Increasing one's wealth in the stock market is very doable, but it typically doesn't happen overnight. Investors typically need to be patient and buy and hold shares of companies that can deliver solid returns in the long run. The biotech industry is a great place to look for such companies.

Drugmakers don't always make the most exciting investments, but the medicines they offer are critical to the well-being of patients, which can allow them to be successful over long periods. Let's look at two biotech stocks that could help make investors richer in the years ahead: Gilead Sciences (GILD 0.91%) and CRISPR Therapeutics (CRSP -1.98%).

1. Gilead Sciences

Gilead Sciences is a biotech giant famous for its leadership in the market for HIV drugs. But over the past few years, its revenue has been kept afloat thanks to its COVID-19 medicine, Veklury, as it encountered regulatory headwinds and failed to launch some products on the market. Now that the worst of the pandemic seems to be behind us, though, Gilead Sciences should be just fine.

In the fourth quarter, the company's revenue increased by 2% year over year to $7.4 billion. Gilead Sciences' top line, excluding Veklury, jumped by a robust 8% year over year. Gilead's Biktarvy and Descovy are its two leading HIV treatments. Sales of the former jumped by 15% year over year to $2.9 billion in Q4. Descovy's revenue came in at $537 million, 13% higher than the year-ago period.

Biktarvy's market share as of December exceeded 45% and grew by more than 3% compared to Q4 of the previous fiscal year. Gilead Sciences' HIV business will continue to rebound from its pandemic lows, especially now that the biotech recently added a new product to its arsenal. In December, Gilead Sciences earned U.S. approval for Sunlenca, a long-lasting HIV regimen.

This twice-a-year treatment is the first of its kind and will likely attract many eligible patients. Beyond its HIV unit, Gilead Sciences is also making serious headway in the cancer treatment market. In Q4, the company's oncology sales soared by 72% year over year to $614 million, a performance driven by the cancer drug Trodelvy.

Gilead Sciences' pipeline across its oncology and HIV units will continue to progress this year, with multiple ongoing phase 2 and phase 3 studies. In the long run, the company should earn new approvals and label expansions just as it has in the past. And Gilead's top-line growth rate will likely improve once the effects of Veklury on its financial results subside.

Gilead Sciences' dividend constitutes one more reason to buy its shares. The biotech just announced a dividend hike -- something it does habitually -- of 2.7%. The stock offers a yield of 3.48%, much higher than the S&P 500's 1.74%. In short, Gilead Sciences is a blue-chip stock with a strong business and solid dividend, which make it a solid pick for long-term investors.

2. CRISPR Therapeutics 

This year could prove crucial for CRISPR Therapeutics as it gets closer to becoming a commercial-stage company. Last year, the gene-editing focused biotech said it planned on submitting exa-cel to regulatory authorities in the U.S. and Europe together with its partner on these programs, Vertex Pharmaceuticals.

Exa-cel is an investigational gene-editing therapy that targets transfusion-dependent beta-thalassemia (TDT) and sickle cell disease (SCD). These two rare, blood-related conditions have few effective therapy options. Exa-cel could be a one-time curative treatment for both. The medicine has consistently shown excellent results in clinical trials, including ridding all SCD patients treated in a study of painful side effects of the disease called vaso-occlusive crises.

Exa-cel's solid results have earned it the attention of regulators in the U.S. and Europe, who have granted it the Fast Track, Priority Medicines, and Orphan Drug designations, among others. These are reserved for medicines that address an unmet need (Fast Track and Priority Medicine) or that could be a new effective treatment for a rare disease (Orphan Drug).

Regulatory agencies do not issue these designations carelessly. So, there is an excellent chance exa-cel will go on to earn approval, which would help validate CRISPR Therapeutics' platform. The company's gene-editing approach could help unlock more therapies for rare or difficult-to-treat illnesses. CRISPR boasts three other products in clinical trials, two of which target various forms of cancer and one of which could help treat type 1 diabetes by allowing patients to produce their own insulin.

CRISPR Therapeutics should continue to make regular pipeline progress with these programs. And once exa-cel hits the market and starts delivering profits -- 40% of which will go to CRISPR Therapeutics per its arrangement with Vertex -- the gene-editing specialist will have even more funds to push its current candidates through the finish line and advance others to clinical trials.

That's why, although not as well-established as Gilead Sciences, CRISPR Therapeutics is a solid option for long-term investors.