New antiviral drug shows promise in fighting the common cold

It may solve the problem of overprescribing antibiotics for the frequent affliction, but some caution that it won't be effective against all cold-causing viruses.

By Victoria Stagg Elliott, amednews staff. April 9, 2001.

Soon, there may be a new alternative to grandma's chicken soup.

Preliminary studies have demonstrated that an antiviral drug can lessen the duration and severity of the common cold.

Why it's so common
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Its potential clinical impact, however, remains unclear.

Pleconaril, an oral medication taken three times a day, could be on the market within a year, according to its manufacturer, ViroPharma Inc. It was effective at reducing the severity of symptoms within 24 hours of administration and lessening the duration by a day.

"These are the first pivotal studies in which patients receiving a drug targeted at the virus that causes the majority of common colds experienced a reduction in the severity and duration of their illness," said Mark McKinlay, PhD, vice president of research and development for ViroPharma Inc.

The study also suggested that the drug might affect the rate at which colds are spread because those who took it did not "shed" as much of the virus. "The reduction in viral shedding early in the treatment period gives us confidence to pursue additional indications for [pleconaril], particularly in the prevention of transmission," said Dr. McKinlay.

Cold experts, however, remain very skeptical. There was a flurry of announcements about potential new drugs approximately two years ago, but none have yet made it to market.

For example, Agouron Pharmaceuticals Inc., a division of Pfizer Inc., has been testing AG7088, a nasal spray that is being reformulated and is in the middle of phase II clinical trials. In addition, Boehringer Ingelheim Pharmaceuticals Inc. was researching a drug named tremacamra. This medication has since been shelved.

The data on pleconaril were not published in a peer-reviewed journal or presented at a conference, but rather released in a company press release, in accordance with Securities and Exchange Commission regulations but not necessarily standard scientific practice. Thus, there still seem to be some unanswered questions about how useful the drug might be.

"The impact on duration of illness [with pleconaril] is fairly modest," said Ronald Turner, MD, head of pediatric infectious diseases at the Medical University of South Carolina in Charleston. "But if it turns out to be a clinically useful reduction in severity, then that may be interesting."

The search for a medication that would address the cause rather than the symptoms of the common cold has long been complicated by the nature of the disease. A cold is caused by hundreds of viruses, and there is no simple test to determine who has what in a doctor's office before the prescription is written. Pleconaril, for example, is effective against colds caused by picornaviruses, but that family of viruses is responsible for only about half of all colds.

"There are no good diagnostics," said Dr. Turner. "And so you are going to have a fairly high failure rate."

There is also a question of economics and how to price a drug that is essentially competing against over-the-counter medications that do not require a doctor's visit.

"The impact of this drug on common-cold illness is less impressive when it's compared to over-the-counter cold medications, and even those have only modest benefit," said Dr. Turner. "The big issue is, how are they going to price this? You've basically got a fairly modest benefit against symptoms, and now you're going to require that these patients go to a physician and get a prescription. Whether people are going to be willing to do that remains to be seen."

Not for everyone

But ordinary cold sufferers are not expected to be the ones who benefit from an antiviral that combats the common cold, at least initially. Experts expect that populations most endangered by colds, such as asthmatics or the elderly, will be the ones to gain the most. Experts also expect that true benefit may not be in reducing the severity of a cold, but by reducing the rate of progression of the infection into other more serious conditions such as sinusitis or otitis media.

Experts also see potential from this medicine to reduce the pressures that contribute to antibiotic resistance. Millions of antibiotic prescriptions are currently written for patients with the common cold, most believed to be unnecessary and ineffective.

Several federal agencies and medical societies have been working on issues related to antibiotic resistance. The American College of Physicians--American Society of Internal Medicine issued guidelines in March saying that antibiotics were not needed for most respiratory tract infections, including colds, and that over-the-counter remedies and salt water gargles were the better choices for otherwise healthy adults.

"Up to 75% of antibiotics prescribed each year are associated with treating upper respiratory tract infections," said Sandra Adamson Fryhofer, MD, ACP-ASIM president. "Unfortunately, most of these are unnecessary."

Research on pleconaril is being submitted for possible presentation at the September meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy.

ADDITIONAL INFORMATION:

Why it's so common

1 billion Colds suffered in the United States annually
62 million Colds required medical attention in 1996
200 Viruses can cause the common cold

Source: National Institute of Allergy and Infectious Diseases

Weblink

Common Cold fact sheet from National Institute of Allergy and Infectious Diseases (http://www.niaid.nih.gov/factsheets/cold.htm)

ViroPharma Inc. (http://www.viropharma.com/)

Position papers on appropriate antibiotic use , Annals of Internal Medicine, March 20 (volume 134, issue 6) (http://www.annals.org/issues/v134n6/toc.html)