Vertex Pharmaceuticals (VRTX 2.38%) is a growing pharmaceutical company with a robust cystic fibrosis (CF) business that generated nearly $10 billion in revenue last year. While there is still more room for the business to get bigger, Vertex is already at a sizable market cap of $100 billion. Does this stock have enough runway to generate significant returns and help you become a millionaire in the long run?

By expanding its scope, Vertex also increases its upside

Vertex is more than just a CF company, and that's why many growth investors remain bullish on its prospects -- they know there are more growth catalysts out there. Vertex's growth opportunities take the company down multiple avenues, including a non-opioid pain medication that has shown promise in clinical trials.

VX-548 is a non-opioid treatment for pain which could be a game changer for the healthcare industry, giving patients a way to address pain with much less fear of getting addicted to opioids. The company plans to apply for regulatory approval this year. At its peak, VX-548 may generate $5 billion in annual revenue for Vertex.

This month, Vertex also announced plans for its largest acquisition: A $4.9 billion cash purchase of Alpine Immune Sciences. It's a clinical-stage company that generates revenue primarily from collaborations. What's appealing to Vertex is the prospect of a treatment for IgA nephropathy, a chronic kidney condition. Alpine's drug for that condition, povetacicept, has been progressing and may begin late-stage trials later this year. It offers Vertex a way to strengthen and further diversify its portfolio.

Earlier this year, Vertex also received positive news about a gene therapy it has been developing with CRISPR Therapeutics -- Casgevy. The U.S. Food and Drug Administration approved Casgevy as a treatment for transfusion-dependent beta thalassemia. Late last year, the treatment was also approved for sickle cell disease.

These developments and new products can help strengthen Vertex's growth potential. This year, the company anticipates that its product revenue will total between $10.55 billion and $10.75 billion, rising by a relatively modest 8% at the midpoint. In 2023, its growth rate was 11%.

Does Vertex's high valuation make it too late to invest in the stock to earn a big return?

Vertex's stock currently trades at 29 times its trailing earnings. That's not a steep multiple for a good growth stock, and it's even cheap compared to the healthcare industry, where the average earnings multiple for the Health Care Select Sector SPDR Fund is 32. There's little doubt that Vertex can still be a good investment at its current price, but the big question is whether it can generate the type of returns you would need to make you a millionaire.

I think it's fair to assume most investors are not going to be investing six figures into a stock. Even $50,000 might be a bit rich to put into one investment. Let's assume that you're planning to invest around $25,000. That's a significant enough amount when you have confidence in the business and its operations. Vertex, after all, has a highly profitable business -- it generates profit margins in excess of 35%. At the same time, it has some solid growth prospects. This is the type of stock where a large investment may be justifiable.

But for a $25,000 investment to grow to $1 million, you'd need Vertex's stock to be a 40-bagger. That's a tall task for any company, especially one that's already at a market cap of $100 billion. If Vertex were to grow to 40 times its valuation, you would have to assume that it would blow by $1 trillion and eventually become a $4 trillion stock.

No stock in the world has a valuation that high today. In 20 or 30 years, higher valuations are likely to be more common. But even then, you would need to assume that Vertex will be among the most valuable companies in the world. It's a bit of a stretch, to say the least.

While the company is growing, it doesn't possess an asset that suggests it is going to transform the healthcare industry and generate significant profit and revenue growth for the business for years to come. That's why the odds of this being a millionaire-making investment look low -- unless you invest a whole lot more money.

Vertex Pharmaceuticals can be a good buy if you temper your expectations

As long as you aren't setting your expectations too high for Vertex, given its modest valuation and increasingly diverse portfolio of assets, this can make for an excellent long-term investment. It may not be able to replicate the 500%-plus returns it has generated over the past 10 years, but there's still room to make a great return from Vertex in the long run.