With U.S. markets abruptly shut last week, companies with milestone-driven news will have to wait until this week to see if the announcements had any effect on valuations. And questions remain as to whether fundamental progress will have any bearing on valuations once the U.S markets re-open, given investors' desire for ultimate liquidity during international emergencies (read: T-bills and cash).

The experience of dual-listed companies last week did not provide grounds for optimism. Of 40 biotech stocks dual-listed on a U.S. and non-U.S. exchange, 36 traded down on their non-U.S. exchanges. Some of the drops were harrowing, with 26 slipping 10% or more (see "Ominous Signs").