Radiogenomics of C9orf72 Expansion Carriers Reveals Global Transposable Element Derepression and Enables Prediction of Thalamic Atrophy and Clinical Impairment.

Hexanucleotide repeat expansion (HRE) within C9orf72 is the most common genetic cause of frontotemporal dementia (FTD). Thalamic atrophy occurs in both sporadic and familial FTD but is thought to distinctly affect HRE carriers. Separately, emerging evidence suggests widespread derepression of transposable elements (TEs) in the brain in several neurodegenerative diseases, including C9orf72 HRE-mediated FTD (C9-FTD). Whether TE activation can be measured in peripheral blood and how the reduction in peripheral C9orf72 expression observed in HRE carriers relates to atrophy and clinical impairment remain unknown. We used FreeSurfer software to assess the effects of C9orf72 HRE and clinical diagnosis (n = 78 individuals, male and female) on atrophy of thalamic nuclei. We also generated a novel, human, whole-blood RNA-sequencing dataset to determine the relationships among peripheral C9orf72 expression, TE activation, thalamic atrophy, and clinical severity (n = 114 individuals, male and female). We confirmed global thalamic atrophy and reduced C9orf72 expression in HRE carriers. Moreover, we identified disproportionate atrophy of the right mediodorsal lateral nucleus in HRE carriers and showed that C9orf72 expression associated with clinical severity, independent of thalamic atrophy. Strikingly, we found global peripheral activation of TEs, including the human endogenous LINE-1 element L1HS L1HS levels were associated with atrophy of multiple pulvinar nuclei, a thalamic region implicated in C9-FTD. Integration of peripheral transcriptomic and neuroimaging data from human HRE carriers revealed atrophy of specific thalamic nuclei, demonstrated that C9orf72 levels relate to clinical severity, and identified marked derepression of TEs, including L1HS, which predicted atrophy of FTD-relevant thalamic nuclei.SIGNIFICANCE STATEMENT Pathogenic repeat expansion in C9orf72 is the most frequent genetic cause of FTD and amyotrophic lateral sclerosis (ALS; C9-FTD/ALS). The clinical, neuroimaging, and pathologic features of C9-FTD/ALS are well characterized, whereas the intersections of transcriptomic dysregulation and brain structure remain largely unexplored. Herein, we used a novel radiogenomic approach to examine the relationship between peripheral blood transcriptomics and thalamic atrophy, a neuroimaging feature disproportionately impacted in C9-FTD/ALS. We confirmed reduction of C9orf72 in blood and found broad dysregulation of transposable elements-genetic elements typically repressed in the human genome-in symptomatic C9orf72 expansion carriers, which associated with atrophy of thalamic nuclei relevant to FTD. C9orf72 expression was also associated with clinical severity, suggesting that peripheral C9orf72 levels capture disease-relevant information.

Preclinical profile of BI 224436, a novel HIV-1 non-catalytic-site integrase inhibitor.

BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3'-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC50s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 µM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC95 values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.

CD160 isoforms and regulation of CD4 and CD8 T-cell responses.

BACKGROUND: Coexpression of CD160 and PD-1 on HIV-specific CD8+ T-cells defines a highly exhausted T-cell subset. CD160 binds to Herpes Virus Entry Mediator (HVEM) and blocking this interaction with HVEM antibodies reverses T-cell exhaustion. As HVEM binds both inhibitory and activatory receptors, our aim in the current study was to assess the impact of CD160-specific antibodies on the enhancement of T-cell activation. METHODS: Expression of the two CD160 isoforms; glycosylphosphatidylinositol-anchored (CD160-GPI) and the transmembrane isoforms (CD160-TM) was assessed in CD4 and CD8 primary T-cells by quantitative RT-PCR and Flow-cytometry. Binding of these isoforms to HVEM ligand and the differential capacities of CD160 and HVEM specific antibodies to inhibit this binding were further evaluated using a Time-Resolved Fluorescence assay (TRF). The impact of both CD160 and HVEM specific antibodies on enhancing T-cell functionality upon antigenic stimulation was performed in comparative ex vivo studies using primary cells from HIV-infected subjects stimulated with HIV antigens in the presence or absence of blocking antibodies to the key inhibitory receptor PD-1. RESULTS: We first show that both CD160 isoforms, CD160-GPI and CD160-TM, were expressed in human primary CD4+ and CD8+ T-cells. The two isoforms were also recognized by the HVEM ligand, although this binding was less pronounced with the CD160-TM isoform. Mechanistic studies revealed that although HVEM specific antibodies blocked its binding to CD160-GPI, surprisingly, these antibodies enhanced HVEM binding to CD160-TM, suggesting that potential antibody-mediated HVEM multimerization and/or induced conformational changes may be required for optimal CD160-TM binding. Triggering of CD160-GPI over-expressed on Jurkat cells with either bead-bound HVEM-Fc or anti-CD160 monoclonal antibodies enhanced cell activation, consistent with a positive co-stimulatory role for CD160-GPI. However, CD160-TM did not respond to this stimulation, likely due to the lack of optimal HVEM binding. Finally, ex vivo assays using PBMCs from HIV viremic subjects showed that the use of CD160-GPI-specific antibodies combined with blockade of PD-1 synergistically enhanced the proliferation of HIV-1 specific CD8+ T-cells upon antigenic stimulation. CONCLUSIONS: Antibodies targeting CD160-GPI complement the blockade of PD-1 to enhance HIV-specific T-cell responses and warrant further investigation in the development of novel immunotherapeutic approaches.

