Study of nirmatrelvir and remdesivir to achieve viral clearance in immunocompromised patients with persistent COVID-19

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What is this study about?

The trial examines people who have a weakened immune system (immunocompromised) and who continue to carry the virus known as SARS‑CoV‑2 for an extended period. The study tests a combination of two antiviral medicines: a pill that contains nirmatrelvir together with ritonavir, and an intravenous infusion of remdesivir. The purpose is to determine whether this drug combination can achieve viral clearance, meaning the virus is no longer detectable in the nose and throat.

Participants are randomly assigned to receive the medicines and are followed for several weeks. They will take the oral tablets for a set number of days and receive the infusion on specific days. Swabs from the nose and throat are collected at multiple time points (for example, day 5, day 15, day 22, and later) and are tested using a laboratory method called PCR to see if viral genetic material is present. The study also records any side effects, serious health problems, and whether treatment is stopped early, with follow‑up visits and sample collections continuing up to about 50 days after treatment begins.

1 baseline assessment

upon joining the study, a health professional collects a combined nose/throat swab to measure the amount of virus present.

you begin a daily diary to record any covid‑related signs or symptoms.

information about your medical history and current medications is recorded.

2 early monitoring period

during the first five days you continue to fill out the symptom diary each day.

on day 5 another combined nose/throat swab is taken to see how the virus level has changed.

3 first combination treatment

on day 15 you receive two types of medication:

paxlovid tablets contain 150 mg of nirmatrelvir and 100 mg of ritonavir; you take the prescribed number of tablets orally as instructed, typically twice a day for five days.

remdesivir is given as an intravenous infusion of 200 mg; the infusion is administered by a health professional on the same day.

a combined nose/throat swab is also taken on day 15 to assess viral clearance.

4 second combination treatment

on day 22 the same regimen is repeated:

you take the prescribed oral paxlovid tablets again according to the dosing schedule.

a second 200 mg intravenous infusion of remdesivir is administered.

another combined nose/throat swab is collected to check for the presence of the virus.

5 final follow‑up

you continue to record symptoms in the diary until day 50.

on day 50 a final combined nose/throat swab is performed.

the results are used to determine whether the virus has been cleared and to evaluate any side effects that may have occurred during the trial.

Who Can Join the Study?

Be 18 years of age or older, and be male or female.
Have a weakened immune system (immunosuppression) that is still active, which can be shown by at least one of the following:
- Having received CAR‑T cell therapy or a blood‑forming (hematologic) stem cell transplant within the past 2 years and still taking medicines that suppress the immune system or still have reduced immune function.
- Having a moderate or severe inherited immune deficiency (examples: DiGeorge syndrome, Wiskott‑Aldrich syndrome).
- Using certain immune‑suppressing medicines, such as:
  - High‑dose steroids (prednisone ≥ 20 mg daily) taken for at least 14 days within the last 30 days, or currently taking that dose.
  - Strong immunosuppressive drugs used in cancer or transplant treatment, including alkylating agents, antimetabolites, transplant‑related drugs, chemotherapy, TNF blockers, or biologic medicines.
  - Past or current treatments that left lasting low antibody levels (for example, low immunoglobulin after anti‑CD20 therapy).
- Having HIV infection with a CD4+ cell count (a type of immune cell) lower than 200 cells per mm³ in the past 6 months.
Show a persistent COVID‑19 infection for at least 28 days before screening. This means:
- A positive PCR test (a lab test that looks for the virus’s genetic material) from a nose swab or other respiratory sample with a cycle‑threshold (Ct) value of 30 or less.
- The first positive test and a second positive test confirming the infection are at least 28 days apart.
- All later positive tests, including the test used to confirm eligibility, are taken no more than 21 days apart from each other.
Be willing and able to sign a written informed consent form.
Be able to understand what the study involves and follow the study procedures.
If you are a female who is not pregnant and could become pregnant, you must use a highly effective birth‑control method consistently and correctly for at least 28 days after the study ends. Highly effective methods include:
- Combination hormonal contraception (pills, patches, rings) that stops ovulation.
- Progestogen‑only hormonal methods (pills, injections, implants) that stop ovulation.
- Intrauterine device (IUD) or intrauterine hormone‑releasing system (IUS).
- Surgical sterilization (tubal ligation) or a partner who has had a vasectomy.
- Abstinence (no sexual activity).
Female participants who could become pregnant must have a negative pregnancy test (blood test) at the screening visit.
Female participants who could become pregnant must agree not to try to become pregnant and not to donate eggs (ova). Male participants do not need any specific birth‑control method for this study.

