The Food and Drug Administration (FDA) has expanded the use of the anticancer drug Imbruvica (ibrutinib) to be used in combination with rituximab for the treatment of the most common type of leukemia in adults, chronic lymphocytic leukemia (CLL), or its variant called small lymphocytic lymphoma (SLL). This approval gives patients with CLL/SLL who have not yet received any treatment for their cancer another chemotherapy-free treatment option and represents the 11th FDA-approved indication for Imbruvica since its initial approval in 2012.
It is estimated that more than 21,000 people in the United States were diagnosed with CLL in 2020. At the time of diagnosis, many patients do not have symptoms, but as time and their cancer progresses, CLL can begin to cause signs and symptoms like severe tiredness, shortness of breath, spleen and lymph node enlargement, and infections.
Imbruvica is in a class of anticancer drugs called targeted therapies, and rituximab is in a class of drugs called monoclonal antibodies. As cancer doctors and researchers have learned more about CLL/SLL and have come to better understand this type of cancer, combining monoclonal antibodies and targeted agents has become an important treatment alternative to chemotherapy-containing regimens.
Brian Koffman, MDCM, DCFP, FCFP, DABFP, MSEd, chief medical officer and executive vice president of the CLL Society, said: “The gold-standard first-line treatment option for many patients with chronic lymphocytic leukemia who were fit enough to tolerate an aggressive treatment course had been the intravenous chemoimmunotherapy of FCR [fludarabine, cyclophosphamide, and rituximab]—that is, until today.”
In a phase 3 clinical trial of patients with CLL/SLL, 529 participants who had not yet received treatment for their cancer were given either Imbruvica/rituximab or FCR. Phase 3 trials compare a new drug or treatment to the best treatment available for a certain type of cancer. These trials involve hundreds of patients and evaluate the effectiveness and side effects of each treatment being studied.
Results from the trial showed that patients given Imbruvica and rituximab had a significant improvement in progression-free survival (PFS) when compared with the 3-drug combination. PFS is defined as the length of time during and after treatment that a patient lives without the cancer getting worse.
How to Take Imbruvica
When given either alone or in combination with rituximab, the recommended dose of Imbruvica for CLL/SLL is 420 mg by mouth once a day until the cancer gets worse or side effects become unmanageable. When Imbruvica is given with rituximab on the same day, Imbruvica should be given before the rituximab infusion.
Imbruvica should be taken at about the same time each day with a full glass of water, and the tablets should not be cut, crushed, or chewed. Patients shouldn’t consume food or drinks containing grapefruit or Seville oranges (often used in marmalades) when taking this drug, because these fruits are considered CYP3A inhibitors and might increase the risk of side effects. Other drugs that are strong inhibitors of CYP3A (like clarithromycin or erythromycin) may also increase the risk of side effects on Imbruvica. CYP3A inducers (like rifampicin or St. John’s wort) should also be avoided during treatment, as they may make the drug less effective.
If a dose is missed, take it as soon as you remember on the same day, and take your next dose at your regular time on the next day. Patients should not take more of this medicine than they’ve been prescribed, even if attempting to make up for missed doses.
Before taking Imbruvica, patients should tell their doctor about any medical conditions, including: if they have had recent surgery or plan to have surgery (the healthcare provider may stop Imbruvica for any planned medical, surgical, or dental procedure); if they have bleeding problems; if they have or have had heart rhythm problems, smoke, or have a medical condition that increases the risk of heart disease (such as high blood pressure, high cholesterol, or diabetes); if they have an infection; or if they have liver problems. Patients should also tell their healthcare provider about any prescription and over-the-counter medicines they take, including vitamins and herbal supplements, because taking Imbruvica with certain other medicines may cause side effects or affect how it works.
Women who are pregnant or plan to become pregnant should not take this drug because it can cause harm to an unborn baby or result in a miscarriage. Females who can become pregnant and males with female partners who can become pregnant should always use effective birth control when taking this drug, and for 1 month after the final dose. Patients should also avoid breastfeeding during treatment and for 1 week after the final dose.
Common Side Effects of Imbruvica
Imbruvica can cause serious and potentially deadly side effects like bleeding problems (hemorrhage). Patients should tell their doctor about any signs of bleeding, like black stools, increased bruising, or pink or brown urine.
Infections (bacterial, viral, or fungal) can occur while taking Imbruvica, so patients who are at increased risk for opportunistic infections should be considered for medication that can prevent infections, and they should tell their doctor right away
if they have fever, chills, weakness, confusion, or other signs of an infection during treatment.
Decreased blood counts (white blood cells, platelets, and red blood cells) are also common and can be severe, so monthly blood tests should be conducted during treatment. Heart rhythm problems (ventricular arrhythmias, atrial fibrillation, and atrial flutter) can occur, especially in people who have an increased risk for heart disease, have an infection, or who have had heart rhythm problems in the past, so tell your healthcare provider about any symptoms of heart rhythm problems, such as feeling like your heart is beating quickly and irregularly, lightheadedness, dizziness, shortness of breath, chest discomfort, or fainting. New or worsening high blood pressure has happened in people treated with this drug, so for some patients, blood pressure medicine or a change of current medicines may be necessary to treat blood pressure.
Imbruvica has also been linked to a risk for second primary cancers (new cancers, most often nonmelanoma skin cancer), as well as tumor lysis syndrome.
Among patients older than 65 years who received treatment with Imbruvica, anemia, pneumonia, thrombocytopenia (low blood platelet count), high blood pressure, and atrial fibrillation (irregular heartbeat) were seen more frequently than in younger patients, although the effectiveness of the drug is no different between these age-groups.
Other common side effects of Imbruvica include diarrhea (so patients should drink plenty of fluids during treatment to reduce the risk of dehydration), tiredness, muscle and bone pain, rash, and bruising. However, patients should note that these are not all of the possible side effects of Imbruvica, so people using this drug should always call their doctor with any concerns.
Imbruvica in combination with rituximab is a combination of targeted (nonchemotherapy) drugs for previously untreated patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. This combination has superior efficacy when compared with the previous “gold standard” treatment of chemoimmunotherapy.