Evaluation of phosphatidylinositol-4-kinase IIIα as a hepatitis C virus drug target.

Phosphatidylinositol-4-kinase IIIα (PI4KIIIα) is an essential host cell factor for hepatitis C virus (HCV) replication. An N-terminally truncated 130-kDa form was used to reconstitute an in vitro biochemical lipid kinase assay that was optimized for small-molecule compound screening and identified potent and specific inhibitors. Cell culture studies with PI4KIIIα inhibitors demonstrated that the kinase activity was essential for HCV RNA replication. Two PI4KIIIα inhibitors were used to select cell lines harboring HCV replicon mutants with a 20-fold loss in sensitivity to the compounds. Reverse genetic mapping isolated an NS4B-NS5A segment that rescued HCV RNA replication in PIK4IIIα-deficient cells. HCV RNA replication occurs on specialized membranous webs, and this study with PIK4IIIα inhibitor-resistant mutants provides a genetic link between NS4B/NS5A functions and PI4-phosphate lipid metabolism. A comprehensive assessment of PI4KIIIα as a drug target included its evaluation for pharmacologic intervention in vivo through conditional transgenic murine lines that mimic target-specific inhibition in adult mice. Homozygotes that induce a knockout of the kinase domain or knock in a single amino acid substitution, kinase-defective PI4KIIIα, displayed a lethal phenotype with a fairly widespread mucosal epithelial degeneration of the gastrointestinal tract. This essential host physiologic role raises doubt about the pursuit of PI4KIIIα inhibitors for treatment of chronic HCV infection.

Nucleotide competing reverse transcriptase inhibitors: discovery of a series of non-basic benzofurano[3,2-d]pyrimidin-2-one derived inhibitors.

A HTS screen led to the identification of a benzofurano[3,2-d]pyrimidin-2-one core structure which upon further optimization resulted in 1 as a potent HIV-1 nucleotide competing reverse transcriptase inhibitor (NcRTI). Investigation of the SAR at N-1 allowed significant improvements in potency and when combined with the incorporation of heterocycles at C-8 resulted in potent analogues not requiring a basic amine to achieve antiviral activity. Additional modifications at N-1 resulted in 33 which demonstrated excellent antiviral potency and improved physicochemical properties.

Identification of potent and orally bioavailable nucleotide competing reverse transcriptase inhibitors: in vitro and in vivo optimization of a series of benzofurano[3,2-d]pyrimidin-2-one derived inhibitors.

Recently, a new class of HIV reverse transcriptase (HIV-RT) inhibitors has been reported. The novel mechanism of inhibition by this class involves competitive binding to the active site of the RT enzyme and has been termed Nucleotide-Competing Reverse Transcriptase Inhibitors (NcRTIs). In this publication we describe the optimization of a novel benzofurano[3,2-d]pyrimidin-2-one series of NcRTIs. The starting point for the current study was inhibitor 2, which had high biochemical and antiviral potency but only moderate permeability in a Caco-2 assay and high B-to-A efflux, resulting in moderate rat bioavailability and low Cmax. We present herein the results and strategies we employed to optimize both the potency as well as the permeability, metabolic stability and pharmacokinetic profile of this series. One of the key observations of the present study was the importance of shielding polar functionality, at least in the context of the current chemotype, to enhance permeability. These studies led to the identification of inhibitors 39 and 45, which display sub-nanomolar antiviral potency in a p24 ELISA assay with significantly reduced efflux ratios (ratios <1.5). These inhibitors also display excellent rat pharmacokinetic profiles with high bioavailabilities and low clearance.

