Cytolin

Candidate Pre Phase 1 Phase 2 Phase 3

Cytolin

Pre-Clinical Phase in progress

Cytolin® for the treatment of HIV infection

Cytolin® is a mouse monoclonal antibody originally developed to identify a specific type of immune cell called a cytotoxic T cell, or CTL. Subsequent work showed that the antigen to which Cytolin® bound was the cellular antigen CD11a, which along with CD18 makes up the cellular adhesion molecule LFA-1. In the 1990s a number of researchers reported that LFA-1 appeared to be critical for HIV infection.

These observations, along with the unique reactivity of Cytolin® for CTLs, prompted the company to explore the administration of Cytolin® to HIV-infected people to determine if it could perturb the natural course of HIV infection. These uncontrolled clinical studies showed treatment with Cytolin® appeared to stabilize immunity, and in some cases reduce viral burden.

Based on these encouraging findings, the company decided to explore exactly where Cytolin® bound to CD11a. LFA-1 normally functions in the body as an adhesion molecule and is a critical component of the immune response. Under normal circumstances, LFA-1 on immune cells binds to its cognate receptor (called ICAM) on the other cells and allows for a tight connection between cells so that a productive immune response can occur. The results of the binding studies with Cytolin® showed that, unlike other CD11a specific antibodies, Cytolin® did not bind to the ICAM binding region of the molecule. As a consequence of this unique specificity, Cytolin® did not block the normal function of CD11a.

In addition to cytotoxic T lymphocytes (CTLs), Cytolin® also appears to bind another type of immune cell called dendritic cells (DCs). Both of these cells are critical to the control of viral burden in HIV infected individuals. By binding to these cells, Cytolin® appears to induce an antiviral activity that can impede infection of new cells and possibly lead to a reduction in viral burden.  At present, the Company is pursuing clinical trials of PRO 140 as the more promising monoclonal antibody to address HIV infection, but may further explore Cytolin at a future date.