Researchers are now studying the causes, diagnosis, supportive care, and treatment of acute myeloid leukemia (AML) at many medical centers, university hospitals, and other institutions.
Genetics of leukemia
Scientists are making great progress in understanding how changes in the DNA inside normal bone marrow cells can cause them to develop into leukemia cells. A greater understanding of the genes (regions of the DNA) involved in certain chromosomal translocations or other 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 of these 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 whether they should receive more or less intensive treatment.
In the future, this information may also be used to help develop newer targeted therapies against AML (see below).
Detecting minimal residual disease
Progress in understanding the DNA changes in AML cells has already provided highly sensitive tests for detecting the smallest amount of leukemia left after treatment (minimal residual disease), even when so few leukemia cells are present 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 translocations or rearrangements. 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.
Many studies are being done to find more effective and safer treatments for AML.
Researchers are looking to find the most effective combination of chemotherapy (chemo) drugs while still avoiding unwanted side effects. This is especially important in older patients, who are less likely to benefit from current treatments.
Researchers are studying many new chemo drugs for use in AML, including:
- Sapacitabine, a type of drug known as a nucleoside analog, which has shown promise as a treatment option for older patients with AML
- Laromustine, a type of chemo drug known as an alkylating agent, which is also being tested as an option for in older adults with AML
- Tipifarnib, a newer type of drug known as a farnesyl transferase inhibitor, which has also shown promise in early studies. This and similar drugs are now being tested in larger clinical trials.
- Bortezomib (Velcade®), a type of drug known as a proteasome inhibitor. It is helpful in treating multiple myeloma and certain types of lymphoma. A recent study looked at adding this drug to chemo for AML with promising results.
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.
Treating acute promyelocytic leukemia (APL)
Most patients with APL are first treated with ATRA combined with chemo. Recent research has shown that combining ATRA with arsenic trioxide is at least as good for many patients. This combination had been used before, but often only for patients who couldn’t get the standard chemo drugs. More patients may now get ATRA plus arsenic as their first treatment, allowing them to avoid some of the side effects of chemotherapy.
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 under way to try to help determine exactly when autologous, allogeneic, and mini-transplants might best be used.
Chemo drugs can help many people with AML, but these drugs don’t always cure the disease. New targeted drugs that specifically attack some of the genetic changes seen in AML are now being developed. These drugs work differently than standard chemotherapy drugs.
In about 1 person out of 3 with AML, the leukemia cells have a mutation in the FLT3 gene. New drugs called FLT3 inhibitors, such as quizartinib, target this gene. They have shown activity against AML in early studies, especially when combined with chemotherapy. But so far, they are only available in clinical trials.
Changes in the c-KIT gene also appear to be important in some cases of AML. Drugs that target this gene, such as dasatinib (Sprycel®), are already used against other types of leukemia, and are now being studied against AML.
Many new drugs that target other changes in AML cells are now being studied as well. Examples include:
- Histone deacetylase (HDAC) inhibitors, such as vorinostat (Zolinza) and panobinostat
- Polo-like kinase (Plk) inhibitors, such as volasertib
- Aurora kinase inhibitors, such as AZD1152
The goal of immunotherapy is 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. Monoclonal antibodies are often used to treat lymphomas, but their use in leukemias has been more limited.
Gemtuzumab ozogamicin (Mylotarg®) is a monoclonal antibody with a cell poison attached to it. At one time was approved to treat AML in older patients, but it was taken off the market when studies found it didn’t seem very helpful in the long term. However, in recent years it is again showing promise in certain patients in clinical trials.
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.
Vaccine therapy: Scientists are studying ways to boost the immune reaction against leukemia cells by using vaccines. For example, in one vaccine, certain types of white blood cells (cells of the immune system) are removed from the patient’s blood and exposed to a protein found on many AML cells called Wilms’ tumor 1 protein (WT1). These cells are then given back to the patient by infusion into a vein (IV). In the body, these cells help other immune system cells to attack the leukemia. An early study of this vaccine showed promising results, but more research is needed to see if it will be useful. Other vaccines are being studied as well.
CAR T-cell therapy: This is a promising new way to get the 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 advanced, hard-to-treat types of lymphocytic 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.
Last Revised: 02/22/2016