Optimization of performance of Dutch newborn screening for cystic fibrosis.

BACKGROUND: Dutch newborn screening (NBS) for Cystic Fibrosis (CF) introduced in 2011 showed a sensitivity of 90% and a positive predictive value (PPV) of 63%. We describe a study including an optimization phase and evaluation of the modified protocol. METHODS: Dutch protocol consists of four steps: determination of immunoreactive trypsinogen (IRT) and pancreatitis-associated protein (PAP), DNA analysis by INNO-LiPA and extended gene analysis (EGA). For the optimization phase we used results of 556,952 newborns screened between April 2011 and June 2014 to calculate effects of 13 alternative protocols on sensitivity, specificity, PPV, ratios of CF to other diagnoses, and costs. One alternative protocol was selected based on calculated sensitivity, PPV and costs and was implemented on 1st July 2016. In this modified protocol DNA analysis is performed in samples with a combination of IRT ≥60 µg/l and PAP ≥3.0 µg/l, IRT ≥100 µg/l and PAP ≥1.2 µg/l or IRT ≥124 µg/l and PAP not relevant. Results of 599,137 newborns screened between 1st July 2016 and 31st December 2019 were similarly evaluated as in the optimization phase. RESULTS: The modified protocol showed a sensitivity of 95%, PPV of 76%, CF to CF transmembrane conductance regulator-related metabolic syndrome/CF screen positive, inconclusive diagnoses (CRMS/CFSPID) ratio 12/1, CF/CF carrier ratio 4/1. Costs per screened newborn were slightly higher. Eleven children, of whom five with classic CF, would not have been referred with the previous protocol. CONCLUSIONS: The modified protocol results in acceptable sensitivity (95%) and good PPV of 76% with minimal increase in costs.

FDA-approved drug screening in patient-derived organoids demonstrates potential of drug repurposing for rare cystic fibrosis genotypes.

BACKGROUND: Preclinical cell-based assays that recapitulate human disease play an important role in drug repurposing. We previously developed a functional forskolin induced swelling (FIS) assay using patient-derived intestinal organoids (PDIOs), allowing functional characterization of CFTR, the gene mutated in people with cystic fibrosis (pwCF). CFTR function-increasing pharmacotherapies have revolutionized treatment for approximately 85% of people with CF who carry the most prevalent F508del-CFTR mutation, but a large unmet need remains to identify new treatments for all pwCF. METHODS: We used 76 PDIOs not homozygous for F508del-CFTR to test the efficacy of 1400 FDA-approved drugs on improving CFTR function, as measured in FIS assays. The most promising hits were verified in a secondary FIS screen. Based on the results of this secondary screen, we further investigated CFTR elevating function of PDE4 inhibitors and currently existing CFTR modulators. RESULTS: In the primary screen, 30 hits were characterized that elevated CFTR function. In the secondary validation screen, 19 hits were confirmed and categorized in three main drug families: CFTR modulators, PDE4 inhibitors and tyrosine kinase inhibitors. We show that PDE4 inhibitors are potent CFTR function inducers in PDIOs where residual CFTR function is either present, or created by additional compound exposure. Additionally, upon CFTR modulator treatment we show rescue of CF genotypes that are currently not eligible for this therapy. CONCLUSION: This study exemplifies the feasibility of high-throughput compound screening using PDIOs. We show the potential of repurposing drugs for pwCF carrying non-F508del genotypes that are currently not eligible for therapies. ONE-SENTENCE SUMMARY: We screened 1400 FDA-approved drugs in CF patient-derived intestinal organoids using the previously established functional FIS assay, and show the potential of repurposing PDE4 inhibitors and CFTR modulators for rare CF genotypes.

Females with cystic fibrosis have a larger decrease in sweat chloride in response to lumacaftor/ivacaftor compared to males.

AIM: To explore which patient-related factors influence sweat test response to CFTR modulators, as well as examining the correlation between the sweat chloride response and ppFEV1 or BMI response, using systematically collected real-life clinical data. METHODS: 160 CF patients were identified who had used lumacaftor/ivacaftor for at least six months. Of these patients, age, sweat chloride levels, ppFEV1 weight and BMI at the start of treatment and after 6 months were collected retrospectively. Pearson and Spearman tests were performed to assess correlations. RESULTS: Females compared to males in this group showed a larger response in sweat chloride (mean difference 10.6 mmol/l, 95% CI: 5.7-15.4) and BMI (mean difference 0.27 kg/m2, 95% CI: 0.01-0.54). A modest but significant correlation was found between patient weight and sweat chloride response (Pearson R = 0.244, p = 0.001), which diminished upon correction for the other factors. The correlation between sex and sweat chloride response remained; R = 0.253, p = 0.001. Sweat chloride response did not correlate with ppFEV1 change or BMI change at 6 months after start of therapy. CONCLUSION: Sweat chloride response is larger in females compared to males, which also explains the negative correlation of weight with the response in sweat chloride concentration after start of lumacaftor/ivacaftor. Sweat chloride response does not correlate with the responses in ppFEV1 and BMI. This information may help the interpretation of sweat test results acquired for the follow up and evaluation of CFTR modulating treatments, and warrants further investigation into the underlying mechanisms of sex differences in response to CFTR modulators.

