Shares of Nabi Biopharmaceuticals ( NABI) shot up 13% in late trading after the company said it will continue development of its staph vaccines. In November, the company halted work on its StaphVax vaccine after a late-stage study failed to meet its goals. The company said Tuesday that an outside advisory panel found "marked differences" in the effectiveness of the vaccine used in the study compared with a previous trial. Nabi plans to seek a partner to develop its vaccines program, and is planning a proof-of-concept study for its next-generation Altastaph product. Shares rose 62 cents to $6.42 after hours Tuesday. Shares of Sigma Designs ( SIGM) fell after the company posted lower-than-expected fourth-quarter earnings. For the quarter ended Jan. 31, the maker of multimedia chips and cards earned $490,000, or 2 cents a share, reversing a year-earlier loss of $17,000, or less than 1 cent a share. Analysts polled by Thomson First Call predicted earnings of 4 cents a share. Revenue rose to $10.5 million from $8.5 million on strength in sales of products for set-top boxes and portable media players. Wall Street's forecast called for revenue of $10.4 million. Shares sank $1.77, or 11%, to $14.10 after hours. Chaparral Steel ( CHAP) shares surged in after-hours trading after the maker of structural beams reported sharply higher third-quarter income. The company earned $49.2 million, or $2.06 a share, in the February quarter, up from $14.2 million, or 62 cents a share, a year ago. Sales rose to $374.6 million from $259.1 million a year ago. "Improved global demand, industry consolidation and low cost production are the primary factors contributing to strong industry results," Chaparral said in a statement. The company said the fourth quarter should have "similarly strong" results. Shares gained $5.18, or 10.5%, to $54.52 after hours. Regis ( RGS) shares were shaved after the hair-care company cut its guidance, citing weaker-than-expected product margins and sales. For the third quarter ending March 31, the company anticipates earnings of 45 cents to 48 cents a share, down from a prior forecast of 56 cents to 60 cents a share. Regis sees revenue of $607 million, with flat same-store sales. Analysts had targeted earnings of 57 cents a share and revenue of $613 million.