Bortezomib Continues Demonstrates Superior Efficacy Compared with High-Dose Dexamethasone in Relapsed Multiple Myeloma: Updated Results of the APEX Trail.
Authors: Richardson Paul , Sonneveld P. , Schuster M. , Irwin D. , Stadtmauer E. , Facon T. , Harousseau J. , Ben-Yehuda D. , Lonial S. , Goldschmidt H. , Reece D. , Miguel J. San , Blade J. , Boccadoro M. , Cavenagh J. , Dalton W. , Boral A. , Schenkein D. , Anderson K. 
Published: April 2020

Introduction: In the international, multicenter phase 3 APEX trial, 669 patients (pts) with multiple myeloma (MM) who had relapsed after 1–3 prior therapies were randomized to receive bortezomib (VELCADE®) 1.3 mg/m2 IV d 1, 4, 8, 11 q3wk for 8 cycles followed by 3 cycles on d 1, 8, 15, 22 q5wk, or dexamethasone (Dex) 40 mg PO d 1–4, 9–12, 17–20 q5wk for 4 cycles followed by 5 cycles on d 1–4 q4wk. Pts refractory to Dex were excluded, and those with progressive disease on Dex were eligible to cross over to bortezomib. Pts receiving bortezomib achieved significant improvement in time to progression (TTP, primary end point), response rate (CR + PR using EBMT criteria), and survival (Richardson. NEJM.2005;352:2487), which resulted in early closure of the trial. The duration of response (DOR) was longer with bortezomib, and infections ≥ grade 3, time to skeletal events, grade 4 adverse events (AE), serious AE, and discontinuations due to AE were similar in the 2 treatment arms.

Methods: In this analysis, updated response rates, time to response (TTR), DOR, survival, and TTP are presented after extended follow-up. A matched-pairs analysis comparing survival and TTP of pts on bortezomib in APEX with those in another trial of MM pts who received bortezomib after Dex will also be presented.

Results: 669 pts received a median of 7 cycles of therapy. Based on a median follow-up of 15.8 months, the median TTP, 1-year and overall survival (OS), response rates, median TTR, and median DOR for pts receiving bortezomib are shown in the table. Median duration of therapy for responders (CR + PR) was 7.2 months. Improved response with longer therapy (after cycle 6) was observed in 76 pts (56% of responders) in the bortezomib arm (20 pts improved from MR or PR to CR, and 56 pts improved from MR to PR). Furthermore, 28 of 135 responders (21%) achieved first response (CR/PR) after cycle 4, including 18 pts (13%) on or after cycle 6, and 10 pts (7%) on or after cycle 8. OS increased substantially with more follow-up. Median TTR was more rapid, and median DOR was longer in pts achieving CR and near CR than in those with PR.

Conclusion: Updated TTP, response rates, survival, TTR, and DOR for the bortezomib group continue to support the findings of the original analysis. Thus, the clinical benefits of single-agent bortezomib in pts with relapsed MM remain robust after extended follow-up, supporting its early use in relapsed MM and its further study in the treatment of newly diagnosed disease.

Efficacy Bortezomib (n = 333) Median TTP, mo 6.2 1-year survival, % 80 Median OS, mo 25.4 Response rate, % (n/N) 43 (135/315) CR 9 (27/315) PR 34 (108/315) -near CR 7 (21/315) Median TTR, mo (range) 1.4 (0.5–6.0) CR 0.8 (0.5–4.0) PR 1.4 (0.5–6.0) -near CR 0.8 (0.6–2.4) Median DOR, mo 7.8 CR 9.9 PR 7.6 -near CR 11.5