Efficacy and Tolerability of Bosutinib and Imatinib in Older Versus Younger Patients with Newly Diagnosed Chronic Phase Chronic Myeloid Leukemia–BELA Trial
Authors: Gambacorti-Passerini Carlo , Brümmendorf Tim H , Kim Dong-Wook , Dyagil Irina , Kantarjian Hagop M , Pavlov Dmitri , Gogat Karin , Duvillie Ladan , Shapiro Mark , Cortes Jorge E 
Published: October 2019

Abstract
Abstract 4442
Bosutinib (BOS) is an orally active, dual Src/Abl kinase inhibitor with activity and manageable toxicity in the phase 3 BELA trial of patients (pts) with newly diagnosed (≤6 mo) chronic phase (CP) chronic myeloid leukemia (CML).
The current analysis of the BELA trial summarizes the activity and tolerability of BOS 500 mg/d and imatinib (IM) 400 mg/d among older (≥65 y; BOS n = 30; IM n = 27) versus younger pts (<65 y; BOS n = 220; IM n = 225). Sokal risk scores were balanced between treatment arms but, as expected, higher among older pts (4% low; 72% intermediate; 25% high) versus younger pts (39% low; 44% intermediate; 17% high). Minimum follow-up duration was 24 mo. BOS was discontinued by 37% of pts (57% older vs 35% younger; P = 0.023); difference between age groups was primarily due to adverse events (AEs; 39% vs 22%; most commonly increased alanine aminotransferase [ALT]). IM was discontinued by 27% of pts (35% older vs 28% younger; P= 0.496); disease progression was the primary reason.
In the intent-to-treat population, cumulative rate of complete cytogenetic response (CCyR) by 24 mo in older/younger pts was 70%/80% on BOS and 78%/80% on IM. Median time to CCyR was 24.0 wk for older versus 12.7 wk for younger pts on BOS and 24.4 wk versus 24.7 wk on IM; in younger pts CCyR was achieved significantly faster on BOS versus IM (P<0.001). Among older/younger pts with a CCyR, 57%/79% on BOS and 76%/85% on IM were still on treatment and retained their CCyR as of the data cutoff.
Cumulative rates of major molecular response (MMR) by 24 mo in older/younger pts were 53%/60% on BOS and 48%/49% on IM. Median time to MMR was 48.1 wk for older versus 48.0 wk for younger pts on BOS and 60.6 wk versus 84.1 wks on IM; for younger pts MMR was achieved significantly faster on BOS versus IM (P<0.001). Among older/younger pts with a MMR, 63%/84% on BOS and 92%/89% on IM were still on treatment and retained their MMR as of the data cutoff.
Kaplan-Meier event-free survival in older/younger pts at 2 y was 100%/91% on BOS and 81%/88% on IM. Kaplan-Meier on-treatment transformation to accelerated/blast phase CML by 2 y was 0% for older and 2% (4 transformations) for younger pts on BOS (4 total), and 9% (2 transformations) for older and 5% (11 transformations) for younger pts on IM (13 total). Kaplan-Meier overall survival in older/younger pts at 2 y was 100%/97% on BOS and 92%/95% on IM. The majority of deaths were due to disease progression (BOS, n = 6; IM, n = 10); few deaths due to AEs on BOS (n = 1) or IM (n = 2) were reported, none treatment related.
BOS was associated with higher rates of gastrointestinal TEAEs, elevated ALT and aspartate aminotransferase (AST), and pyrexia; IM was associated with higher rates of musculoskeletal TEAEs and edema (Table). Rates of common TEAEs were generally similar or higher among older pts. Pleural/pericardial effusion occurred in 6 (21%) older pts (3/6 with treatment-related events; median event duration, 36.5 d) versus 5 (2%) younger pts (all with treatment-related events) on BOS, and in no IM pts. Overall grade 3/4 TEAEs were more frequent among older pts on both BOS and IM, as was dose modification (Table).
Grade 3/4 lab abnormalities of elevated ALT (BOS, 18% older/24% younger; IM, 4% each) and AST (BOS, 7%/12%; IM, 4% each) were more frequent with BOS versus IM, but similar between age groups. Grade 3/4 lab abnormalities of neutropenia were more frequent with IM (23% older/22% younger) versus BOS (11% each) regardless of age; grade 3/4 anemia (6%-14%) and thrombocytopenia (14%-23%) were generally similar regardless of age or treatment arm.
In conclusion, BOS demonstrated activity in both older and younger pts with newly diagnosed CP CML. Although the frequency of certain toxicities as well as treatment discontinuations due to TEAEs was higher among older pts, the toxicity profile of BOS remained manageable and distinct from that of IM regardless of age.
Event, % BOS IM ≥65 y (n = 28) <65 y (n = 220) ≥65 y (n = 26) <65 y (n = 225) Non-hematologic TEAEsa     Diarrhea 86 68 46 22     Rash 36 22 27 18     Nausea 36 32 31 37     Vomiting 32 32 19 15     Dyspnea 32 5 12 3     Pyrexia 29 17 4 13     Elevated ALT 29 32 15 8     Elevated AST 25 27 15 8     Elevated lipase 25 12 19 10     Headache 21 12 8 12     Asthenia 21 5 4 7     Dyspepsia 14 6 23 5     Muscle spasms 14 3 35 21     Periorbital edema 7 <1 35 12 Any grade 3/4 TEAE 89 65 73 56 Dose reduction due to AE 64 40 42 18 Dose interruption due to AE 89 63 69 42 Treatment discontinuation due to AE 39 22 8 9 All treated pts were included in the safety analyses. a Includes TEAEs reported for ≥20% of older or younger pts.

Disclosures:
Gambacorti-Passerini: Pfizer Inc: Consultancy, Research Funding; Novartis, Bristol Myer Squibb: Consultancy. Brümmendorf:Bristol Myer Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy; Patent on the use of imatinib and hypusination: Patents & Royalties. Kim:BMS, Novartis, Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kantarjian:Pfizer Inc: Research Funding. Pavlov:Pfizer Inc: Employment, Equity Ownership. Gogat:Pfizer Inc: Employment, Equity Ownership. Duvillie:Pfizer Inc: Employment. Shapiro:Pfizer Inc: Employment, Equity Ownership. Cortes:Novartis, Bristol Myers Squibb, Pfizer, Ariad, Chemgenex: Consultancy, Research Funding.