Phase I/II Clinical Trial Stem Cell Gene Therapy in RAG1-Deficient SCID (RAG1-SCID)

July 15, 2026 updated by: Videja B.V.

Phase I/II Clinical Trial of Autologous Hematopoietic Stem Cell Gene Therapy in RAG1-Deficient Severe Combined Immunodeficiency

This trial is a prospective, non-randomized, open-label, multicentre single-arm phase I/II intervention trial in children up to 24 months of age with RAG1-deficient SCID and an indication for allogeneic hematopoietic stem cell transplantation but lacking an HLA-matched donor. The trial involves infusion of autologous CD34+ cells transduced with the pCCL.MND.coRAG1.wpre lentiviral vector (hereafter called RAG1 LV CD34+ cells) in up to 10 patients with RAG1-deficient SCID. Patients will be regularly monitored for 5 years after infusion. Follow up as part of routine clinical care for post-transplant patients will be annual after this, for at least 15 years after IMP infusion.

Study Overview

Status

Suspended

Conditions

Intervention / Treatment

Detailed Description

Severe combined immunodeficiency (SCID) is a genetically heterogeneous life-threatening disease characterized by severely impaired T cell development with or without impaired natural killer (NK) and B cell development or function depending on the genetic defect. Mutations in recombination activating genes 1 and 2 (RAG1 and RAG2) represent about 20% of all types of SCID. SCID is a paediatric emergency since it leads to severe, life-threatening and recurrent infections often in combination with protracted diarrhoea and failure to thrive. When left untreated, it is usually fatal within the first year of life. Currently, the only curative treatment option for RAG-deficient SCID is allogeneic hematopoietic stem cell transplantation (HSCT). Despite improvements in HSCT in recent years, this treatment is associated with serious potential complications like graft-versus-host disease which results in an unfavourable outcome, particularly in patients who lack a human leukocyte antigen (HLA)-matched donor. In recent years, gene therapy based on transplantation of autologous gene-corrected hematopoietic stem cells (HSC) has evolved as an effective and safe therapeutic option for X-linked and ADA-deficient forms of SCID. We have recently demonstrated that gene therapy using lentiviral (LV) self-inactivating (SIN) vectors expressing codon-optimized human RAG1 in a mouse model for RAG1-deficient SCID effectively restores T and B cell development and function.

In this phase I/II intervention trial safety and efficacy of gene therapy using gene-corrected autologous CD34+-selected mobilized peripheral cells will be investigated in patients with RAG1-deficient SCID with an indication for allogeneic HSCT but lacking an HLA-identical sibling/ family donor.

Study Type

Interventional

Enrollment (Estimated)

10

Phase

  • Phase 2
  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Netherlands
      • Leiden, Netherlands, 2300RC
        • Leiden University Medical Center
  • Poland
      • Wroclaw, Poland, 50-556
        • Wroclaw Medical University
  • Spain
      • Barcelona, Spain, 08035
        • Hospital Universitari Vall d'Hebron
  • Turkey (Türkiye)
      • Kayseri, Turkey (Türkiye)
        • Erciyes Universitesi Tip Fakultesi

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

1 month to 2 years (Child)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. RAG1-deficient SCID as confirmed by genetic analysis
  2. Peripheral blood CD3+T cells < 300/μL
  3. Absence of peripheral blood naïve CD4+ T cells
  4. Age < 2 years
  5. Age at least 8 weeks by the time of busulfan and fludarabine administration
  6. Lack of an available HLA-identical sibling/family donor
  7. Signed informed consent (parental or guardian)
  8. Able to return to the local HSCT centre for follow-up (per protocol) during the 5-year trial and up to at least 15-year long-term follow-up after IMP administration

Exclusion Criteria:

  1. Omenn syndrome
  2. Previous allogeneic HSCT

  3. Significant organ dysfunction/co-morbidity (including but not limited to the ones listed below):

    1. Mechanical ventilation
    2. Shortening fraction on echocardiogram <25%
    3. Renal failure defined as dialysis dependence
    4. Uncontrolled seizure disorder
  4. Any other condition that the investigator considers is a contraindication to collection and/or infusion of trans-duced cells for that individual or indicate patient's inability to follow the protocol, for example contraindication f to busulfan, major congenital abnormalities, ineligible to receive anaesthesia, or documented refusal or inability of the family to return for scheduled visits.
  5. Human immunodeficiency virus (HIV) infection or Human T-cell Leukemia Virus (HTLV) infection

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Gene therapy
In this arm, 10 patients will be included for gene therarpy
Genetic: Gene therapy
Patients will be infused with autologous CD34+ cells transduced with the pCCL.MND.coRAG1.wpre lentiviral vector (RAG1 LV CD34+ cells).

