FLT3-ITD Archives

Introduction

Mutations in the FLT3 (fms-like tyrosine kinase 3) gene are the most common mutations seen in Acute Myeloid Leukemia (AML) patients. FLT3 mutations are seen in about 30% of AML patients. There are 2 different FLT3 mutations, FLT3-ITD (internal tandem duplication) mutation and tyrosine kinase domain mutations (TKD) mutation. Here I report some newer results of treatments with FLT3 inhibitors, that I have come across in the last several months.

There are quite a few drugs that target the FLT3 gene, including:

First generation drugs:

Sorafenib (Nexavar)
Midostaurin (Rydapt)
Lestaurtinib clinical development of lestaurtinib has been discontinued as it did not provide significant clinical benefit.

Second generation drugs, which tend to have fewer and less severe side effects and are more effective include:

Gilteritinib (Xospata)
Quizartinib (Vanflyta) – Only for ITD mutations.
Crenolanib – Not FDA approved.

FLT3 inhibitors are effective treatments for AML with a FLT3 mutation. However, there are still a number of open questions. How should FLT3 inhibitors be used, with induction chemo, with consolidation chemo and/or for maintenance after a stem cell transplant (SCT) or chemo? Can they be used as a single agent for treating patients who are not good candidates for chemotherapy? Do they work well with newer treatments, specifically with azacitidine and ventoclax regimens? There have not been a lot of comparison between the different drugs. Finally, there is the question of why all these drugs have names that are barely pronounceable!

Gilterinib

There is a new study looking at the use of gilterinib as maintenance after SCT. This was a multi-national randomized study, comparing maintenance with gIlterinib against placebo. The result was overall the patients who received gilterinib had better relapse-free survival (RFS) compared to patients who received placebo. However, this difference was not considered statically significant. However, the trial had a pre-specified secondary objective to look at the subgroup of patients who had measurable residual disease (MRD), that is they were MRD+.

About half of the patients were MRD+ either before SCT or after (or both). In this group, the RFS survival in the patients receiving gilterinib was significantly greater than the placebo group. Unfortunately, there were more side effects in the gilterinib group. It is likely that, because of this study, patients who are FLT3+ and undergoing a transplant will get gilterinib as maintenance if they are MRD+ and not if they are MRD-. The use of gilterinib or other FLT3 inhibitors as maintenance therapy will continue to be a subject of active research.

Quizartinib

I wrote a post on quizartiinb: Quizartinib in FLT3-ITD-Positive AML that was an overview of a trial of this drug along with induction and consolidation chemo and as maintenance after chemotherapy. In July, 2023, Quizartinib was approved for treatment of FLT3-ITD AML in the United States by the FDA.

Crenolanib

Crenolanib is a second-generation FLT3 agent that works for both FLT3-ITD and FLT3-TKD mutations. In Crenolanib and Intensive Chemotherapy for Adults With Newly Diagnosed FLT3-Mutated AML, crenolanib was given with “7+3:” induction and then with consolidation chemotherapy and as maintenance therapy after consolidation chemo and after a SCT. About 2/3 of patients were younger than 60, but patients as old as 75 were included. Although this was not a randomized trial and was fairly small (44 patients), it seemed that Crenolanib added to chemotherapy and as maintenance improved survival compared to midostaurin (the first drug approved for FLT3 AML) and quizartiinb (described above).

Sorafenib

While sorafenib is an FLT3 inhibitor, this first study is on its use in AML patients even if they did have a FLT3 mutation. Previous studies had shown sorafenib improved survival when given with standard “7+3” induction for AML. This study (Sorafenib Plus Cladribine, High-Dose Cytarabine, G-CSF, and Mitoxantrone for Untreated AML) looked at sorafenib with cladribine, high-dose cytarabine, granulocyte colony–stimulating factor, and mitoxantrone (CLAG-M). The first part of the study (Phase I) tried increasing doses of sorafenib and mitoxantrone. The Phase II part of the study used the recommended phase 2 dose (RP2D) to treat more patients. When compared with historical controls who received CLAG-M without sorafenib, the patients who received the RP2D had improved survival.

