Shares of Metabasis Therapeutics ( MBRX) were among the worst-performing health-related stocks Wednesday, falling 43.5% after the company halted two diabetes studies because of adverse events related to lactic acidosis.

The company was notified by its partner Sankyo that two serious cases involving lactic acidosis occurred during an interaction study with Metabasis' CS-917 and the diabetes drug metformin. The adverse reactions, which occurred in two patients, were resolved after medical intervention, Metabasis said. The company also said that a third study evaluating CS-917 as a single agent over three months is currently under review as well. No patients are currently receiving CS-917 at this time, the company said. Shares traded down $3 to $3.90.

Biogen ( BIIB - Get Report) fell 2.3% after warning doctors that some patients taking its multiple sclerosis drug Avonex have developed liver damage. The advisory was included in the Avonex prescription guide and was issued jointly with the Food and Drug Administration. According to Biogen, the symptoms sometimes occurred in patients who were using other liver-damaging substances, such as alcohol. The warning follows last month's rout in Biogen shares when it and partner Elan ( ELN) pulled the MS drug Tysabri from the market. Shares traded down 88 cents to $37.19.

Thoratec ( THOR) rose 7.8% after RBC Capital upgraded shares of the company to outperform from sector perform. The firm said that the company may not see financial benefits from clinical studies of its HeartMate II left ventricular assist system product until 2006, but positive information flow from the trials during the next several quarters should boost the company's stock. In addition to raising its rating on the stock, RBC also raised its price target to $18 from $14. Shares traded up 86 cents to $11.86.

Shares of Bruker BioSciences ( BRKR - Get Report) fell 11.7% after company said that it would lower its previously reported 2004 earnings because of audit adjustments that are expected to have a negative impact and because of a revised tax assessment from German tax authorities that is higher than before. The company now expects to post a loss of 7 cents to 9 cents a share for 2004, higher than the loss of 6 cents a share that it previously reported. Bruker intends to seek a 15-day extension for its 2004 annual report. As a result of the audit adjustments, the company believes that it will report a material weakness in its internal controls when it eventually files its annual report with the Securities and Exchange Commission. Bruker said that adjustments should have no have an effect on its first-quarter guidance or on its 2005 goals. Shares traded down 46 cents to $3.49.

Dendreon ( DNDN) fell 2.8% after the company posted a fourth-quarter loss that was wider than expected. The biotech company posted a loss of $21.7 million, or 37 cents a share, on sales of $75,000. Analysts polled by Thomson First Call expected a narrower loss of 36 cents a share. A year ago the company earned $1.2 million, or 3 cents a share, on sales of $21.7 million. Year-ago sales were driven by the company's licensing agreement with Kirin Brewery. Shares traded down 16 cents to $5.64.

Shares of Keryx Biopharmaceuticals ( KERX) rose 8.2% after the company finalized a special protocol assessment agreement with the Food and Drug Administration for a phase 3 and phase 4 trial of KRX-101, a drug candidate for the treatment of diabetic nephropathy -- a life-threatening kidney disease that is caused by diabetes. The FDA's approval of the endpoint means that the company will be able to launch both trials within the next few months. Keryx said that it plans to initiate both trials during the first half of 2005. Shares traded up 93 cents to $12.23.

Other health care movers included Elan ( ELN), up 11 cents to $7.32; Pfizer ( PFE), down 24 cents to $26.05; Amgen ( AMGN), down 63 cents to $57.98; Genentech ( DNA), up 13 cents to $54.38; Merck ( MRK), down 30 cents to $31.70; Johnson & Johnson ( JNJ), down 21 cents to $67.05; and Schering-Plough ( SGP), down 23 cents to $18.07.