Bydureon, the diabetes drug being developed by Amylin Pharmaceuticals Inc., Eli Lilly and Co. and Alkermes Inc., didn’t control the disease better than Novo Nordisk A/S’s Victoza in a study.

Bydureon lowered average blood-sugar levels by 1.3 percentage points, compared with 1.5 percentage points for Victoza, the developing companies said in a prepared statement Thursday.

“We thought that Bydureon would look at least as good as Victoza,” said Phil Nadeau, an analyst with Cowen & Co. in New York, in a report. “These data give Novo a very powerful marketing message to use against Bydureon when it is launched.”

Amylin stock lost about half its market value Oct. 20 after it disclosed that U.S. regulators wanted a study assessing Bydureon’s heart risks. Amylin and its marketing partners plan to submit a response to the FDA in the second half of 2011, the companies said in a statement Thursday. The drug is a weekly version of Indianapolis-based Lilly’s Byetta, which is injected twice daily. Victoza, approved in the United States last year, is taken once daily.

“While this study did not meet its primary endpoint, these results reinforce the important role” of a new class of diabetes drugs that includes Bydureon, said Gwen Krivi, a vice- president for product development at Lilly, in a prepared statement. “If approved, Bydureon could provide millions of patients with a once-weekly treatment option.”

Amylin shares fell 25 percent, to $11.20 each, in early NASDAQ trading, while Alkermes shares declined 15 percent, to $12.

Lilly shares dropped 1.1 percent in early trading on the New York Stock Exchange, but rebounded by mid-morning for a 10-cent rise, to $34.38 each.

Denmark-based Novo Nordisk A/S gained as much as 4.9 percent in Copenhagen trading, the most in more than four months.

Bydureon revenue may reach $600 million in 2014, pushing combined revenue for Bydureon and Byetta to $965 million, said Joshua Schimmer, a Boston-based analyst for Leerink Swann & Co., in a Jan. 4 note to investors.

Alkermes is based in Waltham, Mass., and Amylin in San Diego.

Almost 24 million Americans have diabetes, which occurs when people don’t have sufficient amounts of the hormone insulin, or are resistant to it, hampering their ability to convert blood sugar to energy.

Amylin lost about half its market value Oct. 20 after saying the U.S. Food and Drug Administration wanted a study assessing Bydureon’s heart risks.

Bydureon’s entrance to the U.S. market “may be more challenged than some expect, particularly given Victoza’s strong launch and the multiple once-daily oral medications approved and in development,” said Robert Hazlett, an analyst with BMO Capital Markets in New York, in a note to clients Thursday. He maintained his peak sales estimate of $1 billion for Bydureon.