Shares of Human Genome Sciences ( HGSI) fell Wednesday after the company announced it will lower the higher, less-frequent dose of its hepatitis C drug Albuferon in late-stage trials because of pulmonary side effects. Shares gave up $4.56, or 45.5%, to $5.46. An independent data monitoring committee flagged the 1200 mgc once-monthly dose in the Achieve trials for safety concerns. The affected dose arms will be lowered to 900 mcg twice-monthly, the dose that the company said in a press release was most likely to be commercialized. The monthly 1200 mcg dose and the twice-monthly 900 mcg dose are designed to offer increased convenience over the weekly Pegasys (Peginterferon alfa-2a). "We continue to believe that a 900 mcg dose of Albuferon given once every two weeks is a significant advantage over Pegasys given weekly in terms of patient convenience," noted Susqehanna analyst Jason Kolbert, who has a positive rating for the stock, in a report on Wednesday. The company noted that the committee found no problems with the 900 mcg dose, but analysts questioned Wednesday whether the safety issues and dose reduction could cast a shadow on the whole program. "While proposed dose reduction may prevent further pulmonary toxicity in phase III we believe that adequacy of dose adjustment could ultimately be questioned by FDA and as such would assess higher risk to the overall Albuferon program," wrote Lehman Brothers analyst Jim Birchenough, who has an equal-weight rating on the stock, in a note to investors Wednesday. And some feel strongly that the 900 mcg dose will follow suit with safety concerns raised in the higher dose. "We continue to believe that the 900 mcg dose will have a worse profile than Pegasys as well (based on the trend we observed in the Phase II trials), making Albuferon an uncompetitive drug," wrote Morgan Stanely analyst Sapna Srivastava who has an underweight rating on the stock. The company said it continues to expect to have all phase III data available by spring 2009 to support the filing of global marketing authorization applications by fall 2009. Human Genome is co-developing the drug with Novartis ( NVS), shares of which were down 0.7% at $51.42.