What happened

Shares of clinical-stage biotech CRISPR Therapeutics (CRSP -1.88%) are down an eye-popping 12% as of 12:05 p.m. EDT Wednesday. The biotech's shares sank in response to a patient death in an early stage study assessing the company's off-the-shelf T-cell therapy, CTX110, in patients with CD19+ B-cell malignancies (blood cancers).

The patient in question was the only one to receive the highest dosage of the experimental cell therapy in the study. Although the patient reportedly exhibited a complete response at day 25 following treatment, he was hospitalized the next day for febrile neutropenia (fever with a low white blood cell count) and short-term memory loss/confusion. Less than four weeks later, the man passed away from additional complications.  

A person removing a piece of DNA from a model with a pair of forceps

Image source: Getty Images.

So what

Off-the-shelf T-cell therapy -- aka allogeneic cell therapy -- would almost certainly be a game-changer in the treatment paradigm for B-cell malignancies. The underlying reason is that the currently approved rendition of these next-generation cancer treatments -- known as autologous CAR T therapies -- require patients to travel to specialized clinics to have their T-cells harvested, genetically modified, and then reinfused back into their body.

This process is costly, labor-intensive, inconvenient for patients, and time-consuming. Off-the-shelf T-cell therapy, by contrast, would allow these powerful new cancer treatments to be vastly more accessible to patients, given that they could be shipped to local clinics. This patient death, however, shows that developing a safe and effective off-the-shelf T-cell therapy won't be an easy task.   

Now what

Despite this fatality, there are several positives from CRISPR's early stage cancer trial. CTX110 did show clear-cut antitumor activity in a small cohort of very sick patients. What's more, the biotech noted that its CRISPR-edited CAR T clinical program will continue as planned. So even though CTX110 did exhibit a worrisome safety signal at the highest dose, this data release probably doesn't deserve such an overtly negative reaction by investors.