This is a phase 1, open-label, non-randomized study enrolling pediatric and young adult research participants with treatment-refractory Systemic Lupus Erythematosus (SLE), to examine the safety, feasibility, and efficacy of administering T cell products derived from peripheral blood mononuclear cells (PBMC) that have been genetically modified to express CD19 specific chimeric antigen receptor (CAR)

A child or young adult meeting all eligibility criteria and meeting none of the exclusion criteria will have their T cells collected. The T cells will then be bioengineered into a CAR T cell that targets circulating and tissue residing B cells.

Inclusion Criteria:

• Male and female subjects aged between 2-30 years old. The first 3 subjects will be aged ≥ 17. The FDA will review safety data to determine if the age can be lowered first to ≥ 12 then, following the treatment of 3 further subjects aged 12-17, to ≥ 2
• Serologically active Systemic Lupus Erythematosus that is refractory to treatment
• Able to tolerate apheresis or already has an apheresis product available for use in manufacturing.
• ≥ 24 weeks post last Rituximab or related B cell depleting therapy
• ≥ 12 weeks post last Belimumab / Anifrolumab therapy
• ≥ 4 weeks post last calcineurin inhibitor treatment
• For subjects receiving non-calcineurin immunosuppressive therapy, on a stable dose for ≥ 8 weeks before enrollment
• For subjects receiving corticosteroid therapy, on a stable dose for ≥ 2 weeks before enrollment
• Adequate organ function
• Adequate laboratory values
• Subjects of childbearing or child-fathering potential must agree to use highly effective contraception from consent through 12 months following infusion of investigational product on trial
• Subjects must be willing to remain within 1 hour's drive of Seattle Children's Hospital for 4 weeks following CAR T cell infusion.
• Subject and/or legally authorized representative has signed the informed consent form for this study

Exclusion Criteria:

• History or presence of active CNS lupus or other CNS disease
• Kidney dysfunction requiring renal replacement therapy
• Pregnant or breastfeeding
• Insufficient pulmonary reserve including history of COPD, >10 pack year smoking history or SLE lung disease with hypoxia at rest with oxygen saturation ≤92% on room air
• Unable to tolerate repletion with any formulation of IgG.
• Active or prior malignancy, unless the malignancy was treated and there is no evidence of recurrent disease <5 years from enrollment.
• Prior solid organ transplantation.
• Presence of an active severe infection
• Presence of any condition that, in the opinion of the investigator, would prohibit the subject from undergoing treatment under this protocol