Embrex

( EMBX), a maker of vaccine-delivery technologies, surged after a unit of

Pfizer

(PFE) - Get Report

agreed to acquire the company for $155 million.

Under the agreement, Pfizer will acquire the shares of Embrex for $17 each. Embrex gained 40% to $16.63. Pfizer rose 1.2% to $26.56.

Shares of

Vanda Pharmaceuticals

(VNDA) - Get Report

soared after the company reported positive late-stage trial results on a proposed insomnia drug.

The drug, dubbed VEC-162, showed a significant difference in leading to the onset of sleep when compared with a placebo. The medication was tested at three different dosage levels in patients with transient insomnia and circadian-rhythm sleep disorders, which are disruptions in the body's normal sleep-wake cycle.

Vanda's stock climbed 53.7% to $15.02, setting a 52-week high. Trading volume was much heavier than normal.

Nabi Biopharmaceuticals

(NABI)

says it has discovered some stock-option accounting errors that it considers "not material" to its financial reporting.

As a result, Nabi has issued third-quarter results, including a $2.6-million noncash compensation expense, or 4 cents a share, which it blamed on "incomplete or missing documentation." The announcement was made Tuesday night after Nabi filed a quarterly financial report with the

Securities and Exchange Commission

.

For the three months ended Sept. 30, Nabi lost $21.8 million, or 36 cents a share, including discontinued operations. For the year-ago quarter, it lost $16.1 million, or 27 cents a share, including discontinued operations. Revenue dropped to $19.6 million vs. the year-ago quarter's sales of $22.4 million. Shares of Nabi rose 6.7% to $6.99.

Vaccine developer

Emergent Biosolutions

(EBS) - Get Report

priced its initial public offering well below its previously expected range, and the stock fell on its first day of trading.

The company is offering 5 million shares for $12.50 a share vs. its previous estimate of between $14 and $16 a share, according to filings with the

Securities and Exchange Commission

. Emergent dropped 90 cents to $11.60.