What are antibody drug conjugates? Antibody drug conjugates were conceived of as a way to deliver chemotherapy precisely to tumor targets. And the way this is accomplished is you have a monoclonal antibody that recognizes a target that's on the surface of your cancer cell. So in myeloma, for example, we have Bilanthamabaphydoton, which is an antibody that recognizes BCMA on the surface of myeloma cells. The additional, the drug part of antibody drug conjugate is that several molecules of a chemotherapy agent are physically attached to that antibody. So it's like a guided missile for lack of a better term. The antibody carries the drugs to the cancer cell. The cancer cell takes them in and then they're killed by the chemotherapy. And this is a strategy that's proved to be effective not just in myeloma but in other cancers as well. Antibodies are blind antibodies, or naked antibodies, I guess is the best way to describe them. They're just designed to recognize something. So you don't really need to know anything more about them than that. So if you have something that recognizes your cancer cells, those antibodies will go to the cancer cell. Some of them will then fix the immune system to that cell. That's powerful. It's the mechanism of action of daratumumab and isotuxumab. Maybe you could make them more powerful by using them to deliver a kind of silver bullet, something that kills the cancer cells. So we can now link drugs to the antibodies, have them only delivered to the cancer cell. So you deliver a big dose to the cancer cell, sufficient to kill it, but then you don't get side effects from having other cells in the body exposed to that toxin. So they're really interesting. And the leading product in this area in myeloma is belantumab, which is an antibody that has MMF attached to it that kind of kills the cellular process of cell division, so it kills the cancer cell stone dead. Are antibody drug conjugates considered immunotherapy or chemotherapy? It's immune in the sense that it uses an antibody and that antibody recognizes targets on the tumor cell. In addition, it's an antibody. So it has an antigen recognition portion, which is the end that sticks to the target. But the other end is called what's called FC portion, also has functions. It attracts things like natural killer cells. There's signaling to other parts of the immune system that occur through the FC fortune. And so it does have some of those functions intact, even in the conjugated form. But it is also chemotherapy. It delivers chemotherapy agents right to the myeloma cell. And those chemotherapy agents kill tumor cells in a way that makes them visible to the immune system as well. So these are combinations of good aspects or favorable aspects, both of immune therapy and of chemotherapy. I think that this is something that is often asked that is an antibody drug conjugate chemotherapy or is it antibody? And honestly, I think it's more chemotherapy in a targeted manner. But obviously, it has the function of an antibody as well. Why don't antibody drug conjugates have the same side effect profile of other chemotherapies like Melfil-An? Part of it is that it is directed directly to the tumor cell. For the most part, the drug is being delivered to cancer cells. And for the most part, normal cells are being spared. Now, there's no perfect therapy. So antibody drug conjugates do have some what are called on-target, off-tumor effects. So other types of cells express BCMA, for example. So there's normal B cells that express BCMA. And they're going to be attacked by an agent that recognizes BCMA. So there are potential side effects. But the kind of broad effects we saw with systemic chemotherapy with infusions with Melfil-An and so forth are largely avoided because there is some precision to the delivery of the chemotherapy. The toxicity of an antibody drug conjugate is heavily dependent on what the antibody is conjugated to, the chemotherapy molecule. And this varies from ocular toxicity to nerve damage to marrow suppression to liver damage, depending on what the payload is. Who would you consider the right patient for an antibody drug conjugate? I think who is the right patient for an antibody drug conjugate is an evolving area. I think as we get more treatments available, the practice patterns change. The use of myeloma is fortunate in having several options available. And for a given patient, I think a physician and the patient has to decide which of the options is best. Is it an antibody drug conjugate or is it an alternative treatment? Often these decisions are made based on the toxicity profile of these drugs, the efficacy profile and the issue about practical issues like how frequently the drug has to be given. So I think one has to individualize the decision.