Shares of

Myogen

( MYOG) were among the best-performing health-related stocks Thursday, rising 62% after the company reported positive results for darusentan in resistant hypertension.

The phase IIb trial showed that 300 milligrams of darusentan dosed once daily demonstrated statistically significant reductions in systolic blood pressure and diastolic blood pressure. Also, clinically meaningful reductions in systolic and diastolic blood pressure were observed at earlier time points and lower doses, the company said. "We are highly encouraged by the results of this trial," the company said. "There are millions of hypertensive patients in the United States currently being treated with three or more antihypertensive therapies."

Based on the results, the company intends to move ahead with phase III clinical development of darusentan. Shares were recently trading up $8.42 to $21.96.

Rita Medical Systems

( RITA) rose 6% after the medical device company said its resection device received Food and Drug Administration marketing clearance. The Habib4X resection device is used in surgical procedures for the resection of tissue. The device, which previously received approval in Europe, will begin shipping in the U.S. in mid-Sept. Shares were trading up 21 cents to $3.55.

Shares of

Ariad Pharmaceuticals

(ARIA)

rose 6% after the company's mTOR inhibitor was granted orphan drug status by the FDA. The inhibitor, designated as AP23573, is used for the treatment of both soft-tissue and bone sarcomas. AP23573, a small-molecule drug, acts to starve cancer cells and shrink tumors by inhibiting mTor - a cell-signaling protein - which regulates the response of tumor cells to nutrients and growth factors, the company said. Shares were recently trading up 39 cents to $7.45.

Dyax

(DYAX)

rose 5% after the company licensed its technology and patent rights to Germany-based Merck KGaA. Specific financial terms were not made available, but Dyax said Merck would pay an upfront technology license fee as well as annual maintenance fees. In addition, Merck will make clinical milestone payments and royalties that are tied to sales that result from the licensing agreement. Shares were trading up 29 cents to $5.88.

Shares of

Pharmacyclics

(PCYC)

rose 6% after the pharmaceutical company posted a narrower-than-expected fourth-quarter loss. The company posted a loss of $8 million, or 40 cents a share. Analysts polled by Thomson First Call were expecting a loss of 44 cents a share. A year ago the company reported a loss of $7.3 million, or 38 cents a share. Operating expenses during the most recent period came in at $8.5 million, up from $7.6 million a year ago. Pharmacyclics attributed the rise in expenses to additional personnel costs and activities related to the company's development of investigational product Xcytrin Injection. Looking ahead, Pharmacyclics expects operating expenses of $8 million to $9 million during the first quarter. Second-quarter operating expenses will be between $11 and $12 million, which includes $2 million in expenses related to drug purchases that will support the potential commercialization of Xyctrin. Shares were trading up 45 cents to $8.43.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, down 14 cents to $26.02;

Schering-Plough

( SGP), down 12 cents to $21.09;

Medtronic

(MDT) - Get Report

, up $1.55 to $56.12;

Amgen

(AMGN) - Get Report

, up 68 cents to $79.68;

ViroPharma

(VPHM)

, up $1.27 to $14.79;

Teva Pharmaceutical

(TEVA) - Get Report

, up 39 cents to $33.58;

Merck

(MRK) - Get Report

, down 3 cents to $30.53; and

Johnson & Johnson

(JNJ) - Get Report

, up 54 cents to $64.04.