Haloperidol-based irreversible inhibitors of the HIV-1 and HIV-2 proteases

Towards a pharmacochemical hypothesis of the prophylaxis of SARS-CoV-2 by psychoactive substances

An increasing body of evidence suggests a protective effect of some psychoactive substances against SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus type 2). Recent findings suggest that patients with psychiatric disorders are less affected by SARS-CoV-2 than their caregivers, which may seem surprising given some of the frequent risk factors for an unfavorable course of the disease (e.g., obesity, diabetes, cardiovascular and pulmonary diseases). We propose here a mixed pharmacoepidemiological and pharmacochemical hypothesis to explain these findings. A number of psychotropic drugs exhibit activities against coronaviruses (Middle East Respiratory Syndrome coronavirus (MERS-CoV), the Severe Acute Respiratory Syndrome coronavirus (SARS-CoV-1) and the Infectious Bronchitis Virus (IBV)) and have been put forward as potentially anti-SARS-CoV-2. These treatments include numerous mee-too drugs (chemically and pharmacologically linked to those which have demonstrated anti-SARS-CoV-2 efficacy) which are frequently prescribed in psychiatric settings. Taken alone or in polypharmacy, these drugs could have a prophylactic anti-SARS-CoV-2 effect, explaining the unexpectedly low proportion of patients with psychiatric disorders and COVID-19. Associated factors such as nicotine can also be considered in the context of a broad chemoprophylactic hypothesis in patients with psychiatric disorders taking different psychoactive substances.

Design, synthesis and evaluation of a potent substrate analog inhibitor identified by scanning Ala/Phe mutagenesis, mimicking substrate co-evolution, against multidrug-resistant HIV-1 protease

Multidrug-resistant (MDR) clinical isolate-769, human immunodeficiency virus type-1 (HIV-1) protease (PDB ID: 1TW7), was shown to exhibit wide-open flaps and an expanded active site cavity, causing loss of contacts with protease inhibitors. In the current study, the expanded active site cavity of MDR769 HIV-1 protease was screened with a series of peptide-inhibitors that were designed to mimic the natural substrate cleavage site, capsid/p2. Scanning Ala/Phe chemical mutagenesis approach was incorporated into the design of the peptide series to mimic the substrate co-evolution. Among the peptides synthesized and evaluated, a lead peptide (6a) with potent activity (IC50: 4.4nM) was identified against the MDR769 HIV-1 protease. Isothermal titration calorimetry data showed favorable binding profile for 6a against both wild type and MDR769 HIV-1 protease variants. Nuclear magnetic resonance spectrum of (15)N-labeled MDR769 HIV-1 protease in complex with 6a showed some major perturbations in chemical shift, supporting the peptide induced conformational changes in protease. Modeling analysis revealed multiple contacts between 6a and MDR769 HIV-1 protease. The lead peptide-inhibitor, 6a, with high potency and good binding profile can be used as the basis for developing potent small molecule inhibitors against MDR variants of HIV.

Solution kinetics measurements suggest HIV-1 protease has two binding sites for darunavir and amprenavir

Darunavir, a potent antiviral drug, showed an unusual second binding site on the HIV-1 protease dimer surface of the V32I drug resistant mutant and normal binding in the active site cavity. Kinetic analysis for wild type and mutant protease showed mixed-type competitive-uncompetitive inhibition for darunavir and the chemically related amprenavir, while saquinavir showed competitive inhibition. The inhibition model is consistent with the observed second binding site for darunavir and helps to explain its antiviral potency.

Epoxide-containing side chains enhance antiproliferative activity of paullones

The introduction of side chains bearing epoxide motifs into the molecular scaffold of kenpaullone and 9-trifluoromethylpaullone led to improved antiproliferative activity of the novel derivatives for human tumor cell lines. The syntheses were accomplished applying Stille coupling for the introduction of unsaturated side chains into the 2-position of the paullones and subsequently employing a hydrogen peroxide/nitrile mixture for the epoxidation of C,C-double bonds.

