When Human Genome Sciences Inc. (HGSI)’s lupus drug, Benlysta, won regulatory approval in March as the first treatment for the disease in more than 50 years, the company estimated the product may be worth $2.5 billion a year. Since then, the Rockville, Maryland-based company’s stock has plunged 47 percent in Nasdaq Stock Market trading. The drop mirrors declines for other biotechnology companies with drug approvals the last two years and spotlights a trend that may slow the pace of acquisitions and decrease returns for potential buyers, analysts and industry officials said.
