A Novel 7<i>H</i>‑[1,2,4]Triazolo[3,4‑<i>b</i>]thiadiazine-based Cystic Fibrosis Transmembrane Conductance Regulator Potentiator Directed toward Treatment of Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal genetic disorder caused by disrupted anion transport in epithelial cells lining tissues in the human airways and digestive system. While cystic fibrosis transmembrane conductance regulator (CFTR) modulator compounds have provided transformative improvement in CF respiratory function, certain patients exhibit marginal clinical benefit or detrimental effects or have a form of the disease not approved or unlikely to respond using CFTR modulation. We tested hit compounds from a 300,000-drug screen for their ability to augment CFTR transepithelial transport alone or in combination with the FDA-approved CFTR potentiator ivacaftor (VX-770). A subsequent SAR campaign led us to a class of 7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines that in combination with VX-770 rescued function of G551D mutant CFTR channels to approximately 400% above the activity of VX-770 alone and to nearly wild-type CFTR levels in the same Fischer rat thyroid model system

Detailed histopathological scores of all animals examined in this study.

Individual clinical scores for alveolitis, bronchiolitis, perivascular cuffing (PVC), vasculitis, interstitial pneumonia (IP), and pleuritis. Columns show data medians, symbols represent individual animals; 1-way ANOVA with Tukey’s post hoc test; p values are specified; n values are specified in Fig 4F. (TIF)</p

Urea-PAGE fractionation (uncropped) of RNA transcripts.

a) Template and primer used in the reaction. b-e) Independent repeats of primer extension assay by IAV polymerase. Dashed rectangle shows insert presented in Fig 1E. Replicates were included in quantitations presented in Fig 1E and 1F. (TIF)</p

All statistical analyses performed for this study.

All statistical analyses performed for this study.</p

Clinical signs of mice involved in mitigation of histopathology study.

a-b) Body weight measurements taken twice daily (a), and rectal body temperature determined once daily (b). Lines intersect, and symbols show, data means ± SD. Dashed line in (a) specifies predefined endpoint. (TIF)</p

Reinfection of 4’-FlU-experienced animals with homotypic H1N1.

a) Schematic of the treatment and reinfection study. For infection and reinfection, mice received aerosolized pdmCa09. b) Survival study of animals infected, treated, and reinfected as shown in (a). Median survival time in days is specified; Kaplan-Meier simple survival analysis. c) Anti-H1N1 neutralizing antibody (nAb) titers developing in animals from (a). Lines intersect, and symbols show, geometric means ± SD; 2-way ANOVA with Tukey’s post hoc test; P values are specified. d) Survival of animals after re-infection. Median survival time in days is specified; Kaplan-Meier simple survival analysis. N numbers for animals in (a-d) are specified in (a).</p

Clinical signs in pdmCa09-infected immunocompromised mice treated with 4’-FlU.

a-c) Shown are body weight measurements taken twice daily (a, c), and rectal body temperature (b, d) determined once daily. Lines intersect, and symbols show, data means ± SD; n values are specified in Fig 5. Results are shown for RAG1 KO (a-b) and IFNAR1 KO (c-d) animals. Dashed lines in (a,c) specify predefined endpoint. (TIF)</p

4’-FlU efficacy confirmation after infection with aerosolized inoculum virus.

a) Efficacy study schematic; n values are specified. b-c) Body weight measurements of animals from (a) taken twice daily (a), and rectal body temperature (b) determined once daily. Lines in (b-c) intersect, and symbols show, data means ± SD. d) Lung viral titers determined 4 days after infection. Columns represent geometric means ± SD, symbols show individual animals; 1-way ANOVA with Dunnett’s post hoc test; P values are specified. Dashed line in (d) specifies limit of detection. (TIF)</p

Efficacy of 4’-FlU in an immunocompromised host and against HPAI.

a) Efficacy study schematic in immunocompromised mice, lacking B and T cells (RAG1 KO) or IFN1 receptor function (IFNar1 KO). b) Survival study of animals treated as shown in (a). Median survival time in days is specified; Kaplan-Meier simple survival analysis. c) Lung viral load in animals from (a), determined 4.5 days after infection. d) Dose-response minigenome assay with RdRP complexes derived from IAV subtypes H1N1, H5N1, and H7N9. Lines represent 4-parameter variable slope regression models; symbols show data medians with 95% CI; n = 3. EC50 concentrations and 95% CI are specified. e) Efficacy study schematic of 4’-FlU against HPAI H5N1. f) Body weight measurements of animals shown in (e). Lines intersect, and symbols show, data means ± SD, normalized to animal body weight at study start. Dashed line shows predefined endpoint. g) Survival study of animals infected with HPAI and treated as shown in (e). Median survival time in days is specified; Kaplan-Meier simple survival analysis. h) Lung virus load on day 3 after infection. Columns in (c,h) represent geometric means ± SD; symbols show individual animals; 1-way ANOVA with Dunnett’s post hoc test; P values and n values are specified.</p

Clinical signs in 4’-FlU-treated mice used in immune response-mitigation study.

a-b) Body weight measurements taken twice daily (a), and rectal body temperature determined once daily (b). Lines intersect, and symbols show, data means ± SD; n values are specified in Fig 4. Dashed line in (a) specifies predefined endpoint. (TIF)</p