CRISPR gene editing has been hailed by some people as "the biotech discovery of the century." Those people could be right. CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats, uses bacterial enzymes to edit targeted DNA sequences. The potential implications for treating genetic diseases of the approach are tremendous.

Two of the top biotechs pioneering CRISPR research and development are Editas Medicine (NASDAQ:EDIT) and CRISPR Therapeutics (NASDAQ:CRSP). CRISPR Therapeutics has been the bigger winner so far in 2018 with its stock more than doubling. Editas Medicine's share price climbed more than 40% earlier in the year, but it's now up by only a single-digit percentage.

Which of these two gene-editing stocks is the better buy now? Here's how Editas and CRISPR Therapeutics stack up against each other.

Someone using tweezers to remove part of a digital DNA strand.

Image source: Getty Images.

The case for Editas Medicine

Editas Medicine's lead candidate is EDIT-101, which uses CRISPR gene editing to treat Leber congenital amaurosis type 10 (LCA10). LCA10 is a rare genetic eye disease that affects less than three out of 100,000 live births. However, it's the top cause of hereditary childhood blindness.

There are several reasons to like the prospects for EDIT-101. Editas plans to file an Investigational New Drug (IND) application for EDIT-101 in October. It's possible that EDIT-101 will be the first in vivo (administered in the body) CRISPR therapy to advance to clinical testing in humans in the U.S.

Another reason to like the prospects for EDIT-101 is that big drugmaker Allergan likes its prospects. In 2017, Allergan paid Editas $90 million up front for options to license up to five CRISPR programs. Allergan exercised its option for EDIT-101 last month for global rights to develop and market the therapy. Editas will split any future profits and losses for EDIT-101 in the U.S. with Allergan.

Editas Medicine's pipeline also includes several other CRISPR candidates. The company is targeting two other rare genetic eye diseases plus blood disorders beta-thalassemia and sickle cell disease. In addition, Celgene is working with Editas to use CRISPR to edit immune cells for treating cancer. By 2022, Editas hopes to have at least two candidates in or ready to advance to late-stage clinical studies. The biotech also plans to have at least three CRISPR therapies in early stage clinical trials by then.

Another plus for Editas is that the company has two CRISPR platforms, one using the Cas9 protein and one using the Cpf1 protein. Both Cas9 and Cpf1 can cut targeted DNA sequences. However, Cpf1 can be used to edit more parts of the genome than Cas9 can and has a higher level of accuracy for some types of gene repair. It's also simpler to engineer than Cas9 is.

The case for CRISPR Therapeutics

CRISPR Therapeutics expects to begin a phase 1/2 clinical trial of its lead candidate, CTX001, later this year in treating transfusion-dependent beta-thalassemia. This will be the first study in humans of CRISPR gene editing outside of China. 

Like Editas, CRISPR Therapeutics attracted the attention of a major partner for its lead program. Vertex Pharmaceuticals gained an exclusive license to CTX001 for treating beta-thalassemia and sickle cell disease last year. The two companies had hoped to begin an early stage clinical study of the therapy in sickle cell disease later in 2018, but the U.S. Food and Drug Administration (FDA) placed a clinical hold on the program in late May.

CRISPR Therapeutics expects to submit an IND application by the end of this year for approval to begin a phase 1 study of CTX110, an allogeneic chimeric antigen receptor T cell (CAR-T) therapy. The company has two other CAR-T therapies in preclinical testing.

CTX001 and the CAR-T programs are ex vivo therapies, but CRISPR Therapeutics' pipeline also includes four experimental in vivo programs. The company has partnered with Vertex on using CRISPR to treat cystic fibrosis. It formed a joint venture with Bayer named Casebia to develop a gene-editing therapy for hemophilia. CRISPR Therapeutics is also exploring CRISPR treatments for rare genetic diseases glycogen storage disease Ia and Duchenne muscular dystrophy.

Better buy

Both of these biotechs have tremendous potential. Overall, though, I lean toward Editas Medicine as the better buy for three reasons.

First, the stock hasn't soared like CRISPR Therapeutics has. In my view, Editas has more room to run if it announces positive developments down the road. Second, I like that Editas has no competition in LCA10 or the other genetic eye diseases that it's targeting. Third, the biotech's CRISPR-Cpf1 program could give it an advantage in addressing some genetic diseases.

Both Editas and CRISPR Therapeutics face significant risks, however. CRISPR gene editing is still in its early stages. But I like the risk-reward proposition for both stocks and especially for Editas.

Keith Speights owns shares of Celgene, Editas Medicine, and Vertex Pharmaceuticals. The Motley Fool owns shares of and recommends Celgene. The Motley Fool owns shares of CRISPR Therapeutics. The Motley Fool recommends Editas Medicine and Vertex Pharmaceuticals. The Motley Fool has a disclosure policy.