Based on the results of the first in-human clinical trial of ibrutinib in chronic lymphocytic leukemia (CLL) – conducted in 2010 at Weill Cornell Medicine/NewYork-Presbyterian Hospital and other centers – researchers led in part by Dr. Richard Furman moved forward with the first phase II trial of the drug. According to a five-year follow-up study recently published in the American Society of Hematology’s Blood journal, ibrutinib continues to demonstrate excellent efficacy and tolerability as a single agent therapy for people with previously untreated and relapsed or refractory CLL.
CLL is characterized by uncontrolled growth of mature B-cells that accumulate in the blood, bone marrow, lymph nodes and spleen. As CLL cells fill these various organs, they interfere with normal cell functions. Ibrutinib is an oral treatment that inhibits Bruton’s tyrosine kinase (BTK), an enzyme involved in B-cell development that plays a critical role in CLL cell survival.
Prior to the Food and Drug Administration (FDA) approval of ibrutinib for CLL in 2014, chemoimmunotherapy (CIT), typically with fludarabine, cyclophosphamide and rituximab (FCR), was one of the only treatment options available for people with CLL. Chemoimmunotherapy often generates deep responses that last a median of five to six years, but it is associated with significant toxicities. When patients relapse after CIT, their disease becomes more resistant to subsequent treatments, and due to the accumulation of toxicities, many patients are unable to receive further CIT. Given the associated toxicities, the use of CIT is limited in older patients with comorbidities – the cohort that comprises the majority of CLL patients.
The phase II study in which Dr. Furman was involved tested ibrutinib as a single agent in over 100 patients – some of whom received no prior therapy, and others who relapsed following initial treatment. Patients received daily oral doses of ibrutinib until their disease progressed or until the presence of side-effects warranted discontinuation of therapy.
Almost 90 percent of all patient participants demonstrated a response to treatment at the five-year mark, and complete remission rates increased over time with ongoing treatment. Ninety-two percent of treatment-naive patients and 44 percent of relapsed/refractory patients remained free of disease progression five years out from the start of treatment.
Side-effects, including infections, diarrhea, bleeding and low-blood counts, were mild. They did not prevent patients from remaining on treatment long-term and often improved with continued dosing.
“These data demonstrate the excellent long-term outcomes for CLL patients treated with ibrutinib, especially those who receive ibrutinib as their first therapy,” says Dr. Furman.
Dr. Furman noted that current CLL therapies are effective, but they often lead to complications. CLL patients treated with standard chemotherapy drug combination fludarabine, cyclophosphamide, rituximab (FCR) are often prone to developing treatment resistance or Richter’s transformations (RT), in which their CLL transforms into a more aggressive diffuse large B-cell lymphoma (DLBCL). They may also succumb to infectious complications, adverse events, or secondary malignancies.
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