What Are Tyrosine Kinase Inhibitors?

Tyrosine kinase inhibitors (TKIs) are a form of targeted therapy used to treat certain types of cancer. TKIs block the action of tyrosine kinase enzymes in cells, which may stop cancer cells from growing and multiplying.

This article will explain how tyrosine kinase inhibitors work and list some of the cancers they are able to treat. It will also describe how TKIs are administered and provide information about their effectiveness.

Definition

Tyrosine kinase inhibitors are targeted therapy drugs. They’re sometimes referred to as cancer growth blockers or cancer growth inhibitors.

TKIs are taken orally in pill, capsule, or liquid suspension form. They work by disrupting the signaling pathways that tyrosine kinases use to control cell growth and division. This may help keep cancer cells from growing and multiplying uncontrollably.

Tyrosine kinases are enzymes (proteins) that control cell functions, such as cell signaling, cell growth, and division. These enzymes become abundant and overactive in some types of cancer cells.

Chemical growth factors that control cell growth trigger the action of tyrosine kinases within cells. Growth factors bind to receptors on the surface of cells. This turns on tyrosine kinases within the cells, signaling them to divide.

Conditions Treated

TKIs are used to treat many types of cancer, including:

• Gastrointestinal stromal tumors: Soft tissue sarcomas found in the digestive tract
• Waldenstrom macroglobulinemia: A rare type of non-Hodgkin's lymphoma
• Kidney cancer: Cancer that begins in kidney cancer cells
• Chronic lymphocytic leukemia: A slow-growing type of blood and bone marrow cancer (leukemia)
• Chronic myeloid leukemia: A slow-growing, chronic form of leukemia that starts in the myeloid line of blood cells
• HER2-positive breast cancer: Breast cancer that tests positive for human epidermal growth factor receptor 2, a type of protein
• Brain-metastatic breast cancer: Breast cancer that has spread (metastasized) to the brain

Process

TKIs are oral medications you take by mouth at home. Some medications must be taken with food. Others may be taken with or without food. You may be instructed to take TKIs at the same time each day, once or twice daily.

The length of time you're required to take TKIs varies. In some instances, you may take this medication for a year or longer. Some chronic cancers may require the daily use of TKIs for an indefinite period of time.

In order for TKIs to be effective, you should use them exactly as your healthcare provider prescribes. Don't skip pills or adjust the dosage without speaking to your healthcare provider first. If you inadvertently miss a dose, let your healthcare provider know.

TKIs can cause serious interactions with other prescribed medications and over-the-counter (OTC) drugs. Let your healthcare provider know about every drug and supplement you currently take. Some foods may also cause serious interactions. These include pomegranates and grapefruit.

TKIs may be the first (frontline) cancer treatment you are given. They may also be given in conjunction with other treatments, such as chemotherapy, radiation, or surgery.

You will be monitored by your healthcare provider while undergoing TKI treatment to see how you're managing and how your cancer is responding. In the beginning, this may require a weekly or biweekly appointment. At appointments, you and your healthcare provider will discuss the side effects you may be having.

The side effects of TKIs vary by drug. Some common side effects are:

• Diarrhea
• Nausea
• Vomiting
• Fluid buildup
• Fatigue
• Skin rashes

These side effects can affect many organ systems (heart, lungs, muscles, bones, nervous system). Some conditions of these systems can make you ineligible for taking some TKIs.

At your exams you may have diagnostic tests done, such as blood tests. Some types of cancer may require bone marrow testing or imaging tests.

If the TKI you're prescribed doesn't work or stops working, your healthcare provider may prescribe a different type of TKI.

Types

There are around 50 TKI drugs for cancer approved by the Food and Drug Administration (FDA). The kind you're prescribed will be determined by the genetic characteristics of the cancer you have and the stage it is in, meaning the extent of your cancer, such as how much cancer there is and whether it has spread. Not every type of cancer can be treated with TKI medication.

Some TKIs only block one type of tyrosine kinase enzyme. These drugs are known as single TKIs. Other TKIs are able to block several types of tyrosine kinase enzymes. These drugs are known as multi TKIs.

Eligibility

To determine your eligibility for a particular TKI drug, your healthcare provider will take your age and overall health into account. Other health conditions you have and the medications used to treat them may also affect eligibility.

Since they can harm an unborn fetus, TKIs are not recommended during pregnancy. If you're pregnant or wish to become pregnant, let your healthcare provider know. Treatment-free remission periods may occur during TKI treatment. It may be possible to schedule pregnancy during one of these time frames.

Your willingness and ability to take your drugs as prescribed may also impact your ongoing eligibility. In some instances, symptom severity may be an issue.

Don't stop taking a drug or skip doses in order to reduce symptoms. In some instances, your healthcare provider may be able to prescribe medications that provide symptom relief. They may decrease the dose and then raise it again stepwise (called titration) while monitoring your symptoms, or they may switch you to another drug.

Outcomes/Recovery

TKIs can be effective for treating certain types of cancer but may not be a cure. Talk to your healthcare provider about the outcome you can expect based on the cancer you have and the stage it's in.

Some drugs, such as Qinlock (ripretinib) and Sutent (sunitinib), have been shown to shrink tumors and slow tumor growth in people with gastrointestinal stromal tumors. Others, such as Gleevec (imatinib) and Sprycel (dasatinib), may prolong the chronic phase of chronic myeloid leukemia.

Whether they're used alone or in conjunction with other treatments, TKIs may provide you with positive therapeutic effects and an optimistic outcome.

Summary

Tyrosine kinase inhibitors (TKIs) are targeted therapy cancer medications. TKIs are used alone or in conjunction with other treatments to treat many cancers, including some types of breast cancer and leukemia.

TKIs have been shown to shrink tumors and slow tumor growth. They are taken as daily or twice-daily oral medications you use at home. TKIs may be prescribed for prolonged use. Side effects can include nausea, vomiting, and diarrhea.

A Word From Verywell

Cancer is a complicated disease to treat. There are many types, and even the same type may not behave the same way in different people. Having cancer is frustrating and scary, to say the least. Fortunately, there are many therapies, including TKIs, that can successfully treat cancer and provide good outcomes.

You and your healthcare provider can discuss TKIs and their viability for your condition. Even if the first one prescribed doesn't work for you, there may be others that will be a better fit.