Retrospective Real-Life Comparison of Obinutuzumab Plus Chlorambucil Versus Ibrutinib in Previously Untreated and Unfit Patients with Chronic Lymphocytic Leukemia without TP53 Disruptions. Interim Results from the Italian CLL Campus
Authors: Visentin Andrea , Mauro Francesca Romana , Pietrasanta Daniela , Fresa Alberto , Vitale Candida , Ciolli Stefania , Cassin Ramona , Cibien Francesca , Sportoletti Paolo , Gentile Massimo , Rigolin Gian Matteo , Quaglia Francesca M. , Murru Roberta , Gozzetti Alessandro , Molica Stefano , Marchetti Monia , Scarfo Lydia , Reda Gianluigi , Coscia Marta , Laurenti Luca , Pizzolo Giovanni , Semenzato Gianpietro , Foà Robin , Cuneo Antonio , Trentin Livio 
Published: November 2020

INTRODUCTION. Kinase inhibitors and glycoengineered monoclonal antibody, such as obinutuzumab (G), have significantly changed the treatment landscape of chronic lymphocytic leukemia (CLL). Both like the BTK inhibitor ibrutinib (IB) and obinutuzumab plus chlorambucil (G-CHL) are approved as first line therapy in CLL patients unfit for a fludarabine-base treatment. While IB has proved to be superior to bendamustine-rituximab in a phase 3 trial and an ongoing retrospective ERIC study, no head-to-head comparison has been done for IB vs G-CHL in a real-world evidence study.
The aim of this study was to compared the clinical efficacy of the fixed duration G-CHL treatment vs continuous treatment with IB.
METHODS. The inclusion criteria for this observational study were patients with a diagnosis of CLL, requiring treatment according to the iwCLL guideline (Hallek M, Blood 2018) and considered unfit for fludarabine-base therapy by the treating physician belonging to the Italian CLL campus. Patients received ibrutinib 420mg daily until progression or unacceptable toxicity, while G was administrated at 100mg on day 1, 900mg on day 2 and 1000mg on days 8 and 15 of the 1st cycle, then at 1000mg from cycles 2-6. Chlorambucil was administrated according to the local policy. An IGHV gene sequence homology ³98% was considered as unmutated (U-IGHV), as opposed to mutated (M-IGHV). TP53 disruptions (TP53dis) included deletions and mutations. Progression-free survival (PFS), time-to-next treatment (TTNT) and overall survival (OS) were calculated according to the iwCLL 2018 guideline. Minimal residual disease (MRD), assessed by flow cytometry, was considered undetectable when &lt;10-4 (uMRD4). Survival curves were compared with the log-rank test and p&lt;0.05 was considered as significant. The study was approved by the ethic committee of Padua university hospital.
RESULTS. We recruited 284 CLL patients from 16 hematologic centers, 104 were treated with G-CHL and 180 with IB as first-line treatment. Once TP53dis cases were excluded, 102 patients treated with G-CHL and 80 treated with IB were included for further analysis. Among patients managed with G-CHL the median age was 75 years and 20% were older than 80 years, 47% had a CIRS≥6 (range 2-18), 68% had a clearance creatinine &lt;70ml/min, 60% showed a Rai stage III-IV, 32% were U-IGHV and 11% harbored 11q deletion by FISH. Patients treated with IB displayed a better renal function (p=0.0011) and were enriched in U-IGHV cases (p=0.0001).
After a median follow-up of 21 months, 23 patients relapsed (20 G-CHL, 3 IB), 16 required a subsequent treatment (14 G-CHL, 2 IB) and 17 died (10 G-CHL and 7 IB). Two patients in the IB arm developed Richter syndrome. After 8 months from the start of treatment, the overall response rates in the G-CHL and IB arms were 86% vs 77% (p=0.1480), including 25% vs 6% complete remissions (CR, p=0.0013) and 61% vs 71% partial responses (PR, p=0.6320). Remarkably, an uMRD4 by flow-cytometry was documented in 42% and 9% of G-CHL patients in the peripheral blood and bone marrow, respectively.
The median PFS was 33 months for G-CHL arm, but not reached for IB patients. The 24months PFS, TTNT and OS was 67% vs 91% (p=0.0012), 83% vs 97% (p=0.0128) and 89% vs 95% (p=0.5314) for the G-CHL and IB arms, respectively. Interestingly, the depth of response influenced PFS only in the G-CHL arm both in terms of clinical response (the median PFS was 8, 29 and 38 months for no responding, PR and CR patients) and MRD status (the 24 months PFS was 82% vs 50% and 100% vs 58% for uMRD4 vs MRD+ evaluated on peripheral blood and bone marrow). While the PFS was significantly better with IB than with G-CHL in U-IGHV (p=0.007), it was superimposable for M-IGHV patients (p=0.1946).
Dose reductions or discontinuations were recorded in 39% and 44% of patients in the G-CHL and IB arms. Atrial fibrillation and infections occurred in 2% and 6% (p=0.0442), and in 25% and 17% (p=0.1455) of patients in the G-CHL and IB arms, respectively.
CONCLUSIONS.
The Italian experience with G-CHL confirms the marked efficacy and safety of this combination, in particular for patients who reach a CR and/or an uMRD4. The continuous treatment with ibrutinib provides a better disease management in CLL patients unfit for fludarabine-base therapy, but some on them - particularly those with a M-IGHV status - can achieve a long-term disease control with a fixed duration obinutuzumab-based chemoimmunotherapy.

Disclosures
Visentin: Janssen: Honoraria; Gilead: Honoraria; Abbvie: Honoraria. Mauro:Takeda: Membership on an entity's Board of Directors or advisory committees; Octopharma: Consultancy; Astrazeneca: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jannsen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Vitale:Janssen: Honoraria. Ciolli:Janssen: Honoraria; Abbvie: Research Funding. Sportoletti:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rigolin:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Murru:Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Gozzetti:Janssen: Honoraria, Research Funding; Takeda: Honoraria; Amgen: Honoraria. Molica:Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees. Marchetti:Pfizer: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees. Scarfo:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Honoraria. Reda:Gilead: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Coscia:Karyopharm Therapeutics: Research Funding; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Laurenti:Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees. Pizzolo:Abbvie: Speakers Bureau; janssen: Speakers Bureau. Semenzato:Takeda: Honoraria; Roche: Honoraria; Abbvie: Honoraria. Foà:Novartis: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees. Cuneo:Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Trentin:Shire: Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Octapharma: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees.