Shares of

Neurocrine Biosciences

(NBIX) - Get Report

were among the worst-performing health-related stocks Friday, plunging 23% after the drug development company said it might need to conduct more tests on its Indiplon sleeping pill before it can be approved.

In mid-May, shares Neurocrine plunged after the Food and Drug Administration gave conditional approval to the company's Indiplon capsules in 5-milligram and 10-milligram doses, but rejected the tablets in a 15-milligram dose strength. Since then, the company has been working on a briefing document that will be submitted to the FDA. "This briefing document will assist the company in articulating its understanding of the issues communicated by the FDA in the May 15 action letters," the company said late Thursday.

The "not approvable" letter for the 15-milligram tablets requested that the company reanalyze certain safety issues and efficacy data. As a result, the company said that additional clinical would likely be required. "On May 17, we notified the FDA that we intend to further amend both applications to respond to the deficiencies raised by the FDA," Neurocrine said. "Our immediate focus is to meet with the FDA to determine the nature and scope of any additional preclinical and/or clinical work the agency may require for approval." Further, the company said it expects to adjust its financial guidance when it reports second-quarter results. Shares were trading down $4.48 to $14.89.

Orthovita

( VITA) jumped 15% after the developer of orthopedic biomaterials received pre-marketing approval from the FDA to sell its Vitagel surgical hemostat. The company, which has already manufactured three lots of Vitagel, said it will begin shipping and selling the product immediately. "A high level of coordination and performance was required throughout our organization to manage existing Vitagel supply and obtain the pre-market approval within a short time frame," Orthovita said. Shares were trading up 64 cents to $4.78.

Shares of

Neurobiological Technologies

(NTII)

fell 3% after the drugmaker announced the resignation of its chief financial officer. The company said that Jonathan Wolter, who is leaving to "pursue other professional opportunities," would continue to work with the company as a consultant over the next year so that he can aid in Sarbanes-Oxley compliance and other financial reporting issues. In the meantime, Neurobiological Technologies will conduct a search for Wolter's replacement. Shares were trading down 7 cents to $2.65.

Medarex

( MEDX) fell 6% after the biotech company said it received a grand jury subpoena from the U.S. Attorney's Office in the District of New Jersey related to past stock option grant practices. The company, which had previously received notification from the

Securities and Exchange Commission

that it was conducting an informal inquiry into the stock option grants, said its board has launched its own investigation into the matter.

In addition, Medarex received notification that it is being sued by investors as part of two derivative shareholder lawsuits in New Jersey. The suits name a number of current and former directors and officers as defendants, the company said. The lawsuits allege breach of fiduciary duty associated with the company's stock-option grant practices. Shares were recently down 59 cents to $9.22.

Shares of

Sangamo BioSciences

(SGMO) - Get Report

slid 9% after the developer of genetic therapies priced 3.1 million shares of stock at $6.75 a share. The company, which expects nearly $20.2 million from the offering, plans to use the proceeds for product development and research programs as well as for general corporate purposes. "As we prepare to enter our first Phase 2 clinical trial, this $20.15 million of additional capital puts us in a stronger position to accelerate this program and to simultaneously bring additional ZFP Therapeutic programs into the clinic," the company said. The proceeds of the offering will leave the company with about $50 million in cash at the end of its fiscal year, instead of the $30 million that it originally expected. Shares were trading down 67 cents to $6.68.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, down 23 cents to $23.30;

Boston Scientific

(BSX) - Get Report

, up 48 cents to $20;

Johnson & Johnson

(JNJ) - Get Report

, up 17 cents to $61.64;

Amgen

(AMGN) - Get Report

, down 44 cents to $67;

Millennium Pharmaceuticals

( MLNM), down 1 cent to $10.08;

Elan

(ELN)

, up 9 cnets to $16.74;

Merck

(MRK) - Get Report

, up 1 cent to $34.34;

UnitedHealth Group

(UNH) - Get Report

, down 35 cents to $44.40; and

Bristol-Myers Squibb

(BMY) - Get Report

, down 9 cents to $25.18.