Highlights d Organoids of CF patients were used to quantitate individual drug response in vitro d Organoid responses correlate with two clinical response parameters ppFEV 1 and SCC d In vivo (non)responders were identified with a PPV of 100% and a NPV of 80%

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Summary This protocol describes the isolation, handling, culture of, and experiments with human colon stem cell organoids in the context of cystic fibrosis (CF). In human colon organoids, the function of cystic fibrosis transmembrane conductance regulator (CFTR) protein and its rescue by CFTR modulators can be quantified using the forskolin-induced swelling assay. Implementation procedures and validation experiments are described for six CF human colon organoid lines, and representative CFTR genotypes are tested for basal CFTR function and response to CFTR-modulating drugs. For complete details on the use and execution of this protocol, please refer to Dekkers et al (2016) and Berkers and van Mourik (2019) .

The potentiator VX-770 (ivacaftor/KALYDECO™) targets defective gating of CFTR and has been approved for treatment of cystic fibrosis (CF) subjects carrying G551D, S1251N or one of 8 other mutations. Still, the current potentiator treatment does not normalize CFTR-dependent biomarkers, indicating the need for development of more effective potentiator strategies. We have recently pioneered a functional CFTR assay in primary rectal organoids and used this model to characterize interactions between VX-770, genistein and curcumin, the latter 2 being natural food components with established CFTR potentiation capacities. Results indicated that all possible combinations of VX-770, genistein and curcumin synergistically repaired CFTR-dependent forskolin-induced swelling of organoids with CFTR-S1251N or CFTR-G551D, even under suboptimal CFTR activation and compounds concentrations, conditions that may predominate in vivo. Genistein and curcumin also enhanced forskolin-induced swelling of F508del homozygous organoids that were treated with VX-770 and the prototypical CFTR corrector VX-809. These results indicate that VX-770, genistein and curcumin in double or triple combinations can synergize in restoring CFTR-dependent fluid secretion in primary CF cells and support the use of multiple potentiators for treatment of CF.

ERSpublicationsCF can be studied using patient-specific intestinal organoids. CFTR protein function in intestinal organoids correlates with clinical disease severity and drug testing in organoids could aid in finding drugs for people with rare CFTR mutations.

Background: Previous in vitro organoid data showed A455E-CFTR, a rare CFTR mutation with 4.1% prevalence in the Netherlands, responds to lumacaftor/ivacaftor (LUM/IVA). We explored LUM/IVA's clinical efficacy in people with CF and ≥1 A455E-CFTR mutation. Methods:Participants aged ≥12 years were randomized to 1 of 2 treatment sequences (LUM/IVA → placebo or placebo → LUM/IVA) with an 8-week washout period between. Primary endpoint was absolute change in ppFEV 1 from study baseline through 8 weeks. Additional endpoints were change in sweat chloride concentration (SwCl) and CFQ-R respiratory domain score. Correlations between organoid-based measurements and clinical endpoints were investigated.Results: Twenty participants were randomized at 2 sites in the Netherlands. Mean absolute change in ppFEV 1 from study baseline through Week 8 showed a treatment difference of 0.1 percentage points (95% CI, -2.5 to 2.7; P = 0.928) between LUM/IVA (within-group mean change, 2.7) and placebo (withingroup mean change, 2.6). The mean absolute change in SwCl concentration from study baseline through Week 8 showed a treatment difference of -7.8 mmol/L between LUM/IVA and placebo ( P = 0.004), while the absolute change in CFQ-R respiratory domain score showed a treatment difference of 3.5 between LUM/IVA and placebo ( P = 0.469). The in vitro organoid-based assay demonstrated a concentrationdependent swelling increase with LUM/IVA. Exploratory correlation analyses between organoid swelling and ppFEV 1 and SwCl outcomes showed correlation coefficients of 0.49 and -0.11, respectively. Conclusions:In this exploratory study, LUM/IVA elicited an in vitro response in organoid swelling and in vivo response in SwCl in participants with CF and ≥1 A455E-CFTR mutation. The primary endpoint (ppFEV 1 ) did not show a statistically significant difference between LUM/IVA and placebo; correlations between in vitro and in vivo responses were not established (NCT03061331).

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