L-chicoric acid inhibits human immunodeficiency virus type 1 integration in vivo and is a noncompetitive but reversible inhibitor of HIV-1 integrase in vitro

The human immunodeficiency virus (HIV) integrase (IN) must covalently join the viral cDNA into a host chromosome for productive HIV infection. l-Chicoric acid (l-CA) enters cells poorly but is a potent inhibitor of IN in vitro. Using quantitative real-time polymerase chain reaction (PCR), l-CA inhibits integration at concentrations from 500 nM to 10 microM but also inhibits entry at concentrations above 1 microM. Using recombinant HIV IN, steady-state kinetic analyses with l-CA were consistent with a noncompetitive or irreversible mechanism of inhibition. IN, in the presence or absence of l-CA, was successively washed. Inhibition of IN diminished, demonstrating that l-CA was reversibly bound to the protein. These data demonstrate that l-CA is a noncompetitive but reversible inhibitor of IN in vitro and of HIV integration in vivo. Thus, l-CA likely interacts with amino acids other than those which bind substrate.

Peptide-based, irreversible inhibitors of gamma-secretase activity

The characterization of the enzymes responsible for amyloid beta-peptide (Abeta) production is considered to be a primary goal towards the development of future therapeutics for the treatment of Alzheimer's disease. Inhibitors of gamma-secretase activity were critical in demonstrating that the presenilins (PSs) likely comprised at least part of the active site of the gamma-secretase enzyme complex, with two highly conserved membrane aspartates presumably acting as catalytic residues. However, whether or not these aspartates are actually the catalytic residues of the enzyme complex or are merely essential for normal PS function and/or maturation is still unknown. In this paper, we report the development of reactive inhibitors of gamma-secretase activity that are functionally irreversible. Since such inhibitors have been shown to bind catalytic residues in other aspartyl proteases (e.g., HIV protease), they might be used to determine if the transmembrane aspartates of PSs are involved directly in substrate cleavage.

Polyoxometalate HIV-1 protease inhibitors. A new mode of protease inhibition

Nb-containing polyoxometalates (POMs) of the Wells-Dawson class inhibit HIV-1 protease (HIV-1P) by a new mode based on kinetics, binding, and molecular modeling studies. Reaction of alpha(1)-K(9)Li[P(2)W(17)O(61)] or alpha(2)-K(10)[P(2)W(17)O(61)] with aqueous H(2)O(2) solutions of K(7)H[Nb(6)O(19)] followed by treatment with HCl and KCl and then crystallization affords the complexes alpha(1)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(1)()1) and alpha(2)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(2)()1) in 63 and 86% isolated yields, respectively. Thermolysis of the crude peroxoniobium compounds (72-96 h in refluxing H(2)O) prior to treatment with KCl converts the peroxoniobium compounds to the corresponding polyoxometalates (POMs), alpha(1)-K(7)[P(2)W(17)NbO(62)] (alpha(1)()2) and alpha(2)-K(7)[P(2)W(17)NbO(62)] (alpha(2)()2), in moderate yields (66 and 52%, respectively). The identity and high purity of all four compounds were confirmed by (31)P NMR and (183)W NMR. The acid-induced dimerization of the oxo complexes differentiates sterically between the cap (alpha(2)) site and the belt (alpha(1)) site in the Wells-Dawson structure (alpha(2)()2 dimerizes in high yield; alpha(1)()2 does not). All four POMs exhibit high activity in cell culture against HIV-1 (EC(50) values of 0.17-0.83 microM), are minimally toxic (IC(50) values of 50 to >100 microM), and selectively inhibit purified HIV-1 protease (HIV-1P) (IC(50) values for alpha(1)()1, alpha(2)()1, alpha(1)()2, and alpha(2)()2 of 2.0, 1.2, 1.5, and 1.8 microM, respectively). Thus, theoretical, binding, and kinetics studies of the POM/HIV-1P interaction(s) were conducted. Parameters for [P(2)W(17)NbO(62)](7)(-) were determined for the Kollman all-atom (KAA) force field in Sybyl 6.2. Charges for the POM were obtained from natural population analysis (NPA) at the HF/LANL2DZ level of theory. AutoDock 2.2 was used to explore possible binding locations for the POM with HIV-1P. These computational studies strongly suggest that the POMs function not by binding to the active site of HIV-1P, the mode of inhibition of all other HIV-1P protease inhibitors, but by binding to a cationic pocket on the "hinge" region of the flaps covering the active site (2 POMs and cationic pockets per active homodimer of HIV-1P). The kinetics and binding studies, conducted after the molecular modeling, are both in remarkable agreement with the modeling results: 2 POMs bind per HIV-1P homodimer with high affinities (K(i) = 1.1 +/- 0.5 and 4.1 +/- 1.8 nM in 0.1 and 1.0 M NaCl, respectively) and inhibition is noncompetitive (k(cat) but not K(m) is affected by the POM concentration).

