A gene therapy to treat a form of blood cancer is just inches away from regulatory approval in the US—putting the world in the throes of a paradigm shift in medicine. If the Food and Drug Administration (FDA) accepts the recommendation of one of its panels and gives the nod to Novartis’s CTL019, the treatment would become the first-ever gene therapy for any disease to be made available commercially. The small matter of the record aside, the treatment’s efficacy in treating B-cell acute lymphoblastic leukaemia that has resisted conventional treatment or relapsed in patients as young as 3 years of age is reason enough to celebrate.
Developed at the University of Pennsylvania and licensed to Novartis, CTL019, or tisagenlecleucel, is what scientists are calling a “living drug”—though it is strictly not a drug—because it involves engineering specific genes in the patient’s T lymphocytes (T-cells) that are a part of the body’s cell-mediated immunity, to attack B-cells that are also a part of the body’s immune system, but become malignant in leukaemia. First, a patient’s T-cells are harvested in millions, and a disabled form of the Human Immunodeficieny Virus is used to transfer the new genetic material to the T-cells’ genome. The altered T-cells are then intravenously returned to the patient’s body.
Due to the modification, T-cells recognise CD-19, a surface protein present on B-cells, as an antigen and mount an immune response. A study of 63 patients who received the treatment between April 2015 and August 2016 is the main evidence of CTL019’s efficacy—52 went into remission while 11 died; 11 of the 52 who had gone into remission had relapsed by November 2016 while, 29 are still in remission. However, there are a few concerns that need addressing. The FDA panel particularly pointed at the severe side-effects—since the modified T-cells don’t differentiate between healthy B-cells and cancerous ones, the immune system collapses—and unclear long-term effects. For the moment, though, the opportunistic infections that may assail the patient are the main worry.
Oncologists, however, sound positive, given the immediate side-effects can be stemmed—patients receiving CTL019 are given immunoglobulin infusions every few months—but a greater length of time must pass before long-term effects, if any, are evident. Given how concentrated management of the therapy along with side-effects is necessary, Novartis will make it available in just 30-35 medical centres in the US initially. The good news is Novartis is not the only horse in the race in a pole position—Kite Pharma, a US-based company, has applied for FDA approval for its Chimeric Antigen Receptor T-cell (CAR-T) therapy that involves similar genetic engineering of T-cells.
Given how difficult it is to ensure consistency—in some cases, the body fails to respond—and scale with biologics, the challenges for all such gene therapies are daunting. CTL019’s success, however, has an important message for India—it is perhaps time to shed the stubborn resistance to genetic engineering when a developed nation is ready to adopt it, long-term risks included.