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Cited by 256Cystic Fibrosis Research AdvancesIon Transport and Channel RegulationInhalation and Respiratory Drug Delivery

Allosteric folding correction of F508del and rare CFTR mutants by elexacaftor-tezacaftor-ivacaftor (Trikafta) combination

Open access
Veit, Guido, Roldan, Ariel, Hancock, Mark A., Da Fonte, Dillon F., Xu, Haijin, Hussein, Maytham, Frenkiel, Saul, Matouk, Elias +2 more·2020·JCI Insight
DOI 10.1172/jci.insight.139983PMC PMC7526550
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Abstract

Based on its clinical benefits, Trikafta — the combination of folding correctors VX-661 (tezacaftor), VX-445 (elexacaftor), and the gating potentiator VX-770 (ivacaftor) — was FDA approved for treatment of patients with cystic fibrosis (CF) carrying deletion of phenylalanine at position 508 (F508del) of the CF transmembrane conductance regulator ( CFTR ) on at least 1 allele. Neither the mechanism of action of VX-445 nor the susceptibility of rare CF folding mutants to Trikafta are known. Here, we show that, in human bronchial epithelial cells, VX-445 synergistically restores F508del-CFTR processing in combination with type I or II correctors that target the nucleotide binding domain 1 (NBD1) membrane spanning domains (MSDs) interface and NBD2, respectively, consistent with a type III corrector mechanism. This inference was supported by the VX-445 binding to and unfolding suppression of the isolated F508del-NBD1 of CFTR. The VX-661 plus VX-445 treatment restored F508del-CFTR chloride channel function in the presence of VX-770 to approximately 62% of WT CFTR in homozygous nasal epithelia. Substantial rescue of rare misprocessing mutations (S13F, R31C, G85E, E92K, V520F, M1101K, and N1303K), confined to MSD1, MSD2, NBD1, and NBD2 of CFTR, was also observed in airway epithelia, suggesting an allosteric correction mechanism and the possible application of Trikafta for patients with rare misfolding mutants of CFTR.

AI snapshot

Written from the paper’s full text.

TL;DR

VX-445 (elexacaftor) behaves as a type III CFTR corrector that binds F508del-NBD1, suppresses its unfolding/aggregation, and synergizes with type I/II correctors to restore F508del-CFTR processing and function. VX-661 plus VX-445 also rescued several rare CFTR folding mutants, reaching therapeutically relevant correction levels in airway epithelial models.

Key findings

  • VX-445 plus VX-661 increased F508del-CFTR plasma membrane density to ~45% of WT with an EC50 of ~0.28 μM; VX-445 alone reached ~15% and VX-661 alone ~3.5% of WT. The VX-445 enantiomer EN2 was less efficacious (~25% of WT, EC50 ~1.1 μM).
  • VX-445 bound F508del–NBD1-1S with a KD of ~80 μM, similar to WT–NBD1-1S, and decreased the rate/extent of F508del–NBD1-1S aggregation by 50% at 100 μM; VX-661 did not suppress aggregation and only partially suppressed thermal ellipticity loss.
  • In homozygous F508del human nasal epithelia, VX-661 plus VX-445 restored F508del-CFTR current to 76% of WT with acute VX-770 and 62% with chronic VX-770; VX-809 increased current from 9% to 25% of WT.
  • VX-661 plus VX-445 significantly increased PM density for 9 of 10 rare mutants tested, reaching >20% of WT for S13F, R31C, E92K, R352G, V520F, and L1077P; corrected Isc in HNE reached 20%, 41%, 50%, and 22% of WT for V520F, G85E, M1101K, and N1303K, respectively, with chronic VX-770.

