Novel P1 chain-extended HIV protease inhibitors possessing potent anti-HIV activity and remarkable inverse antiviral resistance profiles

Drug Design Strategies to Avoid Resistance in Direct-Acting Antivirals and Beyond

Drug resistance is prevalent across many diseases, rendering therapies ineffective with severe financial and health consequences. Rather than accepting resistance after the fact, proactive strategies need to be incorporated into the drug design and development process to minimize the impact of drug resistance. These strategies can be derived from our experience with viral disease targets where multiple generations of drugs had to be developed to combat resistance and avoid antiviral failure. Significant efforts including experimental and computational structural biology, medicinal chemistry, and machine learning have focused on understanding the mechanisms and structural basis of resistance against direct-acting antiviral (DAA) drugs. Integrated methods show promise for being predictive of resistance and potency. In this review, we give an overview of this research for human immunodeficiency virus type 1, hepatitis C virus, and influenza virus and the lessons learned from resistance mechanisms of DAAs. These lessons translate into rational strategies to avoid resistance in drug design, which can be generalized and applied beyond viral targets. While resistance may not be completely avoidable, rational drug design can and should incorporate strategies at the outset of drug development to decrease the prevalence of drug resistance.

Recent Progress in the Development of HIV-1 Protease Inhibitors for the Treatment of HIV/AIDS

HIV-1 protease inhibitors continue to play an important role in the treatment of HIV/AIDS, transforming this deadly ailment into a more manageable chronic infection. Over the years, intensive research has led to a variety of approved protease inhibitors for the treatment of HIV/AIDS. In this review, we outline current drug design and medicinal chemistry efforts toward the development of next-generation protease inhibitors beyond the currently approved drugs.

Recent patents and emerging therapeutics for HIV infections: a focus on protease inhibitors

The inclusion of protease inhibitors (PIs) in highly active antiretroviral therapy has significantly improved clinical outcomes in HIV-1-infected patients. To date, PIs are considered to be the most important therapeutic agents for the treatment of HIV infections. Despite high anti-HIV-1 potency, poor oral bioavailability of PIs has been a major concern. For achieving therapeutic concentrations, large doses of PIs are administered, which results in unacceptable systemic toxicities. Such severe and long-term toxicities necessitate the development of safer and potentially promising PIs. Recently, considerable attention has been paid to the development of newer compounds capable of inhibiting wild-type and resistant HIV-1 protease. Some of these PIs have displayed potent HIV-1 protease inhibitory activity. In this review, we have made an attempt to provide an overview on clinically approved and newly developing PIs, and related recent patents in the development of novel PIs.

In vitro characterization of GS-8374, a novel phosphonate-containing inhibitor of HIV-1 protease with a favorable resistance profile

GS-8374 is a novel bis-tetrahydrofuran HIV-1 protease (PR) inhibitor (PI) with a unique diethylphosphonate moiety. It was selected from a series of analogs containing various di(alkyl)phosphonate substitutions connected via a linker to the para position of a P-1 phenyl ring. GS-8374 inhibits HIV-1 PR with high potency (K(i) = 8.1 pM) and with no known effect on host proteases. Kinetic and thermodynamic analysis of GS-8374 binding to PR demonstrated an extremely slow off rate for the inhibitor and favorable contributions of both the enthalpic and entropic components to the total free binding energy. GS-8374 showed potent antiretroviral activity in T-cell lines, primary CD4(+) T cells (50% effective concentration [EC(50)] = 3.4 to 11.5 nM), and macrophages (EC(50) = 25.5 nM) and exhibited low cytotoxicity in multiple human cell types. The antiviral potency of GS-8374 was only moderately affected by human serum protein binding, and its combination with multiple approved antiretrovirals showed synergistic effects. When it was tested in a PhenoSense assay against a panel of 24 patient-derived viruses with high-level PI resistance, GS-8374 showed lower mean EC(50)s and lower fold resistance than any of the clinically approved PIs. Similar to other PIs, in vitro hepatic microsomal metabolism of GS-8374 was efficiently blocked by ritonavir, suggesting a potential for effective pharmacokinetic boosting in vivo. In summary, results from this broad in vitro pharmacological profiling indicate that GS-8374 is a promising candidate to be further assessed as a new antiretroviral agent with potential for clinical efficacy in both treatment-naïve and -experienced patients.

Synthesis, structural activity-relationships, and biological evaluation of novel amide-based allosteric binding site antagonists in NR1A/NR2B N-methyl-D-aspartate receptors

The synthesis and structure-activity relationship analysis of a novel class of amide-based biaryl NR2B-selective NMDA receptor antagonists are presented. Some of the studied compounds are potent, selective, non-competitive, and voltage-independent antagonists of NR2B-containing NMDA receptors. Like the founding member of this class of antagonists (ifenprodil), several interesting compounds of the series bind to the amino terminal domain of the NR2B subunit to inhibit function. Analogue potency is modulated by linker length, flexibility, and hydrogen bonding opportunities. However, unlike previously described classes of NR2B-selective NMDA antagonists that exhibit off-target activity at a variety of monoamine receptors, the compounds described herein show much diminished effects against the hERG channel and alpha(1)-adrenergic receptors. Selections of the compounds discussed have acceptable half-lives in vivo and are predicted to permeate the blood-brain barrier. These data together suggest that masking charged atoms on the linker region of NR2B-selective antagonists can decrease undesirable side effects while still maintaining on-target potency.

Ultra-potent P1 modified arylsulfonamide HIV protease inhibitors: the discovery of GW0385

A novel series of P1 modified HIV protease inhibitors was synthesized and evaluated for in vitro antiviral activity against wild-type virus and protease inhibitor-resistant viruses. Optimization of the P1 moiety resulted in compounds with femtomolar enzyme activities and cellular antiviral activities in the low nanomolar range culminating in the identification of clinical candidate GW0385.