Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator ( CFTR ) gene that impair the function of CFTR, an epithelial chloride channel required for proper function of the lung, pancreas, and other organs. Most patients with CF carry the F508del CFTR mutation, which causes defective CFTR protein folding and processing in the endoplasmic reticulum, resulting in minimal amounts of CFTR at the cell surface. One strategy to treat these patients is to correct the processing of F508del-CFTR with small molecules. Here we describe the in vitro pharmacology of VX-809, a CFTR corrector that was advanced into clinical development for the treatment of CF. In cultured human bronchial epithelial cells isolated from patients with CF homozygous for F508del, VX-809 improved F508del-CFTR processing in the endoplasmic reticulum and enhanced chloride secretion to approximately 14% of non-CF human bronchial epithelial cells (EC 50 , 81 ± 19 nM), a level associated with mild CF in patients with less disruptive CFTR mutations. F508del-CFTR corrected by VX-809 exhibited biochemical and functional characteristics similar to normal CFTR, including biochemical susceptibility to proteolysis, residence time in the plasma membrane, and single-channel open probability. VX-809 was more efficacious and selective for CFTR than previously reported CFTR correctors. VX-809 represents a class of CFTR corrector that specifically addresses the underlying processing defect in F508del-CFTR.

A number of human cancers harbor somatic point mutations in the genes encoding isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). These mutations alter residues in the enzyme active sites and confer a gain-of-function in cancer cells, resulting in the accumulation and secretion of the oncometabolite (R)-2-hydroxyglutarate (2HG). We developed a small molecule, AGI-6780, that potently and selectively inhibits the tumor-associated mutant IDH2/R140Q. A crystal structure of AGI-6780 complexed with IDH2/R140Q revealed that the inhibitor binds in an allosteric manner at the dimer interface. The results of steady-state enzymology analysis were consistent with allostery and slow-tight binding by AGI-6780. Treatment with AGI-6780 induced differentiation of TF-1 erythroleukemia and primary human acute myelogenous leukemia cells in vitro. These data provide proof-of-concept that inhibitors targeting mutant IDH2/R140Q could have potential applications as a differentiation therapy for cancer.

Negulescu. Rescue of ⌬F508-CFTR trafficking and gating in human cystic fibrosis airway primary cultures by small molecules.

Cancers of origin in the gallbladder and bile ducts are rarely curable with current modalities of cancer treatment. Our clinical application of broad-based mutational profiling for patients diagnosed with a gastrointestinal malignancy has led to the novel discovery of mutations in the gene encoding isocitrate dehydrogenase 1 (IDH1) in tumors from a subset of patients with cholangiocarcinoma. A total of 287 tumors from gastrointestinal cancer patients (biliary tract, colorectal, gastroesophageal, liver, pancreatic, and small intestine carcinoma) were tested during routine clinical evaluation for 130 site-specific mutations within 15 cancer genes. Mutations were identified within a number of genes, including KRAS (35%), TP53 (22%), PIK3CA (10%), BRAF (7%), APC (6%), NRAS (3%), AKT1 (1%), CTNNB1 (1%), and PTEN (1%). Although mutations in the metabolic enzyme IDH1 were rare in the other common gastrointestinal malignancies in this series (2%), they were found in three tumors (25%) of an initial series of 12 biliary tract carcinomas. To better define IDH1 and IDH2 mutational status, an additional 75 gallbladder and bile duct cancers were examined. Combining these cohorts of biliary cancers, mutations in IDH1 and IDH2 were found only in cholangiocarcinomas of intrahepatic origin (nine of 40, 23%) and in none of the 22 extrahepatic cholangiocarcinomas and none of the 25 gallbladder carcinomas. In an analysis of frozen tissue specimens, IDH1 mutation was associated with highly elevated tissue levels of the enzymatic product 2-hydroxyglutarate. Thus, IDH1 mutation is a molecular feature of cholangiocarcinomas of intrahepatic ori-*Andrew X. Zhu and A. John lafrate contributed equally to this project.