Phase II Trial of Ixazomib and Dexamethasone Versus Ixazomib, Dexamethasone and Lenalidomide, Randomized with NFKB2 Rearrangement. (Proteasome Inhibitor NFKB2 Rearrangement Driven Trial, PINR)

Introduction: Proteasome inhibitors (PI) and immunomodulatory drugs have become the backbone of therapy for multiple myeloma (MM). The oral boron-containing selective and reversible proteasome inhibitor ixazomib has shown to induce deep and durable responses (Kumar RK et la, Blood 2016. 128(20):2415-2422). Triplets containing ixazomib, has shown to be more efficacious than doublet regimens in the relapse setting (Moreau P, et al. N Engl J Med 2016. 374:1621-1634).However, to date there is not companion diagnostics capable of predicting PI response.

We have recently discovered that MM patients resistant to PI lack of the ankyrin (ANK) and death domain (DD) present in the 3'-end of NFKB2. Loss of NFKB2 3'end frequently resulted from a structural rearrangements. We found that NFKB2-ANK and -DD are crucial at initiating bortezomib's apoptotic signal by facilitating caspase-8 activation. Activation of this caspase resulted from NFKB2 interaction with FADD/caspase-8/p62 (unpublished data). Based on this findings, we design this study to examine the efficacy of NFKB2 break apart FISH to predict the response to the duplet ixazomib and dexamethasone (Id) vs ixazomib, lenalidomide and dexamethasone (IRd) in early relapse MM patients (1-3 lines of therapy).

Methods: In this phase 2 biomarker driven open label trial, relapse patients with <4 lines of therapy were randomized to ixazomib 4 mg weekly 3 of 4 weeks and 40 mg weekly dexamethasone vs Id plus 25 mg of lenalidomide daily days 21/28, based on the status of NFKB2 rearrangement in plasma cells. Patients were screened for NFKB2 rearrangement was detected by NFKB2 break apart FISH. Patients without NFKB2 rearrangement received Id and patients with NFKB2 rearrangement were subsequently randomized in a 1:1 fashion to receive Id or IRd. The primary endpoint is to compare the response rate of Id or IRd at 4 cycles according to the rearrangement status of NFKB2

Results: At the moment of interim analysis, 26 patients have achieved 4 cycles of treatment. All treatment groups (NFKB2 FISH [-] Id, n=16, NFKB2 FISH [+] Id, n=6 and IRd, n=4) received a median of 2 prior lines of therapy. A higher ORR was observed in NFKB2 FISH negative treated with Id compared with NFKB2 FISH positive (56.3% CI:29.9%-80.3% vs. 16.7% CI:0.4%-64.1%, P=0.16), including significantly higher rates of ≥very good partial response, ≥ partial response, ≥ minimal response (12%, 37.5%, 6% vs. 0%, 0%, 16%, respectively). ORR for IRd arm is for now 25% CI:0.6%-80.6%. Patients that continue treatment after cycle 4 that achieve minimal response or better improved their depth of response in 6% in Id treated NFKB2 FISH negative patients and 25% of IRd treated NFKB2 FISH negative patients.

The most common (≥10%) grade 2/4 include pneumonia 20% (Id treated NFKB2 FISH negative), thrombocytopenia 16% (Id NFKB2 FISH positive), neutropenia 60% (IRd NFKB2 FISH positive. Treatment discontinuations only occurred in 1 Id treated patient (5%).

Conclusion: Interim analysis demonstrate a trend higher efficacy of ixazomib with dexamethasone in MM patients with negative NFKB2 break-apart FISH compared to those with a positive test. Efficacy and toxicity of the triplet regimen are comparable to what is seen in Tourmaline 1 trial. This study was registered at www.clinicaltrials.gov as # NCT02765854.