Affymax Shares Plunge After Trial Raises Heart Safety Concern for Medicine

Affymax Inc. fell 69 percent, the most ever in Nasdaq trading, after the company released results showing greater heart risks among some kidney patients taking its investigational anemia drug Hematide than among users of Amgen Inc.’s Aranesp.

Cardiovascular problems are “a major concern” for the U.S. Food and Drug Administration, Aaron Reames, a Wachovia analyst, wrote today in a note to investors. “There is a good possibility that another trial is required.”

The data may delay the Palo Alto, California-based company’s bid to win regulatory approval for its first marketed product and challenge Amgen in treating anemia in kidney patients, said Arlene Morris, the company’s chief executive officer. The results also may prompt U.S. regulators to require additional studies, Reames said.

“We need time to reconsider our regulatory strategy,” Morris said today in an interview. “The key issue is just the uncertainty right now, not being able to tell people what we’re going to do and when we’re going to do it.”

Affymax fell $15.83 to $7.18, at 4 p.m. New York time in Nasdaq Stock Market composite trading.

Study Results

In the results released today, 22 percent of non-dialysis patients taking Hematide had a cardiovascular complication, compared with 17 percent of those taking the Amgen drug. The biggest difference was in the portion of patients who died of a heart-related problem -- 8.8 percent among the Hematide users compared with 6.7 percent of those taking Aranesp.

In a separate study of dialysis patients, heart-related complications struck 23 percent of Hematide users and 24 percent of patients taking another Amgen drug, Epogen, said Anne-Marie Duliege, Affymax’s chief medical officer.

The dialysis market is about three times larger than the non-dialysis market, Morris said.

“Our data are promising in the dialysis area so we think there’s a nice fit with the dialysis market,” Morris said.

The results are good for Amgen, wrote Geoffrey Meacham, an analyst for JPMorgan, in a note today to investors. Hematide was considered a major competitor to Amgen’s anemia drugs, and today’s data make it less of a threat, Meacham wrote.

Amgen, based in Thousand Oaks, California, rose $1.32, or 2.4 percent, to $56.52, also in Nasdaq trading.

Amgen’s View

It’s too early to say how the results may affect sales of Aranesp, Amgen spokeswoman Emma Hurley said today in an interview. Aranesp generated sales of $2.7 billion in 2009.

Affymax is developing Hematide with Osaka-based Takeda Pharmaceutical Co. Takeda can terminate the collaboration with six months written notice or in the event of “certain specified clinical development events or failures,” according to Affymax’s annual report for 2009.

Takeda’s “collaboration with Affymax is strong and we remain committed to continue developing Hematide,” said Josephine Zammuto, a U.S. spokeswoman for Takeda, in a telephone interview today.

The drug was as effective as Epogen or Aranesp in four studies released by Affymax and Takeda. The average follow-up for patients in all four trials was 1.3 years. Hematide was given once every four weeks; both Amgen drugs require more frequent dosing.

To contact the reporter on this story: Elizabeth Lopatto in New York at elopatto@bloomberg.net; Rob Waters in San Francisco at rwaters5@bloomberg.net.

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