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What's becoming a recurring story at the American Society of Clinical Oncology's annual convention played out again Friday: The early release of -- and subsequent trading on -- supposedly restricted information from drug abstracts.

On the last day of regular trading before drug abstracts are officially released, abstract data that the organization embargoed flew around, in frantic phone calls, in emails and in analysts' notes. And shares of the companies involved moved as well.

How? Abstracts were distributed to conference attendees as they registered early Friday morning. That gave some of them a chance to study, share and trade on the information.

Abgenix ( ABGX), for example, rose 7% Friday morning after a note from CIBC analyst Matt Geller repeated what he described as the "encouraging response data" on the company's cancer drug from the ASCO abstract -- information that was supposed to be withheld until the weekend. Shares drooped in later trading.

Millennium Pharmaceuticals ( MLNM), which has data being released at the meeting, was up $1.05, or 7.2%, to $15.55. OSI Pharmaceuticals ( OSIP), also releasing information on its cancer drug, rose in regular trading 68 cents, or 2.6%, to $26.36. Genentech ( DNA), which is presenting widely anticipated data on Avastin, rose $2.47, or 4.1%, to $62.61.

Geller declined comment when asked if his note violated ASCO's policy. ASCO officials don't have much to say publicly, either. Privately, though, they complain that it would be difficult to distribute the 25,000 copies of the abstracts to attendees after the market closes but before conferences begin tomorrow. And they don't think they can police all the unauthorized leaks that will happen Friday.

It used to be that the prestigious group released the abstracts to members well before its annual convention. That led to the well-publicized "ASCO effect," in which companies whose drugs showed favorably in the abstracts saw their stocks rise, although there was no publicly available reason.

ASCO attempted a crackdown last year, with limited success. It made a new attempt this year, announcing that abstracts wouldn't be available until Saturday.
Adam Feuerstein writes regularly for RealMoney.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. He invites you to send your feedback.