Methods

  • CFBE41o- cells expressing inducible 3HA-tagged CFTR variants were used for PM density measurements by cell-surface ELISA, normalized to viability and CFTR mRNA; primary human nasal epithelia were differentiated at air-liquid interface and assayed by Ussing chamber short-circuit current.
  • Biophysical assays included surface plasmon resonance binding to biotinylated NBD1 constructs, NBD1 aggregation monitored by absorbance at 400 nm, and circular dichroism spectroscopy; corrector combinations were analyzed by combinatorial profiling and clustering.
  • VX-445 and ABBV-2222 were synthesized and validated; statistics used 1-way ANOVA with Tukey’s HSD, paired 2-tailed Student’s t test with Bonferroni’s FDR correction, dose-response fitting, and Heatmapper clustering.

Limitations

  • The paper does not include a dedicated limitations section. It states that the cause of the large variation in CFTR Isc across individuals is not known, and that WT and corrected F508del Isc values partly overlapped.
  • The paper states that combinatorial profiling was not possible for some mutant CFTRs because of nonresponse, high single-corrector PM density, or partial additivity.
  • The paper notes that the apparent discrepancy between only partially mitigated CF lung disease in adults and patient-derived epithelial cell data may be accounted for by long-term chronic infection, inflammation, and tissue damage; it also notes that VX-445’s increased in vivo potency may reflect intracellular accumulation and/or a binding surface modulated by full-length CFTR context.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1172/jci.insight.139983

Cites

59 of 59 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

23 of 39 cited sources checked · 10 supported · 0 flagged · accuracy not yet measured

  • Findingcitation

    Combination of VX-445 with the type II corrector 3151 increased F508del-CFTR PM density to ~25% of WT.

    “Combination of VX-445 with the investigational type II corrector 3151 (21) also increased the F508del-CFTR PM density to ~25% of the WT (Figure 1B).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] source

      The Results (Clustering corrector hits based on mechanism of action; page unavailable) identify 3151 as a type II corrector. The Results (Cooperative rescue of biogenesis, PM expression and stability by corrector combinations; page unavailable) report increased F508del-CFTR PM density with combinations containing 3151, but the combinations described use VX-809 and 4172, not VX-445. Our copy does not establish the claimed VX-445–3151 result or its ~25%-of-WT value. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Findingcitation

    Chronic treatment with 1 μM VX-770 significantly decreased functional correction by VX-809 in the presence of acute potentiator addition.

    “Chronic treatment with 1 μM VX-770, a concentration that is therapeutically reached in respiratory epithelia (34), was reported to significantly decrease the functional correction by VX-809 in the presence of acute potentiator addition (Figure 3, A and B), as observed in CF-HBE (35, 36) and CF-HNE (21).”
    Quote in the paperNot a substantial claim4 of 4 sources checked
    • cites [34] Guimbellot JS, et al. Variable cellular ivacaftor concentrations in people with cystic fibrosis on modulator therapy [published ahead of print February 7, 2020]. J Cyst Fibros. https://doi.org/10.1016/j.jcf.2020.01.011 source
    • cites [35] source

      The Results section on chloride conductance reports that 24 hours of VX-770 reduced VX-809–corrected ΔF508-CFTR current in primary HBE cells, with current measured after acute potentiator addition. But the reported chronic dose for those functional measurements was 100 nM, not the claimed 1 μM; our copy mentions 1 μM in a different, pulse-chase experiment (Materials and Methods). No page numbers are available in our copy. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [36] source

      The Results section on dose dependence (Fig. 4; page unavailable) reports that chronic 1 µM VX-770 reduced VX-809-corrected functional responses and eliminated responses to acute VX-770. It does not report a statistically significant reduction for 1 µM versus VX-809 alone; the stated significant comparison is between the 1 µM and 5 µM conditions. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [21] source

      The Results section on functional correction in bronchial and nasal epithelia (page unavailable) states that chronic VX-770 treatment decreased VX-809 corrector efficacy in CF-HNE, consistent with the reported CF-HBE response. The passages do not establish the specified 1 μM concentration, statistical significance, or that the decrease was measured in the presence of acute potentiator addition. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Premisecitation

    Clinical trials with Trikafta showed only partial normalization of the 60%-65% mean baseline ppFEV1 after 24 weeks in compound heterozygous F508del or at 4 weeks in homozygous F508del patients.

