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Biotech stocks tend to be riskier than average, as the sector is full of companies that have yet to generate any revenue, let alone profits. Many stocks in the sector accordingly have huge volatility, making it feel sometimes as if any investment made in the space demands constant monitoring.

However, not every biotech stock is cut from the same cloth, and there are a handful of companies that are so well diversified that you can safely invest in them without having to follow their every move. Knowing that, we asked our team of Motley Fool healthcare contributors to highlight a biotech stock that they feel doesn't require constant monitoring. Read on to see which stocks they selected and judge for yourself if any of them deserve a spot in your portfolio.

Brian Feroldi: I think Gilead Sciences (GILD 0.28%) is an ideal choice for investors who are interested in the biotech sector but lack the time to constantly monitor the company's every move. Gilead Sciences is so big and its pipeline so large that investors can comfortably buy a few shares and have confidence that the business will take care of itself.

Gilead's stability stems from its commanding position in two multibillion-dollar markets, HIV and hepatitis C. We'll find out soon full-year numbers for 2015, but it's looking like the company should report more than $32 billion in sales over the past year, thanks to its dominant position in these two areas.

Gilead's not resting on its laurels, either. Gilead boasts a huge pipeline of 26 clinical programs, with more being added every year. This deep pipeline, mixed with the company's successful track record, should give investors confidence that at least a few blockbuster drugs are coming in the years ahead. 

Image source: Gilead presentation.

One product candidate that looks particularly promising its Gilead's pan-genotype hepatitis C drug, which is currently pending regulatory approval. If approved, this new drug will eliminate the need for patients to get genotype testing before initiating therapy, which could prove to be a game-changing innovation, since many emerging markets lack the infrastructure to genotype their patients. A single pill would instead treat all six types of hepatitis C and in turn would probably greatly extend Gilead's market-leading position. With the the World Health Organization estimating that 180 million patients around the world need treatment, Gilead looks poised to continue to capture its fair share of that huge market.

Gilead is also using its enormous financial strength to reward shareholders, as it regularly buys back gobs of shares and offers up a dividend that currently yields 1.9%. Add in the fact that the company is headed by John Martin, one of the smartest CEOs in the business, and that the stock trades for less than 9 times earnings, and I think that Gilead Sciences is as close as it gets to a biotech stock that doesn't require constant attention.

Selena Maranjian: Many biotechnology companies demand close attention because their futures rest on just one or two drugs still in development. Biotech giant Amgen (AMGN 1.11%), though, requires little babysitting because it has plenty of approved drugs selling in the market, as well as a generous array of candidates in its pipeline.

Indeed, that pipeline recently featured a dozen drugs in phase 3 testing, meaning they're reaching the finish line of a multi-year development process. About 10 drugs were in phase 2, with more than a dozen in phase 1. Not all will turn out to be winners, of course, but some will. Of particular interest is that Amgen is a leader in the promising field of biosimilars, which are generic versions of biologic drugs. The company's net profit margin of roughly 30% is a bit mind-boggling, too, meaning that with annual revenue topping $21 billion, Amgen gets to keep more than $6 billion in profit.

Amgen has some big winners. It reports its fourth-quarter results soon, but in its third, it posted total sales of about $1.5 billion for Enbrel, $1.3 billion for Neulasta, and about $500 million each for Epogen and Aranesp. There are also high hopes for its recently approved LDL-lowering cholesterol medication Repatha.

Best of all, despite its many virtues, Amgen stock isn't significantly overvalued these days. Its recent P/E ratio is in line with its five-year average P/E of 18, and its forward-looking P/E of 12 is well below that. Better still, it pays a dividend that yields nearly 2.6%. That figure has more than doubled over the past three years, with a 27% increase announced in December. Its payout ratio below 40% suggests plenty of room for further growth.

Sean Williams: If you're interested in a biotech stock you can simply set and forget without the need for constant babysitting, I'd suggest taking a gander at Celgene (CELG)

In my opinion, Celgene has all three aspects of growth you'd look for when evaluating a biotech company. First, Celgene has the ability to grow organically, which is often what Wall Street values most. It has four drugs on pace to deliver $1 billion (or more) in sales in 2016. This list includes multiple myeloma blockbuster Revlimid, which could deliver $7 billion in sales by 2017; Pomalyst, another multiple myeloma treatment; cancer drug Abraxane; and anti-inflammatory pill Otezla. Many of its key therapies have huge label expansion opportunities, which should fuel double-digit percentage sales growth through at least 2020, and perhaps much longer.

Celgene can also grow through collaborations. The company has more than 30 ongoing partnerships on its books that range from oncology to immunology and inflammation. By effectively outsourcing some development via licensing, Celgene has found an innovative way to keep its research and development costs down while maximizing its spending on only the most promising drugs (i.e., by offering development, regulatory, and sales-based milestones to its partners). 

Finally, Celgene can grow by acquisition. It acquired Receptos for $7.2 billion in 2015 to get its hands on ozanimod, an experimental next-generation multiple sclerosis treatment that's been pegged to have peak annual sales potential of $4 billion to $6 billion. The move further helps diversify Celgene's pipeline away from its heavy reliance on Revlimid. 

Adding icing to the cake, Celgene also removed shareholders' biggest cloud of uncertainty by forging a deal with generic-drug developers regarding Revlimid. Although Revlimid's patent protection extends into 2027, it'll allow Natco Pharma to begin producing a small number of generics in March 2022, with a staggered increase every subsequent March through 2025. Still, less than a third of all Revlimid capsules produced should be generic through 2025. Beginning in late January 2026, generics will enter the market fully. This situation should allow for strong cash generation through the mid-2020s.