Identification of benzofurano[3,2-d]pyrimidin-2-ones, a new series of HIV-1 nucleotide-competing reverse transcriptase inhibitors.

Screening of our sample collection led to the identification of a set of benzofurano[3,2-d]pyrimidine-2-one hits acting as nucleotide-competing HIV-1 reverse transcriptase inhibitiors (NcRTI). Significant improvement in antiviral potency was achieved when substituents were introduced at positions N1, C4, C7 and C8 on the benzofuranopyrimidone scaffold. The series was optimized from low micromolar enzymatic activity against HIV-1 RT and no antiviral activity to low nanomolar antiviral potency. Further profiling of inhibitor 30 showed promising overall in vitro properties and also demonstrated that its potency was maintained against viruses resistant to the other major classes of HIV-1 RT inhibitors.

The liver partition coefficient-corrected inhibitory quotient and the pharmacokinetic-pharmacodynamic relationship of directly acting anti-hepatitis C virus agents in humans.

Pharmacokinetic-pharmacodynamic (PK-PD) data analyses from early hepatitis C virus (HCV) clinical trials failed to show a good correlation between the plasma inhibitory quotient (IQ) and antiviral activity of different classes of directly acting antiviral agents (DAAs). The present study explored whether use of the liver partition coefficient-corrected IQ (LCIQ) could improve the PK-PD relationship. Animal liver partition coefficients (Kp(liver)) were calculated from liver to plasma exposure ratios. In vitro hepatocyte partition coefficients (Kp(hep)) were determined by the ratio of cellular to medium drug concentrations. Human Kp(liver) was predicted using an in vitro-in vivo proportionality method: the species-averaged animal Kp(liver) multiplied by the ratio of human Kp(hep) over those in animals. LCIQ was calculated using the IQ multiplied by the predicted human Kp(liver). Our results demonstrated that the in vitro-in vivo proportionality approach provided the best human Kp(liver) prediction, with prediction errors of <45% for all 5 benchmark drugs evaluated (doxorubicin, verapamil, digoxin, quinidine, and imipramine). Plasma IQ values correlated poorly (r(2) of 0.48) with maximum viral load reduction and led to a corresponding 50% effective dose (ED(50)) IQ of 42, with a 95% confidence interval (CI) of 0.1 to 148534. In contrast, the LCIQ-maximum VLR relationship fit into a typical sigmoidal curve with an r(2) value of 0.95 and an ED(50) LCIQ of 121, with a 95% CI of 83 to 177. The present study provides a novel human Kp(liver) prediction model, and the LCIQ correlated well with the viral load reductions observed in short-term HCV monotherapy of different DAAs and provides a valuable tool to guide HCV drug discovery.

Cross-species absorption, metabolism, distribution and pharmacokinetics of BI 201335, a potent HCV genotype 1 NS3/4A protease inhibitor.

The present study describes the cross-species absorption, metabolism, distribution and pharmacokinetics of BI 201335, a potent HCV protease inhibitor currently in phase III clinical trials. BI 201335 showed a good Caco-II permeability (8.7 × 10(-6) cm/sec) and in vitro metabolic stability (predicted hepatic clearence (CL(hep)) <19% Q(h) in all species tested). Single dose PK revealed a clearance of 17, 3.0 and 2.6 mL/min/kg in rat, monkey and dog respectively, with a corresponding oral bioavailability of 29.1, 25.5 and 35.6%. Comparative plasma and liver PK profile in rodents showed a high liver Kp in the rat (42-fold), suggesting high target tissue distribution. Simple allometry based on animal PK predicted a human oral CL/F of 168 mL/min, within two-fold of the observed value (118 mL/min) at 240 mg in healthy volunteers. Allometry of volume of distribution generated a low exponent of 0.59, and a much lower predicted Vss/F (5-fold less than observed). Several different approaches of Vss/F prediction were evaluated and compared with the value observed in human. The averaged Vss/F from preclinical animals provides the best estimation of the observed human value (169 L vs. 175 L). Corresponding human "effective" t(1/2) values were also compared. The predicted human t(1/2) based on the CL from allometry with metabolic corrections and the averaged animal Vss represented the best estimation of the clinical data (12.1 vs. 17.2 hr). The present study demonstrated that the good preclinical ADMEPK profile of BI 201335 is consistent with that observed in the clinic. While preclinical data accurately predicted the human CL, the prediction of human Vss seems to be more challenging. The averaged Vss/F from all tested preclinical animals provided the best prediction of human Vss and the resulting "effective" t(1/2).

