Shares of Genomic Health ( GHDX - Get Report) were among the worst-performing health-related stocks Monday, slumping 17% after Piper Jaffray downgraded the stock to market perform from outperform. The firm also cut its price target on the stock to $14.50 from $18.50.

Piper Jaffray cited increased regulatory risk concerning the company's only product, a breast cancer test called Oncotype DX, for the downgrade. Until the regulatory status of the test is cleared up, the firm said, an overhang on the stock could last for some six to 10 months. In late January, the Food and Drug Administration sent a letter to Genomic inviting the company to meet with regulators to discuss the regulatory status of the test and discuss ways in which the company could fulfill any FDA premarket review requirements that might apply. Shares recently were trading down $2.53 to $12.07.

Oscient Pharmaceuticals ( OSCI) fell 8% Monday, even though the drugmaker posted better-than-expected fourth-quarter results. The company reported a loss of $17.1 million, or 22 cents a share, on revenue of $9.5 million. Analysts polled by Thomson First Call expected a loss of 29 cents a share and revenue of $9.1 million. A year earlier, the company recorded a loss of $32.3 million, or 43 cents a share, on revenue of $2.7 million. The company said its most recent results were fueled by strong sales of Factive tablets and Testim testosterone gel. Shares recently traded at $2, down 18 cents.

Shares of Medicines Co. ( MDCO) fell 2% after the drug developer announced the resignation of its chief financial officer. The company said Steve Koehler, who had served as CFO for four years, will step down on March 17 to take a position with a pharmaceutical company. Koehler will be replaced by Glenn Sblendorio, who most recently served as chief financial officer at Eyetech Pharmaceuticals, which was acquired in November by OSI Pharmaceuticals ( OSIP). Medicines Co. shares were trading down 49 cents to $19.62.

Coherent ( COHR - Get Report) fell 7% after the maker of lasers said it will sell $175 million of convertible subordinated notes due 2011 to institutional investors. The company also expects to grant purchasers a 30-day option to buy an additional $25 million of notes to cover over-allotments.

Coherent plans to use proceeds from the offering to fund a portion of its $376 million acquisition of Excel Technology ( XLTC). If the acquisition of Excel doesn't occur, Coherent said, it plans to use the proceeds to fund working capital and other general corporate purposes. Shares were trading down $2.42 to $30.33.

Shares of Allergan ( AGN - Get Report) rose 1% after the maker of skincare products revised its fourth-quarter profit upward to reflect a tax settlement with the Internal Revenue Service. In early February, Allergan posted fourth-quarter earnings of $122 million, or 90 cents a share. After removing a valuation allowance against a deferred tax asset that was recorded during the fourth quarter and releasing other tax contingencies in prior periods, the company's earnings amounted to $140.1 million, or $1.03 a share.

Separately, Allergan extended the expiration date of its exchange offer for Inamed ( IMDC) shares. The company, which is in the process of acquiring Inamed, said it expects the Federal Trade Commission's review of the acquisition to be completed this week. Allergan shares were up $1.20 to $112.58.

Insmed ( INSM - Get Report) fell 8% after the biopharmaceutical company said that it plans to sell some 20 million shares of stock as part of a shelf registration statement filed in February with the Securities and Exchange Commission. The company also plans to offer underwriters an option to buy an additional 3 million shares to cover over-allotments. The company, whose shares fell 7% Friday after it posted weaker-than-expected fourth-quarter results, said Lazard Capital Markets will lead the underwriting syndicate. The company intends to use proceeds from the offering to fund working capital and other general needs. Shares were down 20 cents to $2.17.

Other health care volume movers included Pfizer ( PFE), down 22 cents to $26.12; Elan ( ELN), up 30 cents to $12.80; Generex Biotech ( GNBT), down 14 cents to $2.18; Boston Scientific ( BSX), up 23 cents to $23.76; Schering-Plough ( SGP), down 15 cents to $18.14; Genta ( GNTA), down 20 cents to $2.40; Johnson & Johnson ( JNJ), up 40 cents to $57.87; Novavax ( NVAX), up 18 cents to $5.58; Amgen ( AMGN), down $1.50 to $73.89; Merck ( MRK), down 23 cents to $34.96; and Bristol-Myers Squibb ( BMY), up 1 cent to $22.91.