PRO 140, a monoclonal antibody targeting CCR5, as a long-acting, single-agent maintenance therapy for HIV-1 infection.

Background PRO 140 is a humanized monoclonal antibody targeting CCR5 with potent antiviral activity in patients with CCR5-tropic HIV-1 infection. In phase 2b studies, we evaluated the long-term efficacy, safety, and tolerability of PRO 140 monotherapy in maintaining viral suppression for over 24 months in patients who were stable on combination antiretroviral therapy on entry into the trials. Methods and Results Forty-one adult patients, infected exclusively with CCR5-tropic HIV-1 with viral loads <50 copies/mL, were switched from daily oral combination ART regimens to weekly PRO 140 monotherapy for 12 weeks.

Protection against Clostridium difficile infection with broadly neutralizing antitoxin monoclonal antibodies.

The spore-forming bacterium Clostridium difficile represents the principal cause of hospital-acquired diarrhea and pseudomembranous colitis worldwide. C. difficile infection (CDI) is mediated by 2 bacterial toxins, A and B; neutralizing these toxins with monoclonal antibodies (mAbs) provides a potential nonantibiotic strategy for combating the rising prevalence, severity, and recurrence of CDI.

Novel small-molecule inhibitors of hepatitis C virus entry block viral spread and promote viral clearance in cell culture.

Combinations of direct-acting anti-virals offer the potential to improve the efficacy, tolerability and duration of the current treatment regimen for hepatitis C virus (HCV) infection. Viral entry represents a distinct therapeutic target that has been validated clinically for a number of pathogenic viruses. To discover novel inhibitors of HCV entry, we conducted a high throughput screen of a proprietary small-molecule compound library using HCV pseudoviral particle (HCVpp) technology.

Phase 2a study of the CCR5 monoclonal antibody PRO 140 administered intravenously to HIV-infected adults.

The anti-CCR5 antibody PRO 140 has shown potent and prolonged antiretroviral activity in subjects infected with CCR5-tropic (R5) HIV-1. Prior studies have examined single intravenous doses ranging up to 5 mg/kg of body weight or up to three subcutaneous doses ranging up to 324 mg. Here we report the results of a randomized, double-blind, placebo-controlled trial that examined the antiviral activity, tolerability, and pharmacokinetics of single 5-mg/kg and 10-mg/kg intravenous infusions of PRO 140 in 31 treated subjects.

Anti-HIV-1 activity of weekly or biweekly treatment with subcutaneous PRO 140, a CCR5 monoclonal antibody.

Background: PRO 140 is a humanized CCR5 monoclonal antibody that has demonstrated potent antiviral activity when it is administered intravenously to adults infected with CCR5-tropic (R5) human immunodeficiency virus type 1 (HIV-1). This study is the first to evaluate subcutaneous administration.

Methods: A randomized, double-blind, placebo-controlled study was conducted among 44 subjects with HIV-1 RNA levels of >5000 copies/mL, CD4(+) cell counts of >300 cells/microL, no receipt of antiretroviral therapy for >or=12 weeks, and only R5 HIV-1 detectable.

Structural and immunogenicity studies of a cleaved, stabilized envelope trimer derived from subtype A HIV-1.

SOSIP gp140 trimers represent a soluble, stabilized, proteolytically cleaved form of the HIV-1 envelope (Env) glycoproteins. SOSIP gp140 derived from a subtype A HIV-1 isolate, KNH1144, forms exceptionally stable trimers that resemble virion-associated Env in antigenicity and topology. Here, we used electron microscopy to demonstrate that KNH1144 SOSIP gp140 trimers bound three soluble CD4 molecules in a symmetrical orientation similar to that seen for native Env.

Antiviral activity of single-dose PRO 140, a CCR5 monoclonal antibody, in HIV-infected adults.

Background: The current goal of human immunodeficiency virus type 1 (HIV-1) therapy is to maximally suppress viral replication. Securing this goal requires new drugs and treatment classes. The chemokine receptor CCR5 provides an entry portal for HIV-1, and PRO 140 is a humanized monoclonal antibody that binds to CCR5 and potently inhibits CCR5-tropic (R5) HIV-1 in vitro.

A novel alphavirus vaccine encoding prostate-specific membrane antigen elicits potent cellular and humoral immune responses.

Purpose: Prostate-specific membrane antigen (PSMA) is an attractive target for active immunotherapy. Alphavirus vaccines have shown promise in eliciting immunity to tumor antigens. This study investigated the immunogenicity of alphavirus vaccine replicon particles (VRP) that encode PSMA (PSMA-VRP).

Purified, proteolytically mature HIV type 1 SOSIP gp140 envelope trimers.