Discovery of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly.

The discovery of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly is described. Synthesis of analogs of the 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione hit established structure-activity relationships. Replacement of the enamine functionality of the hit series with either an imidazole or a pyrazole ring led to compounds that inhibited both capsid assembly and reverse transcriptase. Optimization of the bicyclic benzodiazepine scaffold to include a 3-phenyl substituent led to lead compound 48, a pure capsid assembly inhibitor with improved antiviral activity.

Herpes simplex virus helicase-primase inhibitors are active in animal models of human disease.

Herpes simplex virus infections are the cause of significant morbidity, and currently used therapeutics are largely based on modified nucleoside analogs that inhibit viral DNA polymerase function. To target this disease in a new way, we have identified and optimized selective thiazolylphenyl-containing inhibitors of the herpes simplex virus (HSV) helicase-primase enzyme. The most potent compounds inhibited the helicase, the primase and the DNA-dependent ATPase activities of the enzyme with IC50 (50% inhibitory concentration) values less than 100 nM. Inhibition of the enzymatic activities was through stabilization of the interaction between the helicase-primase and DNA substrates, preventing the progression through helicase or primase catalytic cycles. Helicase-primase inhibitors also prevented viral replication as demonstrated in viral growth assays. One compound, BILS 179 BS, displayed an EC50 (effective concentration inhibiting viral growth by 50%) of 27 nM against viral growth with a selectivity index greater than 2,000. Antiviral activity was also demonstrated for multiple strains of HSV, including strains resistant to nucleoside-based therapies. Most importantly, BILS 179 BS was orally active against HSV infections in murine models of HSV-1 and HSV-2 disease and more effective than acyclovir when the treatment frequency per day was reduced or when initiation of treatment was delayed up to 65 hours after infection. These studies validate the use of helicase-primase inhibitors for the treatment of acute herpesvirus infections and provide new lead compounds for optimization and design of superior anti-HSV agents.

Preclinical characterization of BI 201335, a C-terminal carboxylic acid inhibitor of the hepatitis C virus NS3-NS4A protease.

BI 201335 is a hepatitis C virus (HCV) NS3-NS4A (NS3 coexpressed with NS4A) protease inhibitor that has been shown to have potent clinical antiviral activity. It is a highly optimized noncovalent competitive inhibitor of full-length NS3-NS4A proteases of HCV genotypes 1a and 1b with K(i) values of 2.6 and 2.0 nM, respectively. K(i) values of 2 to 230 nM were measured against the NS3-NS4A proteases of HCV genotypes 2 to 6, whereas it was a very weak inhibitor of cathepsin B and showed no measurable inhibition of human leukocyte elastase. BI 201335 was also shown to be a potent inhibitor of HCV RNA replication in vitro with 50% effective concentrations (EC(50)s) of 6.5 and 3.1 nM obtained in genotype 1a and 1b replicon assays. Combinations of BI 201335 with either interferon or ribavirin had additive effects in replicon assays. BI 201335 had good permeability in Caco-2 cell assays and high metabolic stability after incubation with human, rat, monkey, and dog liver microsomes. Its good absorption, distribution, metabolism, and excretion (ADME) profile in vitro, as well as in rat, monkey, and dog, predicted good pharmacokinetics (PK) in humans. Furthermore, drug levels were significantly higher in rat liver than in plasma, suggesting that distribution to the target organ may be especially favorable. BI 201335 is a highly potent and selective NS3-NS4A protease inhibitor with good in vitro and animal ADME properties, consistent with its good human PK profile, and shows great promise as a treatment for HCV infection.

An NS3 protease inhibitor with antiviral effects in humans infected with hepatitis C virus.

Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 1, and they are poorly tolerated, highlighting the unmet medical need for new therapeutics. The HCV-encoded NS3 protease is essential for viral replication and has long been considered an attractive target for therapeutic intervention in HCV-infected patients. Here we identify a class of specific and potent NS3 protease inhibitors and report the evaluation of BILN 2061, a small molecule inhibitor biologically available through oral ingestion and the first of its class in human trials. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor. Our results further illustrate the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.

