Health care stocks were up slightly Wednesday following successful drug studies, announced stock offerings and mixed earnings.

Advanced Life Sciences Holdings ( ADLS) announced that its respiratory antibiotic, Cethromycin, was shown to be effective in preventing inhalation anthrax infection in a 30-day study involving 30 primates. Shares rose 27 cents, or 7.9%, to $3.67.

Positive study results also sent Nabi Biopharmaceuticals ( NABI) soaring 90 cents, or 17%, to $6.03. The company said a significant number of patients in its phase IIb study for NicVax, a vaccine to treat nicotine addiction, met the primary endpoint of eight weeks of continuous abstinence. Nabi is also set to release first-quarter financial results by end-of-day Wednesday.

Planned stock offerings also moved the market Wednesday. Immunomedics ( IMMU) announced it will sell just over 4.8 million shares of common stock to institutional investors for about $24 million, or $4.95 a share. The stock closed at $5.35 Tuesday. The offering is set to close on or around May 7. Shares were up 4 cents, or 0.8%, to $5.39.

Array BioPharma's ( ARRY) offer to sell 7 million shares for $13 a share did not have the same impact on investors. The company's stock price fell 53 cents, or 3.9%, to $13. The Array BioPharma offering is also expected to close on or around May 7.

A narrowed quarter-over-quarter loss helped make Pozen ( POZN) a winner Wednesday. The pain reduction drug developer reported a net loss of $2.1 million, or 7 cents a share for the first quarter ended March 31, compared to a net loss of $6.4 million, or 22 cents a share for the same quarter last year. The results were good enough to beat the Thomson Financial consensus of a loss of 9 cents a share. Shares hiked 80 cents, or 5.5%, to $15.30.

Other health care companies were less fortunate following earnings reports on Wednesday.

Allergan ( AGN) announced first-quarter net income of $140 million or 92 cents earnings per share, excluding certain items, outperforming the Thomson Financial consensus target of 90 cents a share. In the year-ago quarter, the drugmaker earned $114 million or 82 cents a share. The company increased guidance for earnings per share, excluding certain items for the full year to between $4.28 and $4.32, up a penny from the previous forecast of $4.27 to $4.31. Allergan also announced a 2-for-1 stock split for stockholders of record as of the end of June 11 that is not figured into its guidance. The new shares will be distributed on June 22. Shares fell $3.48, or 2.9%, to $118 on Wednesday.

Also pained, CollaGenex Pharmaceuticals ( CGPI) reported a net first quarter loss of $5 million, or 23 cents a share, compared to a net loss of $9.3 million, or 54 cents a share, in the first quarter last year. Results beat analysts' expectations of a loss of 31 cents a share for the quarter, but the company also announced that it halted new enrollment in a phase II study on acne medication Incyclinide, after a patient had an adverse effect. The company said it will meet with the U.S. Food and Drug Administration to discuss the program for Incyclinide after completing an investigation of the matter. Shares fell $2.44, or 17%, to $11.59.

The Nasdaq Biotechnology Index -- which includes Wednesdays winners Pozen and Immunomedics, as well as losers Array Biopharm and CollaGenex Pharmaceuticals -- was up 11.66, or 1.4%, on Wednesday.

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