TPO Receptor Agonist Selection and Patient Adherence


Ivy Altomare, MD: You mentioned the 2 agents and 1 that may be coming soon. Dr Mehta, how do you decide which TPO [thrombopoietin] receptor agonist to use?

Amit Mehta, MD: Well, I think that’s also a situation in which we don’t have a lot of guidance about 1 versus the other directly.

Ivy Altomare, MD: Sure, and they’ll never be compared with each other, and they shouldn’t be.

Amit Mehta, MD: Yeah, they shouldn’t be. I think 1 key point is mechanistic. As Ralph mentioned earlier, about if 1 TPO drug is not working for some reason, then don’t go to another TPO drug. It’s the same mechanism. But I think as far as choosing between the 2, usually it’s determined more by patient factors. For example, eltrombopag is an oral medication. There are some things we have to be mindful of—like not taking it, it has to be taken on an empty stomach, either 1 hour premeal or 2 hours postmeal. So the patient has to know about the bioavailability side as far as when to take the medication.

But as an oral medication, that can be very useful for the patient who maybe doesn’t want to come to the clinic on a very regular basis or, as you mentioned earlier in North Carolina—where we routinely have patients who drive from an hour-plus away to see us—that can be very appealing that they take an oral medication, just like the appeal of a lot of oral oncolytic drugs that we have nowadays. That being said, romiplostim is also a good medication that can keep them on treatment, so duration of therapy is kind of indefinite as it were. But at least it will typically work in these folks, but they just have to come to the office for administration, because of what Ralph mentioned earlier about the incident of billing and so forth. So they theoretically have to come to the office and get the injection there.

Ivy Altomare, MD: Which is more convenient for some patients, to be honest.

Amit Mehta, MD: Some patients might like it. An issue that might come up for some patients may even be that some clinicians and patients might be compliance considerations. That’s always 1 of those things we think about. Well, oral medication—are they definitely taking it, not taking it, taking it inconsistently. These are considerations for which we might say, OK, well, if it’s not a big inconvenience for the patient to come to the clinic, then perhaps that’s a nice place to get a quick injection by your nurse, and therefore you know the patient received the exact dose that you were administering for the patient. And the other thing with romiplostim, just like with eltrombopag, is that you can tailor the dose based on the response of the platelet count.

Ralph V. Boccia, MD, FACP, LLC: Just to make a couple of other comments. You really only have 3 dose levels—to your point, with eltrombopag, 25, 50, and 75 mg—where you can really better fine-tune or fine adjust the romiplostim between 1 and 10 mg. The other thing that I don’t think is ready for prime time, but is again interesting when we’re talking about correlative studies, is that there’s a paper presented here at this meeting [the American Society of Hematology Annual Meeting and Exposition] looking at autoantibody levels and response rates for both of those 2 drugs.

Ivy Altomare, MD: TPO levels, right?

Ralph V. Boccia, MD, FACP, LLC: TPO levels. I’m sorry, I’m glad you corrected it. Yeah, TPO levels.

Ivy Altomare, MD: Because I saw the paper.

Ralph V. Boccia, MD, FACP, LLC: Right. So for those patients who had normal TPO levels, both drugs worked equivalent. For those patients who had very high TPO levels, and you might think of this almost in the erythropoietin kind of issues that we struggle with anemic patients, …they didn’t respond to either. But those who had sort-of medium levels responded better to romiplostim than they did to eltrombopag. So that’s just also very interesting and may help us, may or may not help us later on again if we ever get to a point where there are certain levels of any of these proteins that we can measure to help us better select the drug that is more likely to be efficacious in the patient.

Ivy Altomare, MD: Yeah, to aid the choice. As you said, it’s a probable, not 100%. But it’s great that we’re starting to crack this to get guidance on appropriate therapy to choose. I want to go back to what you said about taking the medication on an empty stomach when you’re using eltrombopag. I think that that is so key for physicians to recognize, because if you have a patient who is not responding to eltrombopag, it’s really worthwhile to see, indeed, if they are taking it on an empty stomach. Because it will render the drug completely ineffective. So don’t abandon ship, but make sure that people are taking it the right way.

Amit Mehta, MD: Exactly. I think more globally speaking about chronic ITP [idiopathic thrombocytopenic purpura] is that even though we now have multiple new FDA treatments over the past several years, we still have a limited number of very effective options. Therefore, before we abandon ship, let’s say if the patient is taking it correctly or if they are not taking it. So this might be guidance that, who knows, in our busy clinic day, maybe the physician, the nurse, the pharmacist, whoever might have just somehow forgotten to mention it or didn’t reinforce it. Or maybe the patient was doing it, then they kind of fell off the wagon.

Ivy Altomare, MD: That’s true too. When people are on these drugs for years and then they start some new, I don’t know, protein shake or something and you lose a response, it actually might be because of something dietary.

Ralph V. Boccia, MD, FACP, LLC: Or are they taking it at all?

Amit Mehta, MD: Yeah, or are they taking it at all?

Ivy Altomare, MD: True. Though I don’t know, ITP patients are pretty compliant.

Amit Mehta, MD: At least with ITP I feel that clinically we will know if they’re taking it or not taking it. If we suspect they’re not taking it, the platelet count is not going to go up, or it’s going to fall back down to wherever they started at. And with chronic ITP, usually that’s a very low level.

Transcript Edited for Clarity

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