How BTK Inhibitors Can Improve the Treatment of Chronic Lymphocytic Leukemia

Related: The New Approach to CLL Treatment

Although you have an increased number of abnormal white blood cells called lymphocytes in your blood, counts of your other blood cells are normal or close to normal. "The hope is that it’s not going to cause problems for a long time. And so the majority of patients when they’re diagnosed do not need treatment," Dr. Gerson says.

Instead, your doctor will do something referred to as "watchful waiting." They'll monitor your cancer closely during regular follow-up visits, looking for signs that it's starting to grow.

"Most people will need treatment eventually, but we hope that that’s many years down the line and that they’re doing well and feeling well for that entire time," says Dr. Gerson. "When it’s time for therapy, we have lots of treatment options."

Turning Off the ‘Light Switch’

One of those options is a relatively new class of medications called Bruton's tyrosine kinase (BTK) inhibitors, such as ibrutinib (brand name: Imbruvica) and acalabrutinib (brand name: Calquence). These drugs block the action of BTK, a protein that sends out the signals CLL cells need to grow and survive.

Related: How Is Calquence Used for Chronic Lymphocytic Leukemia? 

"BTK inhibitors are really elegantly designed," Dr. Gerson tells SurvivorNet. "The way I like to think about it is that there’s a light switch that’s turned on in the cancer. And if we can just turn off that light switch, then the cancer will stop growing. It won’t necessarily die completely or go away, but it’ll at least stop growing."

BTK inhibitors are targeted drugs. Unlike chemotherapy, which is strong medicine that indiscriminately kills all quickly-dividing cells, these drugs act much more precisely against the cancer. That means there's less harm to healthy cells, or what Dr. Gerson refers to as "collateral damage."

"We’ve moved far away from chemotherapy in the treatment of CLL in the past couple of years," he adds. The first BTK inhibitor to be FDA approved for the treatment of CLL was Imbruvica, which came along in 2013 and was approved in 2014. Calquence came along in 2019, and is now being used "quite extensively" in the treatment of this cancer.

Imbruvica is approved for people with CLL that hasn't responded to treatment, including those who have a change to chromosome 17. This drug is also now approved in combination with the monoclonal antibody, obinutuzumab (Gazyva), as a first treatment.

Another advantage to these new medications is that you take them by mouth, unlike chemotherapy, which is usually delivered through a vein into the bloodstream. The most common side effects with BTK inhibitors include:

• Lower than normal levels of white and red blood cells
• Diarrhea
• Nausea
• Fatigue
• Body aches
• Muscle and joint pain

If your doctor prescribes a BTK inhibitor for you, ask what to expect. Find out how the drug is likely to help you, what side effects it might cause, and what to do if you experience side effects.

The introduction of BTK inhibitors and other targeted drugs has changed the treatment of CLL, and improved the outlook for people with this cancer. Researchers are studying other new therapies that they hope will one day become part of the treatment regimen for this cancer.

"There’s lots of research of exciting things coming down the line," Dr. Gerson says. "We really hope to turn this into a chronic disease. Even though it is a cancer, it’s something that people live with and they live a good life with."

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