November 5, 2007; 10.1073͞pnas.0702843104), the authors wish to add a reference to a paper by A. Shukla et al. (35), in which an intrinsic, nonaromatic fluorescence emission with the same excitation and emission characteristics was observed in different protein crystals and aggregates, upon UV-A excitation, and was attributed to the delocalization of peptide electrons by intra-and/or intermolecular hydrogen bond formation, consistent with the intrinsic blue-green fluorescence we report in amyloid-like nanofibrils. The added reference appears below. Analysis of the x-ray crystal structure of mono-substituted acetylenic thienopyrimidine 6 complexed with the ErbB family enzyme ErbB-4 revealed a covalent bond between the terminal carbon of the acetylene moiety and the sulfhydryl group of Cys-803 at the solvent interface. The identification of this covalent adduct suggested that acetylenic thienopyrimidine 6 and related analogs might also be capable of forming an analogous covalent adduct with EGFR, which has a conserved cysteine (797) near the ATP binding pocket. To test this hypothesis, we treated a truncated, catalytically competent form of EGFR (678 -1020) with a structurally related propargylic amine (8). An investigation of the resulting complex by mass spectrometry revealed the formation of a covalent complex of thienopyrimidine 8 with Cys-797 of EGFR. This finding enabled us to readily assess the irreversibility of various inhibitors and also facilitated a structure-activity relationship understanding of the covalent modifying potential and biological activity of a series of acetylenic thienopyrimidine compounds with potent antitumor activity. Several ErbB family enzyme and cell potent 6-ethynyl thienopyrimidine kinase inhibitors were found to form covalent adducts with EGFR.inhibitors ͉ enzyme ͉ irreversible ͉ thiol ͉ alkylation I nhibition of the ErbB family receptor tyrosine kinases (EGFR, ErbB-2) represents a major advance in the treatment of solid tumors, as demonstrated by the promising clinical activity of gefitinib (1), erlotinib (2), and lapatinib (3) (Fig. 1) (1). These drugs are selective, reversible ATP-competitive EGFR (e.g., 1, 2) or dual EGFR/ErbB-2 inhibitors (3), respectively. An alternative approach for targeting this family of enzymes has been through irreversible alkylation of an ErbB family-conserved cysteine residue (Cys-797 in EGFR, Cys-805 in ErbB-2, and Cys-803 in ErbB-4). i This latter approach led to the discovery of the potent, irreversible agents canertinib (4) and pelitinib (5) (Fig. 1) (2, 3). Both compounds 4 and 5 and other irreversible agents are reported to be in phase II clinical trials (4).To identify potent, efficacious EGFR/ErbB-2 inhibitors structurally distinct from lapatinib, a series of 4-anilino thienopyrimidines containing the fluorobenzyl aniline subunit common to 3 was explored. Optimization of this series on enzyme and cellular assays led to the identification of 6-ethynyl-substituted thieno[3,2-d]pyrimidines and thieno [2,3-d]pyrimidines as represented by the...

Background: PDE12 degrades 2Ј,5Ј-oligoadenylate, a second messenger involved in the antiviral action of interferon. Results: Inactivation of the PDE12 gene and novel inhibitors of the enzyme render cells resistant to more than one virus. Conclusion: PDE12 negatively regulates the innate immune response, and inhibitors of PDE12 have antiviral activity. Significance: PDE12 inhibitors have the potential to be broadly acting antiviral medicines.

A series of imidazo[1,2-a]pyridines which directly bind to HCV Non-Structural Protein 4B (NS4B) is described. This series demonstrates potent in vitro inhibition of HCV replication (EC50 < 10 nM), direct binding to purified NS4B protein (IC50 < 20 nM), and an HCV resistance pattern associated with NS4B (H94N/R, V105L/M, F98L) that are unique among reported HCV clinical assets, suggestive of the potential for additive or synergistic combination with other small molecule inhibitors of HCV replication.