After 4 months of CFTR modulator therapy with ETI, sweat chloride concentrations remained in the PI-CF range (B1: 102 mmol/L, B2: 115 mmol/L, Figure 1A) and only modest improvements in pulmonary function were seen in the LCI2.5 values (B1: 8.66, B2: 9.86, Figure 1B; Table 1). The gene discussed is CFTR; the disease is cystic fibrosis.