    “The clinical trials with Trikafta showed only partial normalization of the 60%–65% mean baseline ppFEV1 after 24 weeks of treatment in compound heterozygous F508del (16) or at 4 weeks in homozygous F508del patients (15).”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [16] source

      The Results (Efficacy; page unavailable) report a sustained improvement in ppFEV1 through 24 weeks in patients with one Phe508del allele and a minimal-function mutation, consistent with improvement short of full normalization. The passages do not give the claimed 60%–65% mean baseline ppFEV1 or a week-24 value establishing the degree of normalization. The homozygous-patient result is attached to a different citation and is not assessed here. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [15] source

      For the homozygous F508del patients to whom this citation is attached, Results > Efficacy reports a 10.0-percentage-point ppFEV1 improvement versus tezacaftor/ivacaftor at week 4. The retrieved passages do not give the claimed 60%–65% mean baseline ppFEV1 or establish the resulting degree of ‘partial normalization.’ The sentence cites a different study for the heterozygous patients’ 24-week result. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Premisecitation

    The splice mutation 1717-1G->A likely does not give rise to correctable protein expression.

    “which likely does not give rise to correctable protein expression (2).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [2] source

      The Results (Functional analysis; page unavailable) say that variants affecting canonical splice-site nucleotides can lead to mRNA decay and no protein production, which supports the claim’s general rationale. Our copy does not identify 1717-1G->A specifically or assess whether protein from that variant is correctable. (LLM, conf=0.78)

      Experimental — accuracy not yet measured
  • Interpretationcitation

    VX-661 plus VX-445 permits allosteric correction of the global conformation defect elicited by other missense CF mutation located in the MSD1, MSD2, NBD1, or NBD2.

    “The VX-661 plus VX-445 also permits allosteric correction of the global conformation defect elicited by other missense CF mutation located in the MSD1, MSD2, NBD1, or NBD2, in agreement with our previous results (21).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] source

      The Discussion (page unavailable) says that corrector combinations can allosterically correct conformational defects caused by missense mutations in MSD1, MSD2, NBD1, or NBD2. The Results identify the combination tested for these mutants as VX-809, 3151, and 4172, not VX-661 plus VX-445. The cited paper therefore supports the allosteric-correction principle but not its attribution to that specific drug pair. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
  • May combine two claims. 27
  • Classified as probably not a substantial claim. 11

  • May combine two claims.

    Premisecitation

    Localized stabilization of CFTR domains by correctors may be propagated to distant regions of the channel, so corrector combinations may synergistically stabilize a variety of mutant proteins.

    “localized stabilization of CFTR domains by correctors (or pharmacochaperones) may be propagated to distant regions of the channel; thereby, corrector combinations may synergistically stabilize a variety of mutant proteins (21).”
    Quote in the paperSubstantial claim1 of 1 sources checked

  • May combine two claims.

    Premisecitation

    F508del impairs NBD1 stability and the coupled or cooperative domain folding of CFTR.

    “F508del impairs the NBD1 stability and the coupled or cooperative domain folding of the channel (9–11).”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [9] source
    • cites [10] source
    • cites [11] source

  • May combine two claims.

    Premisecitation

    Rescuing structural defects of NBD1-MSDs and NBD2-domain interfaces, as well as NBD1 stability by type I, II, and III correctors, reinstated folding for F508del-CFTR and a subset of rare folding mutants located in MSD1, MSD2, and NBD2 domains.

