CTS-1027 for Liver Disease

CTS-1027 is an oral small molecule drug candidate that potently inhibits the activity of key members of a class of proteases, the matrix metalloproteases or MMPs. These proteolytic enzymes are generally known for their role in regulating inflammation and maintaining the integrity of the extracellular matrix. However, it is now well established that these enzymes have a significantly broader role than previously appreciated and are involved in the regulation of cell-cell interactions, cytokine and chemokine processing and cellular homeostasis. In chronic hepatitis C infection, the virus is known to affect the regulation of MMP activity, and viral proteins modulate transcription of various MMPs. As detailed below, some of these in-vitro properties also have potential for interfering with viral infectivity or replication.

CTS-1027 Preclinical Data

Preclinical data suggest that CTS-1027 has the potential to be a hepatoprotective agent in patients with chronic HCV infection via multiple pathways. Its anti-inflammatory and anti-fibrotic effects have been well established in models of acute hepatitis and liver fibrosis. In addition, CTS-1027 has been shown to reduce and/or block HCV replication in in vitro preclinical models. The table below summarizes activity of CTS-1027 in various preclinical models relevant to liver disease.

Activity	Experimental Evidence
Inflammation	Orally active in 4 models of acute hepatitis: TNF-α, α-Fas, Con A, LPS/Gln: Reduces ALT Improves histology Increases survival
Fibrosis	Orally active in bile duct model of cholestasis: Reduces collagen deposition Reduces apoptosis and caspase 3 activation Reduces bile infarcts Reduces gene expression (α-SMA, Col 1) Reduces gene expression in human stellate cell line: TGF-α, α-SMA, Col 1, MMP-2
Viral Replication	Active in HCV replicon: Reduces viral RNA synthesis Protease mutant independent effect Active in primary human hepatocyte infectivity/replication model

Activity

Experimental Evidence

Inflammation

Orally active in 4 models of acute hepatitis: TNF-α, α-Fas, Con A, LPS/Gln:

Reduces ALT
Improves histology
Increases survival

Fibrosis

Orally active in bile duct model of cholestasis:

Reduces collagen deposition
Reduces apoptosis and caspase 3 activation
Reduces bile infarcts
Reduces gene expression (α-SMA, Col 1)

Reduces gene expression in human stellate cell line:

TGF-α, α-SMA, Col 1, MMP-2

Viral Replication

Active in HCV replicon:

Reduces viral RNA synthesis
Protease mutant independent effect

Active in primary human hepatocyte infectivity/replication model

CTS-1027 dose-dependently prevented elevations of plasma alanine aminotransferase (ALT) levels in the tumor necrosis factor alpha (TNF-a) and D-galactosamine (Gln) induced pre-clinical model of hepatitis. Consistent with the reduction in ALT activity, there were improvements in hepatic histology and 24-hour survival. CTS-1027 also reduced ALT levels in pre-clinical studies using an activating Fas antibody, Concanavalin A (Con A), or lipopolysaccharride (LPS) plus Gln to induce hepatitis. In the murine bile-duct ligation model of fibrosis, CTS-1027 significantly reduced the number of bile infarcts, apoptotic hepatocytes, and hepatocytes positive for activated caspases 3 and 7. Biomarkers of fibrogenesis and activation of stellate cells were also reduced.

Preclinical studies with the compound in in vitro models suggest that CTS-1027 has a direct impact on the viral replication process and/or infectivity. First, CTS-1027 was potently effective in a cell-based HCV infectivity model (Figure 1). The observations in this study suggest that the action of the compound occurs early in the process of infection and could lead to a reduced frequency of newly infected cells in HCV patients.

Image: Effect of CTS-1027 in Primary Human Hepatocytes Treated with HCV Infected Human Serum (Genotype 1).

Figure 1. Effect of CTS-1027 in Primary Human Hepatocytes Treated with HCV Infected Human Serum (Genotype 1). *Results significantly different from HCV infected hepatocytes without treatment, p<0.05.

Second, CTS-1027 is effective in an HCV replicon model with an average EC50 of 300 nM against a full length genotype 1b replicon construct (Figure 2). The compound is somewhat less potent in the subgenomic replicon assay (data not shown). Unlike viral protease and polymerase inhibitors, the action of CTS-1027 is believed to be due to activity via a host mechanism rather than a viral target. Support for this hypothesis comes from data showing that CTS-1027 does not inhibit HCV protease or polymerase and that MMPs are over-expressed during the 3-day course of the assay. One would expect that a host mechanism would result in less viral resistance, since viral escape through mutation of the target, as is the case with protease and polymerase inhibitors, is less likely. Consistent with this, CTS-1027 was also effective against three common protease resistant mutants.

CTS-1027 interacted synergistically with interferon (IFN)-α and additively with ribavirin in the HCV replicon model. These data suggest that it may be worthwhile to study CTS-1027 in combination with IFN, ribavirin, protease or polymerase inhibitors.

Image: CTS-1027 dose response in HCV 1b full length replicon mode

Figure 2. CTS-1027 dose response in HCV 1b full length replicon model

The impact of CTS-1027 on an early event in viral infection, coupled with a host-mediated effect on viral replication, suggest that the compound might have an impact on the second phase of anti-viral kinetics. The kinetics for onset of drug effect therefore would be expected to be slower than that observed with protease and polymerase inhibitors that directly interfere with viral replication within infected cells, as shown in Figure 3. In this case, treatment with CTS-1027 would need to be for several months in order to clear out virus infected cells.

ANTI-VIRAL KINETICS Image: Schematic of anti-viral effects on HCV-infected cells.

Figure 3. Schematic of anti-viral effects on HCV-infected cells.

CTS-1027 Development Plan

CTS-1027 has been chronically administered in the context of another disease to over 500 people, some for over 18 months. The Conatus clinical development plan is initially focused on patients infected with the hepatitis C virus (HCV) where the worldwide market potential is estimated to exceed $1 billion. A Phase 2 trial in HCV patients designed to explore anti-inflammatory activities of CTS-1027 was concluded in 2009.

For information regarding additional clinical development of CTS-1027, please select the clinical trials tab.