(Adds stock price, analyst comment)
TORONTO, Nov 21 (Reuters) - Labopharm Inc DDS.TO said on Wednesday the U.S. Food and Drug Administration responded to its appeal of the approvable letter for its once-daily tramadol, and that the agency will not overturn the letter, which was issued in May.
The Canadian biotechnology company said it plans to appeal the matter to the FDA's next supervisory level in the coming weeks.
In response, Labopharm stock shed 17 Canadian cents, or 15.2 percent, to 95 Canadian cents on the Toronto Stock Exchange.
The shares plunged more than 50 percent after the FDA issued its approvable letter in May; since then, they have gradually declined more than 70 percent.
Last month, Labopharm formally appealed the agency's decision on the painkiller, which stated the once-daily formula would not be approved until certain conditions were met.
The Montreal-based firm said it was possible the agency would require additional data before the drug could be approved. It is not clear where, exactly, the dispute lies.
The company said on Wednesday its appeal process "may continue through the agency's chain of command, through the centers to the commissioner of food and drugs."
Douglas Loe, an analyst at Versant Partners, said the FDA's response is "obviously not positive, but certainly predictable and we will be surprised if the formal dispute resolution process does not proceed through one or two more layers of directorship review."
Loe noted the FDA's office of drug evaluation is currently headed by an acting director, Curtis Rosebraugh, who is unlikely to "act boldly" on the tramadol file.
$1=$0.99 Canadian Reporting by Jonathan Spicer