Preparation and in vivo analysis of “mCD4-HS12”, a synthetic glyco-conjugate which inhibits HIV entry. – HEPACLAMP

Human immunodeficiency virus (HIV-1), the virus that causes AIDS has infected 60 million people (half of which has died) and remains one of the leading causes of death worldwide. The availability of some 25 drugs, most of which target HIV-1 enzymes, markedly improved patients’ outcomes. However, their inability to completely eradicate the virus, the emergence of resistant viral strains and the strong adverse side effects associated with long-term exposure to such drugs necessitate the development of new antivirals. Amongst the most promising recent approaches to fight HIV, is the blockade of viral entry, whose applications can be considered both for preventive (virucide) or curative (antiviral) formulations. In this context, we propose to validate the activity of a new type of anti-HIV compound for which we have already demonstrated very strong activities in cellular assays.

Entry begins when the viral envelope glycoprotein gp120 binds to its primary host cell receptor, CD4, and undergoes a conformational change that exposes a second binding site, then recognized by a coreceptor (CCR5 or CXCR4). This CD4 induced domain, which blockade would inhibit viral entry, is an extremely attractive pharmacological target, but its cryptic nature makes this extremely difficult.

Recently however, we developed a new molecule that enables us to reach this objective. This compound, mCD4-HS12, comprises a small CD4 mimetic peptide (mCD4) linked to a heparan sulfate dodecamer (HS12). We showed that the CD4 mimetic binds to gp120, induces the exposure of the cryptic coreceptor binding domain which then is blocked by the HS12 moiety of the molecule.

This compound is thus able to simultaneously target two critical and highly conserved structures of gp120 (the CD4 and the coreceptor binding sites) which are both key for entry. Consequently, mCD4-HS12 displays very strong anti viral activities (IC50: 2 to 5 nM, IC90: 3 to 10 nM depending of the viral strain used) and remarkably, in blood cell culture, neutralizes almost equally well CCR5-, CXCR4- and dual- tropic HIV-1. It was more potent than the reference drug azidothymidine (AZT) and no cytotoxicity was found at concentration up to 1 uM.

This synthetic compound, which is conceptually distinct from any other existing ones, has a number of advantages:

Inhibition of attachment and entry, an early step in the viral life cycle

Targeting the pathogen rather than the host

Simultaneous targeting of two conserved regions of gp120

Strong active against both R5 and X4 viruses (viruses that uses CCR5 or CXCR4 as coreceptor). If a drug blocking CCR5 (maraviroc) has been approved, no effective antagonistic inhibitors yet exist for CXCR4. The mCD4-HS12 glycoconjugate could be a valuable weapon against the more aggressive X4-tropic HIV-1 strains.

These results have been published recently (Nat. Chem. Biol. (2009) 5, 743-748) and are covered by three patents (WO03089000, WO2008015273A1 and WO2009098147A2).

The purpose of the present program is thus to produce batches of mCD4-HS12 in sufficient amount to perform a pharmacokinetic study and to demonstrate the in vivo activity of the molecule using a non human primate model of HIV infection. The proof of concept we intend to make is needed before this molecule can be transferred to companies (some of which have already expressed their interest) and further develop to approach preclinical and clinical studies.