HIV type 1 (HIV-1) envelope is a noncovalent trimer of gp120-gp41 heterodimers, and its lability has hindered structural studies. SOSIP gp140 is a soluble, proteolytically mature form of the HIV-1 envelope wherein gp120-gp41 interactions are stabilized via a disulfide bond and gp41 contains an additional trimer-stabilizing point mutation. We describe the isolation of a substantially pure preparation of SOSIP gp140 trimers derived from KNH1144, a subtype A isolate.

A comparative immunogenicity study in rabbits of disulfide-stabilized, proteolytically cleaved, soluble trimeric human immunodeficiency virus type 1 gp140, trimeric cleavage-defective gp140 and monomeric gp120.

The human immunodeficiency virus type 1 (HIV-1) surface envelope glycoprotein (Env) complex, a homotrimer containing gp120 surface glycoprotein and gp41 transmembrane glycoprotein subunits, mediates the binding and fusion of the virus with susceptible target cells. The Env complex is the target for neutralizing antibodies (NAbs) and is the basis for vaccines intended to induce NAbs. Early generation vaccines based on monomeric gp120 subunits did not confer protection from infection; one alternative approach is therefore to make and evaluate soluble forms of the trimeric Env complex.

Potent antiviral synergy between monoclonal antibody and small-molecule CCR5 inhibitors of human immunodeficiency virus type 1.

The chemokine receptor CCR5 provides a portal of entry for human immunodeficiency virus type 1 (HIV-1) into susceptible CD4(+) cells. Both monoclonal antibody (MAb) and small-molecule CCR5 inhibitors have entered human clinical testing, but little is known regarding their potential interactions. We evaluated the interactions between CCR5 MAbs, small-molecule CCR5 antagonists, and inhibitors of HIV-1 gp120, gp41, and reverse transcriptase in vitro.

L-SIGN (CD209L) isoforms differently mediate trans-infection of hepatoma cells by hepatitis C virus pseudoparticles.

L-SIGN is a C-type lectin that is expressed on liver sinusoidal endothelial cells. Capture of Hepatitis C virus (HCV) by this receptor results in trans-infection of hepatoma cells. L-SIGN alleles have been identified that encode between three and nine tandem repeats of a 23 residue stretch in the juxtamembrane oligomerization domain.

Construction and characterization of soluble, cleaved, and stabilized trimeric Env proteins based on HIV type 1 Env subtype A.

The generation of an antibody response capable of neutralizing a broad range of clinical isolates remains an important goal of human immunodeficiency virus type 1 (HIV-1) vaccine development. Envelope glycoprotein (Env)-based vaccine candidates will also need to take into account the extensive genetic diversity of circulating HIV-1 strains. We describe here the generation of soluble, stabilized, proteolytically cleaved, trimeric forms of Env (SOSIP gp140 proteins) based on contemporary Env subtype A viruses from East Africa.

Potent antitumor activity of an auristatin-conjugated, fully human monoclonal antibody to prostate-specific membrane antigen.

Prostate-specific membrane antigen (PSMA) is the prototypic cell-surface marker of prostate cancer and provides an attractive target for monoclonal antibody (mAb) targeted therapies. In this study, a novel antibody-drug conjugate (ADC) was generated by linking a fully human PSMA mAb to monomethylauristatin E (MMAE), a potent inhibitor of tubulin polymerization. The PSMA ADC was evaluated for antitumor activity in vitro and in a mouse xenograft model of androgen-independent human prostate cancer.

Evaluating the immunogenicity of a disulfide-stabilized, cleaved, trimeric form of the envelope glycoprotein complex of human immunodeficiency virus type 1.

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) complex comprises three gp120 exterior glycoproteins each noncovalently linked to a gp41 transmembrane glycoprotein. Monomeric gp120 proteins can elicit antibodies capable of neutralizing atypically sensitive test viruses in vitro, but these antibodies are ineffective against representative primary isolates and the gp120 vaccines failed to provide protection against HIV-1 transmission in vivo. Alternative approaches to raising neutralizing antibodies are therefore being pursued.

Resistance to HIV-1 entry inhibitors.

Resistance-testing technology has been incorporated into the standard of care for human immunodeficiency virus type 1 (HIV-1) infection and therapy with protease and reverse transcriptase inhibitors. Inhibitors of HIV-1 entry represent an emerging mode of antiretroviral therapy, and HIV-1 entry inhibitors encompass three mechanistically distinct classes of agents known as attachment inhibitors, coreceptor inhibitors, and fusion inhibitors. Each class of agent has demonstrated promise in controlled clinical trials, and understanding the determinants and evolution of viral resistance will be critical for the optimal development and deployment of these new treatment classes.

Treatment of advanced human immunodeficiency virus type 1 disease with the viral entry inhibitor PRO 542.

Viral entry inhibitors represent an emerging mode of therapy for human immunodeficiency virus type 1 (HIV-1) infection. PRO 542 (CD4-immunoglobulin G2) is a tetravalent CD4-immunoglobulin fusion protein that broadly neutralizes primary HIV-1 isolates. PRO 542 binds to the viral surface glycoprotein gp120 and blocks attachment and entry of virus into CD4(+) cells.

