Evolving Unmet Need in Patients Refractory to Lenalidomide: Overview of the Clinical Trials in Relapsed/Refractory Multiple Myeloma
Authors: Mateos Maria-Victoria , Medhekar Rohan , Majer Istvan , Turgut Mehmet 
Published: February 2021

Introduction: The majority of newly diagnosed multiple myeloma (NDMM) patients are currently treated with lenalidomide-based regimens as their first line of therapy. This trend is likely to continue in the coming years. Typically, lenalidomide is administered until disease progression and has significantly contributed to better outcomes in these patients. However, most patients relapse, and prognosis worsens with each relapse. The choice of optimal treatment for patients who relapse while receiving lenalidomide as first line of therapy is unclear. Moreau et al (Blood Cancer J. 9, 38 [2019]) concluded that there is limited data on approved combinations for treating these patients and are restricted by the low number of lenalidomide-refractory patients enrolled in the pivotal trials. Results from the ongoing clinical trials of the combination of carfilzomib and anti-CD38 antibodies were not available at the time of the Moreau et al publication. The aim of this targeted literature review was to include this new data and to summarize currently available evidence on progression-free survival (PFS) for the treatment of RRMM patients who progressed on lenalidomide-based regimens.
Methods: A targeted literature review was conducted to identify registrational clinical trials in patients with RRMM reporting PFS outcomes. PubMed, congress proceedings, and product labels were searched between Jan 2014 to July 2020. In addition to PFS, demographic, disease characteristics and treatment history were extracted for the trial populations to contextualize potential variations in study outcomes. The regimens studied in these trials were classified as lenalidomide-based, proteasome inhibitor (PI)-based and pomalidomide-based. Number of prior lines of therapy, prior exposure and refractoriness to lenalidomide and bortezomib were reported.
Results: Twelve registrational trials were identified based on the search criteria (Table 1). Most pivotal trials assessing lenalidomide-based regimens (POLLUX, ELOQUENT-II, TOURMALINE-MM1) except the ASPIRE trial excluded patients who were refractory to lenalidomide. Trials evaluating PI-based regimens (e.g., CANDOR) or pomalidomide-based regimens (e.g., OPTIMISMM) included these patients, with more recent studies enrolling a larger proportion. Percentage of lenalidomide-exposed (and lenalidomide refractory) ranged from 40% (32%) in CANDOR to 98% (90%) in ELOQUENT III. These studies also enrolled a larger proportion of patients who were bortezomib-exposed, although most of these patients were at first relapse, with the exception of ELOQUENT III and ICARIA where most patients were at third relapse. Among lenalidomide-refractory patients, the median-PFS (mPFS) observed for the pomalidomide-based regimens ranged from 9.5 to 10.1 months and that observed for PI-based regimens ranged from 4.9 to 25.7 months. PFS in the lenalidomide-refractory subgroup was considerably shorter than in the ITT population. The mPFS for patients receiving carfilzomib/daratumumab/dexamethasone (KDd; CANDOR) and isatuximab/carfilzomib/dexamethasone (IsaKd; IKEMA) was not reached at median follow-up of 16.9 and 20.7 months respectively. While the mPFS for (KDd) for lenalidomide-refractory patients in CANDOR trial was not yet reached at median follow up of 16.9 months; the mPFS of 25.7 months for KDd in the MMY-1001 trial appears to be the longest among the assessed regimens.
Conclusion: Patients refractory to lenalidomide have shorter PFS and represent a population with high unmet need. This targeted literature review suggests that the PI-based KDd regimen provides longer PFS compared to other lenalidomide-sparing regimens in lenalidomide-refractory populations. Heterogeneity across trial populations may limit the comparability of these treatments.

Disclosures
Mateos: Regeneron: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Consultancy, Honoraria; Adaptive Biotechnologies: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie/Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; PharmaMar-Zeltia: Consultancy; GlaxoSmithKline: Consultancy. Medhekar:Amgen Inc.: Current Employment, Current equity holder in publicly-traded company. Majer:Amgen (Europe) GmbH: Current Employment, Current equity holder in publicly-traded company.