Gene therapy

There are two main types of gene therapy, a method of shuttling genetic instructions into the body for a one-time, long-lasting disease treatment.

One method is an in vivo process, in which a therapeutic gene is introduced into the patient’s body. The other is the ex vivo variety, in which patients’ stem cells are harvested, equipped with a healthy version of a gene, and then infused back into the body. Everything remains experimental, but in vivo therapy is currently the more common approach, pursued by companies such as Spark Therapeutics (NASDAQ: ONCE), BioMarin Pharmaceutical (NASDAQ: BMRN), and UniQure (NASDAQ: QURE).

Less common is the ex vivo procedure used by companies such as Bluebird Bio (NASDAQ: BLUE), U.K.-based startup Orchard Therapeutics, and Boston-area startup Avrobio. Through this process, a virus from the lentivirus family that has been genetically modified to be harmless carries healthy genes into stem cells harvested from the patient. The stem cells are then grown in a culture and infused back into the patient, where they are supposed to give rise to more cells with the correct gene.