A Small Study Raises Big Hopes That Gene-Editing Can Treat Blood Diseases

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A small study can raise big expectations—especially in the nascent industry of gene-editing to treat serious diseases. Such is the case for CTX001, a closely-watched therapy from upstart biotech CRISPR Therapeutics and its much larger partner, rare disease specialist Vertex Pharmaceuticals, that was developed using CRISPR gene-editing technology.

The early-stage trial in question treated just two—yes, two—patients with the blood disorders sickle cell disease and beta-thalassemia, respectively. But the companies found the initial results so compelling that, even at this preliminary juncture, they decided to share some of the information.

What Did the Data Show?

“The data we announced today are remarkable and demonstrate that CTX001 has the potential to be a curative Crispr/Cas9-based gene-editing therapy for people with sickle-cell disease and beta-thalassemia,” said Vertex CEO Jeffrey Leiden in a statement.

For one, the patient with beta-thalassemia (which can cause severe anemia) went from requiring more than 16 blood transfusions per year before treatment to none nine months after treatment.

Secondly, the patient with sickle cell disease had zero “vaso-occlusive crises” (incidents where the warped blood cells caused by sickle cell can lead to severe pain and obstructions) four months after treatment. That individual had been experiencing about a half dozen incidents every year prior to receiving CTX001.

Cautious Optimism

It’s always prudent to be cautious about these early-stage results, no matter how impressive they sound. But several analysts, including from RBC Capital Markets, sounded cautious optimism.

Investors cheered, too. Shares of Vertex (a $50 billion-plus market value company) rose more than 2% in Tuesday trading, while shares of CRISPR Therapeutics spiked nearly 17%.

Call to Action: FORTUNE provides a discussion on how gene editing can be used responsibly and the implications of designing a world around it. We invited those interested in learning more to see below.