Finally, there is a report on the long term follow-up of a trial looking at using sorafenib as maintenance therapy after a transplant (Sorafenib Maintenance After Allogeneic HSCT in Patients With AML With FLT3 Internal Tandem Duplications). The use of sorafenib as maintenance reduced relapse which improved survival in patients with FLT3-ITD AML. The non-relapse mortality and the incidence of chronic Graft-Versus-Host Disease (GVHD) in those who had a transplant was similar in patients who received sorafenib and those who did not. This result was sustained long-term (with a median follow-up of about 5 years).

Conclusion

The best way to use FLT3 inhibitors in patients with FLT3 mutation is still an area of active research. Newer agents promise better results – fewer side effects and better survival.

Art Flatau lives in Austin, Texas with his wife Gretchen. They have 2 grown children. He was diagnosed with Acute Myeloid Leukemia (AML) in 1992 at the age of 31, while still in graduate school at the University of Texas. Gretchen and Art’s kids were 2 and 4 at the time. He received chemotherapy (both induction chemotherapy and then consolidation). After graduating with a Ph.D. in computer science in December 1992. He relapsed in early 1993 and then had a bone marrow transplant (BMT), his brother was a perfect match.

Advances in the Treatment of Relapsed/Refractory Acute Myeloid Leukemia (AML) from Patient Empowerment Network on Vimeo.

AML expert Dr. Omer Jamy discusses his approach when considering treatment for patients with relapsed or refractory AML, including transplant eligibility, molecular markers, and whether clinical trials may be an appropriate option.

Dr. Omer Jamy is a Leukemia and Bone Marrow Transplant Physician and Assistant Professor at the University of Alabama at Birmingham. Learn more about Dr. Omer Jamy.

See More From INSIST! AML

Related Resources:

What Is the AGILE Study? Research for AML Patients With the IDH1 Mutation

What is the Purpose of AML Genetic Testing?

Essential Testing Optimizing AML Care with Personalized Medicine

Transcript:

Katherine Banwell:

Dr. Jamy, are there any recent advances that may affect the care of patients with relapsed or refractory AML?

Dr. Omer Jamy:

Yeah, that’s a good question. So, patients with relapse refractory AML, of course, carry a poor prognosis. That means that chemotherapy was working and has stopped working or chemotherapy didn’t work from the get-go, right?

So, in my practice I try to divide patients into two different buckets. One is that I need to get them into remission, and they’re fit for a transplant, so I take them to transplant.

So, then my treatment approach is a little different for those patients. As opposed to someone who’s elderly or too frail, that they may go into remission, but they may not be able to proceed to stem cell transplantation after that.

So, what happened in the relapsed/refractory setting also depends on what the patient received in the upfront setting. Ideally, I would recommend a clinical trial enrollment for patients with relapse refractory AML if they have access to it. At the time of relapsed/refractory AML, it is very important to again profile the leukemia to see if there are any mutations that were present at diagnosis or if there are any new mutations for which there may be targeted therapy. Some of those mutations for which we have targeted therapy include FLT3-ITD for which there is a drug called gilteritnib (Xospata), which is FDA-approved in the relapsed/refractory setting.

We spoke about IDH 1 which is ivosidenib, IDH 2 which is enasidenib (Idhifa) is also approved for patients with relapsed/refractory AML. And then more recently the FDA approved another IDH1 compound called olutasidenib (Rezlidhia) which is also for patients with relapse refractory acute myeloid leukemia with an IDH1 mutation. I think these are target therapies which have shown to get people into a second remission and beyond. And these have been approved in the last few years. And I think it is very important to basically test whether the person harbors these mutations so that we can target them accordingly.

For patients who don’t have any mutations we would generally, outside of a clinical trial, probably use the combination of some of the approved agents that may be venetoclax (Venclexta) with azacitidine (Vidaza) or decitabine (Dacogen). Patients who may have received this venetoclax or a hypomethylating agents frontline and may still be eligible for intensive chemotherapy.

You could offer them intensive chemotherapy in the relapsed/refractory setting, but I would say that at this point being at a center where there’s opportunities to enroll in a clinical trial would be really helpful as well.

Tag Archive for: FLT3-ITD

FLT3 Inhibitors for AML Update