Pomalidomide + Bortezomib + Low-Dose Dexamethasone Vs Bortezomib + Low-Dose Dexamethasone As Second-Line Treatment in Patients with Lenalidomide-Pretreated Multiple Myeloma: A Subgroup Analysis of the Phase 3 Optimismm Trial

BACKGROUND

As lenalidomide (LEN) becomes increasingly established as a standard of care in the treatment (Tx) of newly diagnosed multiple myeloma (NDMM), patients (pts) for whom LEN is no longer a Tx option, including those who have become refractory to LEN, represent a clinical reality. These pts represent the largest population with MM at first relapse in the United States and a growing population globally. To date, they have been poorly studied and remain difficult to treat. Previous trials have demonstrated a clinical benefit with pomalidomide (POM) therapy in LEN-refractory pts with relapsed or refractory MM (RRMM), including those who were heavily pretreated (median of 5 prior regimens) (San Miguel et al. Lancet Oncol 2013; Richardson et al. Blood 2014; Dimopoulos et al. Blood 2016). These studies led to the approval of POM + low-dose dexamethasone (LoDEX) in RRMM. The pomalidomide, bortezomib, and low-dose dexamethasone (PVd) regimen has shown promising activity in early-phase clinical trials in LEN-refractory pts. In the phase 3 OPTIMISMM trial, PVd showed significantly improved progression-free survival (PFS) and a manageable safety profile compared with bortezomib and low-dose dexamethasone (Vd) in intent-to-treat population of pts who received 1-3 prior regimens and were 100% LEN pretreated; 70% of pts were LEN refractory (Richardson et al. ASCO 2018 abstract 8001). Here, we present efficacy and safety results in LEN-refractory and -nonrefractory pts treated at first relapse.

METHODS

Pts were randomized 1:1 to receive PVd or Vd in 21-day cycles: POM 4 mg/day on days 1-14 (PVd arm only); bortezomib (BORT) 1.3 mg/m² on days 1, 4, 8, and 11 of cycles 1-8 and on days 1 and 8 of cycles 9+; and DEX 20 mg/day (10 mg/day if aged > 75 yrs) on the days of and after BORT. Key eligibility criteria included ≥ 2 cycles of prior LEN therapy, including LEN-refractory pts. BORT-exposed pts were eligible to enroll, provided they did not have progressive disease during therapy or within 60 days of the last dose of a BORT-containing regimen with BORT dosed at 1.3 mg/m² twice weekly. The primary endpoint was PFS.

RESULTS

Out of 559 pts enrolled patients, 226 were treated in the second line (2L), data cut off October 26, 2017: 111 with PVd and 115 with Vd. Median follow-up for 2L pts was 16.4 mos. Among 2L pts, 129 (57.1%) were LEN refractory (64 PVd; 65 Vd) and 97 (42.9%) were LEN nonrefractory (47 PVd; 50 Vd). In LEN-refractory pts (PVd vs Vd) median age was 68.0 vs 69.0 yrs, 57.8% vs 58.5% were male, and 56.3% vs 47.7% had prior BORT. In LEN-nonrefractory pts, median age was 66.0 vs 65.5 yrs, 63.8% vs 38% were male, and 66.0% vs 72.0% had prior BORT. Other key baseline characteristics were similar between Tx arms and subgroups.

Median PFS was 17.8 mos with PVd vs 9.5 mos with Vd in LEN-refractory (HR 0.55; 95% CI, 0.33-0.94; Figure 1A) and 22.0 vs 12.0 mos in LEN-nonrefractory pts (HR 0.54; 95% CI, 0.29-1.01; Figure 1B). Response outcomes are shown in Figure 2. ORR was 85.9% with PVd vs 50.8% with Vd in LEN-refractory pts (P < .001) and 95.7% vs 60.0% in LEN-nonrefractory pts (P < .001).

In 2L LEN-refractory pts, the most common grade 3 or 4 treatment-emergent adverse events (TEAEs) with PVd vs Vd were neutropenia (35.9% vs 12.9%), thrombocytopenia (17.2% vs 22.6%), and anemia (17.2% vs 8.1%). Grade 3 or 4 infections occurred in 29.7% vs 21.0% of pts. In 2L LEN-nonrefractory pts, the most common grade 3 or 4 TEAEs were neutropenia (36.2% vs 6.3%) and thrombocytopenia (23.4% vs 18.8%). Grade 3 or 4 infections occurred in 27.7% vs 8.3% of pts. In 2L LEN-refractory pts, median Tx duration of PVd vs Vd was 9.7 vs 6.1 mos. In 2L LEN-nonrefractory pts, median Tx duration of Pvd vs Vd was 13.6 vs 6.6 mos.

CONCLUSIONS

To date, OPTIMISMM is the only phase 3 trial to address Tx of pts with RRMM following LEN exposure in early lines and the first to report data in LEN-refractory pts after first relapse. PVd reduced the risk of progression and death by 45% and 46% vs Vd in LEN-refractory and -nonrefractory pts, respectively. Further, in both subgroups, 2L Tx with PVd significantly improved ORR and led to deeper responses compared with Vd. AEs with PVd therapy were generally consistent with the known AEs of POM, BORT, and DEX. These data further demonstrate that PVd is effective and tolerable in pts for whom LEN is no longer a Tx option, including LEN-refractory pts, supporting its use as 2L therapy in RRMM.

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