Table 1.

Characteristics of the Patients.^*

Patient No. (Age at Gene Therapy)	IL2RG Mutation	Maternal T-Cell Engraftment	CD3+ Cell Count	CD19+ Cell Count	CD3− CD56+ Cell Count	Medical History	Busulfan Cumulative AUC	CD34+ Cell Dose	VCN of Graft	Follow-up Duration	Status at Last Follow-up†
		% of T cells		cells/mm3			mg × hr/liter	no. × 10−6/kg	copies/cell	mo
1 (6 mo)	c.720G→A p. Trp240X	100	3916	1210	40	Neutropenia, CMV, coronavirus	20.0	4.46	0.16‡	24.9	CMV and coronavirus resolved, autoimmune cytopenia had developed but resolved
2 (3 mo)	c.270(−15)A→G IVS2 branch point A splice	0	0	2340	13	Rhinovirus	22.5	8.67	1.13	23.1	No longer receiving IV immune globulin, immunized§
3 (4 mo)	c.876(−1)G→A IVS5 splice	0	10	1138	18	Rhinovirus	20.7	9.26	0.80	20.1	No longer receiving IV immune globulin, immunized§
4 (14 mo)	c.562C→T p. Gln188X	0	0	190	4	Disseminated BCG, legionella, rhino‑ virus	23.0	6.93	0.35	17.1	Disseminated BCG and legionella resolved, no longer receiving IV immune globulin, immunized
5 (3 mo)	c.677G→A p. Arg266His	0	0	5832	1094	None	22.8	6.02	0.44	15.7	Outpatient
6 (11 mo)	c.903_910del p. Glu302Argf‑sX11	0	41	1376	19	Disseminated BCG	22.9	4.60	0.17	14.6	Disseminated BCG resolved, no longer receiving IV immune globulin, immunized§
7 (2 (mo)	c.548delT p. Leu183Trpf‑sX90	42	15	1178	11	Neutropenia	20.4	15.10	1.10	11.1	Outpatient
8 (3 mo)	c.326_340del p.Glu109_ Ser113del	1	4	2590	2	Aphthous ulcers	22.2	6.52	0.36	6.7	Outpatient, ulcers resolved

^*AUC denotes area under the curve, BCG bacille Calmette–Guérin, CMV cytomegalovirus, IV intravenous, and VCN vector copy number.

^†All patients are off protective precautions (i.e., not in protective isolation and not receiving prophylactic antimicrobial agents).

^‡Patient 1 received a gene therapy boost without busulfan conditioning 12 months after the first infusion because of poor reconstitution; the CD34+ cell dose of the boost was 2.5×10⁶ cells per kilogram of body weight, and the vector copy number was 0.22 copies per cell. Data for this patient after the gene therapy boost are provided in the Supplementary Appendix.

^§The patient had a response to vaccines.