With plans to fund clinical trials of its lead autoimmune drug, Merrimack Pharmaceuticals Inc. captured $28 million in a Series C financing, its largest to date.

The Cambridge, Mass.-based company, founded in 2000, has raised a total of $50 million since inception as it continues to build a pipeline derived from its drug discovery platform known as Network Biology.

Company officials could not be reached for comment on Tuesday. According to its press release, the company plans to use the Series C funds for patient trials of its lead product, MM-093, as well as to expand development of its pipeline. In addition, the company expects to increase its research, clinical and regulatory personnel. MM-093 is an immunomodulator in development for autoimmune diseases.

Sorenson Development Inc., of Salt Lake City, and its affiliates led the financing. Other new investors included Unilever Technology Ventures Fund BV, of Santa Barbara, Calif., and GTC Biotherapeutics Inc., of Framingham, Mass. Previous investors Wharton Biotechnology Partners II and MS Seed Capital, as well as other institutional and angel investors, also participated.

In conjunction with Sorenson's investment, Gary Crocker is joining Merrimack's board.

Merrimack Pharmaceuticals is named after New England's Merrimack River - the birthplace of America's industrial revolution. Likewise, the company hopes to revolutionize drug discovery and development with its Network Biology approach, which is a study of protein networks and the complex interactions that mediate cellular pathways.

The company focuses on treatments for autoimmune diseases and cancer. Founded by the Massachusetts Institute of Technology and Harvard University scientists, its platform technology, Network Biology, enables the high-throughput profiling of protein networks as a basis for improved validation, lead identification and speed in drug development.

To understand disease, the company believes it is vital to go beyond single gene or protein targets to protein networks, the level at which proteins interact and carry out their function. The Network Biology approach has led to new insights into cell physiology, generated new tools for pharmaco-proteomics and is delivering drug candidates into preclinical development.

MM-093 is the company's first clinical product that has shown potential in treating and preventing T-cell-mediated autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis.

In November, Merrimack completed dosing of volunteers in a Phase I trial of MM-093, which is a recombinant version of human alpha-fetoprotein. A total of 42 subjects in six dose groups completed the single-ascending-dose portion of the study.

So far this year, the company has received two Phase I Small Business Innovation Research grants from the National Cancer Institute. The first one was granted in January to support the development and application of the company's Network Biology platform to the areas of apoptosis and cancer. The second grant, given in March, is to support the design, development and application of antibodies using yeast display technology. The reagents will be used in antibody microarray biochips to interrogate networks of proteins involved in signaling pathways associated with cancer and autoimmune diseases.

Merrimack formed an agreement in October 2002 with new investor GTC Biotherapeutics to use GTC's production technology for MM-093. GTC has developed goats that produce the protein in their milk. The agreement was expanded last year to include the purification of MM-093.

Merrimack also has research collaborations with Cambridge, Mass.-based MIT, the UK's Cambridge University, and Jerusalem-based Hadassah University Hospital.