News that Pfizer (PFE) halted a phase III study of melanoma treatment tremelimumab after an interim review found that the drug would not prolong survival any more than currently prescribed chemotherapy, weighed heavily on Medarex (MEDX), which is developing a drug in same class.

The drug that Medarex and partner Bristol-Myers Squibb ( BMY - Get Report) are developing failed a late-stage study in December, but the companies said they will still file the drug for approval with U.S. regulators before the middle of the year. Investors guessing that the Medarex drug is doomed took shares down $1.80, or 19.3%, to $7.52. Bristol's shares edged down 1% to $21.66.

Smaller-cap biotech Ista Pharmaceuticals ( ISTA) dove after announcing Tuesday post close that a new formulation of its anti-inflammatory drug was no more effective than the original. Shares retracted 69 cents, or 33%, to $1.38.

Shares of Micron Technology ( MU - Get Report) gained 39 cents, or 6.5%, to $6.39 ahead of the company's second-quarter results. Analysts expect Micron to report a loss of 36 cents a share on revenue of $1.41 billion in the quarter and report a loss of 24 cents a share on revenue of $1.53 billion in the current quarter.

EXFO Electro-Optical Engineering ( EXFO - Get Report) jumped 21.7% to $5.90 on second-quarter fiscal 2008 earnings. The Quebec City, Canada-based maker of telecom test measurement and monitoring equipment reported that revenue increased 23% year over year to $43.3 million and GAAP income came in at $4 million, or 6 cents a share, vs. $2.7 million, or 4 cents a share, in the year-ago quarter. For its third quarter, EXFO expects revenue between $45 million and $48 million. Analysts polled by Thomson Financial are looking for revenue of $46.9 million.

Nortel Networks ( NT) added 58 cents, or 8%, to $7.87 after the company launched new mobile communications products at the CTIA conference in Las Vegas.

Meanwhile, LoJack ( LOJN), which makes technology for tracking and recovering mobile assets such as stolen vehicles, saw shares drop 20.4% to $10.14 on lowered guidance. The Westwood, Mass., company forecast full-year 2008 EPS between 75 cents and 85 cents on revenue ranging from $213 million to $218 million. The Street is looking for EPS of $1.15 on revenue of $233.2 million.

This article was written by a staff member of TheStreet.com.