Pomalidomide (POM) + Low-Dose Dexamethasone (LoDEX) Safety and Efficacy in Patients (pts) with Relapsed and/or Refractory Multiple Myeloma (RRMM) Previously Treated with a Proteasome Inhibitor (PI) and in Whom Last Prior Therapy with Lenalidomide (LEN) Failed

BACKGROUND POM + LoDEX is a standard of care for the treatment of pts with RRMM. The MM-014 (NCT01946477) trial is investigating the treatment sequence of POM + LoDEX as third-line treatment in pts with RRMM with LEN-based treatment failure as last prior therapy (cohort A). Outcomes are reported for cohort A, including a subset analysis of pts who received prior PI and/or bortezomib (BORT). METHODS Adult pts with RRMM who had received 2 prior lines of treatment and had progressive disease (PD) after ≥ 2 cycles of second-line LEN-based therapy were eligible. Pts received POM 4 mg/day on days 1 through 21 + LoDEX 40 mg/day (20 mg/day if aged > 75 years) on days 1, 8, 15, and 22 of 28-day cycles, with mandatory thromboprophylaxis. The primary endpoint was overall response rate (ORR; ≥ partial response) by modified International Myeloma Working Group criteria. Secondary endpoints included progression-free survival (PFS), safety, and second primary malignancies (SPMs). RESULTS At the data cutoff date of May 3, 2017, median follow-up was 23.8 months in the surviving pts.Baseline characteristics for all 56 pts enrolled in cohort A and for pt subgroups with prior PI or BORT exposure are shown in Table 1. Of 50 pts with cytogenetic data by fluorescence in situ hybridization, 4, 4, and 2 pts were positive for del17p, t(4;14), and t(14;16), respectively. Median duration of prior LEN-containing treatment was 23.6 months (range, 3.5-107.0 months), with 60.7% of pts receiving an immediately prior LEN dose of 25 mg/day. All pts were refractory or relapsed to their most recent prior LEN-containing regimen: 92.7% and 92.3% of pts were LEN refractory in the prior PI and prior BORT exposure subgroups, respectively. Response and PFS outcomes in the overall cohort A population and by prior treatment exposure are reported in Table 2. Among the 56 pts, 50 discontinued treatment, with 29 pts (58%) discontinuing due to PD, 6 due to withdrawal, 5 due to adverse event (AEs), 3 due to lack of efficacy, 2 due to death, and 5 due to other reasons. Grade 3/4 treatment-emergent AEs included anemia (26.8%), neutropenia (10.7%), and infections (23.2%, including pneumonia [14.3%]). Two pts experienced grade 3/4 pulmonary embolism, and 2 pts had SPMs. CONCLUSIONS POM + LoDEX is safe and effective when sequenced in third line following second-line LEN-based treatment failure in pts with RRMM who had also received prior BORT or other PI. With > 10 months of additional follow-up as previously reported (Siegel et al. EHA 2017 [abstract E1248]), median PFS was sustained at 13.8 months. The nearly 2-year duration of prior LEN treatment is reflective of pts receiving continuous treatment until PD. In cohort A, hematologic AE rates were lower and median PFS was longer with third-line use, including in the subset of pts with prior PI or BORT exposure, than what has been previously reported for any study in which POM + LoDEX was used in later treatment lines. These results support the benefit of third-line POM + LoDEX immediately following LEN + PI-based therapy in pts with RRMM. Disclosures Siegel: Celgene, Takeda, Amgen Inc, Novartis and BMS: Consultancy, Speakers Bureau; Merck: Consultancy. Schiller: bluebird bio: Research Funding; mateon therapeutics: Research Funding. Kaya: Millennium, Novartis, Celgene, Onyx, Amgen: Honoraria, Speakers Bureau. Sebag: Celgene, Janssen: Consultancy. Malek: Celgene: Speakers Bureau; Sanofi: Membership on an entity9s Board of Directors or advisory committees; Takeda: Membership on an entity9s Board of Directors or advisory committees, Speakers Bureau. Talamo: Penn State Hershey Cancer Institute: Employment. Mouro: Celgene Corporation: Employment, Equity Ownership. Zafar: Celgene Corporation: Employment. Chung: Celgene Corporation: Employment, Equity Ownership. Srinivasan: Celgene: Employment. Qian: Celgene Corporation: Employment, Equity Ownership. Agarwal: Celgene Corporation: Employment. Thakurta: Celgene Corporation: Employment, Equity Ownership. Bahlis: Amgen: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau.

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