IPO overallotment sales are closely watched on Wall Street as a barometer of investor appetite for a new security. So perhaps it doesn't bode well that underwriters for the last two biotech IPOs couldn't fill their greenshoes. Underwriters UBS Warburg, Lehman Brothers and Dain Rauscher Wessels last week sold only 63 percent of the overalloted shares in Genomic Solutions' May IPO, which raised $61.3 million for the marketer of instruments, software and consumables for the genomics industry. GNSL is valued at $251.6 million, using Friday's close of $10.375.