Peter van Mourik

45 Potentiator synergy in rectal organoids observed a chloride secretory response to forskolin, which was ~5 times greater in F508del / S1251N compared to F508del / F508del biopsies (Fig. 1a,b). In biopsies expressing S1251N, the response to forskolin was 34% ± 13.1 (mean ± SD) of the average response of 43 healthy controls measured in our centre (Δ Isc of 57 μA/ cm 2 ; data not shown), indicating a detection window for potentiator treatment. We observed that that response to forskolin in biopsies with S1251N was increased by VX-770 and even further enhanced by genistein, while potentiator activity was not detected in F508del homozygous biopsies (Fig. 1a-b). To conclude, these data indicate that ICM can detect potentiator activity on CFTR-S1251N, but not on CFTR- F508del, and that treatment of VX-770 and genistein together is more effective than of VX-770 alone. igure 1. J.F. Dekke s e al . Intestinal curre t measur ments of F508del / S1251N rectal biopsies treated with VX-770 and genistein a 0 1200 2400 3600 4800 6000 7200 -0.2 0.0 0.6 0.4 0.2 0.8 Amiloride Fsk VX-770 Genistein Carbachol Time (sec) Isc ( µ Amp) F508del / S1251N ∆ Genistein ∆ VX-770 ∆ Fsk b Amiloride 0 300 600 900 1200 1500 1800 -0.4 -0.2 0.4 0.2 0.0 0.6 Time (sec) Isc ( µ Amp) Fsk VX-770 Genistein Carbachol F508del / F508del Figure 1. Intestinal current measurements of F508del / S1251N rectal biopsies treated with VX-770 and genistein. (a) Examples of intestinal current measurement (ICM) tracings of a F508del / F508del or F508del / S1251N rectal biopsy incubated with compounds as indicated (amiloride 100 μM; forskolin (fsk) 10/100 μM; VX-770 20 μM; genistein 50 μM; carbachol 100 μM). (b) Delta Isc ICM values of biopsies derived from 17 F508del / F508del (2–4 biopsies per subject) and 7 F508del / S1251N subjects (1–4 biopsies per subject). Forskolin VX-770 Genistein VX-770 + genistein -10 0 10 20 30 40 ∆ Isc ( µ A/cm 2 ) F508del / F508del (n = 17) F508del / S1251N (n = 7) p=0.0004 p=0.0002 p<0.0001 p=0.0163 Figure 1. Intestinal current measurements of F508del / S1251N rectal biopsies treated with VX-770 and genistein. (a) Examples of intestinal current measurement (ICM) tracings of a F508del / F508del or F508del / S1251N rectal biopsy incubated with compounds as indicated (amiloride 100 μM; forskolin (fsk) 10/100 μM; VX-770 20 μM; genistein 50 μM; carbachol 100 μM). (b) Delta Isc ICM values of biopsies derived from 17 F508del / F508del (2–4 biopsies per subject) and 7 F508del / S1251N subjects (1–4 biopsies per subject). 3