients with PCC.
• Comparing the patients in the Plitidepsin group versus the patients in the placebo group with Grade 0 or 1 functional disability, according to PCFS.
• Comparing safety and tolerability of plitidepsin versus placebo in terms of adverse events in patients with PCC.
• Comparing efficacy of plitidepsin versus placebo in terms of symptomatic improvement, quality of life (QoL), neurocognitive symptoms, physical activity, fatigue, evolution of inflammatory markers, immune response, markers of immune response (including autoimmunity), presence of viral components in plasma, and effects on intestinal microbiota in patients with PCC.

The clinical trial involves participants diagnosed with **Post COVID-19** condition, aiming to evaluate the efficacy of plitidepsin 2.5 mg compared to a placebo in improving functional status. The study population includes both male and female individuals aged 18 years or older. Participants must have evidence of a SARS-CoV-2 infection at least 90 days prior to recruitment, confirmed through various testing methods, and exhibit symptoms affecting at least two organs for a minimum of two months. These symptoms must not be attributable to any alternative diagnosis. Participants are required to have a functional status impairment, classified as grades 3 or 4 in the Post-COVID Functional Status (PCFS) scale, indicating an inability to perform all usual duties or activities. The trial does not involve a vulnerable population. The sponsor has not provided information regarding the total number of participants. Participants are expected to comply with the study protocol and be available for follow-up throughout the study duration.

The clinical trial is designed as a **randomized**, **double-blind**, **placebo-controlled** study to evaluate the efficacy and safety of **plitidepsin** in adults with **Post COVID-19** condition. The primary objective is to compare plitidepsin 2.5 mg versus placebo in terms of improvement in functional status. The trial is expected to last until February 28, 2025, with recruitment starting on September 18, 2023. Participants will be involved for a maximum treatment period of three months, with the study including several key visits.

The sequence of study visits begins with an inclusion (screening) visit, where eligibility is assessed based on criteria such as age, evidence of prior **SARS-CoV-2** infection, and symptoms affecting at least two organs. Following the screening, participants will undergo a series of follow-up visits. These visits are scheduled at 10±2, 28±2, and 90±5 days post-drug infusion to monitor the primary and secondary endpoints, including functional status improvement and adverse events. The end-of-study visit will conclude the participant's involvement, assessing long-term outcomes and any changes in health status.

Participants are expected to comply with the protocol requirements and be available for follow-up throughout the study duration. Conditions that may lead to early termination from the study include the occurrence of adverse events leading to discontinuation or non-compliance with study procedures. The trial will utilize various assessment tools, such as the Post COVID-19 Functional Status Scale and quality of life questionnaires, to evaluate the impact of the intervention. The study aims to provide comprehensive data on the safety and efficacy of plitidepsin in managing post-COVID-19 symptoms.

The clinical trial involves the administration of several treatments, including both experimental and non-experimental medications. **Famotidine** is administered in the form of a **tablet**. The maximum daily dose is 40 mg, with a total maximum dose of 120 mg over a treatment period of up to 3 days. The route of administration is **oral**. Famotidine is used for the prevention and treatment of nausea and vomiting.

**Aplidin**, containing the active substance **plitidepsin**, is provided as a **powder and solvent for concentrate for solution for infusion**. The maximum daily dose is 2.5 mg, with a total maximum dose of 7.5 mg over a 3-day treatment period. The administration route is **intravenous**. Aplidin is classified as an antiviral agent.

**Dexamethasone phosphate** is administered as a **solution for injection**. The maximum daily dose is 8 mg, with a total maximum dose of 24 mg over a 3-day period. The route of administration is **intravenous**. This medication is used for managing allergic reactions.

A **placebo** is also included in the study, provided as a **powder and solvent for solution for injection**. It is administered intravenously, with no active dose, serving as a control to evaluate the efficacy of the experimental treatments.

**Dexchlorpheniramine** is administered as a **solution for injection**. The maximum daily dose is 5 mg, with a total maximum dose of 15 mg over a 3-day treatment period. The route of administration is **intravenous**. This medication is used for the treatment of allergic reactions.

**Palonosetron** is provided as a **solution for injection**. The maximum daily dose is 250 µg, with a total maximum dose of 750 µg over a 3-day period. The administration route is **intravenous**. Palonosetron is used for the prevention and treatment of nausea and vomiting.

The efficacy of the clinical trial will be assessed by evaluating the improvement in functional status of patients with post COVID-19 condition (PCC) using the Post COVID-19 Functional Status Scale (PCFS). The primary endpoint is the percentage of patients who improve at least one grade on the PCFS at 28±2 days post-drug infusion. Secondary endpoints include the percentage of patients with PCC who improve at least one grade on the PCFS at 10±2 days post-drug infusion, and the percentage of patients with Grade 0 or 1 functional disability according to PCFS at 10±2, 28±2, and 90±5 days post-drug infusion.

Additional secondary endpoints involve the proportion of adverse events (AEs) coded by MedDRA, including all AEs, AEs leading to study discontinuation, and AEs of special interest such as cardiac, liver, and acute post-infusional reactions. These will be assessed at 1-3, 10±2, 28±2, and 90±5 days post-drug infusion. Other measures include changes in neurocognitive symptoms, physical activity, inflammatory, microbiological, and immunological biomarkers, immune cells, serological assessments, viral components in plasma, immune response markers, and faecal microbiota at specified timepoints post-drug infusion. Tools such as the Can Ruti's Questionnaire, EuroQol-5D, Neu Screen, MEF-30, HADS, PSQI, WHODAS 2.0, International Activity Questionnaire (IPAQ), Fatigue Severe Scale (FSS), and Five Times Sit to Stand Test (5xSTS) will be utilized for these assessments.