Abstract: Background: Multiple myeloma clinical trial CC-4047-MM-014 (NCT01946477) is a Phase II study designed to test the safety and efficacy of pomalidomide and low-dose dexamethasone alone (arm A) or in combination with daratumumab, an anti-CD38 antibody, (arm B) subjects with relapsed or refractory multiple myeloma who have received a first or second line treatment of lenalidomide-based therapy. Immunomodulatory agents (IMiD® compounds) continue to be the backbone of multiple myeloma therapy especially when combined with monoclonal antibodies, more specifically pomalidomide had been shown previously to enhance T cell- and NK cell-mediated immunity. We sought to characterize on-treatment pharmacodynamic changes of immune biomarkers associated with POM + LoDEX + DARA administration (arm B) using multicolor flow cytometry panels designed to characterize T-cell subsets and CD38+ expressing cells. IMiD agents are the backbone of combination regimens in the treatment of patients with newly diagnosed or relapsed and/or refractory multiple myeloma. The anti-myeloma properties of these agents derive from a dual mechanism of pro-apoptotic effects on tumor cells as well as enhanced immune stimulation. An understanding of how IMiD agents interact with new monoclonal antibodies to modify patient immune profiles offers key insights into the role of such in innate and adaptive immunity in determining patient outcomes. Methods and Results: Peripheral blood samples were collected at screening, Cycle1 Days 1, 8, and 15, and Cycle 2 Days 1 and 15 to monitor pharmacodynamic changes in populations of T cells, NK cells, monocytes and MDSCs by flow cytometry. From 112 patients enrolled in Arm B, 98 patients had baseline and post-treatment specimens available for these analyses. As expected, combination treatment with POM + LoDEX + DARA led to decreased peripheral counts of CD56+CD16+ NK cells as well as CD4+CD38+ and CD8+CD38+ T cell subpopulations. Decreased counts were also noted in CD3-CD19+ B cells. In contrast, total counts of CD14+ monocytes and CD3+CD4+ or CD3+CD8+ T cells were stably maintained and pronounced increases were observed in proliferating CD4+Ki-67+ and CD8+Ki-67+ T cells. Further, when examined as a percent of total counts, increases were observed in CD14+ monocytes, CD3+CD4+ and CD3+CD8+ T-cells, with decreases in CD3-CD19+ B-cells and CD3-CD56+CD16+ NK cells. Correlation of these pharmacodynamic changes with clinical outcomes will be presented. In addition, baseline immune profiling of specific cell population subsets and associations with best overall response and progression-free survival is currently being analyzed. Conclusions: The triplet regimen POM + LoDEX + DARA has shown notable clinical activity with deep and durable responses in relapsed multiple myeloma patients progressed and are or refractory to lenalidomide. Immune characterization here is consistent with a model for clinical activity in which the loss of CD56+CD16+ NK cells along with a concomitant immune suppression by loss of CD38+CD4+ and CD38+CD8+ T- cells is offset by an increase in proliferating cytotoxic CD4+Ki-67+ and CD8+Ki-67+ T-cell populations. Our results demonstrate that patients treated with the POM + LoDEX + DARA combination do not demonstrate impairment in the innate and adaptive immune compartments and, in contrast, show significant proliferative activity in the subsets of CD4, CD8 and NK cells following treatment. Pomalidomide had been shown previously to enhance T cell- and NK cell-mediated immunity; these data are consistent with a mechanism of action in which pomalidomide administration facilitates the ability to overcome immunosuppressive effects of Dara and LoDex. Potential associations of immune biomarkers with patient outcomes is ongoing and will be updated. Disclosures Pierceall: Celgene Corporation: Employment, Equity Ownership. Bahlis:Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding. Siegel:Merck: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Karyopharm: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau. Schiller:Astellas Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; bluebird bio: Research Funding. Sebag:Amgen Canada: Membership on an entity's Board of Directors or advisory committees; Takeda Canada: Membership on an entity's Board of Directors or advisory committees; Janssen Inc.: Membership on an entity's Board of Directors or advisory committees; Celgene Canada: Membership on an entity's Board of Directors or advisory committees. Berdeja:Takeda: Research Funding; Genentech: Research Funding; Sanofi: Research Funding; Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Janssen: Research Funding; Glenmark: Research Funding; Amgen: Research Funding; Novartis: Research Funding; Poseida Therapeutics, Inc.: Research Funding; Bluebird: Research Funding; Teva: Research Funding. Ganguly:Amgen: Consultancy; Daiichi Sankyo: Research Funding; Janssen: Consultancy; Seattle Genetics: Speakers Bureau. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Srinivas:VAHCSNJ: Employment. Bar:Celgene: Consultancy. Quick:CTI BioPharma: Research Funding. Fonseca:Celgene: Speakers Bureau. Reece:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Merck: Honoraria, Research Funding; Otsuka: Research Funding. Serbina:Celgene: Employment. Zafar:Celgene: Employment. Agarwal:Celgene Corporation: Employment, Equity Ownership. Thakurta:Celgene Corporation: Employment, Equity Ownership.