Haloperidol catalepsy consolidation in the rat as a model of neuromodulatory integration

Haloperidol, a non-selective D(2) dopamine antagonist, both in vitro (1 microM) and in vivo (2.5 mg/kg i.p.), induced a long-term potentiation of K(+)-induced Ca(2+)-dependent release of endogenous noradrenaline and dopamine in rat brain cortical slices, by increasing the content of noradrenaline and dopamine known to be controlled by dopamine auto- and heteroreceptors. Haloperidol administration (2.5 mg/kg i.p.) evoked catalepsy and increased the content of noradrenaline and dopamine in the same structures of the brain. Haloperidol catalepsy consolidated without any additional learning and could be retrieved up to two weeks later by placing the animals in the test box. The catalepsy is disordered and retrieved only in the test box. The catalepsy was more intense on day 14 than on day 7. Injection of haloperidol immediately after conditioning evened the reflex retrieval on the following days. Moreover, learning increased the intensity of catalepsy in animals tested on the day of injection. Repeated testing of the reflex on the following days led to specific modifications of catalepsy retrieval. Pre-conditioned rats exhibited maximal catalepsy when tested immediately after being placed in the test box. These results suggest that both the processes of long-term potentiation and catalepsy consolidation are mediated by the same type of receptors, long-term modulation-inducing receptors. Endogenous neuromodulators, acting non-specifically or diffusely via their respective long-term modulation-inducing receptors, can initiate and consolidate generalized states which form the basis for emotional and motivational states.

Targeting the dimerization interface for irreversible inhibition of HIV-1 protease

A novel strategy was used to irreversibly inhibit HIV-1 protease. The inhibitor was designed to form a disulfide bond with Cys95, present at the dimerization interface of HIV-1 protease. The inhibitor was shown to be active against HIV-1 protease with K(inact) = 3.7 microM and V(inact) = 0.012 min(-1).

HIV protease as a target for retrovirus vector-mediated gene therapy

The dimeric aspartyl protease of HIV has been the subject of intense research for almost a decade. Knowledge of the substrate specificity and catalytic mechanism of this enzyme initially guided the development of several potent peptidomimetic small molecule inhibitors. More recently, the solution of the HIV protease structure led to the structure-based design of improved peptidomimetic and non-peptidomimetic antiviral compounds. Despite the qualified success of these inhibitors, the high mutation rate associated with RNA viruses continues to hamper the long-term clinical efficacy of HIV protease inhibitors. The dimeric nature of the viral protease has been conducive to the investigation of dominant-negative inhibitors of the enzyme. Some of these inhibitors are defective protease monomers that interact with functional monomers to form inactive protease heterodimers. An advantage of macromolecular inhibitors as compared to small-molecule inhibitors is the increased surface area of interaction between the inhibitor and the target gene product. Point mutations that preserve enzyme activity but confer resistance to small-molecule inhibitors are less likely to have an adverse effect on macromolecular interactions. The use of efficient retrovirus vectors has facilitated the delivery of these macromolecular inhibitors to primary human lymphocytes. The vector-transduced cells were less susceptible to HIV infection in vitro, and showed similar levels of protection compared to other macromolecular inhibitors of HIV replication, such as RevM10. These preliminary results encourage the further development of dominant-negative HIV protease inhibitors as a gene therapy-based antiviral strategy.

