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Evaluating narsoplimab for treating TMA in children after stem cell transplants

A Phase 2 Study Evaluating the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of Narsoplimab in Pediatric Patients (28 Days to ≤ 18 Years of Age.) With High-Risk Hematopoietic Stem Cell Transplant Thrombotic Microangiopathy

Phase 2 Interventional Omeros Corporation · NCT05855083

This study is testing a new treatment called narsoplimab to see if it can help children who are at high risk for blood vessel problems after getting stem cell transplants.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment18 (estimated)
Ages28 Days to 17 Years
SexAll
SponsorOmeros Corporation Industry-sponsored
Drugs / interventionseculizumab, ravulizumab, narsoplimab
Locations16 sites (San Diego, California and 15 other locations)
Trial IDNCT05855083 on ClinicalTrials.gov

What this trial studies

This Phase 2 clinical trial aims to assess the safety and efficacy of narsoplimab in pediatric patients aged 28 days to less than 18 years who are at high risk for thrombotic microangiopathies (TMA) following hematopoietic stem cell transplantation (HSCT). The study will involve an uncontrolled, single-dosing regimen over an 8-week treatment period, with patients monitored for up to 52 weeks. Participants will be grouped into three age cohorts to evaluate the treatment's effects across different developmental stages.

Who should consider this trial

Good fit: Ideal candidates are pediatric patients aged 28 days to less than 18 years who have undergone an allogeneic hematopoietic stem cell transplant and have a diagnosis of HSCT-TMA.

Not a fit: Patients who do not meet the age criteria or do not have a diagnosis of HSCT-TMA will not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly improve outcomes for pediatric patients suffering from TMA after stem cell transplants.

How similar studies have performed: While there have been studies on TMA treatments, this specific approach using narsoplimab in pediatric patients is novel and has not been extensively tested.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

1. Age at least 28 days and less than 18 years prior to informed consent (Visit 0).
2. Have informed consent from at least one parent or legal guardian as required by local law and regulation. Patient informed consent will be required if the patient has reached the local legal age of majority.
3. Assent from patients as required by local law and regulation.
4. Have received an allogeneic hematopoietic stem cell transplant for the treatment of benign or malignant disease.
5. Have a diagnosis of HSCT-TMA defined as meeting both of the following criteria:

   * Platelet count \< 50,000/mL or a decrease in platelet count \> 50% from the highest value obtained following transplant.
   * Evidence of microangiopathic hemolysis (presence of schistocytes, serum lactate dehydrogenase \[LDH\] \> upper limit of normal (\[ULN\], or haptoglobin \< lower limit of normal \[LLN\])
6. Have at least one of the following HSCT-TMA high-risk criteria:

   * HSCT-TMA persistence \> 2 weeks following modification of calcineurin inhibitors or sirolimus OR
   * Have evidence of high-risk HSCT-TMA defined as at least one of the following:

     * Spot protein/creatinine ratio \> 2 mg/mg
     * Serum creatinine \> 1.5 x the creatinine level prior to TMA development
     * Biopsy-proven gastrointestinal TMA
     * TMA-related neurological abnormality
     * Pericardial or pleural effusion without alternative explanation
     * Pulmonary hypertension without alternative explanation
     * Have Grade III or Grade IV graft-versus-host disease (GVHD) or, in the opinion of the Investigator, risk for development of Grade III or Grade IV GVHD if immunosuppression were to be modified
     * Have elevated serum C5b-9 (\> 244 ng/mL)
7. If sexually active and of childbearing potential (for female pediatric patients, defined as starting at onset of menses), must agree to practice a highly effective method of birth control throughout study drug treatment and for at least 12 weeks after the last dose of study drug, such method of birth control defined as one that results in a low failure rate (i.e., less than 1% per year) when used consistently and correctly, such as implants, injectables, combined oral contraceptives, some intrauterine devices, sexual abstinence (abstinence is acceptable when it is in line with the patient's preferred and usual lifestyle and is defined as complete abstinence of sexual intercourse, not periodic abstinence or withdrawal), or vasectomized partner.
8. Male patients must be willing to avoid fathering children for at least 12 weeks following the last dose of study medication.

Exclusion Criteria:

1. All treatments for HSCT-TMA are allowed except eculizumab, ravulizumab, and defibrotide within 3 months prior to informed consent, unless failure of therapy can be documented.

   a. Patients may not be on eculizumab, ravulizumab, or defibrotide for any indication at screening.
2. Have Shiga toxin-producing Escherichia coli haemolytic uraemic syndrome (STEC-HUS). Test results obtained within 28 days prior to informed consent may be used.
3. Have ADAMTS13 activity \< 10%. Test results obtained within 28 days prior to informed consent may be used.
4. Have a severe, uncontrolled systemic bacterial or fungal infection requiring antimicrobial therapy, or a severe uncontrolled viral infection (as determined by the investigator); prophylactic antimicrobial therapy administered as standard of care is allowed.
5. Have malignant hypertension (blood pressure \[BP\] \> 99th percentile plus 5 mmHg with bilateral hemorrhages or "cotton-wool" exudates on fundoscopic examination).
6. Due to conditions other than HSCT-TMA, have a poor prognosis with a life expectancy of less than 3 months in the opinion of the Investigator.
7. If pregnant or lactating.
8. Have received treatment with an investigational drug or device within 4 weeks of entering study.
9. Have abnormal liver function tests defined as alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 5 times ULN within 28 days prior to informed consent.
10. Have a positive test by antigen or polymerase chain reaction (PCR) for human immunodeficiency virus (HIV), if negative within 28 days prior to informed consent, the test does not need to be repeated.
11. Patient or one or more of the patient's parents or legal guardians are is an employee or an immediate family member of Omeros, the Clinical Research Organization (CRO), an Investigator, or a study staff member.
12. Have a known hypersensitivity to any constituent of the product.
13. Presence of any condition that the Investigator believes would put the patient at risk.

Where this trial is running

San Diego, California and 15 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Thrombotic MicroangiopathiesHematopoietic Stem Cell TransplantationTMAHSCTPediatricBMTOMS721Narsoplimab
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.