Don't think that a head start for a biotech automatically makes its stock a better pick. Sangamo Therapeutics Inc. (SGMO -5.99%), for example, claims a big pipeline lead over CRISPR Therapeutics AG (CRSP 1.08%). And yet CRISPR Therapeutics stock has trounced the performance of Sangamo this year.

On the other hand, don't think that stronger performance over a relatively short period of time necessarily makes a stock the better long-term choice. Which of these two gene-editing biotech stocks really is the smarter alternative for long-term investors? Here's how CRISPR Therapeutics and Sangamo Therapeutics compare.

DNA in foreground with physician in background pointing to a lighted segment of DNA

Image source: Getty Images.

The case for CRISPR Therapeutics

As its name indicates, CRISPR Therapeutics focuses on using CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) gene editing to treat diseases. The biotech was co-founded by CRISPR pioneer Emanuelle Charpentier. 

There are a couple of key reasons to like CRISPR Therapeutics. One is its CTX-001 therapy that targets editing of the HBB gene. Mutations in this gene cause several rare blood diseases, notably including beta thalassemia and sickle cell disease.

CRISPR Therapeutics and its partner, Vertex Pharmaceuticals, are currently enrolling patients in a phase 1 clinical study evaluating CTX-001 in treating beta thalassemia. The two companies also expect to soon begin another phase 1 study of CTX-001 in treating sickle cell disease (SCD).

Targeting these two diseases appears to be a great place to start for CRISPR Therapeutics. Around 60,000 babies worldwide each year are diagnosed with beta thalassemia, while roughly 300,000 babies are diagnosed with SCD. Both diseases have high mortality rates, and patients frequently must be hospitalized and require blood transfusions. 

Another reason to like CRISPR Therapeutics is its immuno-oncology program. The biotech has two gene-editing therapies in preclinical testing that could lead to clinical studies. Both are off-the-shelf cell therapies that could support faster treatment than current cell therapies that require engineering of the patients' T cells allow.

Over the longer run, there could be even more reasons for investors to like CRISPR Therapeutics. The company has early research underway for using CRISPR gene editing in treating type 1 diabetes as well as several genetic diseases. 

The case for Sangamo Therapeutics

Sangamo Therapeutics uses a different approach to gene editing called zinc-finger nuclease (ZFN) technology. ZFN has a much longer track record than CRISPR does. And it has put Sangamo at the forefront of developing gene-editing therapies.

The biotech claims three phase 1/2 clinical studies in progress that are evaluating in vivo (in the body) ZFN gene-editing therapies. Two of them target genetic metabolic diseases mucopolysaccharidosis type I (MPS I) and mucopolysaccharidosis type II (MPS II). Another targets hemophilia type B.

Sangamo presented disappointing interim data in September from its MPS II study. It's still too early to know how the other gene-editing studies will go. The biotech is also working with Bioverativ, which is now part of Sanofi, on using ZFN with a cell therapy to treat beta thalassemia.

But that's not all the biotech has in the works. In addition to gene editing, Sangamo also focuses on gene therapy. This approach involves the addition of a corrected foreign gene rather than modifying the DNA sequences within the gene. 

Pfizer partnered with Sangamo on hemophilia A therapy SB-525. An update from the two companies' phase 1/2 study is expected next year. Sangamo and Bioverativ expect to begin a phase 1/2 study of BIVV-003, a cell therapy targeting sickle cell disease, next month. 

Sangamo's pipeline includes three preclinical gene-editing and gene therapy programs. Perhaps the most significant of these is the company's partnership with Gilead Sciences' Kite Pharma subsidiary to develop cell therapies using ZFN.   

Better buy

Ordinarily, my take on choosing between clinical-stage biotechs would be to go with the one that had more shots on goal. In this case, that biotech would definitely be Sangamo. However, Sangamo's disappointing data for its MPS II gene-editing therapy and its decision to delay presentation of data from its phase 1/2 study of hemophilia A gene therapy SB-525 raise concerns. 

This is purely a gut call, but I think that CRISPR Therapeutics could be the bigger winner over the long haul. Granted, it's still very early for the biotech. There could be major setbacks down the road. For now, though, I'm sticking with my hunch and picking CRISPR Therapeutics as the better buy.