Peter van Mourik

57 Potentiator synergy in rectal organoids act on limited amounts of available surface CFTR-F508del than promoting CFTR- F508del trafficking. Aside their action as CFTR potentiators we focussed on above, both genistein and curcumin possess various other biological effects (not reported as yet for VX-770) including antioxidation, antiproliferation and anticarcinogenic, and many clinical trails have been performed to study their clinical efficacy as mono-treatment for various diseases. The low oral bioavailability of both compounds due to poor absorption and rapid metabolism may relate to the ambiguous therapeutic effects and large inter-subject variation observed in these studies 53-55 . Pharmacokinetic studies indicated that plasma levels of active compound can be reached in the nM range for curcumin and µM range for genistein, conditions that induced only limited clinical effects in mono-therapy studies 53,54 . However, the strong synergistic potentiator effects observed here suggest that even low curcumin and genistein plasma levels may be sufficient to functionally repair CFTR-dependent fluid secretion either by duo-treatment or triple-treatment including VX-770, especially if drugs would further accumulate in the affected tissues. In conclusion, functional CFTR measurements in rectal CF tissue support that (i) organoid measurements can detect potentiator activity more sensitive and robustly compared to ICM, (ii) VX-770, curcumin and genistein have different mechanisms of CFTR potentiation, (iii) the gating defects in CFTR-S1251N, -G551D and F508del are functionally different from each other, (iv) acute addition of potentiator combinations at suboptimal or near-saturating dosage synergistically repaired gating of CFTR- S1251N and -G551D and to a lesser extent of VX-809-repaired CFTR-F508del, (v) stimulating interactions between different potentiators are detected within a wide range of forskolin concentrations and (vi) expression of CFTR-S1251N and CFTR- G551D are modestly affected some chronic potentiator combination treatments. These results highlight the potential of combining potentiators for the therapy of Cystic Fibrosis. 3