Who Cannot Join the Study?

Having taken more than 5 consecutive days of nirmatrelvir/ritonavir for the current infection.
Having taken more than 5 consecutive days of remdesivir for the current infection.
Having taken more than 3 days of the combination of nirmatrelvir/ritonavir plus remdesivir for the current infection.
Currently using or planning to use medicines that are cleared by a body protein called CYP3A and can cause dangerous high drug levels, or using strong medicines that increase CYP3A activity, or having used such medicines recently. (CYP3A is a protein that helps break down many drugs in the body.)
Taking chloroquine or hydroxychloroquine at the same time.
Having liver test results (AST or ALT) that are more than 5 times the normal upper limit. (These tests measure how well the liver is working.)
Having a known allergy (hypersensitivity) to any of the study drugs, their breakdown products, or inactive ingredients.
Being pregnant, planning to become pregnant, or breastfeeding now or up to 28 days after the study ends.
Participating in another interventional trial that could affect this study’s results.
Having taken part in this trial before.
Having ongoing or past abuse of medication, drugs, or alcohol.
Having a dependent relationship (such as employment) with the sponsor or the investigator.
Being in jail or placed in an institution by a court or administrative order.

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

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Other Sites

Site Name	City	Country
Staedtisches Klinikum Dessau	Dessau-Roßlau	Germany
Otto Von Guericke Universitaet Magdeburg	Magdeburg	Germany
Hospital General Universitario Gregorio Maranon	Madrid	Spain
Ufnuabodhy Hjpzdlug Clebimq	Cologne	Germany
Gdsevk Ubrmlpqcow Feoffdfbc	Frankfurt	Germany
Uegxgznnifkddgljdjxzk Wyqjevjts Aih	Wuerzburg	Germany
Uaoafqjennkmtlbkxwfnt Emqer Amw	Essen	Germany
Ffjgnjzee Pudr Ly Icebixinrlcut Bkriqpoft Dhp Hbftbwtu Uazfxqkylsekr La Pvw	Madrid	Spain

Trial status

Country	Status	Recruitment Start
Germany	Not yet recruiting	30.06.2026
Spain	Not yet recruiting	30.06.2026

Trial locations

Investigated Drugs:

Paxlovid is an oral tablet taken by mouth. It contains antiviral medicines that stop the coronavirus from making more copies of itself. In this trial participants swallow the tablets as part of a combination treatment aimed at clearing the virus from their bodies.

Veklury is a medicine given through a drip into a vein (intravenous infusion). It also works by blocking the virus’s ability to multiply. In the study it is given together with Paxlovid on specific days to help the immune‑compromised participants get rid of the persistent SARS‑CoV‑2 infection.

Investigated Diseases:

COVID-19

Long‑term persistence of SARS‑CoV‑2 – It is a condition where the SARS‑CoV‑2 virus remains detectable in the body for an extended period after the initial infection. It often occurs in people whose immune systems are weakened. The virus continues to replicate in the respiratory tract, leading to ongoing positive test results. Over time, the amount of virus may fluctuate, sometimes decreasing but staying above the detection threshold. The condition can cause persistent mild symptoms or no symptoms at all while the virus persists.

Trial ID:

2025-524442-10-00

Protocol code:

CLEAR

Trial Phase:

Therapeutic exploratory (Phase II)

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Study of nirmatrelvir and remdesivir to achieve viral clearance in immunocompromised patients with persistent COVID-19

What is this study about?

Who Can Join the Study?

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