    “This hypothesis gained traction by demonstrating that rescuing the structural defects of the NBD1-MSDs and NBD2-domain interfaces — as well as the NBD1 stability by type I, II, and III correctors, respectively — reinstated folding for not only the F508del-CFTR (18, 19, 21), but also a subset of rare folding mutants located in the MSD1, MSD2, and NBD2 domains (21).”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [18] source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [19] source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [21] source

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductcitation

    PM density values were normalized with cell viability measured by alamarBlue Assay and related to WT-CFTR by normalizing with CFTR mRNA abundance determined by qPCR.

    “PM density values were normalized with cell viability measured by alamarBlue Assay (Invitrogen) and related to WT-CFTR by normalizing with CFTR mRNA abundance determined by qPCR as previously (21).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] source

      The Online Methods section “PM density measurement” (page unavailable) explicitly says PM density was normalized to cell viability measured by the alamarBlue Assay. The “qPCR” section describes measuring CFTR transcript abundance, but our copy does not say that PM density was normalized by that abundance to relate it to WT-CFTR. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Patient-derived HNE are precision medicine tools that can predict clinical responsiveness of individuals and likely inform on the theratype of individual mutations or mutation combinations.

    “Patient-derived HNE are precision medicine tools that can predict the clinical responsiveness of individuals and likely inform on the theratype of individual mutations or mutation combinations (38–40).”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [38] source
    • cites [39] source
    • cites [40] Brewington, 2018, Brushed nasal epithelial cells are a surrogate for bronchial epithelial CFTR studies, JCI Insight source

  • May combine two claims.

    Findingown data

    VX-445 displayed saturable, dose-dependent binding to immobilized F508del-NBD1-1S with a KD of ~80 μM, similar to 4172.

    “VX-445 displayed saturable, dose-dependent binding to immobilized F508del–NBD1-1S with a KD of ~80 μM, similar to the type III corrector 4172 (21) (Figure 2, A and B; Supplemental Figure 2; and Supplemental Table 1).”
    Quote in the paperSubstantial claim1 of 1 sources checked

  • May combine two claims.

    Premisecitation

    The concentrations of VX-661 and VX-770 used for this study fall within the range of VX-661 plasma concentrations and of VX-770 concentrations in the plasma and nasal tissue of CF patients.

    “The concentrations of VX-661 and VX-770 used for this study fall within the range of VX-661 plasma concentrations and of VX-770 concentrations in the plasma and nasal tissue of CF patients (34).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [34] Guimbellot JS, et al. Variable cellular ivacaftor concentrations in people with cystic fibrosis on modulator therapy [published ahead of print February 7, 2020]. J Cyst Fibros. https://doi.org/10.1016/j.jcf.2020.01.011 source

      The Results sections report tezacaftor (VX-661) concentrations in plasma and ivacaftor (VX-770) concentrations in plasma and nasal biopsy cells from people with CF. Those measurements provide the cited patient ranges, but our copy does not give the concentrations used in the citing study, so it cannot establish that those concentrations fall within the reported ranges. (LLM, conf=0.78)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Correction of distinct folding defects is required to robustly restore mutant channel folding.

    “it was suggested that the correction of distinct folding defects is required to robustly restore the mutant channel folding (18–20).”
    Quote in the paperSubstantial claim3 of 3 sources checked

  • May combine two claims.

    Findingown data

    CFTR Isc varied between 19 and 36 μA/cm2 in corrected CF-HNE and between 14 and 50 μA/cm2 in WT-HNE.

    “The magnitude of CFTR Isc varied between 19 and 36 μA/cm2 in corrected CF-HNE and between 14 and 50 μA/cm2 in WT-HNE, isolated from different individuals.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    VX-445 efficacy was increased in the presence of type I or type II correctors, similar to 4172.

    “Similar to 4172, the efficacy of VX-445 was increased in the presence of type I or type II correctors (Figure 1C and Supplemental Figure 1B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cluster analysis of combination profiles in these mutant proteins and M1101K-CFTR indicated 3 clusters: type I correctors VX-661, VX-809, ABBV-2222, and FDL169 clustered together; type III correctors 4172 and VX-445 formed a cluster; and type II corrector 3151 formed its own category.

