ASPEN is an open-label, randomized, phase 3 study comparing the safety, efficacy and clinical benefit of zanubrutinib with that of ibrutinib in patients with myeloid differentiation factor 88 mutant (MYD88L265P) Waldenström’s macroglobuliemia (WM). In an additional cohort, the efficacy and safety of zanubrutinib in MYD88 wild type (MYD88WT) WM participants was evaluated.
Although not statistically significant, a higher rate of VGPR was observed for zanubrutinib vs ibrutinib in patients with MYD88L265P WM. The incidence and severity of most BTK-associated toxicities (including atrial fibrillation) were lower with zanubrutinib than ibrutinib. Zanubrutinib showed clinically meaningful antitumor activity and was considered well-tolerated with a low discontinuation rate due to AEs, in patients with MYD88WT WM.