Editor’s Note: In last week’s issue of Money & Medicine, we inadvertently cited Seattle Genetics’ (NSDQ: SGEN) quarterly revenue when referring to its cash on the balance sheet. Rather than $64 million, the company actually held a substantial $364 million in cash as of the end of December.

When most people are told they have a potentially life-threatening illness, their first instinct is to seek immediate treatment. But these days, a growing number of hepatitis C (HCV) sufferers are opting to delay treatment.

HCV is a virus that mainly affects a patient’s liver, causing scarring and cirrhosis, which can eventually lead to liver failure or make a patient much more likely to develop liver cancer. It’s most often contracted through intravenous drug use or improperly sterilized medical equipment, or in some parts of the world, unscreened donor blood.

At present, it is estimated that there are about 4 million HCV patients in the US and as many as 200 million around the world.

While most of those who have access to proper medical care will ultimately be cured of the virus, many of them will suffer an unpleasant array of side effects during treatment, which involves taking a type of drug known as interferon.

Interferons are proteins made by cells that are released when viruses, tumors, bacteria or other pathogens are present. They impede the ability of most pathogens to reproduce. They also serve as a systemic warning system; when an infected cell dies, the interferon it releases warns nearby cells that an infection is present, basically priming the body’s natural defenses.

Interferon is widely used to treat numerous illnesses–including HCV–and has proved to be extremely effective. But the high level of interferon necessary for effective treatment can also cause flulike systems, including fatigue, headaches and body aches, and nausea. It can also cause fever, diminished appetite, hair loss, depression, and poor sleep.

Since the side effects of treatment are often perceived as worse than the disease itself, particularly if it’s been diagnosed early and hasn’t yet caused any significant liver damage, a growing number of patients are avoiding treatment. Because the disease typically progresses fairly slowly, often taking decades to do any real damage in patients who are otherwise healthy, many patients are delaying treatment with the hope that a new class of HCV treatments will become available.

In fact, drug manufacturers are aggressively competing to develop the next generation of treatments for this disease.

Gilead Sciences (NSDQ: GILD) currently has an experimental drug called sofosbuvir in phase III clinical trials. The drug is a nucleotide analogue inhibitor, which means that it interferes with a virus’s ability to produce ribonucleic acid (RNA). Viruses propagate themselves by inserting RNA into a normal cell to “trick” it into producing the virus itself, instead of healthy cells.

Thus far, trials have shown that sofosbuvir has an extremely high virological response rate. In fact, when combined with another of Gilead’s experimental drugs called ledipasvir, the response rate rises as high as 100 percent, even in patients who haven’t responded to prior treatment. Ledipasvir is a polymerase inhibitor that also acts to prevent HCV from replicating itself.

AbbVie (NYSE: ABBV), which Abbott Laboratories (NYSE: ABT) spun off late last year, is also working on its own HCV treatment in a separate class of drugs known as interferon-free combination treatment.

While AbbVie’s drug is also in late-stage trials, Gilead’s compound appears poised to hit the market first, possibly sometime next year. AbbVie’s treatment isn’t likely to become available in the US until sometime in 2015, and so far doesn’t appear to have achieved as impressive results in testing.

Given that patients are delaying HCV treatment in anticipation of new drugs, these treatments have huge pent-up demand, which is a good sign for those companies developing them. I expect both drugs will ultimately be approved, particularly since they are in two different classes and provide another option for patients who may only respond well to one of them.

But I suspect Gilead’s sofosbuvir/ledipasvir combination will be a blockbuster right out of the gate, thanks to its high efficacy and first-mover advantage. By contrast, AbbVie will essentially be playing catch-up by the time its drug hits the market.

For now, Gilead’s stock doesn’t appear to have caught much of a tailwind from anticipation of this potential blockbuster. While the drug could still hit a snag in the regulatory process, the positive data from the clinical trials augur well for its approval.