The health care sector was relatively flat Thursday, as investors weighed an array of regulatory and clinical trial updates from companies.

BSD Medical ( BSM) said Thursday that the Food and Drug Administration completed a pre-approval audit -- which included a five-day onsite inspection of its manufacturing process -- of its BSD-2000 hyperthermia system.

The company said the FDA didn't provide any written inspectional deficiencies, but it didn't allude to when it expects an approval decision. Shares added 51 cents, or 9.4%, to $5.96.

But ZymoGenetics ( ZGEN) fell Thursday after announcing after the prior bell that the FDA review of its rThrombin blood clotting product would take an additional three months. The FDA needs the extra time to review additional data on a manufacturing facility. Shares were down $1.30, or 9.8%, at $11.98.

Other companies got a slight bump out of initiating or reporting data from mid-stage trials. CollaGenex Pharmaceuticals ( CGPI) said a phase II dose-finding study achieved its primary endpoint and showed a statistically significant dose-response relationship of COL-118, a topical treatment for Erythema, a bright redness of the skin which is associated with certain dermatological conditions. Shares rose 18 cents, or 1.5%, to $12.18.

Regeneron Pharmaceuticals ( REGN) said Thursday that it initiated two double-blind, placebo-controlled phase III trials evaluating the safety and efficacy of aflibercept, which it's developing with Sanofi-Aventis, in combinations with standard chemotherapy regimens in patients with prostate cancer and nonsmall cell lung cancer.

Shares fell 16 cents, or 0.9%, to $18.29. Both Regeneron and CollaGenex are components of the Nasdaq Biotechnology Index, which was down 0.45, or 0.06%, to 802.48.

Biopharmaceutical company Targacept ( TRGT) said its partner AstraZeneca ( AZN) initiated a phase IIb clinical trial on AZD3480 for cognitive deficits in schizophrenia.

Targacept edged down a penny to $9.53, while AstraZeneca added 27 cents, or 0.6%, to $48.18.

MedImmune, a unit of AstraZeneca, said it licensed its reverse genetics -- a method by which viruses can be generated from segments of DNA -- intellectual property to Novartis ( NVS) to support new vaccine strains for influenza vaccines.

MedImmune, which exclusively owns licenses for key patent estates for use of the reverse genetics technology in human influenza vaccines, has offered other influenza vaccine manufacturers nonexclusive licenses for use in manufacturing seasonal or pandemic vaccines.

Financial terms of the agreement with Novartis weren't disclosed, but MedImmune said it would receive an upfront payment from Novartis and has the potential to receive royalties on certain vaccine stockpiles or sales of other influenza products developed using the technology. Novartis shares rose 18 cents, or 0.3%, to $52.50.

Small-cap pharmaceutical development company Gene Logic ( GLGC) said it entered into an agreement with Merck's ( MRK) Merck Serono division to reposition some of the unit's drugs that were deprioritized or discontinued in trials for reasons other than safety. The company didn't disclose the amount of the agreement, but said significant payments were tied to success. Shares rose 12 cents, or 10.2%, to $1.30.

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