    “Cluster analysis of the combination profiles in these mutant proteins and M1101K-CFTR, similar to that of F508del-CFTR, indicated 3 clusters of compounds; type I correctors VX-661, VX-809, ABBV-2222, and FDL169 clustered together; type III correctors 4172 and VX-445 formed a cluster; and the type II corrector 3151 formed its own category with variable distance to the other clusters (Figure 4B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Y569D and V520F-CFTR were responsive to VX-445 plus type I corrector combinations.

    “this mutant protein and V520F-CFTR were responsive to VX-445 plus type I corrector combinations (Figure 5, B and C).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At concentrations of ≥10 μM, VX-445 decreased F508del-CFTR PM density without affecting cell viability.

    “At concentrations of ≥ 10 μM, VX-445 decreased F508del-CFTR PM density without affecting the cell viability (Figure 1A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the presence of VX-661, both VX-445 preparations increased the PM density of F508del-CFTR to ~45% of WT, with an EC50 of ~0.28 μM.

    “In the presence of VX-661, both VX-445 preparations increased the PM density of F508del-CFTR to ~45% of the WT, with an EC50 of ~0.28 μM (Figure 1A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    VX-445, but not VX-661 or 3151, decreased the rate and extent of F508del-NBD1-1S aggregation by 50% at 100 μM.

    “VX-445, but not VX-661 or 3151, decreased the rate and the extent of F508del–NBD1-1S aggregation by 50% at 100 μM (Figure 2C and Supplemental Figure 2D).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The extent of aggregation inhibition of F508del-NBD1 by VX-445 was similar to that by the bacterial DnaK-DnaJ-GroE chaperone system and to that reported for the Hsc70/Hdj-2 chaperone/cochaperone pair.

    “The extent of aggregation inhibition of the F508del-NBD1 by VX-445 was similar to that by the bacterial DnaK-DnaJ-GroE chaperone system and to that reported for the Hsc70/Hdj-2 chaperone/cochaperone pair (30)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [30] source

  • May combine two claims.

    Findingown data

    VX-445 EN2 exhibited ~50% reduced efficacy in the presence of VX-661, rescuing ~25% of WT PM density with an EC50 of ~1.1 μM.

    “Interestingly, the enantiomer of VX-445 (VX-445 EN2), harboring a (4R)-methyl instead of (4S)-methyl in the trimethylpyrrolidin ring, exhibited ~50% reduced efficacy in presence of VX-661, rescuing ~25% of the WT PM density with an EC50 of ~1.1 μM (Figure 1A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    VX-445 suppresses the unfolding trajectory and the aggregation propensity of the mutant F508del-NBD1 domain.

    “suppresses the unfolding trajectory and the aggregation propensity of the mutant domain”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In combination with type I correctors, VX-445 is synergistic and increases F508del-CFTR PM density to 42%-56% of WT.

    “In combination with these type I correctors, the impact of the VX-445 is synergistic and increases the F508del-CFTR PM density to 42%–56% of the WT (Figure 1B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    VX-445 but not VX-661 partially suppressed F508del-NBD1-1S thermal ellipticity loss.

    “Importantly, VX-445 but not the type I corrector (VX-661) partially suppressed the F508del–NBD1-1S thermal ellipticity loss (Figure 2, D and E).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    To analyze the VX-661 plus VX-445 response on individual mutations rather than compound heterozygous genotypes, homozygous HNE with G85E, Y569D, M1101K, D1152H, or N1303K, and HNE with G85E or V520F on one allele and the splice mutation 1717-1G->A on the second allele, were used.

    “To analyze the VX-661 plus VX-445 response on individual mutations rather than compound heterozygous genotypes, we used homozygous HNE with the mutations G85E, Y569D, M1101K, D1152H, or N1303K, as well as HNE with the folding mutation G85E or V520F on 1 allele and the splice mutation 1717-1G->A on the second allele”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The isolation of HNE from healthy and CF human subjects was performed under the protocol and consent form approved by the McGill MUHC Research Ethics Board (MP-37-2018-4089).

