Mosunetuzumab plus Pola-CHP compared with Pola-R-CHP in previously untreated DLBCL: final results from a phase 2 study
Jason R. Westin, Tycel Phillips, Amitkumar Mehta, Marc Hoffmann, Eva González‐Barca, Catherine Thiéblemont, Mariana Bastos‐Oreiro, Richard Greil, Sebastian Giebel, Michael C. Wei, Jue Wang, Reinhard Bucher, Jason Sit, Elicia Penuel, Enkhtsetseg Purev, Donald L. Yee, Juan Bergua
Abstract
ABSTRACT: This phase 2 study evaluated mosunetuzumab plus cyclophosphamide, doxorubicin, prednisone, and polatuzumab vedotin (Pola-M-CHP) vs Pola-rituximab (R)-CHP for first-line treatment of diffuse large B-cell lymphoma. Patients were randomized 2:1 to receive 6 cycles of Pola-M-CHP or Pola-R-CHP on day 1 of each 21-day cycle. Mosunetuzumab was administered intravenously via step-up dosing during cycle 1 and at 30 mg on day 1 of subsequent cycles. The primary end point was independent review committee-assessed complete response (CR) rate by positron emission tomography-computed tomography. Overall, 62 patients were enrolled and received Pola-M-CHP (n = 40) or Pola-R-CHP (n = 22). CR rates were similar in both arms (72.5% with Pola-M-CHP vs 77.3% with Pola-R-CHP); the 24-month investigator-assessed progression-free survival rate was 70.8% (95% confidence interval [CI], 55.6-86.1) with Pola-M-CHP vs 81.8% (95% CI, 65.7-97.9) with Pola-R-CHP. The most common adverse event (AE) was cytokine release syndrome (68.4%; mostly grade 1 [52.6%], and primarily confined to cycle 1) with Pola-M-CHP and neutropenia/neutrophil count decreased (54.5%) with Pola-R-CHP. Neutropenia/neutrophil count decreased was the most frequently observed grade ≥3 AE in both arms (Pola-M-CHP, 36.8%; Pola-R-CHP, 22.7%). Rates of grade ≥3 AEs (86.8% vs 59.1%), serious AEs (63.2% vs 13.6%), and AEs leading to treatment discontinuation (13.2% vs 0%) were higher with Pola-M-CHP than Pola-R-CHP, respectively. Pharmacodynamic changes were supportive of mosunetuzumab's mechanism of action and its addition to the Pola-CHP combination. Pola-M-CHP, although an active combination, did not demonstrate a clinical benefit over Pola-R-CHP in this small study. This trial was registered at www.clinicaltrials.gov as #NCT03677141.