Now is a great time for long-term investors to load up on some quality growth stocks. Although the bear market may be a frightening time to buy shares, there are many quality businesses that are safe to hang on to for the long haul.

A couple of top growth stocks you can buy today include Vertex Pharmaceuticals (VRTX 0.78%) and Alphabet (GOOG -0.02%). Here's why you shouldn't expect the growth opportunities for these businesses to run out anytime soon.

Vertex Pharmaceuticals

Vertex has been one of the better growth stocks to be holding this year. Up 30% thus far, the stock has dwarfed the S&P 500, which is down 20%. And it still could have much more room to rise in value.

That's because Vertex is a unique stock that offers growth investors the best of both worlds: solid results today, along with a promising future. Today, it dominates the cystic fibrosis (CF) market with multiple drugs, including top-selling product Trikafta, which generated $5.7 billion in sales last year while growing by 47% year over year. It's still in its early growth stages as regulators in the U.S. only approved it for children from the ages of six to 11 in June 2021.

In the longer term, it has a gene-editing therapy in exa-cel which could generate billions in revenue down the road. The healthcare company has been working on that with its partner CRISPR Therapeutics, and the two plan to apply for exa-cel's regulatory approval later this year.

What makes me confident that the business is unstoppable is that Vertex is incredibly profitable, reporting net income of more than $2.4 billion over the trailing 12 months on revenue of $7.9 billion, equating to a profit margin of over 30%. It also generates billions in free cash that can enable it to invest in its future growth.

Earlier this month, Vertex announced it would be paying $320 million to acquire cellular therapy company ViaCyte for $320 million in an all-cash deal. Vertex hopes the acquisition will help accelerate its development of VX-880, a multiple cell replacement therapy that could become a functional cure for type 1 diabetes (it's currently in phase 1/2 trials).

With so much potential, it's easy to see why Vertex can continue delivering strong returns for investors for years to come.

Alphabet

Internet giant Alphabet is another cash-rich business that investors can feel comfortable adding to their portfolios. Its free cash flow over the trailing 12 months is a whopping $69 billion -- some three times the $22.8 billion it generated in 2018. Cash creates potential and allows businesses to pursue growth opportunities. And Alphabet is among the most active on that front.

The company isn't content just focusing on its Google search engine or video-sharing platform, YouTube. In 2020, it completed a $2.6 billion acquisition of data analytics company Looker. Last year, it closed on its $2.1 billion acquisition of smartwatch maker Fitbit. Most recently, Alphabet announced plans this year to buy cybersecurity business Mandiant for $5.4 billion.

Alphabet's robust business continues to find ways to get bigger. And that wheeling and dealing has been working well for it as the company's financials look better than ever. Last year, Alphabet reported a profit of $76 billion that was more than twice the size of the $34 billion it posted two years earlier.

The tech company has uncovered many more growth opportunities thanks to its strong results, and there's no reason to expect that to change in the foreseeable future, which is why Alphabet makes for an excellent buy-and-hold investment.