Optimization of Small Molecules That Sensitize HIV-1 Infected Cells to Antibody-Dependent Cellular Cytotoxicity

Optimization of a Piperidine CD4-Mimetic Scaffold Sensitizing HIV-1 Infected Cells to Antibody-Dependent Cellular Cytotoxicity

The ability of the HIV-1 accessory proteins Nef and Vpu to decrease CD4 protects infected cells from antibody-dependent cellular cytotoxicity (ADCC) by limiting the exposure of vulnerable epitopes to envelope glycoprotein (Env). Small-molecule CD4 mimetics (CD4mcs) based on piperidine scaffolds represent a new family of agents capable of sensitizing HIV-1-infected cells to ADCC by exposing CD4-induced (CD4i) epitopes on Env that are recognized by non-neutralizing antibodies which are abundant in plasma of people living with HIV. Here, we employed the combined methods of parallel synthesis, structure-based design, and optimization to generate a new line of piperidine-based CD4mcs, which sensitize HIV-1 infected cells to ADCC activity. The X-ray crystallographic study of the CD4mcs within the gp120 residues suggests that the positioning of the CD4mc inside the Phe43 cavity and synergistic contact of the CD4mc with the β20-21 loop and the α1-helix lead to improved antiviral activity.

A Chemoselective Polarity-Mismatched Photocatalytic C(sp3 )-C(sp2 ) Cross-Coupling Enabled by Synergistic Boron Activation

We report the development of a C(sp3 )-C(sp2 ) coupling reaction using styrene boronic acids and redox-active esters under photoredox catalysis. The reaction proceeds through an unusual polarity-mismatched radical addition mechanism that is orthogonal to established processes. Synergistic activation of the radical precursor and organoboron are critical mechanistic events. Activation of an N-hydroxyphthalimide (NHPI) ester by coordination to boron enables electron transfer, with decomposition leading to a nucleofuge rebound, activating the organoboron to radical addition. The unique mechanism enables chemoselective coupling of styrene boronic acids in the presence of other alkene radical acceptors. The scope and limitations of the reaction, and a detailed mechanistic investigation are presented.

Piperidine CD4-Mimetic Compounds Expose Vulnerable Env Epitopes Sensitizing HIV-1-Infected Cells to ADCC

The ability of the HIV-1 accessory proteins Nef and Vpu to decrease CD4 levels contributes to the protection of infected cells from antibody-dependent cellular cytotoxicity (ADCC) by preventing the exposure of Env vulnerable epitopes. Small-molecule CD4 mimetics (CD4mc) based on the indane and piperidine scaffolds such as (+)-BNM-III-170 and (S)-MCG-IV-210 sensitize HIV-1-infected cells to ADCC by exposing CD4-induced (CD4i) epitopes recognized by non-neutralizing antibodies that are abundantly present in plasma from people living with HIV. Here, we characterize a new family of CD4mc, (S)-MCG-IV-210 derivatives, based on the piperidine scaffold which engages the gp120 within the Phe43 cavity by targeting the highly conserved Asp368 Env residue. We utilized structure-based approaches and developed a series of piperidine analogs with improved activity to inhibit the infection of difficult-to-neutralize tier-2 viruses and sensitize infected cells to ADCC mediated by HIV+ plasma. Moreover, the new analogs formed an H-bond with the α-carboxylic acid group of Asp368, opening a new avenue to enlarge the breadth of this family of anti-Env small molecules. Overall, the new structural and biological attributes of these molecules make them good candidates for strategies aimed at the elimination of HIV-1-infected cells.

Piperidine CD4-mimetic compounds expose vulnerable Env epitopes sensitizing HIV-1-infected cells to ADCC

The ability of HIV-1 accessory proteins Nef and Vpu to decrease CD4 levels contributes to the protection of infected cells from antibody-dependent cellular cytotoxicity (ADCC) by preventing the exposure of Env vulnerable epitopes. Small-molecule CD4 mimetics (CD4mc) based on the indane and piperidine scaffolds such as (+)-BNM-III-170 and ( S )-MCG-IV-210 sensitize HIV-1 infected cells to ADCC by exposing CD4-induced (CD4i) epitopes recognized by non-neutralizing antibodies abundantly present in plasma from people living with HIV. Here, we characterize a new family of CD4mc, ( S )-MCG-IV-210 derivatives, based on the piperidine scaffold which engage the gp120 within the Phe43 cavity by targeting the highly-conserved Asp ³⁶⁸ Env residue. We utilized structure-based approaches and developed a series of piperidine analogs with improved activity to inhibit infection of difficult-to-neutralize tier-2 viruses and sensitize infected cells to ADCC mediated by HIV+ plasma. Moreover, the new analogs formed an H-bond with the α-carboxylic acid group of Asp ³⁶⁸ , opening a new avenue to enlarge the breadth of this family of anti-Env small molecules. Overall, the new structural and biological attributes of these molecules make them good candidates for strategies aimed at the elimination HIV-1-infected cells.

Recent research results have converted gp120 binders to a therapeutic option for the treatment of HIV-1 infection. A medicinal chemistry point of view

Current therapeutic armamentarium for treatment of HIV-1 infection is based on the use of highly active antiretroviral therapy that, unfortunately, does not act as a curative remedy. Moreover, duration of the therapy often results in lack of compliance with the consequent emergence of multidrug resistance. Finally, drug toxicity issues also arise during treatments. In the attempt to achieve a curative effect, in addition to invest substantial resources in finding new anti-HIV-1 agents and in optimizing antiviral lead compounds and drugs currently available, additional efforts should be done to deplete viral reservoir located within host CD4⁺ T cells. Gp120 binders represent a class of compounds able to affect the interactions between viral envelope proteins and host CD4, thus avoiding virus-to-cell attachment and fusion, and the consequent viral entry into host cells. This review summarizes the efforts done in the last five years to design new gp120 binders, that finally culminated in the approval of fostemsavir as an anti-HIV-1 drug.

Opening the HIV envelope: potential of CD4 mimics as multifunctional HIV entry inhibitors

PURPOSE OF REVIEW

Close to 2 million individuals globally become infected with HIV-1 each year and just over two-thirds will have access to life-prolonging antivirals. However, the rapid development of drug resistance creates challenges, such that generation of more effective therapies is not only warranted but a necessary endeavour. This review discusses a group of HIV-1 entry inhibitors known as CD4 mimics which exploit the highly conserved relationship between the HIV-1 envelope glycoprotein and the receptor, CD4.

RECENT FINDINGS

We review the structure/function guided evolution of these inhibitors, vital mechanistic insights that underpin broad and potent functional antagonism, recent evidence of utility demonstrated in animal and physiologically relevant in-vitro models, and current progress towards effective new-generation inhibitors.

SUMMARY

The current review highlights the promising potential of CD4 mimetics as multifunctional therapeutics.