Laith Q. Al-Mawsawi

HIV-1 integrase inhibitors: an emerging clinical reality.

From the discovery of HIV-1 integrase (IN) inhibitors using enzyme-based assays in 1992, it has taken 15 years to achieve success in human clinical trials. Currently available antiretroviral drugs set high clinical standards in efficacy and long-term safety for upcoming novel HIV/AIDS therapeutic agents. The results from advanced stages of human clinical trials with IN inhibitors indicate a promising future for these compounds as a novel class of antiretroviral drugs. Success and failure of previously discovered antiretroviral drugs have taught us that there are no magic bullets in eradicating HIV. However, approval of drugs selectively targeting IN has long been awaited. There is once again a surge of interest in the field focusing on clinical development of IN inhibitors. Here, we summarise the current status of IN inhibitors under clinical development. These agents include S-1360, GSK-364735, L-870,810, L-870,812, MK-0518, GS-9137, L-900564, GS-9224, and BMS-707035. Promising antiviral activity has already been achieved with MK-0518 and GS-9137 in late-stage clinical studies.

Quinolone 3-carboxylic acid pharmacophore: design of second generation HIV-1 integrase inhibitors.

Two decades of intensive research efforts have led to the discovery of a large number of HIV-1 integrase (IN) inhibitors. Recently, the United States Food and Drug Administration (US FDA) approved MK-0518, or raltegravir ( 1), as the first IN inhibitor for HIV/AIDS treatment. Growing clinical evidence also demonstrates that the emergence of HIV-1 virus strains bearing IN amino acid substitutions that confer resistance to IN inhibitors is inevitable. The discovery of second generation inhibitors with potency against viral strains bearing drug resistant IN substitutions is necessary for ongoing effective treatment of viral infections. We generated common feature pharmacophore hypotheses using a training set of quinolone 3-carboxylic acid IN inhibitors, including the clinical candidate GS-9137 ( 2). A database search of small molecules using the quinolone 3-carboxylic acid pharmacophore model, followed by in vitro evaluation of selected hits in an assay specific to IN, resulted in the discovery of potential leads with diverse structural scaffolds useful for the design of second generation IN inhibitors.

Allosteric Inhibitor Development Targeting HIV-1 Integrase

HIV‐1 integrase (IN) is one of three essential enzymes for viral replication, and is a focus of ardent antiretroviral drug discovery and development efforts. Diligent research has led to the development of the strand‐transfer‐specific chemical class of IN inhibitors, with two compounds from this group, raltegravir and elvitegravir, advancing the farthest in the US Food and Drug Administration (FDA) approval process for any IN inhibitor discovered thus far. Raltegravir, developed by Merck & Co., has been approved by the FDA for HIV‐1 therapy, whereas elvitegravir, developed by Gilead Sciences and Japan Tobacco, has reached phase III clinical trials. Although this is an undoubted success for the HIV‐1 IN drug discovery field, the emergence of HIV‐1 IN strand‐transfer‐specific drug‐resistant viral strains upon clinical use of these compounds is expected. Furthermore, the problem of strand‐transfer‐specific IN drug resistance will be exacerbated by the development of cross‐resistant viral strains due to an overlapping binding orientation at the IN active site and an equivalent inhibitory mechanism for the two compounds. This inevitability will result in no available IN‐targeted therapeutic options for HIV‐1 treatment‐experienced patients. The development of allosterically targeted IN inhibitors presents an extremely advantageous approach for the discovery of compounds effective against IN strand‐transfer drug‐resistant viral strains, and would likely show synergy with all available FDA‐approved antiretroviral HIV‐1 therapeutics, including the IN strand‐transfer‐specific compounds. Herein we review the concept of allosteric IN inhibition, and the small molecules that have been investigated to bind non‐active‐site regions to inhibit IN function.

Inhibitory profile of a LEDGF/p75 peptide against HIV-1 integrase: insight into integrase-DNA complex formation and catalysis.

A lens epithelium‐derived growth factor (LEDGF)/p75 peptide was evaluated for human immunodeficiency virus type 1 integrase (IN) inhibitory activity. The LEDGF/p75 peptide modestly inhibited IN catalysis and was dependent on IN–DNA assembly. The peptide was also effective at disrupting LEDGF/p75–IN complex formation. We next investigated the activity of the LEDGF/p75 peptide on IN mutant proteins that are unable to catalyze the DNA strand transfer reaction. The LEDGF/p75 peptide displayed an increased potency on these IN proteins, from 5‐fold to greater than 10‐fold, indicating the IN multimeric state greatly influences the peptide inhibitory effects. These results shed light on IN–DNA multimeric formation, and how this process influences the LEDGF/p75–IN interaction.

Anti-infectives: clinical progress of HIV-1 integrase inhibitors.

Background: HIV-1 integrase (IN) represents a therapeutically advantageous viral target to treat HIV/AIDS in the clinic. Over a decade of progress in the field has resulted in IN inhibitor chemical classes that display specificity for strand transfer catalysis of the enzyme, thus blocking viral DNA integration into host cell nuclear DNA, an essential step for viral infectivity. Objective: In this manuscript we provide an update on recent HIV-1 IN inhibitors that have been clinically evaluated, which include MK-0518, MK-2048, GS-9137, GS-9160, GS-9224, GSK-364735, and BMS-707035. The information presented here can aid in the IN drug developmental process. Methods: We have limited the scope of this review to information available on the clinical evaluation of promising strand transfer-specific IN inhibitors and their potential drug–drug interaction profiles with other antiretroviral agents. Results/conclusion: The development of strand transfer-specific inhibitor classes is an important achievement for the IN drug design and development field. However, continued drug development is needed given that the ability of HIV to replicate under therapeutic pressure will undoubtedly lead to the emergence of IN drug-resistant viral strains.

