For symptom relief, better than chicken soup

Medicine: Two new drugs promise to stop a cold in its sneezing tracks, not just mask symptoms.

Health & Fitness

February 03, 2002|By Linda Marsa | Linda Marsa,Special to the Sun

As we cough, sneeze and sniff our way through the cold season, it may comfort us to know that technology has finally caught up with our expectations. Two new medicines promise to cure the common cold.

The drugs, one of which may be available within the next several months, stop cold viruses in their tracks -- not just mask symptoms, as current remedies do. Patients who have taken them report feeling better almost immediately, sleeping through the night and having to use fewer tissues on the cold's hallmark runny nose.

"These drugs are part of a revolution in the treatment of virally caused diseases," said Catherine Laughlin, chief of virology at the National Institute of Allergies and Infectious Diseases in Bethesda.

Researchers fighting cold viruses have benefited from the massive research effort to combat AIDS, a viral disease caused by HIV, and the development of tools that allow them to peer deep inside a cell. With these advances, they've learned how to overcome two major hurdles in devising an effective cold medicine.

The first hurdle was that viruses are tough to hit with any accuracy because they insinuate themselves inside cells. In contrast, bacteria colonize in bodily fluids and cavities, making them easy pickings for antibiotics.

Added to this was the fact that there wasn't just one kind of pesky microbe to keep at bay. A couple of different families of viruses, including rhinoviruses and coronaviruses, cause the majority of colds.

"The challenge has been to find a single drug that would work against the different families of viruses as well as one that would precisely target the virus without hurting the cells," Laughlin said.

Viruses are tiny capsules of protein that are much smaller than bacteria -- the common analogy is that if a bacterium is equivalent to the size of a human, then a virus would be as large as an arm. Unlike almost any other living organism, viruses are incapable of reproducing themselves.

Instead, they must slither through a cell's wall and commandeer the host's genetic machinery, using it to churn out identical copies of themselves.

The two cold remedies now in the pipeline prevent this replication without causing any apparent collateral damage in the host cells.

Each drug attacks the virus at a different stage of its life cycle but ends up with the same result -- the virus can't make copies of itself. One drug, called AG7088 for now because it's in an early stage of development, is a protease inhibitor similar to the drugs that revolutionized AIDS treatment.

"The protease inhibitor halts the action of a key enzyme that the virus needs to replicate," preventing the virus from squirting its genetic information into the cell's DNA, Laughlin said.

The drug, a nasal spray that is inhaled several times daily, is made by Agouron Pharmaceuticals, a La Jolla, Calif., biotechnology company. It is now in the middle of the second phase of human testing, according to an Agouron representative. (New drugs normally go through three phases of human trials before they're submitted for FDA approval.)

Preliminary tests show that AG7088 reduces cold symptoms, while people who received a placebo or dummy pill experienced a full-blown cold. AG7088 isn't expected on the market for several years.

The other new medicine is Picovir, which is awaiting FDA approval and may be available in your local pharmacy within the next year. Taken in a pill form, Picovir prevents the cold virus from entering the cell.

Scientists discovered this approach because of the development of an X-ray in the mid-1980s that had enough magnification to take detailed photographs of viruses. The X-rays revealed that picornaviruses, of which the cold-causing rhinoviruses are one, have a deep pocket or canyon that runs across the viral surface, or coat. Picovir wedges firmly inside this pocket, like a plug in a drain, and stops the virus from shedding its outer coating. If it can't shed its coat, the virus can't penetrate the cell membrane and infect the cell.

"We didn't really know if blocking that one site would interfere with the life cycle of all these viruses," said Mark McKinlay, vice president of research and development for ViroPharma, the Exton, Pa., company that makes Picovir. "But after much trial and error, we discovered a compound that locks tightly on to that site. The more tightly the drug binds, the greater the potency of the drug."

In drug tests of more than 4,000 patients, people felt less miserable within 24 hours, and those who received the drug recovered a day sooner than the control group.

Picovir may prove most beneficial for people who are more vulnerable to a viral onslaught -- the elderly, people with defective immune systems or those who suffer from ills like asthma.

Still, there are a few drawbacks that may stand in the way of Picovir or AG7088 becoming true blockbusters. Though they reduce the severity and duration of cold symptoms -- without the unpleasant side effects of current medications -- they aren't instant cures.

By the time you start feeling sick, you've been under siege for two to three days, which means the virus has established a firm toehold in the body. To get the maximum benefit from an antiviral medication like Picovir, you need to get a prescription the minute you start feeling sick.

Linda Marsa is a reporter for the Los Angeles Times, a Tribune Publishing newspaper.

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