The potential to reengineer a patient's immune system to identify and kill cancer cells more accurately, without damaging a patient's healthy cells, is endlessly intriguing and offers an interesting opportunity for investors. Is it worth the risk investing in the biotech stocks developing this CAR-T technology? To answer that question, we asked two top Motley Fool healthcare contributors to evaluate key players Juno Therapeutics (NASDAQ:JUNO) and Bellicum Pharmaceuticals (NASDAQ:BLCM).

Todd Campbell: Juno Therapeutics is an undeniably intriguing company that is working on attacking cancer in an entirely new way.

Juno's immunotherapy strategy attempts to do away with chemotherapy's shock-and-awe approach of destroying both cancerous and healthy cells. Instead, immunotherapy battles back against cancer by reengineering the body's own immune system. Juno hopes to do this by altering the genetic code of the immune system's T-cells to allow them to more easily recognize and kill cancer cells.

Juno is mostly focused on therapies for the treatment of B-cell lymphomas and leukemias, and early-stage results are intriguing. For example, 20 out of 22 patients with relapsed/refractory B cell acute lymphoblastic leukemia saw remission when treated with Juno's JCAR015. However, before investors get too far out in front of their skis, they may want to bear in mind that this was a phase 1 trial, and the overwhelming majority of cancer drugs that enter clinical trials end up failing. A lot of those drugs end up in the dustbin because of toxicity, and it shouldn't be ignored that the FDA temporarily halted Juno's JCAR015 trial last year when two patients passed away from a condition that may have been caused by taking the drug. That suggests Juno may be best suited only for the most aggressive of investors.

Brian Orelli: Like Juno, Bellicum Pharmaceuticals is harnessing the power of the immune system to attack cancer. The main problem with using chimeric antigen receptors, or CARs, to train T cells to attack tumor cells is that the immune system can become overactive to the point where it starts damaging healthy tissue.

Bellicum's Chemical Induction of Dimerization, or CID, technology is a safety switch that can either turn on the CAR-T or can be built to activate a signal that tells the CAR-T cells to kill themselves. Genes that code for the proteins that make the biologic switch are added to cells, which are then put in the patient. The biological switch is activated by giving the patients rimiducid, which brings the two parts of the switch together, making it active.

Source: Bellicum Pharmaceuticals.

In addition to CAR-T, Bellicum is also using the CID technology in hematopoietic stem cell transplantation, a treatment that can cure patients of their blood cancer but can lead to graft-versus-host disease where the patient's immune cells attack the donor stem cells. By incorporating CID into the donor host cells, the cells can be programmed to die with the addition of rimiducid if they cause graft-versus-host disease. Cure rates could also be raised by giving higher doses of stem cells that would normally be more likely to cause graft-versus-host disease. The first phase of a phase 1/2 trial of Bellicum's BPX-501 in patients with mis-matched donors dosed its first patients this month.

It's clear CAR-T has potential, but given how early it is, it's really hard to know if Bellicum's technology is the answer -- and/or whether Juno can solve its toxicity problem on its own. Promising new technology can take a decade to work out, and it's not guaranteed. If you've got a long-term time horizon with money you can afford to risk for a potentially high return, buying a basket of immuno-oncology drug companies including Juno, Bellicum, and others -- so you don't have to pick the eventual winner -- could be a good investment.