Ibrutinib and Obinutuzumab in CLL: Improved MRD Response Rates with Substantially Enhanced MRD Depletion for Patients with >1 Year Prior Ibrutinib Exposure

• Published in: Blood 2018-11, Vol.132 (Supplement 1), p.181-181
• Main Authors: Rawstron, Andy, Munir, Talha, Brock, Kristian, Webster, Nichola, Munoz Vicente, Samuel, Yates, Francesca, Cramp, Sophie, Bishop, Rebecca, Dalal, Surita, De Tute, Ruth M, Sheehy, Oonagh, Pettitt, Andrew, Fox, Christopher P., Devereux, Stephen, Fegan, Christopher, MacDonald, Donald, Bloor, Adrian, Hillmen, Peter
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2018-181

Background: Ibrutinib inhibits CLL cell proliferation and results in prolonged remission, but MRD responses are rare. Obinutuzumab is a second generation anti-CD20 monoclonal antibody that is effective in CLL and can result in MRD responses. In the IcICLLe study (ISRCTN12695354), 40 participants with CLL requiring treatment (20 treatment-naïve, 20 with relapsed/refractory [R/R] disease) received ibrutinib until complete remission with 1 year prior ibrutinib. Patients: The IcICLLe Extension Study recruited 40 participants with relapsed/refractory CLL requiring treatment. They received continuous ibrutinib (420mg OD) with 6 cycles of obinutuzumab given over 6 months (M). Ten participants had >1 year of prior ibrutinib monotherapy in IcICLLe and 30 were ibrutinib-naïve with obinutuzumab started 24 hours after first ibrutinib dose. Patient characteristics and Adverse Events (AEs, collected from registration until 30 days after treatment cessation and reported at 1, 3, and 6M, and 6-monthly thereafter using the Common Terminology Criteria for Adverse Events v4.0) are shown in Table 1. MRD assessment was performed according to ERIC guidelines with a maximum detection limit of 0.001%/10-5. Results: In the 20 R/R patients treated with ibrutinib monotherapy there were no IWCLL CR/CRi responses and no patients achieved