We are enrolling adults with weakened immune systems who have COVID-19, developed symptoms within the last 5 days, and are at increased risk of prolonged or severe illness
If you have a weakened immune system, a COVID-19 diagnosis can have a significant impact on your daily life and cause prolonged illness, even if you were previously exposed or vaccinated. Though there are medications approved for the treatment of COVID-19, not all patients can take those medications. Additionally, some patients with certain medical conditions may benefit from longer treatment durations or a combination of treatments.
That is why we are researching a potential medication (ibuzatrelvir) to determine if it is safe and effective for adults who are at increased risk of prolonged or severe illness from COVID-19.
By choosing to participate, you will receive study-related care from a team of dedicated healthcare professionals while helping to advance what could be a breakthrough treatment for people around the world. So, thank you for taking the time to learn more.
Who may participate
This clinical trial is enrolling adults who have weakened immune systems and are at an increased risk of prolonged or severe illness or complications from COVID-19.
This clinical trial may be an option if you:
- Are at least 18 years old
- Have COVID-19 and developed signs or symptoms within the last 5 days
- Have a weakened immune system due to at least 1 of the following:
o Current immunosuppressive therapy after receiving a solid organ or islet cell transplant
o Blood cancers including chronic lymphocytic lymphoma, non-Hodgkin lymphoma, multiple myeloma, or acute leukemia
o CAR-T-cell therapy or hematopoietic cell (blood marrow) transplantation (HCT) in the last 2 years (or if over 2 years ago, are currently receiving immunosuppressive therapy)
o Currently taking a drug that affects B-cell levels (e.g., rituximab, ocrelizumab, ofatumumab, epratuzumab)
- Are not currently receiving antiviral treatment for COVID-19
Participants will need to meet a few other criteria to take part in this clinical trial. The team will discuss these with you in person.
Condition
COVID-19
Age
Adults 18+ years
Sex
Male or Female
Each clinical study has its own guidelines for who can participate, called eligibility criteria. However, only the research study staff can determine if you qualify to enroll in the study.
Get started — See if you may be eligible
Answer a 3-minute questionnaire.
A first step as you consider these studies is to answer a 3-minute online questionnaire about your health and medical history. If your answers show these studies might be a good fit for you, you may choose to be referred to a study clinic that you select.
Speak with a study representative.
If you’re interested, you will then be asked to provide your contact information for a study representative to contact you and discuss the next steps.
Confirm your eligibility.
Your answers to these questions will only be linked to you if your responses indicate that you may be eligible to participate in this study and you choose to share your contact information with the study team. Pfizer study team members and our partners will have access to reports containing aggregated data that will not be directly linked back to you. Only the study staff can determine if you meet the study’s eligibility criteria and are able to enroll in the study.
What to expect
If this clinical trial is a good fit for you and you agree to take part, you will be assigned to 1 of the following 3 treatment groups:
- Potential medication (ibuzatrelvir)
- Approved medication (remdesivir)
- Combination of both
All participants will receive both an intravenous (IV) drip and oral tablets. The tablets will be taken daily during the treatment period, and the IV drip will be given on the first 3 days. You may also take approved medications for COVID-19 symptoms such as fever, pain, cough or nausea.
The clinical trial doctor will discuss the treatment period with you in more detail. The clinical trial will last for around 24 weeks, and you will have at least 10 appointments (most will occur in the first month). During your time in the clinical trial, you will need to perform at-home nasal swabs to test for COVID-19 and complete electronic diary (eDiary) entries. The team will provide more information about these requirements.
The clinical trial treatments and procedures will be provided at no cost. You will also be compensated for completing clinical trial activities.
Number of visits
At least 10
Long-term follow up
About 6 months (24 weeks)
About the potential medication
The potential medication being studied is called ibuzatrelvir. It is an oral antiviral (taken by mouth) designed to prevent the virus that causes COVID-19 from multiplying in the body. Ibuzatrelvir may help people with weakened immune systems get better and stay out of the hospital.
This clinical trial will evaluate ibuzatrelvir when given alone and in combination with a medication called remdesivir. Remdesivir is a prescription antiviral approved by the US Food and Drug Administration (FDA) for adults who have mild-to-moderate COVID-19 and are at increased risk for progression to severe COVID-19.

Frequently asked questions
Coronaviruses comprise a large family of viruses, some of which cause respiratory illnesses in humans, ranging from common colds to more severe conditions. The coronavirus involved in the outbreak that began in 2019 was named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease it causes was named “coronavirus disease 2019” or “COVID-19.”
Having a severely weakened immune system means that your body’s defense mechanism against harmful viruses and bacteria isn’t working as well as it should. People with severely weakened immune systems have a hard time fighting off infections and are much more likely to become really sick and/or stay sick for longer. A severely weakened immune system may be caused by medical conditions like cancer, treatments like hematopoietic stem cell (bone marrow) transplant, or medications that suppress (reduce) the function of the immune system.
Getting vaccinated against common infections can help to protect people with severely weakened immune systems from severe illness, hospitalization, and other complications.



