Safety of Belimumab for Idiopathic CD4 Lymphopenia
This study, called Phoebe, is looking at the safety of belimumab in people with Idiopathic CD4 Lymphopenia (ICL). ICL is a condition where you have low numbers of CD4 cells, a type of white blood cell that helps fight infections. There are currently no approved treatments for ICL. Researchers believe belimumab, a monoclonal antibody, might help. You may be able to join if you are 18-70 years old, have ICL, and are already part of NIH study 09-I-0102. The main goal is to see how many side effects (adverse events) are related to belimumab. The study is currently not recruiting new participants, and plans to enroll 20 people.
- Study design
- This is an interventional study, meaning participants will receive a specific treatment. It is a single-arm study, with a planned enrollment of 20 participants.
- What's involved
- Participants will receive belimumab through an IV infusion every two weeks for three doses, then every four weeks for five doses. You will also have screening tests including medical history, physical exam, questionnaires, and blood and urine tests.
- Compensation
- Not stated in the trial record.
- Follow-up
- The study will track adverse events from Week 2 through Week 48 after starting treatment.
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NCT04097561
Safety of Belimumab in People With Idiopathic CD4 Lymphopenia and Autoantibodies (Phoebe)
Recruiting
PHASE1Ages 18–70InterventionalTreatmentNational Institute of Allergy and Infectious Diseases (NIAID)Government-funded
~20 participants
Updated 2026-08-27 on ClinicalTrials.gov
What's tested:Belimumab
At a glance
Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Incidence of adverse events (AEs) that are possibly, probably, or definitely related to belimumab.
Measured over Week 2 through Week 48
Conditions
Where it's being run
1 sites across 1 statesMaryland1
Study leadership
- Irini Sereti, M.D. · PRINCIPAL_INVESTIGATOR · National Institute of Allergy and Infectious Diseases (NIAID)
Who to contact
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Do you actually qualify for this trial?
Add a private profile and we'll compare every criterion below against your situation — and tell you which ones are met, uncertain, or excluding.
Eligibility criteria
Inclusion
Aged 18-70 years.
Enrolled in study 09-I-0102.
Has a documented diagnosis of ICL, defined as the following:
CD4 count \< 300 cells/microliter in at least 2 separate measurements 6 weeks apart at any point in the past, AND
CD4 count \< 300 cells/microliter within previous 90 days.
Evidence for autoantibody positivity (eg, ANA or in the research flow method looking for antilymphocyte antibodies).
Female participants of childbearing potential must agree to use adequate contraception when engaging in sexual activities that can result in pregnancy, beginning at day 0 (or day 30 for hormonal contraception) until 4 months after the last dose of belimumab.
Hormonal contraception.
Male or female condom.
Diaphragm or cervical cap with a spermicide.
Intrauterine device.
Able to provide informed consent.
Willing to allow samples to be stored for future research.
Exclusion
Prior receipt of belimumab. Exception: If an individual had been previously enrolled in this study and received up to 3 doses of belimumab but had to withdraw for reasons that were not related to safety or clinical concerns, they may be re-enrolled. In this case, at least 6 months must have passed from the last prior infusion and they will restart the protocol and drug administration from the beginning.
Allergy to any component of belimumab formulation.
HIV infection or other recognized congenital or acquired immunodeficiency.
Current moderate or severe acute illness (eg, febrile illness, seizure, myocardial infarction, cerebrovascular accident, pulmonary embolism) or progressive serious infection related to ICL that, in the opinion of the principal investigator, would make the participant unsuitable for the study. Pre-existing infections that have been stable both clinically and with laboratory (eg, cryptococcal antigen titer or histoplasma antigen level) and radiographic evaluations on maintenance therapy over at least a year will be eligible.
Untreated hepatitis B or C (acute or chronic).
Active tuberculosis infection.
Serum creatinine \> 1.5 times the upper limit of normal (ULN).
Hemoglobin \< 8 g/dL.
Alanine transaminase or aspartate transaminase \> 2 times ULN.
Serum IgG \< 400 mg/L.
Current use of systemic glucocorticosteroids, with the exception of corticosteroid nasal spray or inhaler and topical steroids.
Any cancer diagnosis or autoimmune condition requiring systemic chemotherapy or immunomodulant-affecting antibody responses (eg, rituximab, ibrutinib), IV or SC Ig supplementation, radiation therapy, or any such treatment within the previous 6 months. Apremilast, Plaquenil, or nonsteroidal anti-inflammatory drugs will not be exclusionary.
Severe depression. Psychiatry may be consulted prior to final eligibility decision.
Infections (recently acquired or exacerbation of a chronic infection) that required new medications for management within the past 60 days.
Receipt of any vaccination within the past 30 days.
Pregnant.
Breastfeeding.
Any behavioral or substance use issue that would compromise appropriate follow up and participation in this study.
What this trial measures
- Incidence of adverse events (AEs) that are possibly, probably, or definitely related to belimumab.Week 2 through Week 48
Incidence of AEs that are possibly, probably, or definitely related to belimumab.