Biotech companies CRISPR Therapeutics (CRSP 0.34%) and Vertex Pharmaceuticals (VRTX -0.06%) are often mentioned in the same sentence. That's because they have been partnering to develop a groundbreaking gene-editing therapy for a long time, and their efforts are about to pay off.

However, there are important differences between these two drugmakers. Vertex is a much larger company with proven innovative abilities, and it has generated strong and consistent revenue, earnings, and stock-market performance in the past decade. CRISPR is a much younger company with a much shorter track record, but could it one day become as successful as its larger partner?

A leap forward for CRISPR Therapeutics

Let's briefly consider how Vertex Pharmaceuticals achieved its success. The biotech company develops and markets therapies that treat the underlying causes of a rare disease called cystic fibrosis (CF), which affects patients' internal organs, especially the lungs. Vertex is the only company in this small niche, which grants it pricing power with patients and third-party payers. So even though there are only 88,000 patients in the areas it targets, Vertex has made a fortune.

CRISPR Therapeutics has a long way to go to get to Vertex's level of success, but the company is starting pretty well. Together with its larger collaborator, it recently earned approval for Casgevy in the U.K.

Casgevy is that gene-editing treatment the two entities have been working on for years, to treat sickle cell disease (SCD) and transfusion-dependent beta-thalassemia (TDT). These rare blood-related illnesses typically cause substantial financial and personal burdens to patients and their families, and there are few effective therapies available. For instance, TDT patients typically need regular blood transfusions.

Astonishingly, Casgevy is a one-time curative treatment that promises to rid eligible patients of the need for these transfusions, among other perks. The recent approval in the U.K. in treating both TDT and SCD is just the first -- more should follow suit in the rest of Europe and in the U.S.

Casgevy won't be the only game in town the same way Vertex's CF products are. It will face competition from Zynteglo in treating TDT and, potentially, from lovo-cel (which isn't yet approved in the U.S.) in SCD. Both were developed by Bluebird Bio, but there are a few things to keep in mind.

First, Bluebird Bio no longer operates in Europe, so its challenge will only come in the U.S. Second, Vertex's size and experience in negotiating deals with insurers will come in handy in helping it and CRISPR dominate this market against the small-cap Bluebird Bio. Vertex and CRISPR plan to target 32,000 SCD and TDT patients in Europe and the U.S. initially, a number that could rise to the hundreds of thousands if they manage to earn label expansions.

Third, Casgevy will almost certainly cost well over $1 million -- with a price of around $2 million considered more or less cost-effective. That means there is a massive market opportunity for CRISPR Therapeutics, even if it has to share the profits and costs associated with Casgevy on a 40-60 basis (it will get 40% of the profits) with Vertex Pharmaceuticals.

The future looks bright

CRISPR Therapeutics has a pipeline full of promising early- and mid-stage potential gene-editing therapies. The approval of Casgevy could be only the first step, allowing the company to bring in more funds for research and development. CRISPR should earn approval for more products in the next five years while generating solid sales from Casgevy.

Perhaps CRISPR Therapeutics won't have a monopoly on treating a single disease as Vertex Pharmaceuticals does in CF, but that would be a relatively superficial similarity. What's more important is whether CRISPR Therapeutics can deliver the kinds of returns Vertex has over the long run. And so far, the evidence suggests that it can.

To be clear, that's not a certain bet -- there is hardly such a thing on the stock market. However, CRISPR Therapeutics has now proven that it can develop a breakthrough therapy, and is on its way to doing so again. The biotech's financial results will also start ramping up relatively soon. So, if you're afraid that you missed the boat by not investing in Vertex Pharmaceuticals when it was smaller, it's worth seriously considering adding shares of CRISPR Therapeutics to your portfolio.