It's not the easiest of task to find large biopharmaceutical companies with stocks trading at low valuations. But there are some relatively inexpensive alternatives out there.

Teva Pharmaceutical (NYSE:TEVA), Mylan Pharmaceuticals (NASDAQ:MYL), and Gilead Sciences (NASDAQ:GILD) are three big pharma stocks that are ridiculously cheap right now. The main question for investors, though, is: Do these stocks deserve to stay in the bargain bin?

Three scientists working in a lab

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Teva: Stock slumping amid a streak of bad news

Teva's share price has fallen over 30% in the last 12 months. After this sharp decline, the drugmaker's stock trades at less than eight times forward earnings estimates. However, Teva faces some serious headwinds. 

The company's former CEO, Erez Vigodman, suddenly resigned earlier this month. Vigodman had led Teva since 2014. His departure came in the midst of lower profits and allegations that Teva had bribed officials in several countries. 

Replacing Vigodman could be the easiest hurdle for the company to overcome. Teva recently received another blow when a U.S. District Court ruled that four of its key patents for Copaxone 40 mg/mL were invalid. This could open the door to additional generic competition for the multiple sclerosis drug, which generated almost one-fifth of the Teva's total revenue last year.

There is some good news for Teva, though, that could help the company grow earnings. The 2016 acquisition of Actavis Generics from Allergan (NYSE: AGN) is already helping Teva's top and bottom lines. 

Mylan: Bouncing back

Another major generic drugmaker, Mylan, experienced its own share of bad news last year. Mylan came under attack for drastically increasing the prices of its EpiPen auto-injectors. Its stock dropped more than 20% before regaining much of the losses. Mylan now trades at just under eight times forward earnings estimates.

Mylan has received only good news in recent months. The company launched a generic version of EpiPen in December that was 50% cheaper than the brand version. Mylan announced the acquisition of global rights to the Cold-EEZE brand cold remedy line in January. The U.S. Food and Drug Administration (FDA) accepted Mylan's Biologics License Application (BLA) for a biosimilar to bone marrow stimulant Neulasta only a few days ago.

Teva's pain could also be Mylan's gain. It was Mylan that came out victorious in the court ruling that invalidated Teva's patents on Copaxone. The company has been on a roll.

Wall Street analysts project that Mylan's earnings will grow by an average annual rate of almost 9% over the next five years. Although that's lower than what the company has achieved in recent years, this growth rate makes Mylan's current valuation appear to be inexpensive.

Gilead Sciences: Looking for a catalyst

Gilead Sciences' stock currently trades at less than nine times forward earnings estimates. That's the highest level among these three big pharma stocks. Unlike those of Teva and Mylan, Gilead's revenue and earnings are expected to slip over the next few years.

The primary issue for Gilead relates to plunging sales for its hepatitis C virus (HCV) franchise. Gilead has become in large part a victim of its own success. The company's HCV drugs cured so many patients that there aren't as many sick patients left.

Although Gilead's HIV drugs continue to perform strongly, the biotech needs additional help to restore its growth. That help is likely to come from acquisitions. 

CEO John Milligan has indicated that Gilead Sciences is aggressively looking for a catalyst this year in the form of an acquisition to boost revenue. Money shouldn't be a problem. The company has a strong cash flow thanks to its HCV and HIV drugs and boasts a cash stockpile of more than $32 billion, including cash, cash equivalents, and marketable securities.

Two out of three ain't bad

All three of these big pharma stocks are ridiculously cheap. I suspect that a couple of them won't remain cheap for much longer. 

Mylan seems likely to keep the rebound going. The company continues to strengthen its position in the generic-drug market. Gilead Sciences will almost certainly make one or more acquisitions in the not-too-distant future that will change its outlook. 

I'm not so sure about Teva, however -- at least not in the near term. Teva could be a decent investment over the long run, but currently has some big hurdles to overcome. I expect Teva to remain in the bargain bin for a while, with Mylan and Gilead rewarding investors over the next couple of years. Two out of three ain't bad.

Keith Speights owns shares of Gilead Sciences. The Motley Fool owns shares of and recommends Gilead Sciences. The Motley Fool recommends Mylan and Teva Pharmaceutical Industries. The Motley Fool has a disclosure policy.