AMEX INDEX DRIFTS DOWN WITH XOMAXoma Corp. stock, wracking up a second consecutive day ofvery heavy trading, fell 50 cents a share on Friday to close at$14.75. Biotechnology sector stocks posted a small decline.

Xoma stock (NASDAQ:XOMA), which shed $4.75 a share lastThursday following an announcement that its flagship E5 drugmay need more clinical study, was the fourth most heavilytraded NASDAQ issue on Friday with 2.2 million shareschanging hands. The stock was down $6 for the week.

Rival Centocor Inc. (NASDAQ:CNTO), which received newsWednesday that the FDA had approved a protocol for testing itsanti-bacterial drug, rose 25 cents on Friday and was up $2.50for the week.

The AMEX Biotechnology Stock Index declined 1.30 to 156.09on Friday, while the NASDAQ index closed up 0.75 at 589.93.The AMEX Index reached a five-week high last Wednesday at162.7, but retreated Thursday following Xoma's announcement.

DeKalb Genetics Inc. (NASDAQ:SEEDB), down $1.50 to $30.50,was the only biotech stock to change by more than $1 onFriday. Newcomer PerSeptive Biosystems (NASDAQ:PBIO),which went public May 29 at $7 a share, dropped 25 cents onFriday to close at $8.75.

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