Safety and Efficacy of Bosutinib in Fourth Line Therapy of Chronic Myeloid Leukemia Patients
Authors: García-Gutiérrez Valentín , Milojkovic Dragana , Martín Mateos María Luisa , Claudiani Simone , Boque Concepcion , Casado Luis Felipe , González Gloria , Jiménez Antonio , Martinez Trillos Alejandra , Mata Vázquez Isabel , Ramírez Payer Ángel , Álvarez Larran Alberto , Amutio Díez Elena , Bárez García Abelardo , Bautista Carrascosa Guiomar , Bobillo Varela Sabela , Cuevas Ruiz Beatriz , Fernández Fernández Mª Ángeles , García Garay María del Carmen , Giraldo Pilar , Guinea de Castro Jose María , De Las Heras Rodríguez Natalia , Hernanz Soler Nuria , Iglesias Pérez Ana , López Lorenzo José Luis , Martí Tutusaus Josep Maria , Omar Vallansot Rolando , Ortega Rivas Fernando , Puerta Jose Manuel , Ramírez Sánchez Maria Jose , Romero Picos Esperanza , Romo Collada Mario Andrés , Rosell Mas Ana , Saavedra Gerosa Silvana , Sebrango Sadia Ana , Tallón Pérez José , Valencia Sandra , Steegmann Juan Luis 
Published: October 2019

Abstract
BACKGROUND: Despite the excellent prognostic of chronic myeloid leukemia (CML) patients since the introduction of tyrosine kinase inhibitors (TKIs), approximately 50% of patients that are treated with TKIs will discontinue first line treatment due to lack of efficacy or intolerance. Once patients need a second line treatment, a considerable proportion of patients will need third or even fourth line therapy during further evolution. At this moment, there is a lack of data about real benefit of this group of patients. We have recently published our experience of 30 CML patients treated with bosutinib in 4th line. We present an update of the study where we have increased the number of patients, and the follow-up. The aim of this study is to present safety and efficacy data CML chronic phase patients treated with bosutinib in 4th line.
METHODS: We have collected data from 59 CML patients treated with bosutinib in 4th line after resistance or intolerance to IM, NI and DA. 51 patients have been treated under the Spanish compassionate use program (36 centers) and 10 patients were treated in a single institution from United Kingdom. Median age of patients at diagnosis was 53 years. The percentage of low, intermediate and high risk Sokal groups were 47%, 37% and 16%. Median time TKIs exposure before bosutinib was 9 years. The most common indication (30/59) was intolerant to DA and NI. Patients' dispositions and main line characteristics are shown in table 1.
RESULTS: Median follow-up was 14.3 months. All patients started bosutinib at 500mg/d, median dose of was 450mg/d. Overall probabilities to either achieve or maintain previous response were 96% (57/59), 62% (37/59), 40% (24/59) and 17% (10/59) for complete hematological response (CHR), complete cytogenetic response (CCyR), major molecular response (MMR) and MR4.5 respectively. However, probabilities to obtain responses (in patients without response evaluated at baseline) were 27% (7/26), 26% (12/45) and 12% (7/55) for CCyR, MMR and MR4.5. As expected, probabilities to obtain CCyR were lower for patients resistant to DA and NI patients than for patients intolerant to DA and NI (8% VS 44%). Event free survival (EFS) and progression free survival (PFS) probabilities were 50% and 83% by 27 month. Treatment was discontinued in 20/58 (34%), most frequent reasons being adverse events 9/59(15%), lack of efficacy 5/59 (8.5%), disease progression 2/59 (3.4%) and death 1/59 (1.7%). Two patients discontinued due to stem cell transplantation. The adverse events that led to treatment discontinuation were pleural effusion (3), diarrhea (2), rash, renal impairment, auricular fibrillation and liver enzyme elevation one patient each. Overall, bosutinib was well tolerated. Grade 3-4 hematological toxicities were 3%, 6% and 6% for anemia, thromboctytopenia and neutropenia. Most common non hematological side effects were diarrhea (39%, nauseas 13% and liver alterations 14% and pleural effusion 14%.
CONCLUSIONS: Little is known about the therapeutic role of Bosutinib in 4th line. The series presented here is, to our knowledge, the largest being presented. Bosutinib seems to be an appropriate treatment option for patients resistant or intolerant to three prior TKIs.
Table 1. IM+NI-I+DA-R (N=4) IM+NI-R+DA-R (N=18) IM+NI-I+DA-I (N=30) IM+NI-R+DA-I (N=7) Total (N=59) Sex, N (%) Male 2 (50) 11 (61.1) 16 (53.3) 2 (28.6) 31 (52.5) Median age of diagnosis, yr (range) 57.32 (50-64) 49.19 (23-73) 54.95 (21-89) 48.87 (26-68) 53.15 (21-89) Median age of Bosutinib initiation, yr (range) 69.13 (61-70) 62.27 (39-79) 64.85 (25-90) 64.79(35-74) 63.7 (25-9) Median follow up, months (range) 18.5(7.8-34.1) 8.4(1.22-36.1) 16.3(0.5-34.7) 23.4(3.3-28.9) 14.3(0.7-36.1) SOKAL Index at diagnosis, N (%) High 2(50.0) 4 (23.5) 1 (4.3) 1 (20) 8 (16.3) Intermediate 1 (25.0) 5 (29.4) 10(43.5) 2 (40) 18 (36.7) Low 1 (25.0) 8 (47.1) 12 (52.2) 2 (40) 23 (46.9) Median Time from first TKI to BOS, (yr, range) 10.3 (4.8-11.9) 9.3 (2.0-11.4) 8.8 (0.7-13.6) 8.2 (5.1-12.3) 8.8 (0.7-13.6) Median duration of prior therapy, months (range) Imatinib 38.8 (11.8-69.8) 32.6 (6.3-96.8) 26.2 (1.6-102.6) 23.1 (8.3-66.8) 28.8 (1.6-102.6) Dasatinib 21.5 (12.6-75) 21.8 (7.7-69) 31.4 (0.4-87.1) 23.7 (10.3-53.6) 23.44 (0.4-87.1) Nilotinib 19.1 (2.1-46.2) 16.7 (5-65.6) 8.9 (0.2-58.5) 30.9 (6.9-49.3) 14.3 (0.2-65.6) BOS: bosutinib, IM, imatinib; DA, dasatinib; NI, nilotinib, I: Intolerance, R: Resistant, Yr: year

Disclosures
García-Gutiérrez: Ariad: Consultancy; Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Milojkovic:Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Ariad: Consultancy, Honoraria; BMS: Consultancy, Honoraria. Boque:Novartis: Honoraria; BMS: Honoraria; Celgene: Honoraria. Casado:Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding. Jiménez:Pfizer: Consultancy, Honoraria. Giraldo:Pfizer: Consultancy. Steegmann:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pfizer: Consultancy, Honoraria, Research Funding, Speakers Bureau; Ariad: Consultancy, Honoraria, Research Funding, Speakers Bureau.