According to the results of a new study published in Science Translational Medicine, a combination regimen consisting of a BCR-ABL tyrosine kinase inhibitor (TKI) and a B-cell lymphoma 2 (BCL-2) inhibitor may one day result in a cure for chronic myeloid leukemia (CML).

Researchers have tested the treatment in mice, where it completely eradicated the disease. The finding is significant because current CML treatments with BCR-ABL TKIs alone only suppress the cancer, not eliminate it, and patients must be on those TKIs the rest of their lives. Additionally, after long-term use of TKIs, some patients can acquire mutations that result in drug resistance and progress to blast crisis, which is fatal.

The new approach adds a BCL-2 inhibitor to reactivate apoptosis in tumor cells. The U.S. Food and Drug Administration approved the BCL-2 inhibitor in April 2016 for the treatment of patients with chronic lymphocytic leukemia with 17p deletion.

And the new drug offers fast results in clinical trials. The mouse study saw increased survival after only 23 days, and a small study from 2013 found results in just 24 hours after a single dose. However, the researchers cautioned that human studies are needed to confirm the results and move the treatment forward.

The discovery is significant because as a class of drugs, TKIs are extremely expensive. Another recent study, published in the Journal of Clinical Oncology, looked at the cost burden of the drugs on patients. Patients with Medicare Part D could pay $3,000 out of pocket for their first month’s supply, although the cost lowers to about $550 per month after they reach an annual spending threshold. But even patients with private insurance pay high rates, with estimates of about $8,500 per year out of pocket.

Winn et al.’s study found that the cost was a deterrent to patients starting the life-saving treatment. They analyzed Surveillence, Epidemiology, and End Results program and Medicare data for patients with CML from 2007 to 2011 to determine the time interval from when patients were diagnosed to when they began TKI therapy. Of the 393 patients with data available, almost 32% had not started therapy within six months of their diagnosis.

The authors noted that clinical guidelines recommend that TKI treatment begins immediately after a CML diagnosis. Delaying the treatment can lead to worse clinical outcomes, increased risk of stem cell transplantation, and potentially decreased life expectancy. 

After six months, most of the patients who had delayed treatment did begin TKI therapy. The researchers hypothesized that patients were using the delay to find the funds to pay for the treatment.