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
To evaluate the effect of RAG1 gene therapy on overall survival.
Time Frame: 5 years
Overall survival
5 years
To evaluate the efficacy of RAG1 gene therapy in achieving reconstitution of the T and B cell immune system in patients with RAG1-SCID at 6 months.
Time Frame: 6 Months

Evaluation of immune reconstitution at Month 6 defined as

  • Presence of naive CD4+ T cells
  • Total CD3+ T-cells > 300 cells/μL
  • Total CD4+ T-cells > 200 cells/μL
6 Months
To evaluate the safety and tolerability of the RAG1 gene therapy product, including identification of short- and long-term adverse events.
Time Frame: 5 years
  • Number of patients with adverse events (AEs), serious adverse events (SAEs) and adverse events of special interest (AESIs, e.g. insertional mutagenesis) and relatedness of the events to intervention, treatment and/or investigational drug
  • Incidence of new or worsening abnormalities in laboratory safety parameters and clinical assessments (including hematology, biochemistry, endocrinology, physical examination findings, vital signs, cardiac ultrasound, and Lansky performance score).
5 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
To evaluate the effect of RAG1 gene therapy on event-free survival.
Time Frame: 1 year
Event-free survival (survival without the need for rescue treatment defined as infusion of autologous unmanipulated backup stem cell product and/or allogeneic HSCT)
1 year
To evaluate the efficacy of RAG1 gene therapy in achieving independence of Immunoglobulin substitution
Time Frame: 2 years
Ability to mount humoral immune responses will be assessed by measuring the levels of IgG, IgA, IgM and IgE antibody production, following standard practice.
2 years
To evaluate the long-term efficacy of RAG1 gene therapy in reconstituting the immune system in patients with RAG1-SCID.
Time Frame: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60 Months

Immune system reconstitution

  • T-cell repopulation:

    • Total CD3+ T-cells > 300 cells/μL (at Month 12, 18, 24, 30, 36, 42, 48, 54, 60)
    • Total CD4+ T-cells > 200 cells/μL (at Month 12, 18, 24, 30, 36, 42, 48, 54, 60)
    • Presence of naive CD4+ T cells (at Month 12, 18, 24, 30, 36, 42, 48, 54, 60)

  • B-cell repopulation:

    • Total B-cell counts (at Month 6, 12, 18, 24, 30, 36, 42, 48, 54, 60)
    • Memory B-cell count (at Month 6, 12, 18, 24, 30, 36, 42, 48, 54, 60)
    • Switched memory B-cell count (at Month 6, 12, 18, 24, 30, 36, 42, 48, 54, 60)

  • Immune function:

    • Level of IgG (at Month 6, 12, 18, 24, 36, 48, 60)
    • Level of IgA (at Month 6, 12, 18, 24, 36, 48, 60)
    • Level of IgM (at Month 6, 12, 18, 24, 36, 48, 60)
    • IG repertoire and T cell receptor (TCR) repertoire on PBMCs at Month 12
6, 12, 18, 24, 30, 36, 42, 48, 54, 60 Months
To evaluate the pharmacodynamic effects of RAG1 gene therapy.
Time Frame: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60 Months
  • Vector copy number (VCN) in PBMCs and granulocytes at Month 6, 12, 18, 24, 30, 36, 42, 48, 54, 60
  • TRECs and KRECs at Month 12 and 24
6, 12, 18, 24, 30, 36, 42, 48, 54, 60 Months
To evaluate the effects of RAG1 gene therapy on quality of life
Time Frame: 2 years
Quality of life at 2 years (assessed using PedsQL by proxy).
2 years
To evaluate the efficacy of RAG1 gene therapy in enabling a successful serologic response to vaccination
Time Frame: 2 years
Measured as protective antibody titers elicited upon vaccination against tetanus and pneumococcus conjugate
2 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Videja B.V.

Collaborators

CR2O B.V.

Investigators

  • Principal Investigator: Arjan C Lankester, Prof.dr., Leiden University Medical Center

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 23, 2021

Primary Completion (Estimated)

December 31, 2031

Study Completion (Estimated)

December 31, 2031

Study Registration Dates

First Submitted

March 11, 2021

First Submitted That Met QC Criteria

March 11, 2021

First Posted (Actual)

March 15, 2021

Study Record Updates

Last Update Posted (Actual)

July 16, 2026

Last Update Submitted That Met QC Criteria

July 15, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • RAG1-2019-01
  • 2023-510204-50-00 (Ctis)
  • 2019-002343-14 (EudraCT Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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