The homodimer of prostate-specific membrane antigen is a functional target for cancer therapy.

Prostate-specific membrane antigen (PSMA) is a type 2 integral membrane glycoprotein that serves as an attractive target for cancer immunotherapy by virtue of its abundant and restricted expression on the surface of prostate carcinomas and the neovasculature of most other solid tumors. However, relatively little is known about the molecular structure of this target. Here, we report that PSMA is expressed on tumor cells as a noncovalent homodimer.

L-SIGN (CD 209L) is a liver-specific capture receptor for hepatitis C virus.

Hepatitis C virus (HCV) infects nearly 3% of the population of the world and is a major cause of liver disease. However, the mechanism whereby the virus targets the liver for infection remains unknown, because none of the putative cellular receptors for HCV are both expressed specifically in the liver and capable of binding HCV envelope glycoproteins. Liver/lymph node-specific intercellular adhesion molecule-3-grabbing integrin (L-SIGN) is a calcium-dependent lectin expressed on endothelial cells of liver and lymph nodes.

Stabilization of the soluble, cleaved, trimeric form of the envelope glycoprotein complex of human immunodeficiency virus type 1.

The envelope glycoprotein (Env) complex of human immunodeficiency virus type 1 has evolved a structure that is minimally immunogenic while retaining its natural function of receptor-mediated virus-cell fusion. The Env complex is trimeric; its six individual subunits (three gp120 and three gp41 subunits) are associated by relatively weak, noncovalent interactions. The induction of neutralizing antibodies after vaccination with individual Env subunits has proven very difficult, probably because they are inadequate mimics of the native complex.

Oligomeric and conformational properties of a proteolytically mature, disulfide-stabilized human immunodeficiency virus type 1 gp140 envelope glycoprotein.

We describe the further properties of a protein, designated SOS gp140, wherein the association of the gp120 and gp41 subunits of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is stabilized by an intersubunit disulfide bond. HIV-1(JR-FL) SOS gp140, proteolytically uncleaved gp140 (gp140(UNC)), and gp120 were expressed in stably transfected Chinese hamster ovary cells and analyzed for antigenic and structural properties before and after purification. Compared with gp140(UNC), SOS gp140 reacted more strongly in surface plasmon resonance and radioimmunoprecipitation assays with the neutralizing monoclonal antibodies (MAbs) 2G12 (anti-gp120), 2F5 (anti-gp41), and 17b (to a CD4-induced epitope that overlaps the CCR5-binding site).

Human immunodeficiency virus type 1 entry inhibitors PRO 542 and T-20 are potently synergistic in blocking virus-cell and cell-cell fusion.

Human immunodeficiency virus type 1 (HIV-1) entry proceeds via a cascade of events that afford promising targets for therapy. PRO 542 neutralizes HIV-1 by blocking its attachment to CD4 cells, and T-20 blocks gp41-mediated fusion. Both drugs have shown promise in phase 1/2 clinical trials.

Potent, broad-spectrum inhibition of human immunodeficiency virus type 1 by the CCR5 monoclonal antibody PRO 140.

CCR5 serves as a requisite fusion coreceptor for clinically relevant strains of human immunodeficiency virus type 1 (HIV-1) and provides a promising target for antiviral therapy. However, no study to date has examined whether monoclonal antibodies, small molecules, or other nonchemokine agents possess broad-spectrum activity against the major genetic subtypes of HIV-1. PRO 140 (PA14) is an anti-CCR5 monoclonal antibody that potently inhibits HIV-1 entry at concentrations that do not affect CCR5's chemokine receptor activity.

Recombinant CD4-IgG2 in human immunodeficiency virus type 1-infected children: phase 1/2 study. The Pediatric AIDS Clinical Trials Group Protocol 351 Study Team.

The use of recombinant CD4-IgG2 in pediatric human immunodeficiency virus type 1 (HIV-1) infection was evaluated by single and multidose intravenous infusions in 18 children in a phase 1/2 study. The study drug was well tolerated, and dose proportionality was observed in terms of area under time-concentration curve and peak serum concentration. Acute decreases of >0.

Single-dose safety, pharmacology, and antiviral activity of the human immunodeficiency virus (HIV) type 1 entry inhibitor PRO 542 in HIV-infected adults.

PRO 542 (CD4-IgG2) is a recombinant antibody-like fusion protein wherein the Fv portions of both the heavy and light chains of human IgG2 have been replaced with the D1D2 domains of human CD4. Unlike monovalent and divalent CD4-based proteins, tetravalent PRO 542 potently neutralizes diverse primary human immunodeficiency virus (HIV) type 1 isolates. In this phase 1 study, the first evaluation of this compound in humans, HIV-infected adults were treated with a single intravenous infusion of PRO 542 at doses of 0.