Biotechs, notably smaller-cap names with experimental therapies, have been skyrocketing lately as investors have jumped on word of any development in their research or product prospects -- even though in many cases that product might still be a long way from commercial viability. That trend was being reinforced again on Tuesday, as Geron ( GERN) saw its shares rise $1.72, or 25%, to $8.68 after the company said it has received a patent that could be used in stem-cell research. The process would be used, if it's ever needed, to provide an additional level of safety for cell therapies made from human embryonic stem cells, the company said. Human embryonic stem cells can become any type of cell in the body. Potentially, they could be differentiated or harnassed to produce therapeutic cells to treat diseases. But if transplanted therapeutic cells contain undifferentiated cells, they can form cell types that aren't needed for the therapy. Geron's patent covers a technology used to eliminate the undifferentiated cells. Geron traded as high as $9.75 earlier in the session, and it is still eclipsing the 52-week high of $7.40. More than 10 million shares have already traded, five times the normal volume for a full day. Another company in this biotech subsector, StemCells ( STEM), was higher by 21 cents, or 10%, to $2.37. Meanwhile, the broader biotechnology group measures were ticking lower. The Amex Biotech Index was down 0.3%, and the Nasdaq Biotech Index was slipping 0.2%. Among the other tiny biotechs going higher, Genaera ( GENR) was adding 16% to $2.46 after receiving a patent; Aastrom Bioscience ( ASTM) rose 17% to $1.41 as investors cheered a partnership involving bone grafts; and VaxGen ( VXGN) was climbing nearly 17% to $5.94 on news the company received a National Institutes of Health grant to identify novel antigens that could be used in future HIV vaccine candidates. Each new day seems to bring new big winners in the biotech field, and one of Monday's gainers, Oxigene ( OXGN), was giving back some ground in the session currently under way. The stock, which added more than $5 yesterday to $13.80, was lately losing $1.66 to $12.14. The decline came after the company said it has reached an agreement to sell 1.5 million common shares at $10 each to three institutional investors. Before yesterday's run-up, Oxigene's 52-week high was $8.96.