I invest in FTSE 100-listed stocks, but when I want greater exposure to growth, I tend to look to the US markets.

Obviously, building the perfect portfolio for my age group and risk profile requires me to pick my stocks carefully. And by investing in US markets, I have much greater choice when it comes to growth-oriented investments.

So here’s one incredible growth stock that’s actually dipped in recent weeks. It’s gene therapy leader CRISPR Therapeutics (NASDAQ:CRSP).

What is gene editing?

Gene editing is a novel technology that offers us the opportunity to treat a range of illnesses that were previously untreatable and gives us a new tool to tackle conditions like cancer and heart disease.

CRISPR Therapeutics uses a gene-editing technology with the name’s acronym standing for ‘clustered regularly interspaced short palindromic repeats‘.

Inspired by bacteria’s built-in editing tools, the technology used by this Swiss firm allows scientists to design custom-guide sequences that precisely target specific regions of DNA.

It’s incredibly complex, utilising RNA and a Cas9 — CRISPR-associated protein 9. The RNA’s job is to recognise the target DNA and Cas9 snips it at the right juncture.

After the snip’s been made, scientists can then add or remove bits of genetic material, and the cell’s repair machinery takes over, patching things up.

There are still plenty of things we don’t know about CRISPR treatments, but trial data suggests it’s safe and effective. CRISPR Therapeutics isn’t the only company using gene editing therapies, but it’s the first to market.

It’s also worth noting that peer Beam Therapeutics uses something called base editing technology. It’s more nascent, but supposedly safer as it only modifies a single chemical unit (a base) within the DNA code.

First to market

Early CRISPR treatments have targeted sickle cell disease (SCD) and beta-thalassemia. Both SCD and beta-thalassemia are caused by mutations in a single gene.

This makes them well-suited for CRISPR’s function of editing specific DNA sequences. In fact, SCD is caused by a single, well-defined and traceable mutation in the beta-globin gene.

And CRISPR Therapeutics’s first treatment, which it owns in partnerships with Vertex (40%/CRISPR and 60%/Vertex) does indeed treat these two illnesses.

Understanding the exact commercial value of this treatment isn’t easy. It’s received regulatory approval in the UK, US, EU, and Saudi, among other places — first-to-market along with bluebird bio — but the next step is getting healthcare providers to pay for it.

I’ve seen estimates suggesting the treatment, priced at $2.2m a patient, could be worth around $70.4bn based on an initial patient cohort of 32,000 sufferers.

The company recently received a boost on reports that the US Centers for Medicare and Medicaid Services could received enhanced payments under proposed guidelines in an effort to encourage more innovation in the space.

The drawback is that we’re not sure whether these $2.2m treatments will cure sufferers for life. That said, the data has been very positive to date.

The bottom line

I’m already an investor in CRISPR Therapeutics, but I’m tempted to increase my position. The stock’s dipped because of an absence of news, rather than any negative reports.

In addition to its SCD and beta-thalassemia treatments, CRISPR Therapeutics has an attractive and innovative pipeline that could save lives and deliver commercial value in the future.