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HIV-1 nonnucleoside reverse transcriptase inhibitors (NNRTIs) are part of the combination therapy currently used to treat HIV infection. The features of a new NNRTI drug for HIV treatment must include selective potent activity against both wild-type virus as well as against mutant virus that have been selected by use of current antiretroviral treatment regimens. Based on analogy with known HIV-1 NNRTI inhibitors and modeling studies utilizing the X-ray crystal structure of inhibitors bound in the HIV-1 RT, a series of substituted 2-quinolones was synthesized and evaluated as HIV-1 inhibitors.

Background: HIV reverse transcriptase (RT) is a key target of anti-AIDS therapies. Structural studies of HIV-1 RT, unliganded and complexed with different non-nucleoside inhibitors (NNIs), have pointed to a common mode of binding and inactivation through distortion of the polymerase catalytic site by NNIs containing two hinged rings. The mode of binding of the TIBO family of inhibitors is of interest because these compounds do not fit the two-hinged-ring model. Results The structure of HIV-1 RT complexed with 9-chloro-TIBO (R82913) has been determined at 2.6 a resolution. As reported for the lower resolution analysis of another TIBO compound, this inhibitor binds at the same site as other NNIs, but our higher resolution study reveals the Cl-TIBO is distorted from the conformation seen in crystals of the inhibitor alone. This allows Cl-TIBO to mimic the binding of NNIs containing two hinged rings. Inhibitor–protein interactions are again predominantly hydrophobic and the protein conformation corresponds to that seen in complexes with other tight-binding NNIs. Conclusion Although Cl-TIBO is chemically very different from other NNIs, it achieves remarkable spatial equivalence and shape complementarity with other NNIs on binding to RT. Comparison of the different RT–NNI complexes suggests modifications to the TIBO group of inhibitors which might enhance their binding and hence, potentially, their therapeutic efficacy.

We have determined the crystal structures of thiazoloisoindolinone non-nucleoside inhibitors in complex with HIV-1 reverse transcriptase to high-resolution limits of 2.7 A (BM +21.1326) and 2. 52 A (BM +50.0934). We find that the binding modes of this series of inhibitors closely resemble that of "two-ring" non-nucleoside reverse transcriptase inhibitors. The structures allow rationalization of stereochemical requirements, structure-activity data, and drug resistance data. Comparisons with our previous structures suggest modifications to the inhibitors that might improve resilience to drug-resistant mutant forms of reverse transcriptase. Comparison with earlier modeling studies reveals that the predicted overlap of thiazoloisoindolinones with TIBO was largely correct, while that with nevirapine was significantly different.

The carboxanilides are nonnucleoside inhibitors (NNIs) of HIV-1 reverse transcriptase (RT), of potential clinical importance. The compounds differ in potency and in their retention of potency in the face of drug resistance mutations. Whereas UC-84, the prototype compound, only weakly inhibits many RTs bearing single point resistance mutations, inhibition by UC-781 is little affected. It has been proposed that UC-38 and UC-781 may form quaternary complexes with RT at a site other than the known binding pocket of other NNIs. X-ray crystal structures of four HIV-1 RT-carboxanilide complexes (UC-10, UC-38, UC-84, and UC-781) reported here reveal that all four inhibitors bind in the usual NNI site, forming binary 1:1 complexes with RT in the absence of substrates with the amide/thioamide bond in cis conformations. For all four complexes the anilide rings of the inhibitors overlap aromatic rings of many other NNIs bound to RT. In contrast, the second rings of UC-10, UC-84, and UC-781 do not bind in equivalent positions to those of other "two-ring" NNIs such as alpha-APA or HEPT derivatives. The binding modes most closely resemble that of the structurally dissimilar NNI, Cl-TIBO, with a common hydrogen bond between each carboxanilide NH- group and the main-chain carbonyl oxygen of Lys101. The binding modes differ slightly between the UC-10/UC-781 and UC-38/UC-84 pairs of compounds, apparently related to the shorter isopropylmethanoyl substituents of the anilide rings of UC-38/UC-84, which draws these rings closer to residues Tyr181 and Tyr188. This in turn explains the differences in the effect of mutated residues on the binding of these compounds.

We have used a structure-based approach to design a novel series of non-nucleoside inhibitors of HIV-1 RT (NNRTIs). Detailed analysis of a wide range of crystal structures of HIV-1 RT-NNRTI complexes together with data on drug resistance mutations has identified factors important for tight binding of inhibitors and resilience to mutations. Using this approach we have designed and synthesized a novel series of quinolone NNRTIs. Crystal structure analysis of four of these compounds in complexes with HIV-1 RT confirms the predicted binding modes. Members of this quinolone series retain high activity against the important resistance mutations in RT at Tyr181Cys and Leu100Ile.

