4WHIM TRIAL

The 4WHIM Trial is a phase 3 clinical research study now enrolling people living with WHIM syndrome to see if mavorixafor, an investigational treatment, can lower
infections and warts

What is WHIM syndrome?

WHIM syndrome is a rare and difficult-to-diagnose primary immunodeficiency in which the body’s immune system does not function properly and has trouble fighting infections. Some doctors also call primary immunodeficiencies inborn errors of immunity, which are genetic mutations that cause immunodeficiencies. WHIM syndrome is caused by mutations in the CXCR4 gene which causes white blood cells to get trapped in the bone marrow.

WHIM syndrome was named after four symptoms that most diagnosed patients have experienced: Warts, Hypogammaglobulinemia, Infections, Myelokathexis. There are no existing treatments that specifically target the underlying problem of WHIM syndrome—new treatments are needed.

4WHIM trial overview

The goals of the new phase 3 study are to find out if the investigational oral drug mavorixafor can safely reduce bacterial infections and warts in people with WHIM syndrome.

The 4WHIM Trial is a phase 3, randomized, double-blind, placebo-controlled study in patients with WHIM syndrome with an open-label extension study.

What did we learn from earlier studies?

Researchers learned in phase 1 and phase 2 studies that mavorixafor may help people with WHIM syndrome by targeting the way the disease manifests.

Interested in learning more about the 4WHIM Trial?

Talk to your doctor to see if joining a clinical trial is a good option for you.

The study is now enrolling up to 28 people who meet the following criteria.

  • Age 12+
  • Diagnosis of WHIM syndrome
  • Low neutrophil count

Additional criteria will need to be met and can be discussed with your doctor. There is no cost to participate in the trial.

What to expect if you participate in the trial

Potential study participants will meet with the study team for a screening visit to see if they meet the criteria and understand the risks and benefits. This is called the informed consent process.


Once the study participant is enrolled, they will be assigned to receive the study treatment or a placebo. The participant will be assigned by chance, and no one will know who is taking the study drug or the placebo is until the study is over.


Participants will receive 4 capsules with a total of 400 mg of mavorixafor or placebo which they will take once a day by mouth for 52 weeks. Each participant will be regularly monitored by the study team.


There is no cost to participate in the trial. If needed, travel and lodging will be paid by the study sponsor, X4 Pharmaceuticals.


At study appointments, the study team will measure infection rates and count the number of warts on the hands and feet. The study team will also ask how participants are feeling and about their daily life.

What to expect after the 4WHIM Trial

All study participants will have an opportunity to receive 400 mg of mavorixafor until it is commercially available, or the study ends. This is called an open-label extension study. The results will be shared.

How to join the 4WHIM Trial

The 4WHIM Trial is being conducted at multiple medical centers around the world. Study sites are now open in the U.S. and now enrolling volunteers who are living with WHIM syndrome.

You do not need to live near a study site to participate in the 4WHIM Trial. If you need to travel to a study site, the study sponsor, X4 Pharmaceuticals, will pay for travel and lodging. Also, for some study participants, visits can occur at home through video calls and home visits.

For more study details, including a list of recruiting study sites, visit www.clinicaltrials.gov, Identifier: NCT03995108. Recruiting means a study site is enrolling patients.

If you are interested in the 4WHIM Trial, you can also contact patientinfo@x4.com.

Study Sponsor

The 4WHIM Trial is sponsored by X4 Pharmaceuticals, Inc., a global pharmaceutical company developing treatments that may have a profound impact for patients with rare diseases (such as WHIM syndrome) and cancer.

To learn more about X4 Pharmaceuticals, visit www.X4Pharma.com.