Background: BOS is an oral dual Src/Abl kinase inhibitor with potent activity in Ph+ leukemia. Methods: Efficacy and safety of BOS 500 mg/d was evaluated in older (≥65 y; n = 119) and younger (<65 y; n = 451) pts in 3 cohorts: chronic phase chronic myeloid leukemia (CP CML) after imatinib (IM; CP2L cohort; n = 287); CP CML after IM + dasatinib (DAS) and/or nilotinib (NIL; CP3L cohort; n = 119); and accelerated/blast phase (AP/BP) CML or acute lymphoblastic leukemia after IM ± DAS and/or NIL (ADV cohort; n = 164). Results: Baseline events (≥65 y vs <65 y) included respiratory disorders (35% vs 13%), cardiac disorders (29% vs 9%), and diabetes (4% vs 4%). Median baseline medications were 3 (≥65 y) and 5 (<65 y). Median BOS duration was 11 mo and median follow-up was 31 mo for all pts. 80% of ³65 y and 67% of <65 y pts discontinued BOS, including 32% and 18% due to an adverse event (AE; most commonly thrombocytopenia [6% vs 3%]). Rates of response were similar or lower in older versus younger pts (Table). On-treatment transformation to AP/BP CML was similar between groups. Incidences of nonhematologic treatment-emergent AEs were generally similar between older and younger pts, notably (all grades/grade ≥3 for ≥65 y vs <65 y): diarrhea (85%/9% vs 81%/8%), infection (56%/15% vs 49%/10%), and edema (8%/0% vs 4%/<1%). Common grade ≥3 lab abnormalities (≥65 y vs <65 y) were thrombocytopenia (35% vs 35%), neutropenia (21% vs 25%), and anemia (19% vs 19%). Conclusions: BOS demonstrated similar efficacy and acceptable safety in both older and younger pts across Ph+ leukemia cohorts.

	CP2L		CP3L		ADV
	≥65 y	<65 y	≥65 y	<65 y	≥65 y	<65 y
na	63	223	25	92	29	122
MHR	-	-	-	-	28%	30%
CHR	81%	87%	72%	74%	14%	25%
2-y probability of maintaining CHRb	67%	75%	65%	69%	75%	54%
na	61	204	22	88	26	116
MCyR	43%	57%	27%	34%	23%	32%
CCyR	38%	45%	23%	24%	19%	22%
2-y probability of maintaining MCyRb	73%	74%	83%	56%	20%	31%
n	63	224	26	93	30	134
Transformation to AP/BP	3%	5%	4%	4%	4%	3%
2-y probability of survivalb	87%	92%	80%	85%	43%	46%

Abbreviations: MHR, major hematologic response; CHR, complete hematologic response; MCyR, major cytogenetic response; CCyR, complete cytogenetic response.

^aEvaluable pts had received ≥1 dose of BOS and a valid baseline assessment.

^bKaplan-Meier estimate.