Irish drug maker Elan Corp. PLC (ELN) said Tuesday it received a subpoena from the U.S. Securities and Exchange Commission seeking information related to disclosures last year about Elan's multiple-sclerosis drug Tysabri and an experimental Alzheimer's disease drug - disclosures that battered Elan shares.

Wyeth (WYE), Elan's partner in the Alzheimer's drug program, also received an SEC subpoena related to disclosure of clinical-trial data for the drug last year. A Wyeth spokesman said the company, which has agreed to be acquired by Pfizer Inc. (PFE), is working to provide the SEC with the information.

Elan disclosed in a regulatory filing it received the subpoena Sept. 24 from the SEC's New York office, and it intended to provide the SEC with materials in connection with the commission's investigation into Elan.

The exact nature of the SEC's investigation wasn't immediately known, and a commission spokesman declined comment. An Elan spokesman reiterated that the company would provide the SEC with the information, but didn't provide additional details about the exact nature of the probe.

The subpoenas concern two separate announcements related to Elan last year. On July 31, 2008, Elan and its marketing partner, Biogen Idec Inc. (BIIB) notified regulatory agencies of two confirmed cases of a rare brain infection called progressive multifocal leukoencephalopathy, or PML, in multiple-sclerosis patients treated with Tysabri. Tysabri had previously been withdrawn from the market due to PML risk, then relaunched, and the companies have monitored the side effect closely.

There have been at least 16 PML cases in Tysabri patients in total, 13 of which occurred after the drug was brought back to the market in 2006 under rules meant to reduce the PML risk, such as preventing patients from taking another MS drug at the same time.

Separately, on July 29, 2008, researchers presented the results of a mid-stage patient trial of bapineuzumab, an Alzheimer's drug Elan co-developed with Wyeth (WYE), at a medical-meeting in Chicago. Wyeth and Elan said the data supported their prior decision to move the drug into late-stage trials, which are still underway.

But the full data presentation for bapineuzumab disappointed many investors, who felt it was less impressive than the preliminary findings Wyeth and Elan had included in a June 2008 press release.

Elan's American depositary receipts were quite volatile during this period. They closed at $33.75 in regular trading on July 29, 2008, and the bapineuzumab data were released after market hours. The stock proceeded to lose 40% in value the next day, then dropped 50% on Aug. 1 after the disclosure of the PML cases.

Elan's ADRs ended Tuesday at $7.27, off 7 cents.

In February 2009, Elan disclosed in a regulatory filing that the SEC had begun an informal inquiry related to the disclosure of the Tysabri PML cases. Also, the SEC previously conducted an informal inquiry of securities trading surrounding the February 2005 announcement of the suspension of marketing of Tysabri.

Separately, lawsuits seeking class-action status have been filed against Elan on behalf of purchasers of Elan shares between May 2007 and October 2008, alleging Elan issued false and misleading public statements about the safety and efficacy of bapineuzumab. Similar lawsuits alleging Elan made false and misleading statements prior to Tysabri's withdrawal were dismissed.

Johnson & Johnson (JNJ) recently acquired Elan's rights in the Alzheimer's disease partnership with Wyeth, and acquired a minority stake in Elan.

Spokespeople for J&J and Biogen declined to comment.

-By Peter Loftus, Dow Jones Newswires; 215-656-8289; peter.loftus@dowjones.com

(Thomas Gryta in New York and Keith Winstein in Boston contributed to this article.)