Photo courtesy of Janssen
Health Canada has approved the Bruton’s tyrosine kinase inhibitor ibrutinib (Imbruvica®) as a first-line treatment for patients with active chronic lymphocytic leukemia (CLL).
This is the fourth approval for ibrutinib in Canada. The drug is now approved for use in all CLL patients, patients with Waldenström’s macroglobulinemia, and patients with relapsed or refractory mantle cell lymphoma (conditional approval).
Ibrutinib is jointly developed and commercialized by Pharmacyclics LLC, an AbbVie company, and Janssen Biotech, Inc.
The latest approval of ibrutinib is based on results from the phase 3 RESONATE-2 trial
(PCYC-1115), which were presented at the 2015 ASH Annual Meeting and
simultaneously published in NEJM.
RESONATE-2 enrolled 269 treatment-naïve patients with CLL or small lymphocytic lymphoma who were 65 or older.
Patients were randomized to receive ibrutinib (n=136) at 420 mg once a day until progression or unacceptable toxicity, or chlorambucil (n=133) on days 1 and 15 of each 28-day cycle for up to 12 cycles. The starting dose for chlorambucil in cycle 1 was 0.5 mg/kg and was increased based on tolerability in cycle 2 by increments of 0.1 mg/kg to a maximum of 0.8 mg/kg.
The primary endpoint of the study was progression-free survival (PFS), as assessed by an independent review committee (IRC) according to the International Workshop on Chronic Lymphocytic Leukemia (iWCLL) 2008 criteria, with modification for treatment-related lymphocytosis.
Key secondary endpoints included overall response rate (based on the same iWCLL criteria), overall survival (OS), and safety.
Ibrutinib significantly prolonged PFS, as determined by the IRC, reducing the risk of progression or death by 84% compared to chlorambucil. The hazard ratio was 0.16 (P<0.001). The median PFS was not reached in the ibrutinib arm but was 18.9 months for the chlorambucil arm.
Ibrutinib significantly prolonged OS as well, although the median OS was not reached in either treatment arm. The OS rate at 24 months was 98% with ibrutinib and 85% with chlorambucil. The relative risk of death with ibrutinib was 84% lower than that with chlorambucil. The hazard ratio was 0.16 (P=0.001).
Ibrutinib was associated with a significantly higher IRC-assessed overall response rate compared to chlorambucil—82% and 35%, respectively (P<0.0001). Five
patients (4%) in the ibrutinib arm achieved a complete response, as did 2 patients (2%) in the chlorambucil arm.
The median duration of treatment was 17.4 months in the ibrutinib arm and 7.1 months in the chlorambucil arm.
The most common adverse events of any grade—in the ibrutinib and chlorambucil arms, respectively—were diarrhea (42% and 17%), fatigue (30% and 38%), cough (22% and 15%), nausea (22% and 39%), peripheral edema (19% and 9%), dry eye (17% and 5%), arthralgia (16% and 7%), neutropenia (16% and 23%), and vomiting (13% and 20%).
Adverse events of grade 3 or higher—in the ibrutinib and chlorambucil arms, respectively—were neutropenia (10% and 18%), anemia (6% and 8%), hypertension (4% and 0%), pneumonia (4% and 2%), diarrhea (4% and 0%), maculopapular rash (3% and 2%), decreased platelet count (3% and 1%), abdominal pain (3% and 1%), hyponatremia (3% and 0%), thrombocytopenia (2% and 6%), febrile neutropenia (2% and 2%), upper respiratory tract infection (2% and 2%), pleural effusion (2% and 1%), cellulitis (2% and 0%), fatigue (1% and 5%), syncope (1% and 2%), and hemolytic anemia (0% and 2%).
