Investors got a look at data from additional patients treated with CRIPSR Therapeutics (NASDAQ:CRSP) and Vertex Pharmaceuticals' (NASDAQ:VRTX) CTX001 in an abstract for a presentation at the American Society of Hematology (ASH) Meeting next month.

Shares of CRISPR are up more than 10% at 12:36 pm EST as the CRISPR-based treatment continues to help patients with transfusion-dependent beta thalassemia (TDT) and sickle cell disease (SCD). Vertex, which is much larger and less dependent on the development of CTX001, is up 3.3%, about the same as the S&P 500.

CTX001 works by editing the patient's DNA so that the cells start expressing fetal hemoglobin, which makes up for the lack of hemoglobin in TDT and SCD patients. CRISPR and Vertex had previously disclosed data for two patients with TDT and one patient with SCD. The new report adds three TDT patients and one SCD patient and updates on the earlier patients.

Doctor listening to a boy's heart with a stethoscope.

Image source: Getty Images.

In TDT, all of the new patients started expressing fetal hemoglobin, which allowed them to stop receiving blood transfusions, the typical treatment for TDT. The first patient has now been followed for 15 months with the amount of fetal hemoglobin continuing to rise. The patient continues to not require transfusions.

In SCD, the patients also expressed fetal hemoglobin, which appears to be making up for the sickled hemoglobin. The first treated patient has been followed for over a year and hasn't had a vaso-occlusive crisis (VOC), a painful and life-threatening episode where the blood flow is restricted due to the sickled red blood cells. The patient had previously averaged 7 VOCs per year. The new patient hasn't had a VOC since treatment, but there's only been three months of follow up.

The abstracts for ASH were submitted back in August, so CRISPR and Vertex's presentation at the meeting on Dec. 6, 2020 should include further updates on the patients and possibly provide investors with data on additional patients.

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