P668: ACALABRUTINIB VS RITUXIMAB PLUS IDELALISIB OR BENDAMUSTINE IN RELAPSED/REFRACTORY CHRONIC LYMPHOCYTIC LEUKEMIA: ASCEND RESULTS AT ~4 YEARS OF FOLLOW-UP

Background: Acalabrutinib (acala) is a next-generation, highly selective, covalent Bruton tyrosine kinase (BTK) inhibitor approved for patients (pts) with chronic lymphocytic leukemia (CLL). In the primary analysis of ASCEND (median follow-up 16.1 mo), acala showed superior efficacy with an acceptable tolerability profile vs idelalisib (Id) plus rituximab (R) (IdR) or bendamustine (B) plus R (BR) in pts with relapsed/refractory (R/R) CLL (Ghia et al. J Clin Oncol. 2020;38:2849-2861). Aims: We report the results of the ASCEND study at ~4 years of follow-up. Methods: In this multicenter, randomized, open-label, phase 3 study (NCT02970318), pts with R/R CLL received oral (PO) acala 100 mg BID until progression or unacceptable toxicity or investigator’s (INV) choice of IdR (Id: 150 mg PO BID until progression or unacceptable toxicity; R: 375 mg/m2 x1 then 500 mg/m2 IV [8 total infusions]) or BR (B: 70 mg/m2 IV; R: 375 mg/m2 x1 then 500 mg/m2 IV [6 cycles]). Progression-free survival (PFS), overall survival (OS), overall response rate (ORR), and safety were assessed. Results: A total of 310 pts (acala, n=155; IdR, n=119; BR, n=36) were randomized (median age 67 y; del(17p) 15%, unmutated IGHV 74%, Rai stage 3/4 42%). At median follow-up of 46.5 mo (acala) and 45.3 mo (IdR/BR), acala significantly prolonged INV-assessed PFS vs IdR/BR (median not reached [NR] vs 16.8 mo; P<0.0001); 42-mo PFS rates were 62% for acala vs 19% for IdR/BR. In pts with del(17p), median PFS was NR (acala) vs 13.8 mo (IdR/BR; P<0.0001). In pts with unmutated IGHV, median PFS was NR (acala) vs 16.2 mo (IdR/BR; P<0.0001). Median OS was NR in both arms; 42-mo OS rates were 78% (acala) vs 65% (IdR/BR). ORR was 83% (acala) vs 84% (IdR/BR) (ORR + partial response with lymphocytosis: 92% [acala] vs 88% [IdR/BR]). AEs led to drug discontinuation in 23% of acala, 67% of IdR, and 17% of BR pts. Events of clinical interest (acala vs IdR/BR) included all-grade atrial fibrillation/flutter (8% vs 3%), all-grade hypertension (8% vs 5%), all-grade major hemorrhage (3% vs 3%), and grade ≥3 infections (29% vs 29%). Image:Summary/Conclusion: At ~4 years of follow-up, acala maintained efficacy compared with standard-of-care regimens and a consistent tolerability profile in R/R CLL.