Novel 8-substituted dipyridodiazepinone inhibitors with a broad-spectrum of activity against HIV-1 strains resistant to non-nucleoside reverse transcriptase inhibitors.

A series of novel 8-substituted dipyridodiazepinone-based inhibitors were investigated for their antiviral activity against wild type human immunodeficiency virus (HIV-1) and the clinically prevalent K103N/Y181C mutant virus. Our efforts have resulted in a series of benzoic acid analogues that are potent inhibitors of HIV-1 replication against a panel of HIV-1 strains resistant to non-nucleoside reverse transcriptase inhibitors (NNRTIs). Furthermore, the combination of good antiviral potency, a broad spectrum of activity, and an excellent pharmacokinetic profile provides strong justification for the further development of compound (7) as a potential treatment for wild type and NNRTI-resistant HIV-1 infection.

Selection and characterization of HIV-1 showing reduced susceptibility to the non-peptidic protease inhibitor tipranavir.

Tipranavir is a novel, non-peptidic protease inhibitor, which possesses broad antiviral activity against multiple protease inhibitor-resistant HIV-1. Resistance to this inhibitor however has not yet been well described. HIV was passaged for 9 months in culture in the presence of tipranavir to select HIV with a drug-resistant phenotype. Characterization of the selected variants revealed that the first mutations to be selected were L33F and I84V in the viral protease, mutations which together conferred less than two-fold resistance to tipranavir. At the end of the selection experiments, viruses harbouring 10 mutations in the protease (L10F, I13V, V32I, L33F, M36I, K45I, I54V, A71V, V82L, I84V) as well as a mutation in the CA/SP1 gag cleavage site were selected and showed 87-fold decreased susceptibility to tipranavir. In vitro, tipranavir-resistant viruses had a reduced replicative capacity which could not be improved by the introduction of the CA/SP1 cleavage site mutation. Tipranavir resistant viruses showed cross-resistance to other currently approved protease inhibitors with the exception of saquinavir. These results demonstrate that the tipranavir resistance phenotype is associated with complex genotypic changes in the protease. Resistance necessitates the sequential accumulation of multiple mutations.

HPMPC therapy of MCMV-induced retinal disease in the SCID mouse measured by electroretinography, a non-invasive technique.

The purpose of these studies was to investigate the use of non-invasive electroretinography for the evaluation of retinal disease and its treatment in an ocular murine cytomegalovirus (MCMV) disease model. While under anesthesia, 10(2.6)plaque forming units (pfu) of salivary gland passaged, Smith strain MCMV was injected in the anterior chamber of 6- to 8-week-old severe combined immunodeficiency (SCID) mice. At various times post-inoculation, bright-flash scotopic electroretinogram, viral titer, and histology were obtained from the injected eye. Antiviral therapy was tested using 0.1 and 5mg/kg/day subcutaneous injections of HPMPC (Cidofovir) once daily for 5 consecutive days. In infected animals, the a- and b-waves of the electroretinographic (ERG) signal were significantly reduced as of 10 days post-inoculation when compared to control animals. Therapy with HPMPC 0.1mg/kg/day subcutaneously (s.c.) once daily for 5 consecutive days was able to delay the decrease in ERG wave amplitude and inhibit viral replication, whereas 5mg/kg/day s.c. significantly protected the ERG, completely inhibited viral replication, and maintained ocular viral titer below the limit of detection for up to 17 days post-infection. The reduction of ERG activity during progression of retinal disease correlated well with reduction of disease pathology. ERG recording represents a valuable non-invasive technique to measure the progression of the retinal disease induced by MCMV and the efficacy of antiviral treatment in the ocular MCMV disease model.

Isolation and characterization of herpes simplex virus type 1 resistant to aminothiazolylphenyl-based inhibitors of the viral helicase-primase.

