David D. Anderson

Enhancing Protein Backbone Binding—A Fruitful Concept for Combating Drug‐Resistant HIV

Abstract The evolution of drug resistance is one of the most fundamental problems in medicine. In HIV/AIDS, the rapid emergence of drug‐resistant HIV‐1 variants is a major obstacle to current treatments. HIV‐1 protease inhibitors are essential components of present antiretroviral therapies. However, with these protease inhibitors, resistance occurs through viral mutations that alter inhibitor binding, resulting in a loss of efficacy. This loss of potency has raised serious questions with regard to effective long‐term antiretroviral therapy for HIV/AIDS. In this context, our research has focused on designing inhibitors that form extensive hydrogen‐bonding interactions with the enzyme’s backbone in the active site. In doing so, we limit the protease’s ability to acquire drug resistance as the geometry of the catalytic site must be conserved to maintain functionality. In this Review, we examine the underlying principles of enzyme structure that support our backbone‐binding concept as an effective means to combat drug resistance and highlight their application in our recent work on antiviral HIV‐1 protease inhibitors.

Impact of exercise on bone health and contraindication of oral contraceptive use in young women.

PURPOSE The effect of quantified resistance and high impact exercise training on bone mass as modified by age and oral contraceptive (OCont) use in young women was studied. METHODS Women were categorized by age (18-23 vs 24-31 yr) and OCont use, and were then randomized into either three sessions of resistance exercise plus 60 min.wk-1 of jumping rope or a control group for 24 months. Total body, spine, femoral neck, greater trochanter, Wards area, and radial bone mineral density (BMD) and/or content (BMC), biochemical markers of bone turnover, dietary intake of calcium, lean body mass, maximal oxygen uptake, and strength were determined at baseline and every 6 months. RESULTS Total body (TB) BMC percent change from baseline was higher in exercisers compared with nonexercisers at 6 and 24 months. OCont users had lower bone turnover at baseline and a decrease in TBBMC from baseline compared with non-OCont users at 24 months. Spine BMC and BMD decreased in the exercise and OCont group at 6 months and remained significantly below nonexercisers who used oral contraceptives at 2 yr. Femoral neck BMD also decreased in the exercise and oral contraceptive group at 6 months. CONCLUSIONS Exercise prevented a decline in TBBMC seen in the nonexercisers. On the other hand, exercise in oral contraceptive users prevented the increase observed in the spine of the nonexercise plus OCont group.

Coherence between Cellular Responses and in Vitro Splicing Inhibition for the Anti-tumor Drug Pladienolide B and Its Analogs

Background: Pladienolide B is a complex natural product that potently inhibits pre-mRNA splicing. Results: The same molecular features of pladienolide B are required for the drugs effects on cell growth, morphology, and splicing. Conclusion: Simplified synthesis and modification of active pladienolide B is possible. Significance: Pladienolide B analogs can be used to study the relationship between splicing and cancer cell function. Pladienolide B (PB) is a potent cancer cell growth inhibitor that targets the SF3B1 subunit of the spliceosome. There is considerable interest in the compound as a potential chemotherapeutic, as well as a tool to study SF3B1 function in splicing and cancer development. The molecular structure of PB, a bacterial natural product, contains a 12-member macrolide ring with an extended epoxide-containing side chain. Using a novel concise enantioselective synthesis, we created a series of PB structural analogs and the structurally related compound herboxidiene. We show that two methyl groups in the PB side chain, as well as a feature of the macrolide ring shared with herboxidiene, are required for splicing inhibition in vitro. Unexpectedly, we find that the epoxy group contributes only modestly to PB potency and is not absolutely necessary for activity. The orientations of at least two chiral centers off the macrolide ring have no effect on PB activity. Importantly, the ability of analogs to inhibit splicing in vitro directly correlated with their effects in a series of cellular assays. Those effects likely arise from inhibition of some, but not all, endogenous splicing events in cells, as previously reported for the structurally distinct SF3B1 inhibitor spliceostatin A. Together, our data support the idea that the impact of PB on cells is derived from its ability to impair the function of SF3B1 in splicing and also demonstrate that simplification of the PB scaffold is feasible.

Novel protease inhibitors (PIs) containing macrocyclic components and 3(R),3a(S),6a(R)-bis-tetrahydrofuranylurethane that are potent against multi-PI-resistant HIV-1 variants in vitro.

ABSTRACT Natural products with macrocyclic structural features often display intriguing biological properties. Molecular design incorporating macrocycles may lead to molecules with unique protein-ligand interactions. We generated novel human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs) containing a macrocycle and bis-tetrahydrofuranylurethane. Four such compounds exerted potent activity against HIV-1LAI and had 50% effective concentrations (EC50s) of as low as 0.002 μM with minimal cytotoxicity. GRL-216 and GRL-286 blocked the replication of HIV-1NL4-3 variants selected by up to 5 μM saquinavir, ritonavir, nelfinavir, lopinavir, or atazanavir; they had EC50s of 0.020 to 0.046 μM and potent activities against six multi-PI-resistant clinical HIV-1 (HIVmPIr) variants with EC50s of 0.027 to 0.089 μM. GRL-216 and -286 also blocked HIV-1 protease dimerization as efficiently as darunavir. When HIV-1NL4-3 was selected by GRL-216, it replicated progressively more poorly and failed to replicate in the presence of >0.26 μM GRL-216, suggesting that the emergence of GRL-216-resistant HIV-1 variants is substantially delayed. At passage 50 with GRL-216 (the HIV isolate selected with GRL-216 at up to 0.16 μM [HIV216-0.16 μM]), HIV-1NL4-3 containing the L10I, L24I, M46L, V82I, and I84V mutations remained relatively sensitive to PIs, including darunavir, with the EC50s being 3- to 8-fold-greater than the EC50 of each drug for HIV-1NL4-3. Interestingly, HIV216-0.16 μM had 10-fold increased sensitivity to tipranavir. Analysis of the protein-ligand X-ray structures of GRL-216 revealed that the macrocycle occupied a greater volume of the binding cavity of protease and formed greater van der Waals interactions with V82 and I84 than darunavir. The present data warrant the further development of GRL-216 as a potential antiviral agent for treating individuals harboring wild-type and/or HIVmPIr.

Tetrahydrofuran, tetrahydropyran, triazoles and related heterocyclic derivatives as HIV protease inhibitors

HIV/AIDS remains a formidable disease with millions of individuals inflicted worldwide. Although treatment regimens have improved considerably, drug resistance brought on by viral mutation continues to erode their effectiveness. Intense research efforts are currently underway in search of new and improved therapies. This review is concerned with the design of novel HIV-1 protease inhibitors that incorporate heterocyclic scaffolds and which have been reported within the recent literature (2005-2010). Various examples in this review showcase the essential role heterocycles play as scaffolds and bioisosteres in HIV-1 protease inhibitor drug development. This review will hopefully stimulate the widespread application of these heterocycles in the design of other therapeutic agents.

L-selectride-mediated highly diastereoselective asymmetric reductive aldol reaction: access to an important subunit for bioactive molecules.

L-selectride reduction of a chiral or achiral enone followed by reaction of the resulting enolate with optically active alpha-alkoxy aldehydes proceeded with excellent diastereoselectivity. The resulting alpha,alpha-dimethyl-beta-hydroxy ketones are inherent to a variety of biologically active natural products.