Do all myeloma cells express the same amount of BCMA?

Do all myeloma cells express the same amount of BCMA? Can BCMA expression be measured? 
that's a very interesting question. I mean, the amount of BCMA expression that constitutes positivity is not really well known. in general, we think that if we can find BCMA expression on the surface of a cell, then that's a BCMA, a positive cell.  And it, it only takes a little bit for the cells for the treatments that we have to target them. So in general, when we're looking for BCMA expression and there there isn't a commercially available test, there's not something that you can order through your computer or anything like that, but you can send it to more experimental labs and you can stain it and do things like flow cytometry to look for BCMA expression. again, I would be more concerned with positive versus negative and if it's positive, then I would feel comfortable treating a patient with a BCMA targeting therapy. We do have some tests that look at something called soluble BCMA and  what that is, it's a cleaved form of BCMA that is shaved off the surface of the cell. And it's thought to be one of the mechanisms by which some people develop resistance to BCMA targeting therapies. If this is cleaved off the surface of the cell, then it no longer is expressed there. Additionally, it's soluble, so it's it's floating around in your blood. And when we infuse you with a BCMA targeting therapy, oftentimes those therapies will be bound up to that soluble BCMA. That's not really doing much. So it's just sort of a sink, a reservoir where the medicine gets stuck. So we do think that elevated levels of soluble BCMA may be indicative of patients that aren't going to have as good a response to a BCMA targeting therapy.

Is the soluble BCMA test available for everyday use.

No. It's also an experimental, test. So it would have to be done, you know, through an experimental means it's not something that most labs can run. It has to be sent to a reference lab. And I typically would only send it if I have a patient who doesn't appear to be having an appropriate response to a BCMA therapy. you know, there's a couple of different mechanisms that we think are the cause of, well, lack of response to a BCMA or resistance to a BCMA targeting therapy when someone's previously responded. And you know what, what mechanism by which they may be escaping can help us determine what the next best step would be. Should we have to change therapy. Because sometimes people, they escape BCMA, therapy by having what's called T cell anergy, meaning that their T cells are no longer stimulatable. So if you're giving a patient a medicine that requires their T cells to be activated, but their T cells are not able to be activated, then using a different T cell, activating medicine is probably not going to work. If they've lost BCMA expression, then you can use a different T-cell activating agent as long as it doesn't target BCMA. So those kinds of, you know, subtleties may make, allow us to determine what the next best line of therapy would be for someone who is no longer responding or didn't respond in the first place to a BCMA therapy.