Drug-likeness is a key consideration when selecting compounds during the early stages of drug discovery. However, evaluation of drug-likeness in absolute terms does not reflect adequately the whole spectrum of compound quality. More worryingly, widely used rules may inadvertently foster undesirable molecular property inflation as they permit the encroachment of rule-compliant compounds towards their boundaries. We propose a measure of drug-likeness based on the concept of desirability called the quantitative estimate of drug-likeness (QED). The empirical rationale of QED reflects the underlying distribution of molecular properties. QED is intuitive, transparent, straightforward to implement in many practical settings and allows compounds to be ranked by their relative merit. We extended the utility of QED by applying it to the problem of molecular target druggability assessment by prioritizing a large set of published bioactive compounds. The measure may also capture the abstract notion of aesthetics in medicinal chemistry.

Pandemic, epidemic and endemic infectious diseases are united by a common problem: how do we rapidly and cost-effectively identify potential pharmacological interventions to treat infections? Given the large number of emerging and neglected infectious diseases and the fact that they disproportionately afflict the poorest members of the global society, new ways of thinking are required to develop high productivity discovery systems that can be applied to a large number of pathogens. The growing availability of parasite genome data provides the basis for developing methods to prioritize, a priori potential drug targets and analyze the pharmacological landscape of an infectious disease. Thus the overall objective of infectious disease informatics is to enable the rapid generation of plausible, novel medical hypotheses of test-able pharmacological experiments, by uncovering undiscovered relationships in the wealth of biomedical literature and databases that were collected for other purposes. In particular our goal is to identify potential drug targets present in a pathogen genome and prioritize which pharmacological experiments are most likely to discover drug-like lead compounds rapidly against a pathogen (i.e. which specific compounds and drug targets should be screened, in which assays and where they can be sourced). An integral part of the challenge is the development and integration of methods to predict druggability, essentiality, synthetic lethality and polypharmocology in pathogen genomes, while simultaneously integrating the inevitable issues of chemical tractability and the potential for acquired drug resistance from the start.

Sole reliance on one drug, Praziquantel, for treatment and control of schistosomiasis raises concerns about development of widespread resistance, prompting renewed interest in the discovery of new anthelmintics. To discover new leads we designed an automated label-free, high content-based, high throughput screen (HTS) to assess drug-induced effects on in vitro cultured larvae (schistosomula) using bright-field imaging. Automatic image analysis and Bayesian prediction models define morphological damage, hit/non-hit prediction and larval phenotype characterization. Motility was also assessed from time-lapse images. In screening a 10,041 compound library the HTS correctly detected 99.8% of the hits scored visually. A proportion of these larval hits were also active in an adult worm ex-vivo screen and are the subject of ongoing studies. The method allows, for the first time, screening of large compound collections against schistosomes and the methods are adaptable to other whole organism and cell-based screening by morphology and motility phenotyping., Author Summary Schistosomiasis is a severe helminth infection affecting an estimated 600 million people. The one drug widely available, praziquantel (PZQ), is not ideal. PZQ kills the adult worms but not the developing juveniles so the treated patient may not be cured long-term. In addition, use of repeated mass treatment campaigns with PZQ to control morbidity raises concerns about the development of drug resistance. Our work is aimed at providing starting points for drug discovery programs for schistosomiasis by screening large compound libraries against whole organisms. Praziquantel and several other known anti-schistosomal drugs are also active in vitro against the adult worms and the larval stages, schistosomula. The latter are ideal for novel drug screening as they can be produced in large numbers in vitro, are small and so are amenable to screening in microwell plates. Drug activity can be assessed visually but this is subjective and laborious. We have built an automated system for assessing drug action involving the collection of images of the larvae and the development of computer algorithms to analyze their morphology and motility, defining them as "hits" or "nonhits." The method is reliable, consistent and efficient, making it feasible, for the first time, to screen large compound collections.

HIV reverse transcriptase (RT) is one of the main targets for the action of anti-AIDS drugs. Many of these drugs [e.g., 3′-azido-3′-deoxythymidine (AZT) and 2′,3′-dideoxyinosine (ddI)] are analogues of the nucleoside substrates used by the HIV RT. One of the main problems in anti-HIV therapy is the selection of a mutant virus with reduced drug sensitivity. Drug resistance in HIV is generated for nucleoside analogue inhibitors by mutations in HIV RT. However, most of these mutations are situated some distance from the polymerase active site, giving rise to questions concerning the mechanism of resistance. To understand the possible structural bases for this, the crystal structures of AZT- and ddI-resistant RTs have been determined. For the ddI-resistant RT with a mutation at residue 74, no significant conformational changes were observed for the p66 subunit. In contrast, for the AZT-resistant RT (RTMC) bearing four mutations, two of these (at 215 and 219) give rise to a conformational change that propagates to the active site aspartate residues. Thus, these drug resistance mutations produce an effect at the RT polymerase site mediated simply by the protein. It is likely that such long-range effects could represent a common mechanism for generating drug resistance in other systems.