17th International HIV Drug Resistance Workshop 10-14 June 2008, Sitges, Spain

POTENT HIV-1 ENTRY INHIBITORS WITH A RESERVE OF BINDING ENERGY AGAINST RESISTANCE MUTATIONS

Antivir Ther. 2008; 13(Suppl. 3):A3 (abstract no. 1)

BD Welch¹, JP Redman¹, S Paul², MJ Root² and MS Kay^1
1Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA; ²Department of Biochemistry and Molecular Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA

BACKGROUND: Enfuvirtide is the first approved HIV-1 entry inhibitor and is particularly useful for ‘salvage therapy’ in patients resistant to highly active antiretroviral therapy. Unfortunately, resistance to enfuvirtide rapidly emerges in vitro and in vivo. During HIV-1 entry, the gp41 HR1 trimer ‘pocket’ region becomes transiently exposed and vulnerable to inhibition. This pocket is an attractive inhibitory target because it is extremely well-conserved and essential for viral entry.<//p>

METHODS: In contrast to natural peptides, D-peptides are promising therapeutic agents due to their insensitivity to degradation by proteases. Using mirror-image phage display and structure-assisted design, we have produced D-peptides that bind the gp41 pocket with high affinity and potently inhibit viral entry. To further improve binding and potency via avidity, we have designed trimeric D-peptides connected via flexible polyethylene glycol linkers that simultaneously bind all three pockets in the gp41 HR1 trimer.

RESULTS: Our lead trimeric D-peptide (PIE12-trimer) potently inhibits a diverse panel of primary isolates (clades A–G) with an average IC₅₀ >60-fold better than enfuvirtide. Viral strains resistant to other HIV entry inhibitors (including enfuvirtide, C34 and 5-helix) remain sensitive to the D- peptide trimer. Interestingly, for our ultra-high affinity (subpM) inhibitors, potency appears to be determined by association rate rather than affinity due to limited time-window of exposure of the target during viral entry. We exploit this property to ‘over-engineer’ our inhibitors with a reserve of binding energy against affinity-perturbing resistance mutations. This ‘resistance capacitor’ also deprives HIV of an evolutionary pathway for the step-wise accumulation of subtle resistance mutations by uncoupling affinity and inhibitory potency. Initial passaging data show a superior resistance profile compared with other fusion inhibitors, such as enfuvirtide, C34 and earlier generation D-peptides.

CONCLUSIONS: Our D-peptide trimer is a broad and potent inhibitor of HIV entry that has been designed to prevent or delay the development of resistance. This inhibitor addresses limitations associated with enfuvirtide and is a strong candidate for the prevention and treatment of HIV/AIDS.

ACKNOWLEDGEMENTS: Supported by NIH grants GM082545 and AI076168.

2008-06-10
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