Bear Stearns ( BSC) was among the volume leaders after the New York broker said that $1.9 billion in mortgage-related writedowns disintegrated its bottom line to a loss of $878 million, or $6.90 a share, in the fiscal fourth quarter. Just last month, CFO Sam Molinaro had pegged the writedowns at just $1.2 billion, though he has also proved prescient in adding, " I don't want to predict that things couldn't get worse, because things keep surprising." The report came a day after Britain's Barclays ( BCS) sued Bear over one of its troubled subprime-focused hedge funds , according to several published reports. Bear shares, following some mixed trading, closed up 0.9% at $91.42. Bond insurer MBIA ( MBI) fared much worse, with shares tanking more than 26% on a crushing disclosure . The Armonk, N.Y., firm said it has $8.14 billion in exposure to collateralized debt obligations (CDOs) backed by high-grade collateral, 85% of which consists of other CDOs -- in other words, CDOs backed by other CDOs, or CDO squareds. A Morgan Stanley analyst said he was "shocked" at the lateness of this revelation. Altus Pharmaceuticals ( ALTU) tumbled $4.38, or 44%, to $5.50 Thursday. After the close on Wednesday, the company said that it's regaining the North American commercialization rights to ALTU-238, a once-weekly IV human growth hormone product that uses its drug delivery technology, from Genentech ( DNA). Altus said it still plans to resume clinical study of the drug, which is in midstage development, in mid-2008.