Design of second generation HIV-1 integrase inhibitors

The prospect of HIV-1 integrase (IN) as a therapeutically viable retroviral drug target is on the verge of realization. The observed preclinical and clinical performance of beta-diketo containing and naphthyridine carboxamide compounds provides direct proof for the clinical application of IN inhibition. These validated lead compounds are useful in the design and development of second generation IN inhibitors. The results from preclinical and clinical studies on the first generation IN inhibitors reiterate a demand for novel second generation inhibitors with improved pharmacokinetic and metabolic properties. Pharmacophore-based drug design techniques facilitate the discovery of novel compounds on the basis of validated lead compounds specific for a drug target. In this article we have comprehensively reviewed the application of pharmacophore-based drug design methods in the field of IN inhibitor discovery.

Are we living in the end of the blockbuster drug era

For the last two decades, we have seen remarkable growth in the pharmaceutical industry. This growth has mainly been due to the approximately 100 new blockbuster drugs, such as Lipitor® (atorvastatin) and Plavix® (clopidogrel). More than half of the revenue of major pharmaceutical companies and above one-third of the total pharmaceutical revenues came from the sales of these blockbuster drugs. Questions concerning the fate of these blockbuster drugs are beginning to surface as they are approaching their patent expiration dates, and as they are expected to face significant competition from generic versions. Branded drugs with more than USD 120 billion in sales (as of 2008) are expected to lose their patent protection in the next 3 to 4 years, while the less expensive generic versions are ready to enter the market. It is plausible that a major paradigm shift in our thinking is needed to stay innovative, competitive and economically feasible in this new era of drug development. A new wave of innovations is expected to boost the blockbuster regime. Herein, we discuss the different threats facing the branded monopoly, as well as some of the hopeful expectations for the blockbuster drug.

A Symmetric Region of the HIV-1 Integrase Dimerization Interface Is Essential for Viral Replication

HIV-1 integrase (IN) is an important target for contemporary antiretroviral drug design research. Historically, efforts at inactivating the enzyme have focused upon blocking its active site. However, it has become apparent that new classes of allosteric inhibitors will be necessary to advance the antiretroviral field in light of the emergence of viral strains resistant to contemporary clinically used IN drugs. In this study we have characterized the importance of a close network of IN residues, distant from the active site, as important for the obligatory multimerization of the enzyme and viral replication as a whole. Specifically, we have determined that the configuration of six residues within a highly symmetrical region at the IN dimerization interface, composed of a four-tiered aromatic interaction flanked by two salt bridges, significantly contributes to proper HIV-1 replication. Additionally, we have utilized a quantitative luminescence assay to examine IN oligomerization and have determined that there is a very low tolerance for amino acid substitutions along this region. Even conservative residue substitutions negatively impacted IN multimerization, resulting in an inactive viral enzyme and a non-replicative virus. We have shown that there is a very low tolerance for amino acid variation at the symmetrical dimeric interface region characterized in this study, and therefore drugs designed to target the amino acid network detailed here could be expected to yield a significantly reduced number of drug-resistant escape mutations compared to contemporary clinically-evaluated antiretrovirals.

Single amino acid substitution in HIV-1 integrase catalytic core causes a dramatic shift in inhibitor selectivity

HIV‐1 integrase (IN) mediates the insertion of viral cDNA into the cell genome, a vital process for replication. This step is catalyzed by two separate DNA reaction events, termed 3′‐processing and strand transfer. Here, we show that six inhibitors from five structurally different classes of compounds display a selectivity shift towards preferential strand transfer inhibition over the 3′‐processing activity of IN when a single serine is substituted at position C130. Even though IN utilizes the same active site for both reactions, this finding suggests a distinct conformational dissimilarity in the mechanistic details of each IN catalytic event.

Recent advances in the design and discovery of small-molecule therapeutics targeting HER2/neu

The human epidermal growth factor receptor (HER) family is a highly explored and promising anticancer drug target. At present, several investigational agents targeted to the HER family of receptors are in various stages of development. Five drugs are already in the clinic for the treatment of cancers that overexpress HER family receptors. Two FDA-approved small-molecule drugs, gefitinib and erlotinib, inhibit HER1 tyrosine kinase activity. Two mAbs, cetuximab and panitumumab, target the extracellular domain of HER1, and another, trastuzumab, targets the extracellular domain of HER2. HER2 is a prominent member of the HER family of receptor tyrosine kinases and serves as a preferred dimerization partner for other HER family members. This paper reviews recently patented small-molecule inhibitors of HER2 receptor kinase activity, and inhibitors of HER2 expression and shedding. Apart from the well-explored quinazoline class of compounds (e.g., lapatinib), arylazole, benzodithiazole, pyrrolopyridazine, pyrrolotriazine and pyrrolopyrimidine classes of compounds were also claimed as HER2 tyrosine kinase inhibitors. Most of these compounds show considerable activity against all the HER family as well as members from different families of tyrosine kinases. It remains to be established how the combination of selective HER inhibitors compare with the single-agent pan-kinase inhibitors in disrupting HER family mediated signalling pathways. Such information is of paramount importance in the clinical development of HER-targeted inhibitors.