A Phase II Study of Isatuximab in Combination with Pomalidomide and Dexamethasone in Patients with Multiple Myeloma Progressing on or after One Line of Lenalidomide-Containing Therapy

Introduction

Relapse in patients (pts) with multiple myeloma (MM) is a common occurrence, resulting in a continued need for novel treatment approaches. Isatuximab (Isa), a monoclonal antibody (mAb), combined with pomalidomide (Pom) and dexamethasone (Dex), is indicated for the treatment of pts with relapsed/refractory multiple myeloma who have received ≥2 prior therapies including lenalidomide and a proteasome inhibitor and have demonstrated disease progression on the last therapy. The current study aims to evaluate the efficacy and safety of IsaPomDex in pts with MM relapsing for the first time after one line of treatment containing lenalidomide (Len).

Methods

EAE115 (NCT05298683) is an ongoing, investigator-initiated, phase II, prospective, open-label, multicenter study aiming to enroll 108 pts. Eligible pts are adults with documented MM who have evidence of progressive disease, by the International Myeloma Working Group criteria, on or after treatment with only one prior line of anti-myeloma therapy with lenalidomide (≥2 cycles, alone or in combination) and a proteasome inhibitor. Pts must also have adequate bone marrow and hepatic function and an Eastern Cooperative Oncology Group performance status (ECOG PS) ≤2. Excluded are pts with previous anti-myeloma therapy with any anti-CD38 mAb, pomalidomide, or stem cell transplant within 12 weeks before treatment initiation.

Pts receive six 28-day cycles of Isa 10 mg/kg (once weekly [QW] by intravenous [IV] infusion on days 1, 8, 15, and 22 in cycle 1 and days 1 and 15 in subsequent cycles), Pom 4 mg (per Os on days 1-21, each cycle), and Dex 40 mg or 20 mg for pts ≥75 years old (per Os or IV on days 1, 8, 15 and 22, each cycle). Fifteen to 60 minutes before Isa infusions, patients receive pre-medications to mitigate potential infusion-related adverse reactions.

Following initial 6 cycles, pts achieving at least very good partial response (VGPR) are randomized 1:1 to receive Isa (Q2W or Q4W) plus PomDex, and pts achieving <VGPR continue treatment with Isa (Q2W) plus PomDex. Treatment is given until progressive disease, death, unacceptable adverse events (AEs), lost to follow-up, or consent withdrawal.

The study primarily evaluates the overall response rate (ORR; defined as partial response [PR] or better) to IsaPomDex therapy at six months. Adverse events are classified using the Medical Dictionary for Regulatory Activities. Herein, we present safety and efficacy data for all treated patients (cut-off date 15/05/23.

Results

Twenty pts had received at least one dose by the cut-off date, of whom 16 (80.0%) were continuing with IsaPomDex treatment; four (20.0%) pts had discontinued due to physician or pt decision or progressive disease or death. At baseline (cycle 1, day 1), pts had a median age of 72.0 years (range: 60.0-85.0), 10 (50.0%) were male, and 13 (65.0%) had ECOG PS 0. Eleven (55.0%) pts were at stage II by the revised International Staging System, 9 (45.0%) pts had lytic bone lesions, 5 (25.0%) pts had high-risk cytogenetics, and 1 (5.0%) pt had soft-tissue plasmacytomas (Table 1).

Regarding previous treatment outcomes, 14 (70.0%) pts had achieved ≥VGPR (stringent complete response, 2 [10.0%] pts; complete response, 2 [10.0%] pts; VGPR, 10 [50%] pts). Five (25%) and 1 (5.0%) pts achieved partial and minimal response, respectively. Six (30.0%) pts had received ASCT in the prior line.

At a median follow-up of 3.4 (range: 0.6-6.1) months, the median number of IsaPomDex cycles received was 3.0 (range: 1.0-7.0); one (5.0%) pt received six treatment cycles. Of the 18 (90.0%) response evaluable pts (2 pts were ongoing without 2 efficacy assessments) VGPR and PR were achieved by 4/18 (22.2%) and 9/18 (50.0%) pts, respectively. ORR was achieved by 13/18 (72.2%) pts, and the median (range) time from IsaPomDex study dose to first response (≥PR) was 1.0 (range: 0.9-1.3) months.

Thirteen (65.0%) pts had ≥1 treatment-emergent adverse events (TEAE). Of these pts, 10 (50.0%) had a ≥1 grade (gr)≥3 TEAE and 4 (15.0%) had ≥1 gr ≥3 serious TEAE. The most common TEAEs were neutropenia in 9 pts (45.0%), anaemia in 3 pts (15.0%) and fatigue in 3 pts (15.0%). The most common gr ≥3 TEAE was neutropenia in 7 pts (35.0%) (Table 2).

Conclusions

Second-line treatment with IsaPomDex in pts with MM who have progressed on or after one Len-containing line of treatment appears to be effective, although longer follow-up is needed to assess its efficacy. No new safety signals were observed with the combination.