    “The isolation of HNE from healthy and CF human subjects was performed under the protocol and consent form approved by the McGill MUHC Research Ethics Board (MP-37-2018-4089).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The rescue effect of corrector pairs on F508del-CFTR PM density was determined at or near saturating concentrations, to minimize possible additivity of compounds competing for the same binding site.

    “The rescue effect of corrector pairs on the F508del-CFTR PM density was determined at or near saturating concentrations, to minimize possible additivity of compounds competing for the same binding site, and the results were analyzed by combinatorial profiling.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Structural validation of ABBV-2222 and VX-445 was performed by 1H-NMR and liquid chromatography-mass spectrometry (LC-MS).

    “Structural validation of ABBV-2222 and VX-445 were performed by 1H-NMR and liquid chromatography–mass spectrometry (LC-MS).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    All double-referenced SPR data presented are representative of duplicate injections acquired from at least 3 independent trials.

    “All double-referenced data (55) presented are representative of duplicate injections acquired from at least 3 independent trials.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [55] source

  • May combine two claims.

    Premisecitation

    F508del leads to severely impaired processing, plasma membrane expression, and stability, as well as defective gating of F508del-CFTR.

    “This leads to a combination of defects, consisting of severely impaired processing, plasma membrane (PM) expression, and stability, as well as defective gating of the F508del-CFTR (12–14).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [12] source
    • cites [13] source
    • cites [14] source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Study design and conductnone given

    The rapid, steady-state binding responses (Req) were independent of mass transport limitations and subjected to DMSO solvent correction.

    “The rapid, steady-state binding responses (Req) were independent of mass transport limitations and subjected to DMSO solvent correction.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    VX-445 was synthesized according to the publicly available patent description WO 2018/107100, and its structure was validated as described in Methods.

    “VX-445 was synthesized according to the publicly available patent description (WO 2018/107100), and its structure was validated as described in Methods.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    VX-445 is potentially the first FDA-approved type III corrector with possible utility for a wide range of folding mutants.

    “these findings suggest that VX-445 is potentially the first FDA-approved type III corrector with possible utility for a wide range of folding mutants.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    VX-445 clusters with 4172 and likely exerts a type III corrector mechanism.

    “In light of these observations and VX-445 clustering with 4172, it is likely that VX-445 exerts a type III corrector mechanism.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Values of WT samples partly overlapped with VX-661 plus VX-445 corrected F508del-CFTR Isc, suggesting near WT-like channel activity could be achieved in F508del-CFTR HNE.

    “While the cause for the large variation of the CFTR Isc is not known, values of the WT samples partly overlapped with the VX-661 plus VX-445 corrected F508del-CFTR Isc, suggesting that near WT-like channel activity could be achieved in F508del-CFTR HNE (Supplemental Figure 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    VX-445 binds to and changes the unfolding trajectory of the NBD1 domain, consistent with a type III corrector mechanism.

    “These results jointly suggest that VX-445 binds to and changes the unfolding trajectory of the NBD1 domain, consistent with a type III corrector mechanism.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The transepithelial resistance of differentiated HNE was 423 ± 71 Ω × cm2.

    “The transepithelial resistance of differentiated HNE was 423 ± 71 Ω × cm2.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Statistical analysis was performed with the means of at least 3 independent experiments.

    “Unless otherwise specified, statistical analysis was performed by 1-way ANOVA with post hoc Tukey’s HSD test with the means of at least 3 independent experiments, and the 95% CI was considered significant.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    VX-661 bound to F508del-NBD1-1S but saturation of binding sites was not reached up to 200 μM, suggesting a weak or unspecific interaction.

