Imbruvica (ibrutinib) produces long-lasting anti-cancer responses among patients with newly diagnosed chronic lymphocytic leukemia (CLL), as well as those who have received prior therapies. These results were recently presented at the 2016 annual meeting of the American Society of Clinical Oncology (ASCO).
Chronic lymphocytic leukemia is the most common form of adult leukemia. The American Cancer Society estimates that approximately 15,000 people will be diagnosed with CLL this year. Currently, there are approximately 95,000 people in the United States living with CLL.
CLL is characterized by the production of atypical lymphocytes. Lymphocytes are specialized immune cells that exist in two forms: B- and T-cells. These cells are produced in the bone marrow and each serves a specific function in aiding the body to fight infection. The large majority of CLL cases involve mature B-lymphocytes that tend to live much longer than normal. B-lymphocytes accumulate in the blood, bone marrow, lymph nodes, and spleen. This results in overcrowding of these areas and suppression of the formation and function of blood and immune cells. Additionally, the cancerous lymphocytes themselves do not function normally, leading to a further reduction in the body’s ability to fight infection.
CLL is diagnosed most commonly in elderly patients (65 years or greater). Since these patients are often unable to tolerate aggressive therapies compared to their younger counterparts due to additional medical conditions and/or differences in the metabolizing of the agents, the toxicity of treatment is an important issue.
Ibrutinib is a first-in-class oral agent that inhibits the activity of Bruton’s tyrosine kinase (BTK). Within CLL cells, BTK is a protein/carbohydrate complex that is involved in maintaining cellular survival and replication. By inhibiting the activity of BTK, ibrutinib reduces the growth of cancer and causes cellular death. Ibrutinib is approved for the treatment of CLL, and continues to be studied in different types of cancers.
Researchers recently analyzed data from two different large trials (the RESONATE and RESONATE-2 trials) in an attempt to determine the effectiveness of ibrutinib in different lines of therapy among patients with CLL.
Some patients had not received prior therapy to ibrutinib (referred to as treatment naïve or TN), while other patients had received at least one prior therapy before starting treatment with ibrutinib (referred to as previously treated or PT). Patients with the del17p mutation were not included in this analysis.
- At 2 years, the median survival time without progression of disease, as well as the median overall survival time had not yet been reached for either TN or PT patients.
- Patients treated with a greater number of prior therapies before receiving ibrutinib had an increased likelihood of discontinuing ibrutinib due to disease progression, compared to those who had received 0-1 prior therapies before receiving ibrutinib.
- Among patients who discontinued treatment with ibrutinib, those who received 0-1 prior therapies have not yet reached median overall survival following discontinuation of ibrutinib; however, those who received 2 or more prior therapies had a median overall survival of 7-9 months following discontinuation of ibrutinib.
- Side effects of ibrutinib were comparable between TN and PT patients.
- Anti-cancer responses with ibrutinib were high, despite the number of prior therapies received.
The researchers concluded that ibrutinib produces favorable anti-cancer responses, survival without progression of cancer, and overall survival among patients with CLL, regardless of the number of prior therapies. However, patients who had received 0-1 prior therapies were less likely to experience cancer progression on ibrutinib, and demonstrated an improved survival following discontinuation of ibrutinib, compared to those who received 2 or more prior therapies.
Reference: O’Brien S, Byrd J, Hillmen P, et al. Outcomes with ibrutinib by line of therapy in patients with CLL: Analyses from phase III data. Proceedings from 2016 ASCO. Abstract # 7520. Available at: http://meetinglibrary.asco.org/content/164543-176. Accessed June 29, 2016.
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