There are different approaches in different studies, ranging from a single infusion to two infusions. In general current CAR-T cell therapies for the same target often require only one infusion.
Tumor antigen CD19 CAR-T cell therapy often results in an On target/off tumor effect, i.e. B cell depletion. Targeting with B-cell surface targets causes impaired B-cell maturation, causing severe hypogammaglobulinemia. Therefore B-cell testing is required in all patients receiving anti-CD19 CAR-T therapy.
The American Cancer Institute (NCI) recommends that patients with serum IgG below 40 mg/L should be treated with intravenous gammaglobulin supplementation.