Published on February 21, 2020
- There are two NCCN-approved JAK2 inhibitors – ruxolitinib (Jakafi) and fedratinib (Inrebic).
- For PV patients, treatments include peginterferon alfa-2a (Pegasys), fedratinib (Inrebic) and ruxolitinib (Jakafi).
- ET patients might respond well to Bcl-2 and Bcl-X inhibition.
Myeloproliferative neoplasm expert Dr. Catriona Jamieson, from UC San Diego Moores Cancer Center, gives an update on new treatment options and those in development for myelofibrosis (MF), polycythemia vera (PV) and essential thrombocythemia (ET).
This is an MPN Research Foundation program produced by Patient Power. We thank Celgene for their financial support through grants to the MPN Research Foundation. These organizations have no editorial control, and the program is produced solely by Patient Power.
Transcript | Treatment Options for Myelofibrosis, Polycythemia Vera and Essential Thrombocythemia
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Greetings, I'm Andrew Schorr. We're in Orlando, Florida and this is our live MPN Ask the Expert program. And I've been living with an MPN about eight years now, so I am vitally interested. Now let's take your questions as well. So, joining us is my doctor, Dr. Catriona Jamieson. Thank you so much for being with us.
Oh, it's really my pleasure, Andrew.
New MPN Drug
What are some headlines from what you're hearing or participating in that we want to tell the community that gives us hope?
Well, I think the great news is we have another approved drug. So, that's good this year.
Inrebic. So, this is a JAK2 FLT3 inhibitor. It was in clinical trials for over five years. Went on clinical hold because of a concern of possible neurologic toxicity related to thymine deficiency, which goes back to the previous question about not wanting to eat, because your spleen is too big.
So, I think what we learned there is people with myelofibrosis who have big spleens don't eat that much and they can become thymine deficient. And that's sort of a headline, because it's a quality of life issue, but it's—it restricts what you can take. So, now we know to measure thymine levels. We know that people who take fedratinib (Inrebic) tend to do well. It's not a happy pill. It doesn't make people's inflammatory cytokines go away right away, so they don't feel better immediately, but as the spleen starts to shrink, their counts start to normalize, and they start to feel better.
So, we've got two JAK2 inhibitors.
Others that are still remaining in trials.
Right. So, we've got two JAK2 inhibitors that are NCCN panel recommended standard of care. Jakafi and now Inrebic. They're different. JAK2 inhibition with ruxolitinib (Jakafi), tends to make people a little bit better from a symptom standpoint. And then Inrebic tends to make people feel a little better after a few months when it really starts working on the spleen. But both effective options.
In terms of clinical trials, momelotinib, they're still moving through the clinical trials. It's maybe less of a problem for anemia. That's a suggestion. And maybe a little bit better in some ways or symptomatic improvement but may not be as effective for reducing the actual disease burden in the spleen and in the bone marrow.
There's another drug from a company called NS Pharma, called NS-108. It's a very selective JAK2 inhibitor. Extremely well tolerated. Takes a long time to work, but in some people, it really works to reduce the spleen by 50 percent to get the bone marrow scarring down by a little bit. It's just not as potent as the other JAK2 inhibitors, but still a well-tolerated option.
Treatments for ET and PV
Okay. And then for our friends with ET and PV, new thinking there?
I think there is new thinking. I think for ET—let's just start with PV. I think there is a role for peginterferon alfa-2a (Pegasys) in some people with PV who are symptomatic, as the idea is to get back to that and know we've got a good drug there. There is a role for JAK2 inhibition in PV, where 97.5 percent of people have a JAK2 mutation. Whether that be with ruxolitinib or fedratinib. So, in other words, Jakafi and Inrebic.
I think we'll have to do the trials. We did trials for both drugs. They looked pretty effective, but I think we mixed up PV and ET, and they're really different. So, I think if we just did a purely PV study, I think we'll see benefit. We already have approval for Jakafi in people with polycythemia vera who have bigger spleens, but I think when you start to see those bigger spleens, they really have probably transitioned to myelofibrosis. So, I think we're too reluctant to do bone marrow biopsies in this disease where bone marrow fibrosis can only be diagnosed really by looking at the level of scarring in the bone marrow.
Have a bone marrow biopsy if you can with sedation. I did it. She asked—she ordered it. I just took a snooze. So, it wasn't so bad. And ET. Any news there?
Can Inhibitors Help Essential Thrombocythemia?
ET is very interesting. So, essential thrombocythemia, as I mentioned earlier, we see the CALR mutation a little bit more frequently there. But also, I think that that may respond to Bcl-2 and Bcl-X inhibition, because you make a lot of platelets. And that was the problem where we did the navitoclax studies in CLL. Their platelet counts plummeted.
Well, when we did the navitoclax study, and that will be presented here at this ASH meeting, with Jakafi plus navitoclax, there was a decline in the platelet count. But if you start earlier in ET, it might be all you need. So, I think it would be fantastic to do a single agent study with navitoclax and essential thrombocythemia.
I think it could be very useful. And then the question is, back to the immune system, can we start looking at the immune system's ability to gobble up these cells when they're not normal by using an anti-CD47 strategy. So, CD47 is the "don't eat me signal." It's upregulated by some cells that say to their macros, "Just don't eat me." Anyway, we can—there's now an antibody.
So, we need a Pac-Man.
We need a Pac-Man. So, this antibody induces that Pac-Man effect. And that's made by a company called Forty Seven, Inc. They're using it in other diseases, other tumors right now, AML and some solid tumors, but it would be fantastic if they go into this disease.
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