There are reasons to be wary of the stock market right now. Chief among them is the fact that the economy continues to be somewhat uncertain, making it difficult to predict how things will develop in the next year. But the short-term prospects of equities are almost always challenging to predict.

Although the current environment has some particularities, it's always essential to focus on the long run when looking for stocks in which to invest. With that said, let's consider two biotech stocks, neither of which is a household name, that could deliver solid returns over the next five years and more: Exelixis (EXEL -3.50%) and Sarepta Therapeutics (SRPT 1.64%)

1. Exelixis 

Oncology is one of the most fiercely competitive therapeutic areas in the biotech industry. Exelixis, a mid-cap biotech, is just a small player in the field. However, it has a major claim to fame. The company's crown jewel, Cabometyx, is the top-prescribed tyrosine kinase inhibitor -- a kind of therapy that specifically targets and attacks cancer cells -- in renal cell carcinoma (RCC, a type of kidney cancer) and second-line hepatocellular carcinoma (HCC, a variety of liver cancer).

Exelixis has been riding Cabometyx for years, and the company's ongoing programs targeting new indications for this medicine and its ability to develop new cancer treatments constitute solid reasons to invest in the stock. Cabometyx is still being tested in dozens of clinical studies. The company expects two major data readouts from phase 3 trials for its crown jewel later this year.

Meanwhile, its most advanced candidate not named Cabometyx is Zanzalintinib. Exelixis is running a duo of late-stage studies for this product targeting advanced colorectal and kidney cancer. In both cases, there are few treatment options once the illnesses have metastasized. Exelixis is also running many more early-stage trials.

The company has entered into agreements to co-develop cancer therapies with other companies, including privately held Cybrexa Therapeutics and Sairopa B.V. These collaborations could lead to important new approvals down the line. In the first quarter, Exelixis' revenue increased by almost 15% year over year to $408.8 million.

Its net earnings per share declined to $0.12 from the $0.21 net income per share reported during the year-ago period due to increased expenses, especially research and development-related ones. Investors should welcome the increased R&D spending. Exelixis ended the first quarter with $2.1 billion in cash and investments, which isn't bad for a mid-cap biotech company.

Exelixis should be able to enlarge its portfolio and decrease its reliance on Cabometyx in the next few years, leading to stronger financial results and stock market performances. 

2. Sarepta Therapeutics 

Rare diseases expert Sarepta Therapeutics is best known for its medicines that target Duchenne muscular dystrophy (DMD), a rare, genetic, progressive neuromuscular disorder. With three products that target this illness already in its portfolio, the company is close to adding another one. On May 12, a panel of experts convened by the U.S. Food and Drug Administration (FDA) voted 8 to 6 in favor of the agency granting accelerated approval to SRP-9001, a potential DMD medicine Sarepta is co-developing with Roche.

While the FDA does not always follow the recommendation of these experts, it usually does. So this is a good sign for SRP-9001. It could help Sarepta improve its already solid financial results. In the first quarter, its revenue increased by 20% year over year to $253.5 million. The biotech isn't profitable yet; its adjusted loss per share of $0.97 in the first quarter was worse than the $0.56 loss per share reported in the first quarter of the previous fiscal year.

However, Sarepta Therapeutics estimates peak annual sales of $4 billion for SRP-9001 if it does earn approval. In addition, the company has many more pipeline candidates, some of which still target DMD. The company is also going after other rare illnesses, such as limb-girdle muscular dystrophy, a group of muscle-related diseases. Sarepta has more than 40 programs in its pipeline.

Although it is not one of the most prominent biotechs around, its focus on rare diseases, an already existing portfolio of medicines that generate solid revenue, and partnerships with a larger drugmaker in Roche make Sarepta Therapeutics an attractive long-term prospect.