Leukemia is a group of blood cancers that results in excess amounts of white blood cells.
There are both chronic forms of leukemia that progress slowly over many years and acute types of leukemia that evolve rapidly.
AML affects more than 20,000 people in the United States each year, and the mortality rate is high especially in older patients.
In a study from Karolinska Institutet and SciLifeLab, scientists found a common and inexpensive drug may be used to counteract treatment resistance in patients with acute myeloid leukemia (AML), one of the most common forms of blood cancer.
The researchers will now launch a clinical study to test the new combination treatment in patients.
One of the most common drugs to treat AML is cytarabine (ara-C), a cytotoxic drug that interferes with DNA replication.
However, many patients do not respond to the treatment because their leukemic cells express high levels of the enzyme SAMHD1, which breaks down the active metabolite of cytarabine, ara-CTP.
These patients have a significantly worse survival rate than patients with low leukemic levels of SAMHD1. Therefore, one promising strategy to improve the treatment of AML is to inhibit the effects of this enzyme on cytarabine.
In this study, the researchers tested the impact of more than 33,000 different substances on SAMHD1’s ability to break down ara-CTP in leukemia cells treated with cytarabine.
They found three different substances, so-called ribonucleotide reductase inhibitors (RNRi), that all reduced SAMHD1’s ability to deactivate ara-CTP: hydroxyurea, gemcitabine and triapine.
They found adding any of these three substances significantly improved the effectiveness of the cytarabine treatment in cell samples with high levels of SAMHD1.
This was true for AML samples from both adults and children. In AML-mice, we also saw that the median survival was significantly prolonged when cytarabine was combined with an RNR inhibitor.
Hydroxyurea is an inexpensive drug that is used to treat blood diseases such as AML. However, it has not systematically been used in combination with cytarabine.
Gemcitabine is a potent drug that is used to treat many different types of cancers, but it can be toxic if given repeatedly.
Triapine is a drug currently undergoing clinical studies for cancer treatment.
In animal studies, the combination therapies did not exhibit any excess side effects beyond those already established in cytarabine-treatments.
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The study was conducted by Nikolas Herold et al and published in EMBO Molecular Medicine.
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