Synthesis and preliminary pharmacological evaluation of some cytisine derivatives

Thirty-one N-derivatives of cytisine were prepared in order to modify its pharmacological profile and to obtain compounds of potential therapeutic interest either at a peripheral or central level, particularly as nicotinic ligands with improved ability to cross the blood-brain barrier. Actually, with the introduction of different kinds of substituent on the basic nitrogen of cytisine a variety of activities were observed, both in vivo (analgesic, dopamine antagonism, antihypertensive, inhibition of stress-induced ulcers, antiinflammatory, protection from PAF-induced mortality, hypoglycemic) and in vitro (positive cardio-inotropic, beta-adrenergic antagonism, alpha 1- and alpha 2-antagonism, inhibition of PAF-induced platelet aggregation). Six randomly selected compounds were tested for the ability to recognize a central nicotinic receptor and four of them exhibited Ki values in the range 30-163 nM.

The discovery, characterization and crystallographically determined binding mode of an FMOC-containing inhibitor of HIV-1 protease

A pharmacophore derived from the structure of the dithiolane derivative of haloperidol bound in the active site of the HIV-1 protease (HIV-1 PR) has been used to search a three-dimensional database for new inhibitory frameworks. This search identified an FMOC-protected N-tosyl arginine as a lead candidate. A derivative in which the arginine carboxyl has been converted to an amide has been crystallized with HIV-1 PR and the structure has been determined to a resolution of 2.5 A with a final R-factor of 18.5%. The inhibitor binds in an extended conformation that results in occupancy of the S2, S1', and S3' subsites of the active site. Initial structure-activity studies indicate that: (1) the FMOC fluorenyl moiety interacts closely with active site residues and is important for binding; (2) the N(G)-tosyl group is necessary to suppress protonation of the arginine guanidinyl terminus; and (3) the arginine carboxamide function is involved in interactions with the water coordinated to the catalytic aspartyl groups. FMOC-protected arginine derivatives, which appear to be relatively specific and nontoxic, offer promise for the development of useful HIV-1 protease inhibitors.

Structure-assisted design of nonpeptide human immunodeficiency virus-1 protease inhibitors

The discovery of therapeutic agents has, in the past, started primarily with random screening efforts. These screens, although effective, are time-consuming and expensive. Attempts are now being made to design more efficient methods of screening that take into account available information about the three-dimensional structure of a target receptor or enzyme. In the case of acquired immunodeficiency syndrome, the structure of a proteolytic enzyme, the human immunodeficiency virus (HIV) protease, an aspartyl protease that plays a crucial role in the viral life cycle, has been determined and extensively characterized. Using the protease structure and the computer program DOCK, the active site of the protease was mapped and its shape used to screen a subset of the Cambridge Structural Database. Among the molecules whose shape was complementary to the active site was the antipsychotic agent haloperidol. This molecule and several chemically modified derivatives were shown to bind competitively with micromolar affinity to the HIV protease but not to cellular aspartyl proteases. X-ray structures of the HIV protease complexed with haloperidol derivatives show the molecules binding in the predicted position at the active site. In an attempt to overcome the problems associated with low-affinity competitive inhibitors, reactive groups that enable the molecule to serve as a specific irreversible inhibitor of the HIV protease were introduced onto the haloperidol scaffold. These inhibitors demonstrated an ability to block viral polyprotein processing in a tissue culture model of HIV-1 infection, although their cytotoxicity is pronounced.(ABSTRACT TRUNCATED AT 250 WORDS)