Like many people, I'm rooting for Gilead Sciences' (NASDAQ:GILD) experimental drug remdesivir to be successful in clinical studies targeting COVID-19. There have been some early hints at positive results, but it's too soon to know for sure how safe and effective remdesivir will actually be in treating the novel coronavirus disease. 

In the meantime, I think that Gilead Sciences is a great stock to buy regardless of what happens with its coronavirus program. Here are three reasons why.

Smiling scientist holding a test tube with a rack of other test tubes

Image source: Getty Images.

1. A big new market opportunity 

Quite a few big drugmakers have made fortunes in the immunology market. EvaluatePharma ranks three immunology drugs in the top six best-selling drugs over the next four years. Gilead Sciences hasn't been a player in the immunology market yet. But that should soon change.

Gilead currently awaits U.S. and European regulatory approvals for filgotinib in treating rheumatoid arthritis. The big biotech is also evaluating the drug in clinical studies targeting several other immunology indications, including Crohn's disease, psoriatic arthritis, and ulcerative colitis. Filgotinib holds the potential to generate peak annual sales of $4 billion to $6 billion if approved for all of these indications, with around half of its total sales stemming from treating rheumatoid arthritis.

And filgotinib is just the start of Gilead's immunology hopes. Gilead paid $5.1 billion to gain access to Galapagos' entire pipeline and an increased stake in the smaller biotech. Two of Galapagos' immunology candidates that Gilead has already expressed interest in are in phase 2 clinical studies. It also has a late-stage experimental drug targeting idiopathic pulmonary fibrosis.

2. A continuing juggernaut

While Gilead should soon make its mark in immunology, the biotech remains a juggernaut in HIV. The company's first approved product treated an eye disease in patients with HIV. Gilead rose to success on the back of HIV drugs such as Atripla, Truvada, and Viread. 

Today, Gilead's HIV franchise boasts five blockbuster drugs. Biktarvy ranks as the leader in the group, generating sales topping $4.7 billion last year. It's a virtual shoo-in to soon become of the best-selling HIV drug of all time. 

More winners are likely on the way. Gilead is evaluating long-acting HIV capsid GS-6207 in a couple of phase 2 clinical studies. GS-6207 could be the future of Gilead's HIV franchise and potentially even top Biktarvy if it's successful in clinical testing. Gilead also could have an HIV cure or two waiting in the wings. The biotech is testing two experimental drugs, vesatolimod and elipovimab, in early stage clinical trials that just might be able to cure HIV.

3. A fantastic dividend

Most biotech stocks don't pay dividends. But Gilead isn't like most biotech stocks. 

Gilead Sciences initiated its dividend program in 2015. The company was making so much money that returning some of its profits to shareholders made sense. Over the past five years, Gilead boosted its dividend payout by 58%.

Its dividend yield now stands at 3.2%. That level was much higher, but Gilead's shares have jumped nearly 30% this year, causing the dividend yield to decline significantly.

There's no reason to worry about Gilead's dividend shrinking anytime soon. The company's payout ratio is below 60%. With the potential for improved earnings growth in the future from filgotinib and other new drugs, Gilead should be able to keep the dividends flowing and growing.

Lagniappe

I think that these three reasons are enough to justify buying Gilead Sciences stock all on their own. However, I worked for several years in New Orleans where there's a tradition of lagniappe -- giving a little something extra.

Another good reason to like the stock is the duopoly that it shares with AbbVie in the hepatitis C virus (HCV) market. Although its HCV franchise isn't a growth driver for Gilead, it does still make the company a lot of money.

Gilead is also a leader in oncology. Yescarta is the top cancer cell therapy and could pick up regulatory approvals for additional indications in the not-too-distant future. Gilead's acquisition earlier this year of Forty Seven should boost its position in the oncology market as well.

There's still a chance that Gilead could make a big splash in treating nonalcoholic steatohepatitis (NASH), an indication that some think could be a $35 billion market. The biotech has had some pipeline setbacks with its NASH program but has three drugs targeting the disease in phase 2 clinical testing.

And, yes, Gilead could be successful with remdesivir in treating COVID-19. While that would be great news for people across the world, the great news for investors considering Gilead is that the coronavirus drug truly is lagniappe for an already-promising stock.