Isolation and characterization of selective and potent human Fab inhibitors directed to the active-site region of the two-component NS2B-NS3 proteinase of West Nile virus

PCA062, a P-cadherin Targeting Antibody-Drug Conjugate, Displays Potent Antitumor Activity Against P-cadherin-expressing Malignancies

The cell surface glycoprotein P-cadherin is highly expressed in a number of malignancies, including those arising in the epithelium of the bladder, breast, esophagus, lung, and upper aerodigestive system. PCA062 is a P-cadherin specific antibody-drug conjugate that utilizes the clinically validated SMCC-DM1 linker payload to mediate potent cytotoxicity in cell lines expressing high levels of P-cadherin in vitro, while displaying no specific activity in P-cadherin-negative cell lines. High cell surface P-cadherin is necessary, but not sufficient, to mediate PCA062 cytotoxicity. In vivo, PCA062 demonstrated high serum stability and a potent ability to induce mitotic arrest. In addition, PCA062 was efficacious in clinically relevant models of P-cadherin-expressing cancers, including breast, esophageal, and head and neck. Preclinical non-human primate toxicology studies demonstrated a favorable safety profile that supports clinical development. Genome-wide CRISPR screens reveal that expression of the multidrug-resistant gene ABCC1 and the lysosomal transporter SLC46A3 differentially impact tumor cell sensitivity to PCA062. The preclinical data presented here suggest that PCA062 may have clinical value for treating patients with multiple cancer types including basal-like breast cancer.

Vaccines and immunotherapeutics for the prevention and treatment of infections with West Nile virus

The emergence of West Nile virus (WNV) in North America in 1999 as a cause of severe neurological disease in humans, horses and birds stimulated development of vaccines for human and veterinary use, as well as polyclonal/monoclonal antibodies and other immunomodulating compounds for use as therapeutics. Although disease incidence in North America has declined since the peak epidemics in 2002-2003, the virus has continued to be annually transmitted in the Americas and to cause periodic epidemics in Europe and the Middle East. Continued transmission of the virus with human and animal disease suggests that vaccines and therapeutics for the prevention and treatment of WNV disease could be of great benefit. This article focuses on progress in development and evaluation of vaccines and immunotherapeutics for the prevention and treatment of WNV disease in humans and animals.

High affinity human antibody fragments to dengue virus non-structural protein 3

Background

The enzyme activities catalysed by flavivirus non-structural protein 3 (NS3) are essential for virus replication. They are distributed between the N-terminal protease domain in the first one-third and the C-terminal ATPase/helicase and nucleoside 5′ triphosphatase domain which forms the remainder of the 618-aa long protein.

Methodology/Principal Findings

In this study, dengue full-length NS3 protein with residues 49 to 66 of NS2B covalently attached via a flexible linker, was used as bait in biopanning with a naïve human Fab phage-display library. Using a range of truncated constructs spanning the NS2B cofactor region and the full-length NS3, 10 unique Fab were identified and characterized. Of these, monoclonal Fab 3F8 was shown to bind α3″ (residues 526 through 531) within subdomain III of the helicase domain. The antibody inhibits the ATPase and helicase activites of NS3 in biochemical assays and reduces DENV replication in HEK293 cells that were previously transfected with Fab 3F8 compared with mock transfected cells.

Conclusions/Significance

Antibodies such as 3F8 are valuable tools for studying the molecular mechanisms of flaviviral replication and for the monospecific detection of replicating dengue virus in vivo.

Dengue virus is the most prevalent mosquito transmitted infectious disease in humans and is responsible for febrile disease such as dengue fever, dengue hemorrhagic fever and dengue shock syndrome. Dengue non-structural protein 3 (NS3) is an essential, multifunctional, viral enzyme with two distinct domains; a protease domain required for processing of the viral polyprotein, and a helicase domain required for replication of the viral genome. In this study ten unique human antibody fragments (Fab) that specifically bind dengue NS3 were isolated from a diverse library of Fab clones using phage display technology. The binding site of one of these antibodies, Fab 3F8, has been precisely mapped to the third α-helix within subdomain III of the helicase domain (amino acids 526–531). The antibody inhibits the helicase activity of NS3 in biochemical assays and reduces DENV replication in human embryonic kidney cells. The antibody is a valuable tool for studying dengue replication mechanisms.

Structural and functional parameters of the flaviviral protease: a promising antiviral drug target

Flaviviruses have a single-strand, positive-polarity RNA genome that encodes a single polyprotein. The polyprotein is comprised of seven nonstructural (NS) and three structural proteins. The N- and C-terminal parts of NS3 represent the serine protease and the RNA helicase, respectively. The cleavage of the polyprotein by the protease is required to produce the individual viral proteins, which assemble a new viral progeny. Conversely, inactivation of the protease blocks viral infection. Both the protease and the helicase are conserved among flaviviruses. As a result, NS3 is a promising drug target in flaviviral infections. This article examines the West Nile virus NS3 with an emphasis on the structural and functional parameters of the protease, the helicase and their cofactors.