Synthetic Biologics Inc., of Rockville, a biotechnology company focused on the development of treatments to halt pathogens that cause serious infections and diseases, announced positive results on Tuesday from its final preclinical toxicology study of SYN-004. The product is an anti-infective designed to prevent the devastating effects of Clostridium difficile (C. difficile). The dificile infection affects 1.1 million Americans and causes 30,000 deaths each year, according to the federal government. It attacks the gastrointestinal system. Synthetic Biologics is in the final stages of preparing its SYN-004 IND application for submission to the Food and Drug Administration, with the expectation of initiating clinical trials in the fourth quarter of 2014.