The makers of Cold-FX have sat for years on a study that suggested Canada’s most popular cold and flu remedy was no more effective than a placebo in treating symptoms of the viruses.

The 2004 trial was conducted by Dr. Gerry Predy, a top Alberta public-health official, at a time when the supplement’s makers told consumers the product would bring fast relief from the effects of such ailments.

Predy continued to do other research on Cold-FX — based on people taking it over months as a preventive measure – and spoke of its prophylactic benefits well after 2004.

But it appears neither he nor the manufacturers have ever publicly divulged results of the short-term treatment trial.

The study has just surfaced in a class-action lawsuit against Valeant Pharmaceuticals, the Quebec drug giant that now owns the product after buying Edmonton’s Afexa Life Sciences in 2011.

“If true, this kind of information should have been disclosed,” argues John Green, the Vancouver lawyer spearheading the class action. “If it had been disclosed, it would probably have been the end of Afexa Life Sciences.”

Companies like Afexa and Valeant are not legally obliged in this country to release any trial results. The Cold-FX report was filed with Health Canada, according to the court document, but the government is barred from making such proprietary information public.

Other, more positive Cold-FX studies, looking at its effects when taken preventively over a number of months, have been published in peer-reviewed journals.

Renée Soto, a spokeswoman for Valeant, said the company would not discuss any matter related to ongoing litigation.

Predy, who is now Alberta’s senior medical officer of health, said he can’t recall if the study was submitted to a journal for publication and rejected or “if we decided not to submit it given that it was not likely to be published given the results.”

Cold-FX, invented in Edmonton and promoted by sports celebrities like Hockey Night in Canada’s Don Cherry, had Canadian sales in 2011 of more than $117 million, suggests data disclosed in the lawsuit. The substance is based on a specially prepared Ginseng extract and, unlike most natural-health products, has actually undergone fairly rigorous scientific study.

Some of the resulting evidence suggests that if people take the supplement daily for two months or more, the number and severity of respiratory illnesses they suffer will be modestly reduced.

But the lawsuit Green is handling alleges the company misled consumers until the last few years by suggesting Cold-FX could treat colds and flu after they start.

Packaging and other marketing, for instance, used to say the supplement could “stop cold and flu in their tracks,” “help provide effective relief” or bring “immediate relief” of symptoms.

Until now, no studies have surfaced publicly that actually addressed the pills’ value in treating — rather than preventing — bugs.

An “interim clinical report” divulged by the company as part of the court case and marked “Confidential” indicates one was launched in 2004, with 128 participants eventually taking Cold-FX for three days when they developed symptoms, and 119 a placebo. They were followed for 14 days after the start of their illnesses.

The results for the two branches of the trial appear largely similar, but symptoms actually lasted slightly longer for people taking Cold-FX. And the total score for severity of symptoms was lower for those on the placebo during most of the 14 days, according to a graph in the report.

Graphs tracking four separate symptoms show runny noses were slightly less severe for Cold-FX users over about three days of the study, but the placebo group seemed to fare better on stuffy nose, cough and sore throat.

Still, the internal company report concludes the results indicate “treatment with Cold-FX is associated with efficacy in reducing the severity of runny nose during the early part of a respiratory infection.”

Critics are not convinced.

The actual data are sparse, making it difficult to assess, but it would seem there was virtually no difference between the placebo and Cold-FX groups, said James McCormack, a pharmacy professor at the University of British Columbia who has followed the supplement for years.

“I don’t see that it shows any benefit,” he said.

The study should have been divulged publicly long ago, said both McCormack and Tim Caulfield, a health law and policy professor at the University of Alberta who has also tracked the Cold-FX story.

“It’s unfortunate this study had to come to light through a lawsuit,” said Caulfield. “Negative results are … scientifically and clinically meaningful. You’re including human beings to be part of these studies. They should be adding to the body of knowledge out there.”

I don’t see that it shows any benefit

Evidence suggests that, in fact, pharmaceutical companies often keep unfavorable results under wraps, leading to a growing push for more transparency in clinical trials.

Health Canada recently began a database of the trials registered with it, but companies don’t have to post their results, or register with international databases, as other countries require.

The Cold-FX episode suggests natural-health firms can be as selective as pharma companies in what trial data they release, said Caulfield.

The class action against Valeant continues with a hearing in April to determine if it will be “certified,” meaning it could move ahead toward trial or settlement.