    “Although VX-661 bound to F508del–NBD1-1S, saturation of the binding sites was not reached up to 200 μM, suggesting a weak or unspecific interaction (Supplemental Figure 2B).”
    Quote in the paperNot a substantial claim
35 of 35

  • The paper relies on this without support.

    Heterozygous carriers of F508del lack disease symptoms.

    “since heterozygous carriers lack disease symptoms.”

  • The paper relies on this without support.

    A CFTR PM density of >20% of WT is therapeutically significant.

    “reaching therapeutically significant levels of > 20% of WT in S13F-, R31C-, E92K-, R352G-, V520F-, and L1077P-CFTR (Figure 4A).”

  • The paper relies on this without support.

    A CFTR activity correction reaching 20%–50% of WT Isc is associated with therapeutic benefit.

    “indicating that the fraction of CFTR activity correction of these mutants would likely be associated with therapeutic benefit.”

  • The paper relies on this without support.

    Correction levels of >20% of WT CFTR are therapeutically relevant.

    “reaching therapeutically relevant correction levels of > 20% of the WT in CFBE41o- cells or HNE”

  • The paper relies on this without support.

    Binding of VX-445 to isolated F508del–NBD1-1S reflects its interaction with full-length F508del-CFTR.

    “The increased in vivo potency of VX-445, however, may indicate its intracellular accumulation similar to that observed for VX-770 (36) and/or the exposure of a VX-445 binding surface, which is either modulated by or also constitutes the MSD1/2 and/or NBD2 segments in the context of the full-length F508del-CFTR.”

  • The paper relies on this without support.

    Selection of modulator combinations requires knowledge of the mechanism of action of individual CFTR modulators.

    “Selection of modulator combinations, however, requires the knowledge of the mechanism of action of individual CFTR modulators.”
6 of 6

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • VX-661 is assigned two different drug names

    Minor

    The Methods identify VX-661 as lumacaftor, whereas the abstract identifies it as tezacaftor.

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Authors
Veit, G., Roldan, A., Hancock, M. A., Da Fonte, D. F., Xu, H., Hussein, M., Frenkiel, S., Matouk, E., Velkov, T., & Lukacs, G. L.
Affiliations
  • Department of Physiology and
  • McGill University (CA)
  • The University of Melbourne (AU)
  • Department of Otolaryngology-Head and Neck Surgery,
  • Montreal Chest Institute (CA)
Corresponding author
Veit, Guido
ORCID
Venue
JCI Insight
Publisher
American Society for Clinical Investigation
Published
2020-09-17
Volume
5
Issue
18
ISSN
2379-3708 (ISSN-L)
DOI
10.1172/jci.insight.139983
PMC
PMC7526550
OpenAlex
W3081438953
Semantic Scholar
71ed07362e7120150975302f83921245a657c47e
Cited by
250
References
59
Citations by year
2026: 18 · 2025: 45 · 2024: 39 · 2023: 38 · 2022: 58 · 2021: 48 · 2020: 4
FWCI
21.23
Type
journal article
Language
en
Open access
Licence
Locations
  • JCI Insight (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Minerva Access (University of Melbourne) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Canadian Institutes of Health Research (MOP-142221,PJT-153095)
  • National Institute of Diabetes & Digestive & Kidney Diseases (5R01DK075302)
Topics
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Cystic Fibrosis Research Advances
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Ion Transport and Channel Regulation
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Inhalation and Respiratory Drug Delivery
Keywords
cystic fibrosis, CFTR, F508del mutation, elexacaftor/tezacaftor/ivacaftor, elexacaftor, tezacaftor, ivacaftor, NBD1, transmembrane domain, protein folding, chloride channel function, airway epithelium
MeSH terms
Aminophenols, Bronchi, Cells, Cultured, Cystic Fibrosis, Drug Combinations, Humans, Indoles, Mutation, Pyrazoles, Pyridines, Quinolines, Protein Folding, Cystic Fibrosis Transmembrane Conductance Regulator, Benzodioxoles

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-11-04.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-11-04.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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