What’s New in Acute Myeloid Leukemia (AML) Research?

Researchers are now studying the causes, diagnosis, and treatment of acute myeloid leukemia (AML) at many medical centers, university hospitals, and other institutions.

Genetics of AML

There has been great progress in understanding how changes in the DNA (genes) inside normal bone marrow cells can cause them to develop into leukemia cells. A greater understanding of the gene changes that often occur in AML is providing insight into why these cells become abnormal. As researchers have found more of these changes, it is becoming clear that there are many types of AML. Each might have different gene changes that affect how the leukemia will progress and which treatments might be most helpful. Doctors are now learning how to use these changes to help them determine a person’s outlook and if they should receive more or less intensive treatment.

Perhaps even more important, this knowledge is now being used to help develop newer targeted therapies against AML (see below).

Detecting minimal residual disease

In recent years, highly sensitive tests have been developed to detect even the smallest amount of leukemia left after treatment (known as minimal residual disease, or MRD), even when there are so few leukemia cells left that they can’t be found by routine bone marrow tests.

For example, the polymerase chain reaction (PCR) test can identify even very small numbers of AML cells in a sample, based on their gene changes. A PCR test can be useful in determining how completely the treatment has destroyed the AML cells.

Doctors are now trying to determine what effect minimal residual disease has on a patient’s outlook, and how this might affect the need for further or more intensive treatment.

Improving treatment

Treatment for AML can be very effective for some people, but it doesn't cure everyone, and it can often cause serious or even life-threatening side effects. Many studies are being done to find more effective and safer treatments for AML.

Chemotherapy

Chemotherapy (chemo) is still the main treatment for most types of AML. Researchers are looking for the most effective combination of chemotherapy (chemo) drugs that will avoid unwanted side effects. This is especially important for older patients, who are less likely to benefit from current treatments.

Researchers are studying many new chemo drugs for AML, including:

• Sapacitabine, a drug that has shown promise as a treatment option for older patients with AML
• Laromustine, a drug also being tested as an option for older adults with AML
• Guadecitabine, a drug which has also shown promise in early studies.

The effectiveness of chemo may be limited in some cases because the leukemia cells become resistant to it over time. Researchers are now looking at ways to prevent or reverse this resistance by using other drugs along with chemo. They are also looking at combining chemo with a number of newer types of drugs to see if this might work better.

Stem cell transplants

Researchers continue to refine stem cell transplants to try to increase their effectiveness, reduce complications, and determine which patients are likely to be helped by this treatment. Many studies are trying to determine exactly when autologous, allogeneic, and mini-transplants might best be used.

Targeted therapy drugs

Chemo drugs can help many people with AML, but these drugs don’t always cure the disease. Newer targeted drugs that specifically attack some of the gene changes seen in AML cells are now becoming an important part of treatment for some people with AML. These drugs don't work the same as standard chemotherapy drugs. Some examples include:

• FLT3 inhibitors. In some people with AML, the leukemia cells have a mutation in the FLT3 gene. Newer drugs called FLT3 inhibitors target cells with this gene change. Midostaurin (Rydapt) and gilteritinib (Xospata) are now approved to treat people whose AML has an FLT3 mutation. Other FLT3 inhibitors, such as crenolanib, have also shown activity against AML in early studies, and are now being studied further.
• IDH inhibitors. In some people with AML, the leukemia cells have a mutation in the IDH1 or IDH2 gene, which stops the cells from maturing properly. IDH inhibitors can help the leukemia cells mature into normal blood cells. Some of these drugs, such as enasidenib (Idhifa) and ivosidenib (Tibsovo), are now approved to treat AML with certain IDH gene mutations. Several other IDH inhibitors are now being studied as well.
• Histone deacetylase (HDAC) inhibitors, such as vorinostat (Zolinza) and panobinostat (Farydak)
• BCL-2 inhibitors, such as venetoclax (Venclexta)
• Polo-like kinase (Plk) inhibitors, such as alisertib

Immunotherapy

Immunotherapy works to boost the body’s immune system to help fight off or destroy cancer cells.

Monoclonal antibodies: These are man-made versions of immune system proteins (antibodies) that are designed to attach to specific targets, such as substances on the surface of cancer cells. Some work by boosting the body’s immune response against the cancer cells. Others have radioactive chemicals or cell poisons attached to them. When they are injected into the patient, these antibodies act like a homing device, bringing the radioactivity or poison directly to the cancer cells, which kills them.

Gemtuzumab ozogamicin (Mylotarg) is a monoclonal antibody with a cell poison attached to it. It is now approved to treat AML in some patients. Several other monoclonal antibodies are now being studied as well.

Immune checkpoint inhibitors: An important part of the immune system is its ability to keep itself from attacking other normal cells in the body. To do this, it uses “checkpoints” – molecules on immune cells that need to be turned on (or off) to start an immune response. Cancer cells sometimes use these checkpoints to avoid being attacked by the immune system. But newer drugs that target these checkpoints hold a lot of promise as treatments. Some of these drugs are already being used to treat other types of cancer, and they are now being studied for use in AML as well.

CAR T-cell therapy: This is a promising new way to get the patient's immune system to fight leukemia. For this technique, immune cells called T cells are removed from the patient’s blood and altered in the lab so they have specific substances (called chimeric antigen receptors, or CARs) that will help them attach to leukemia cells. The T cells are then grown in the lab and infused back into the patient’s blood, where they can now seek out the leukemia cells and attack them.

This technique has shown very promising results in early clinical trials against some other types of advanced, hard-to-treat leukemias. Although it’s not yet clear if it will work against AML, clinical trials are now in progress to find out. One concern with this treatment is that some people have had very serious side effects, including very high fevers and dangerously low blood pressure in the days after it’s given. Doctors are learning how to manage these side effects.