Hairy Cell Leukemia: Achieving a Positive Response to Therapy
Dr. Robert J. Kreitman reflects on Vince’s, and other patients’, response to moxetumomab pasudotox in the setting of hairy cell leukemia.
PUBLISHED June 18, 2019
Robert J. Kreitman, M.D.: The other thing that we find is the more cycles of MOXE [moxetumomab pasudotox] you have, the more likely you are to get rid of this culprit that we call MRD, the minimal residual disease, that can cause the hairy cell to come back again if you don’t get rid of it. Now, do you remember how many cycles you got of the moxetumomab pasudotox?
Vince Fazio: I think it was four. I think it was four periods where I came down here and stayed for eight days.
Robert J. Kreitman, M.D.: Right. My memory is it was five, but you could be right. But basically, we believe that it takes at least two cycles, one or two cycles, to get a complete remission. And then we like to give extra cycles, so that we could get rid of that minimal residual disease. So to get a complete remission with hairy cell only requires not being able to see the hairy cell in the bone marrow and the blood by the regular stains, the kind of stains that we’ve been using for the last 50 years. But the minimal residual disease, as I said before, requires special antibody tests. And so we want to get extra cycles of moxetumomab pasudotox, so that we can get rid of the minimal residual disease that could be detected by those highly specialized tests. So we were able to give you several of those extra cycles. You’ve now been going on for about 10 years, is that right? Or eight-and-a-half years?
Vince Fazio: No, it was December of 2008 when you said it was gone.
Robert J. Kreitman, M.D.: OK, very good. So we’re now at about the 10, 10-1/2 year point. So we check patients. This is something that’s not absolutely necessary to do in clinical practice, but because this is a clinical trial, we’re following patients about every two years with bone marrow tests to determine if we’ve gotten rid of the minimal residual disease. And so far, at least up to a couple years ago, we couldn’t find any trace of hairy cell. We are very happy about that. There are other patients on the trial, of course, who have had that as well, who have also not had minimal residual disease. But some patients have had minimal residual disease. They haven’t been able to take as many cycles as you have, or some people have had as many cycles, but we couldn’t get rid of the minimal residual disease. But in any case, most of the patients, fortunately, who got complete remission on the trial are able to get rid of the minimal residual disease. And so we believe that this is an important advance in hairy cell that you can get rid of the minimal residual disease without chemotherapy.