Clinical effect of lumacaftor/ivacaftor in F508del homozygous CF patients with FEV1 ≥ 90% predicted at baseline.

OBJECTIVE: The first available CFTR modulator combination for homozygous F508del patients, lumacaftor/ivacaftor, has not been tested in patients with percentage predicted (pp)FEV1 > 90 in the phase III trials. The objective of this study is to share real life experience about treatment results in this group. METHODS: In this retrospective observational study, patients aged 6 years or older starting on lumacaftor/ivacaftor in standard care were in strict follow up. For these patients, data were obtained about FEV1, BMI, CFQ-R and sweat chloride before start and after 6 months of treatment, and data about FEV1 and BMI were recorded every 3 months. Exacerbations were recorded continuously. RESULTS: We identified 40 patients with a ppFEV1 ≥ 90 at the start of lumacaftor/ivacaftor who had been in follow up for at least 12 months. After 12 months, ppFEV1 was unchanged, whereas mean absolute change in BMI was +0.88 (p = 0.001) with a mean change in SDS for BMI of +0.26 (p = 0.014). Mean CFQ-R overall score at 6 months improved by 2.6% (p = 0.004) and mean decrease in sweat chloride was -27.3 mEq/L (p = 0.000). Exacerbation rate declined from 1.03 to 0.53/person/year (p = 0.003). One patient discontinued treatment in the first 12 months because of progression of CFRLD, two paused treatment but resumed later. CONCLUSION: Homozygous F508del patients starting lumacaftor/ivacaftor at ppFEV1 ≥ 90 improved significantly in nutritional status, sweat chloride levels and exacerbation rate, but did not respond in ppFEV1. Treatment is well tolerated in this patient group. These effects make it worth considering to treat this group of patients with lumacaftor/ivacaftor.

Limited premature termination codon suppression by read-through agents in cystic fibrosis intestinal organoids.

Premature termination codon read-through drugs offer opportunities for treatment of multiple rare genetic diseases including cystic fibrosis. We here analyzed the read-through efficacy of PTC124 and G418 using human cystic fibrosis intestinal organoids (E60X/4015delATTT, E60X/F508del, G542X/F508del, R1162X/F508del, W1282X/F508del and F508del/F508del). G418-mediated read-through induced only limited CFTR function, but functional restoration of CFTR by PTC124 could not be confirmed. These studies suggest that better read-through agents are needed for robust treatment of nonsense mutations in cystic fibrosis.

A bioassay using intestinal organoids to measure CFTR modulators in human plasma.

Treatment efficacies of drugs depend on patient-specific pharmacokinetic and pharmacodynamic properties. Here, we developed an assay to measure functional levels of the CFTR potentiator VX-770 in human plasma and observed that VX-770 in plasma from different donors induced variable CFTR function in intestinal organoids. This assay can help to understand variability in treatment response to CFTR potentiators by functionally modeling individual pharmacokinetics.

Measurement of nasal nitric oxide: evaluation of six different sampling methods.

BACKGROUND: Specific guidelines are developed for the measurement of bronchial FE(NO), however, nasal nitric oxide (nNO) measurement is not standardised yet, resulting in divergent nNO values. This study compares six different sampling methods for nNO as described in the literature, to analyse their outcome and short term and long term reproducibility. DESIGN: nNO concentrations were measured in 38 healthy subjects. Each subject performed nNO measurements during tidal breathing (nNO-TB), single breath quiet exhalations (nNO-QE), QE with oral exhalation against a resistance (nNO-QE + R), breath holding (nNO-BH) and during single-breath humming exhalations at 128 and 440 Hz (nNO-HE(128) and nNO-HE(440), respectively). To assess short term and long term reproducibility all manoeuvres were repeated after one and 24 h. RESULTS: Lowest values were found during quiet exhalation (mean nNO-QE was 364 p.p.b., SEM 27). Methods in which there is turbulence of nasal flow (as in TB, HE(128) and HE(440)) result in higher nNO levels. Highest values were found in methods with decreased nasal flow [when there is no nasal flow as in BH or when the velum is closed as in QE + R: mean nNO 763 p.p.b. (SEM 61)]. NNO during humming at 440 Hz was significantly higher than at 128 Hz (P < 0.01). The within-subject coefficient of variation of repeated measurements was lowest during humming and breath holding, 3.4 and 3.8%, respectively. Concerning short term and long term reproducibility, best agreement is reached with humming and second best with breath holding. CONCLUSIONS: Different methods result in different levels and reproducibility of nNO. In regard to this, methods of humming and breath holding are recommended for standardised measurement of nasal NO.