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Leading antiviral treatments have made Gilead Sciences (NASDAQ:GILD) more profitable than any of its Big Pharma peers, but the stock is trading at bargain-bin prices. Sales of its lead product have fallen in recent quarters, and investors are wondering if now is a good time to buy or stay on the sidelines. Here are a few charts to help you decide for yourself.

Bottom-line delivery

Although Gilead Sciences was already putting up big sales with leading HIV treatments, trailing revenues have more than tripled since its hepatitis C antiviral, Sovaldi, earned FDA approval at the end of 2013.

GILD Revenue (TTM) Chart

GILD Revenue (TTM) data by YCharts

At just $32.37 billion, Gilead's revenue over the trailing-12-month period is below five of the world's largest pharmaceutical companies, and less than half that of the world's largest healthcare conglomerate, Johnson & Johnson.

When it comes to the bottom line, though, Gilead Sciences has them all beat. With trailing net income of $16.35 billion, it has the largest bottom line in healthcare. In fact, among the 10 largest companies in the S&P 500, only five produced more profit over the past year.

Giving back

Rather than bloat up with enormous acquisitions, Gilead Sciences has been using its massive cash flows to increase shareholder returns through stock repurchases. While we all prefer to see a rise in the numerator used to calculate earnings per share, shrinking the denominator has the same effect.

Over the past four reported quarters, Gilead spent around $15.1 billion buying back about 154 million shares of its own stock. A 341.8% increase in quarterly net income since Sovaldi's approval less than three years ago is stunning, but shareholders' slice of quarterly profits have risen by a far more exciting 460.9% over the same period.

GILD Net Income (Quarterly) Chart

GILD Net Income (Quarterly) data by YCharts

That denominator is about to get even smaller. In February, Gilead's board authorized an additional $12 billion for share repurchases, and about $8.1 remained at the end of June. At recent prices that's enough to buy back about 100.7 million shares, or about 7.6% of the total outstanding.

In addition to repurchases, the company began paying a quarterly dividend of $0.43 per share in the second quarter last year. It's since raised the payout to $0.47 without increasing its overall obligation. Because of the reduced share count, Gilead spent about $7 million less making dividend payments in the second quarter this year compared with the same period last year, despite giving 9.3% more to each shareholder. 

Gilead's management has been on the receiving end of criticism for avoiding big acquisitions in favor of its own stock. To these critics I'd like to point out that Pfizer went down this road in 2009, purchasing Wyeth with $68 billion in cash, stock, and debt. Last year, Pfizer earned $1.13 per basic share, or $0.06 less than it earned the year before the Weyth acquisition. 

Pfizer's shareholders had it rough, but my heart bleeds for Merck & Co. investors. Its trailing EPS was about one-third higher before announcing a $41 billion acquisition of Schering-Plough in 2009 than it is today.

Crazy cheap

One of the biggest reasons Gilead has favored its own shares over other assets is their insanely low multiple. Incoming competition in the hepatitis C space has knocked Gilead's trailing earnings down to $11.35 per share from a peak of $11.91 at the end of last year, but the stock is still trading at about 7.1 times trailing earnings.

GILD EPS Diluted (TTM) Chart

GILD EPS Diluted (TTM) data by YCharts

Past performance doesn't guarantee future success, but Gilead's ability to grow in the face of competition surprised the market not long ago. Sovaldi-based combination pill Harvoni earned approval in October 2014, but pessimism about the its future took hold when AbbVie earned approval for its hepatitis C combo, Viekira Pak, a couple of months later. Gilead's trailing P/E ratio plunged below 14, as Harvoni wiped the floor with Viekira Pak.

Another competitor, Zepatier, from Merck has since entered the ring, but Gilead just launched its best hepatitis C combination yet, Epclusa. It's the only pill that can treat all six genotypes of the virus, and the competition pales in comparison.

The market clearly undervalued Gilead Sciences during the months following Harvoni's launch, and I think it's wrong again. This time the stock is so cheap, earnings could remain flat into eternity, and it would still provide market-beating returns over the long run.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.