Source: National Institutes of Health.

While the broader market indexes have danced around the flat-line all year long, the SPDR S&P Biotech ETF has advanced by more than 35%! The biotech sector is absolutely on fire, and investors with an appetite for risk (both low and high) have wanted a taste of this phenomenal growth. 

With this is mind, we asked three of our healthcare analysts which biotech stock could be worth buying in August. Here's what they had to say. 

Todd Campbell 
Any number of things can cause highly-volatile biotech stocks to pop and drop, and that makes picking a top stock to buy in this industry at any given point in time a bit challenging. But for my money, picking up shares of Gilead Sciences (NASDAQ:GILD) in August may be smart.

Source: Gilead Sciences.

The company is the market share leader in both HIV and hepatitis C treatment, and it just reported blockbuster second quarter financial results that led to it boosting its full year sales outlook by another $1 billion. It's also on tap to announce trial results for its next generation hepatitis C cocktail soon, and if those results are positive Gilead Sciences could have yet another blockbuster hepatitis C drug on its hands to complement Sovaldi and Harvoni, two drugs that posted a combined $4.9 billion in sales last quarter.

Because Gilead Sciences boasts a bulletproof balance sheet and could have another top seller on the market as early as next year, it's one stock that could be worth stashing away in portfolios sooner rather than later.

Cheryl Swanson 
's (NASDAQ:ILMN) stock just got a 9% haircut after the company reported a narrow revenue miss on earnings. For my money, the military buzz cut Illumina is now sporting makes this market leader in genomics an even better bet for high risk/high reward investors.

NextSeq 550. Source: Illumina.

Revenue came in at $539 million, below the expected $541.77 million. Compared to Q2 last year, it was still a 21% increase. And as Keith Speights pointed out, the company's revenue would have been 25% higher if currency rates had remained constant.

Government cutbacks and foreign exchange headwinds are taking a bit of wind out of Illumina's sails. But new product introductions in liquid biopsies (which are cheaper, faster, and less invasive than tissues biopsies) should expand Illumina's cancer market considerably. In addition, the company just signed a commercialization agreement with NeogenThe deal could lead to higher revenues for Illumina's lagging array business.

While this stock's not a bargain at 60 times 2015 EPS, with an 80% market share it not only dominates, but its technology is advancing so fast no one can catch up. But what really excites me about Illumina is the rise of personalized medicine. Major cancer centers such as Sloan Kettering are already using DNA-sequencing systems to pick treatment. As that trend gains steam, Illumina seems well poised to keep building wealth for its investors.

Sean Williams 
My colleagues have offered up two biotech behemoths that offer substantial profits and quite a bit of downside protection. So, to balance that out, I'm digging into something a little bit riskier in the small-cap realm and suggesting you consider dipping your toes into the water with Endocyte (NASDAQ:ECYT).

If the name sounds familiar, it's because Endocyte shares were absolutely destroyed in 2014, falling from a peak of $33-plus in March to just $5 and change by May. The culprit was the failure of vintafolide (brand-name Vynfinit) in a late-stage study as a treat for platinum-resistant ovarian cancer. The failure caused Endocyte's collaborative partner Merck to give up its worldwide rights to the drug and walk away from the deal. With Merck gone, Endocyte became fully exposed to the costs of developing its pipeline, which is rarely a good thing for a wholly clinical-stage company.

Source: Merck.

What intrigues me about Endocyte is its relatively deep development pipeline and its substantial cash runway.

Keep in mind that experimental therapies have the potential to fail in one cancer and succeed in others. Vynfinit may still be useful in treating non-small cell lung cancer. Even if it's not, Endocyte has dose-escalating studies ongoing for EC1456 in various solid tumors and EC1169 as a treatment for prostate cancer. All told, Endocyte has six clinical and three preclinical studies ongoing. That may not sound like a lot, but for a $200 million market value biotech it's pretty substantial.

Then there's Endocyte's $196.8 million in cash, cash equivalents, and investments as of the end of the first-quarter. Based on Endocyte's market value this past Friday, you're looking at its pipeline being valued at just $20 million over cash. Understand that Endocyte will continue to burn cash as its research and trials continue, but it still anticipates ending the year on the plus side of $155 million in cash. In other words, you have some semblance of a downside buffer in Endocyte's cash.

It's certainly a riskier bet than Gilead or Illumina, but calculated biotech investors would be wise to dig more deeply into Endocyte.