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Study of Plitidepsin Treatment for Adults with Post-COVID-19 Condition

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial focuses on studying Post-COVID-19 Condition (also known as Long COVID), a condition where symptoms persist or develop after the initial COVID-19 infection. The study will evaluate a medication called plitidepsin, which will be given through intravenous infusion. Some participants will receive a placebo instead of the active treatment. The purpose is to determine if plitidepsin is effective and safe for treating adults with Post-COVID-19 Condition.

During the study, participants will receive either plitidepsin or placebo along with several supportive medications including palonosetron, famotidine, dexamethasone phosphate, and dexchlorpheniramine. These additional medications help manage potential side effects of the treatment. The study will last for 90 days after treatment, during which participants' overall health and symptoms will be monitored.

Throughout the study, various aspects of participants' health will be evaluated, including physical activity levels, mental health, sleep quality, and general well-being. The researchers will also examine blood samples to study changes in inflammation markers and immune system responses. This comprehensive approach will help determine how well the treatment works for people with Post-COVID-19 Condition.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    You will receive either plitidepsin or a placebo (inactive substance) through an intravenous infusion

    Before the infusion, you will receive preventive medications:

    - Palonosetron (given through intravenous injection)

    - Famotidine (taken by mouth)

    - Dexamethasone phosphate (given through intravenous injection)

    - Dexchlorpheniramine (given through intravenous injection)

  2. Step 2

    First follow-up visit

    Visit occurs on day 10 (plus or minus 2 days)

    Your overall health will be evaluated using various questionnaires

    Physical activity tests will be performed

    Blood samples will be collected to check inflammation markers and other health indicators

    A stool sample will be collected to analyze intestinal microbiota

  3. Step 3

    Second follow-up visit

    Visit occurs on day 30 (plus or minus 2 days)

    Similar evaluations as the first follow-up visit will be performed

    Your physical and mental health will be assessed through questionnaires

    Additional blood and stool samples will be collected

  4. Step 4

    Final follow-up visit

    Visit occurs on day 90 (plus or minus 5 days)

    Final comprehensive health assessment will be conducted

    All questionnaires will be completed again

    Final blood and stool samples will be collected

    Your overall progress will be evaluated comparing all results from previous visits

Who can join the trial?

10 criteria

  • Age requirement: Must be 18 years or older, both men and women can participate
  • Must have documented evidence of previous SARS-CoV-2 infection at least 90 days before study entry through one of these tests:
    • Positive PCR test (a laboratory test that detects viral genetic material)
    • Positive rapid antigen test (a quick test that detects virus proteins)
    • Positive blood test showing antibodies against the virus
    • Must have at least 3 symptoms affecting at least two different body systems that:
      • Have lasted for at least 2 months
      • Started at least 90 days after COVID-19 infection
      • Cannot be explained by another medical condition
      • Must have significant limitations in performing regular daily activities
      • Must be willing to follow study requirements and attend all scheduled follow-up visits
      • Must be able to understand study information and provide informed consent

Who cannot join the trial?

15 criteria

  • Age below 18 years or above 65 years
  • Inability to provide informed consent
  • Presence of severe mental health conditions that could interfere with study participation
  • Current participation in other clinical trials
  • Pregnancy or breastfeeding
  • Active cancer treatment
  • Severe heart, kidney, or liver disease
  • Uncontrolled diabetes (high blood sugar levels)
  • History of organ transplantation
  • Severe respiratory conditions requiring oxygen therapy
  • Major surgery within the past 3 months
  • Unable to complete questionnaires or follow study procedures
  • Unstable medical conditions requiring frequent hospitalization
  • Current substance abuse or dependence
  • Use of medications that could interfere with study results
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Investigated drugs

Plitidepsin is a medication originally derived from a marine organism. It is being studied as a potential treatment for Post-COVID-19 Condition (also known as Long COVID). The medication works by targeting certain cellular processes that may be involved in the persistence of COVID-19 symptoms. This treatment is being tested to see if it can help improve the overall health and quality of life of people who continue to experience symptoms after their initial COVID-19 infection.

What is already known about the treatment

Plitidepsin - A cyclic peptide originally derived from the marine tunicate Aplidium albicans, administered through intravenous infusion in clinical settings. This investigational drug is currently being studied for its potential therapeutic benefits in treating post-COVID-19 Condition (PCC), also known as Long COVID. Plitidepsin works by targeting the eEF1A protein, which plays a crucial role in viral protein synthesis and cellular stress response, and belongs to the class of antiviral and antitumor compounds. The medication has shown promising results in early studies for treating viral infections, and its safety and efficacy are being evaluated in Phase II clinical trials for patients experiencing persistent symptoms after COVID-19 infection.

Investigated diseases

Post-COVID-19 Condition (PCC) - A complex health condition that develops following COVID-19 infection, characterized by persistent symptoms lasting at least two months. The condition typically involves multiple body systems and can include ongoing fatigue, shortness of breath, cognitive difficulties (often called "brain fog"), muscle weakness, and various other symptoms. PCC can affect daily activities and quality of life, with symptoms that may fluctuate in intensity over time. The condition can occur regardless of the initial severity of COVID-19 infection, affecting both those who had mild and severe cases.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-516378-31-00Protocol codeTHALASSA 2.0Estimated enrolment90 patientsSponsorFundacion Fls De Lucha Contra El Sida Las Enfermedades Infecciosas Y La Promocion De La Salud Y La Ciencia

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