The extra session was a little on the slow side, but enough companies had news after the close to impact their stock prices. Idec Pharmaceuticals ( IDPH) was in the cross hairs after the company said it would halt clinical trials of an experimental drug because of safety concerns. Idec was falling 7.5% to $35.48 on Instinet after the close. The top volume mover was Nortel ( NT), which was flat with the 4 p.m. EDT close at $1.79. The telecom equipment provider said it brought in $1.475 billion with a recent financing deal. On the whole, volume was somewhat light. In the first hour and 15 minutes of extended action, about 2.3 million shares changed hands among the 20 most active stocks on the Instinet platform. Lucent ( LU) and Intel ( INTC) were unchanged. Cisco ( CSCO) was down 0.8%, and WorldCom ( WCOM) was off 0.6%. Tyco ( TYC) climbed 13% in regular trading but slipped 0.9% to $11.30 in extended activity. Comcast ( CMCSK) closed at a 52-week low, but ticked up 0.3% to $24.30 after the bell. The Nasdaq 100 Unit Trust ( QQQ) was inching ahead 0.2%, while Sun ( SUNW) and Microsoft ( MSFT) were slightly lower. The biggest loser was Numerical Technologies ( NMTC), which plunged 31% to $4.26. The company, a designer of products for integrated circuit makers, lowered its guidance for the second quarter and full year, sparking the selloff.