You have probably heard it before: CRISPR has the potential to change our lives for the better. But first, we need to give it an opportunity.

In December, gene-editing firm CRISPR Therapeutics announced a partnership with biotech firm Vertex to develop CTX001, the world’s very first gene-based treatment for sickle cell disease (SCD). Now, the U.S. Food and Drug Administration (FDA) has rejected the companies’ request to move forward with a early-phase trial of CTX001in adult volunteers, putting a “clinical hold” on the application.

According to a CRISPR Therapeutics press release, the FDA has “certain questions” it wants resolved before it provides the consent to the human CRISPR research. The company seems to be waiting for extra info on those concerns and plans to resolve them “rapidly.” SCD is a hereditary blood condition in which a protein in red blood cells called hemoglobin does not carry oxygen throughout the body the way it should. This can trigger a host of health issues, from chronic pain to strokes to blindness.

When we are born, our blood contains a different variation of hemoglobin referred to as fetal hemoglobin (HbF). Usually, the adult variation of hemoglobin replaces HbF post-birth, however in some cases HbF stays in the blood through the adult years. When that occurs to an individual with SCD, it can reduce the severity of their symptoms. CTX001 is meant to duplicate this unusual fluke of nature in patients. The primary step in the treatment is to extract cells from the patient. Then, the scientist genetically modifies the cells in the laboratory to produce considerable quantities of HbF. Finally, they reintroduce the cells to the patient’s body where they produce new red blood cells with greater levels of HbF.

The laboratory outcomes have at least been promising enough for the scientists to move to human research. But until they get the consent to move forward with their human CRISPR study, we cannot know for sure whether CTX001 will work as anticipated.

This trial, should it move on, will not be the first time CRISPR has actually been tested in humans — that first attempt was in China in 2016. But this trial would mark one of the first to take place in the U.S., as MIT Tech Review reports (several others, including some to treat SCD, are also progressing, and it’s unclear which group will get there first).

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Hopefully, CRISPR Therapeutics and Vertex have the ability to answer the FDA’s concerns in a manner in which promotes confidence in the treatment. While it’s true that we are exploring uncharted area with gene-editing in humans and have to proceed with caution, millions of people presently struggle with SCD. CRISPR may provide a life-changing treatment.

The catch is that we will not know for sure until we try.