Ian W. Flinn, MD, PhD: Amit, there are some other differences. We talked about the time to give the therapy once you’ve acquired the T cells. There is some variability. It appears that the vein-to-vein time is quicker for some products. Regarding the patients, are there differences that change this vein-to-vein time? Are T cells easier to produce with 1 product or another, or 1 patient vs another?
Amitkumar Mehta, MD: We still need more data. There are reports. In my practice, there are very few chances for failure to produce a product. That has been published on. Failure ranges from 1% to 2%. However, it also depends on what kind of treatment they received before. As you mentioned, if you have used more lymphotoxic regimens before the leukapheresis because a patient is progressing very fast, there is a chance that they may not be able to produce or collect enough T cells.
The other factor is that most of the centers that are certified to treat with CAR [chimeric antigen receptor] T are also part of the expanded-access program. What I mean is that most of these studies have shown that cell viability of more than 80% would successfully hold up to the results and outcomes as published. However, some patients with even lower viability, like 70%, also held responses. By default, the way FDA has approved the therapy option, cell viability needs to be 80% or more. Those patients who don’t meet that criteria or other specifications are enrolled in a different protocol and still have significant or almost similar responses. That will also be helpful for patients who are not able to have viability cutoff for FDA.
Ian W. Flinn, MD, PhD: John, in your mind what is a reasonable amount of time, regarding the struggle of acquiring the CAR T cells? What is a reasonable amount of time to wait for these CAR T cells to come back and get infused? These patients are often very sick and have very aggressive disease. How do you manage them?
John M. Burke, MD: Some of these patients have very rapidly progressing disease. The reasonable amount of time depends on the patient. Some patients can’t wait the 2½ to 3 weeks that it generally takes to manufacture the product, so they need this bridging therapy sooner—something to control the disease before they get treated. For others, they may have time. You catch the relapse relatively early, and they’re not in dire straits at the time you’ve picked this up, so 3, 4, 5 weeks may not be a problem. It depends on the individual, regarding how much time is reasonable.
Transcript Edited for Clarity