Biotechnology stocks slipped a bit on Thursday. The CBOEBiotech Index declined 2.05 to 143.12, while the AMEXBiotechnology Stock Index fell .83 to 150.13.

Among the bigger declining issues was Deprenyl USA Inc. units(NASDAQ:DUSA), which dropped $1.75 a unit to $18.50following its report of second-quarter results. Ecogen (EECN)was off 50 cents to $7.63 a share after posting earnings. Otherdeclining issues included Genzyme (GENZ), down $3.37 a shareto $43.13; and Alteon Inc. (ALTN), off $1.50 to $13.

The few big gainers included Vertex Pharmaceuticals (VRTX),which gained 87 cents to close at $10 a share, and SomatogenInc. (SMTG), up $1 to $19 a share.

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