Target Proteins in Plasma
“We are investigating the use of mass spec-based biomarker screening as an alternative to liver biopsy in the diagnosis of liver diseases with Naga Chalasani’s group at the Indiana School of Medicine,” said Jinsam You, Ph.D., chief scientist at Monarch LifeSciences.
The company focuses its efforts on protein analysis, using mass spectrometry in order to develop new protein biomarkers for use as diagnostic tools.
An area of current interest for the firm is a panel of proteins, the Apolipoprotein family, which is essential for cholesterol transport. Through the development of mass spec-based assays the company intends to build rapid noninvasive assays that will allow investigators and clinicians to monitor liver and cardiovascular disease progression.
As a tool for developing high-throughput assays, mass spec has much to recommend itself. It can distinguish proteins that differ in as few as one amino acid, as well as different isoforms, and when the technology is installed and running it can be surprisingly economical.
“We are particularly interested in hepatic steatosis, a fibrotic disease of the liver brought on by high-fat diets,” Dr. You said. “At present this condition can only be diagnosed through the use of highly invasive and painful hepatic biopsies. At the end stage of the disease, when cirrhosis occurs, the condition is fatal, so it is extremely important to obtain early diagnosis.”
Dr. You and his colleagues found that there are significant gender-based quantitative differences in some of the apoproteins, so it is necessary to take this variable into account in developing a reliable assay. Sample preparation is also critical for good reproducibility, and the team has developed some novel approaches to limit variability.
The study was fostered by a growing clinical need. Non-alcoholic steatohepatitis (NASH) has mortality as high as one in four over the long term. In seeking an alternative to the liver biopsy, the Monarch group is studying individuals in the three stages of NASH, from early fatty liver (which frequently goes undiagnosed) through inflammation and finally fibrosis, with the overall goal of distinguishing these groups without resorting to biopsy.
When mass spec investigations were carried out, it was observed that Apo A1 was significantly higher in steatosis and NASH, Apo B was higher in NASH, and one of the lipoproteins (which Dr. You refrained from designating) was high in all three conditions.
“By building a multiplex panel of proteins we were able to diagnose with 100% accuracy the different stages of NASH in a group of 85 samples,” Dr. You said. “This was used to build a training set of discriminatory markers. Now we will continue into expanded studies with thousands of patient samples in order to provide definitive clinical support for this technology and the specific markers.”