The aminothiazolylphenyl-containing compounds BILS 179 BS and BILS 45 BS are novel inhibitors of the herpes simplex virus helicase-primase with antiviral activity in vitro and in animal models of HSV disease. To verify the mechanism of antiviral action, resistant viruses were selected by serial passage or by single-step plaque selection of HSV-1 KOS in the presence of inhibitors. Three resistant isolates K138r3, K22r5, and K22r1 were found to be 38-, 316-, and 2500-fold resistant to BILS 22 BS, a potent analog of BILS 45 BS. All three viruses had growth properties in vitro similar to wild-type HSV-1 KOS but they were sensitive to acyclovir. Cutaneous and intra-cerebral inoculation of mice with K22r1 or K22r5 resulted in pathogenicity equivalent to that of HSV-1 KOS. Both isolates were fully competent for reactivation from latency following corneal inoculation. Helicase-primase purified from cells infected with resistant viruses showed decreased inhibition in an in vitro DNA-dependent ATPase assay that correlated well with antiviral resistance. Marker transfer experiments and DNA sequence analysis identified single base pair mutations clustered in the N-terminus of the UL5 gene that resulted in single amino acid changes in the UL5 protein. Taken together, the results indicate that helicase-primase inhibitors prevent HSV growth by inhibiting HSV helicase-primase through specific interaction with the UL5 protein.

A novel model of HPV infection in meshed human foreskin grafts.

The present study describes a novel meshing procedure that provided successful low-risk papillomavirus propagation and reproducible wart induction in human foreskin xenografts. The initial HPV6 and/or 11 inocula were collected from clinically excised human wart tissues and confirmed to be free of HPV16, 18 and 31 by PCR analysis. Human foreskin grafts were collected from a circumcision clinic, and pre-inoculated with HPV virions by scarification. Meshing was carried out with a Zimmer Skin Grafter Mesher. Grafts were cut to appropriate size (1cm x 1cm or 5mm x 5mm) for cutaneous or subcutaneous grafting to NIH-nu-bg-xid mice under halothane anesthesia. Cutaneous xenografts were dressed with antibiotics and protective band-aids for 3 weeks. In the paralleled experiment using the same viral stock containing both HPV6 and 11, and matched grafts, no visible papillomas were observed in non-meshed cutaneous xenografts (n = 4 up to 6 months). In comparison, six of eight cutaneous xenografts treated with the meshing procedure formed visible papillomas within 4 months. This high frequency of distinct papilloma induction over the surface of meshed xenografts were reproduced in subsequent experiments with viral stocks containing both HPV11 and 6 (8 out of 10 grafts), or with a single-type HPV11 inoculum (80-100%). In contrast, an initial viral stock of single-type HPV6 provided lower frequency and more delayed papilloma induction. Serial passage of HPV6 in the meshed xenograft appeared to improve both the induction frequency and growth rate up to the 3rd generation. Histology, in situ hybridization, and immunohistochemical analysis revealed similarity of xenograft warts to those observed in the clinic. The highly reproducible papilloma induction rate and successful viral stock propagation associated with the meshing procedure provide a novel feature in the HPV xenograft model.

Discovery of BI 207524, an indole diamide NS5B thumb pocket 1 inhibitor with improved potency for the potential treatment of chronic hepatitis C virus infection.

The development of interferon-free regimens for the treatment of chronic HCV infection constitutes a preferred option that is expected in the future to provide patients with improved efficacy, better tolerability, and reduced risk for emergence of drug-resistant virus. We have pursued non-nucleoside NS5B polymerase allosteric inhibitors as combination partners with other direct acting antivirals (DAAs) having a complementary mechanism of action. Herein, we describe the discovery of a potent follow-up compound (BI 207524, 27) to the first thumb pocket 1 NS5B inhibitor to demonstrate antiviral activity in genotype 1 HCV infected patients, BILB 1941 (1). Cell-based replicon potency was significantly improved through electronic modulation of the pKa of the carboxylic acid function of the lead molecule. Subsequent ADME-PK optimization lead to 27, a predicted low clearance compound in man. The preclinical profile of inhibitor 27 is discussed, as well as the identification of a genotoxic metabolite that led to the discontinuation of the development of this compound.

Discovery of BI 224436, a Noncatalytic Site Integrase Inhibitor (NCINI) of HIV-1.

An assay recapitulating the 3' processing activity of HIV-1 integrase (IN) was used to screen the Boehringer Ingelheim compound collection. Hit-to-lead and lead optimization beginning with compound 1 established the importance of the C3 and C4 substituent to antiviral potency against viruses with different aa124/aa125 variants of IN. The importance of the C7 position on the serum shifted potency was established. Introduction of a quinoline substituent at the C4 position provided a balance of potency and metabolic stability. Combination of these findings ultimately led to the discovery of compound 26 (BI 224436), the first NCINI to advance into a phase Ia clinical trial.