Abstract: BACKGROUND Lenalidomide (LEN) until progressive disease (PD) is an established treatment (Tx) in newly diagnosed and relapsed and/or refractory multiple myeloma (RRMM); thus, patients (pts) for whom the benefit of LEN has been exhausted are a clinically relevant population. However, LEN-refractory pts have typically been excluded from recent clinical trials investigating triplet regimens after ≤ 3 prior Tx lines. MM-014 (NCT01946477) is an ongoing phase 2 study that was designed to assess the safety and efficacy of pomalidomide (POM)-based Tx regimens in pts with RRMM and first- or second-line LEN Tx failure immediately before study entry. Earlier results from cohort A (POM + low-dose dexamethasone [LoDEX]) and cohort B (POM + LoDEX + daratumumab [DARA] ) indicate that POM-based Tx is safe and effective in this setting. Here we report updated results from cohort B. METHODS Eligible pts had RRMM, had 1 or 2 prior lines of Tx, received LEN-based Tx as their most recent Tx regimen, and had PD during or after their last line of Tx. 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 and DARA 16 mg/kg intravenously on DEX dosing days of cycles 1 and 2, days 1 and 15 of cycles 3 through 6, then day 1 of cycle 7 and beyond. Each Tx cycle lasted 28 days. Thromboprophylaxis was mandatory. The primary endpoint for cohort B is overall response rate (ORR) by modified International Myeloma Working Group criteria. Secondary endpoints include time to response (TTR), progression-free survival (PFS), time to progression (TTP), and safety. RESULTS The intention-to-treat (ITT) population comprised 112 pts (median follow-up, 8.2 mos); data cutoff was April 30, 2018. Median age was 66.5 years, 67.9% of pts were male, and 111 (99.1%) had ECOG PS ≤ 1. A total of 34 pts discontinued Tx: 19 due to PD, 9 due to study withdrawal, 2 due to adverse events (AEs), and 4 due to other reasons. All pts received prior LEN, and 87 (77.7%) received prior bortezomib; 84 pts (75.0%) were refractory to LEN, while 28 (25.0%) relapsed after LEN-based Tx. Median duration of the most recent prior LEN-based Tx was 23.9 mos, with 36 pts (32.1%) receiving LEN 25 mg/day during their last LEN-based Tx. ORR was 77.7%, with 33.9% of pts achieving ≥ very good partial response. Median TTR was 1.0 mo. The clinical benefit rate (≥ minimal response [MR]) was 85.7%. ORR was 80.6% in the efficacy-evaluable population (n = 108; defined as all pts who received ≥ 1 dose of study drug and had ≥ 1 post-baseline response assessment), 75.0% in LEN-refractory pts, and 76.2% in pts with 2 prior lines of Tx (n = 42). The 9-mo PFS rate was 86.3% (range, 76.5%-92.2%); median PFS was not estimable (NE; Figure). The 9-mo TTP rate was 88.1% (range, 78.3%-93.6%); median TTP was NE. The most common grade 3/4 hematologic treatment-emergent AE (TEAE) in the safety population (n = 112) was neutropenia (61.6%; Table); pneumonia was the most common grade 3/4 nonhematologic TEAE (7.1%). POM dose reductions occurred in 31 pts (27.7%); per protocol, DARA dose reductions were not allowed. POM dose interruptions due to AEs were reported in 69 pts (61.6%) and DARA dose interruptions due to AEs were reported in 82 pts (73.2%). POM and DARA dose interruptions due to neutropenia were reported in 39 (34.8%) and 42 (37.5%) pts, respectively; 25 pts (22.3%) had DARA dose interruptions due to infusion-related reactions. Median durations of POM and DARA Tx were 6.0 mos (range, 0.3-17.7 mos) and 6.6 mos (range, 0.3-18.6 mos), respectively; among those who achieved ≥ MR, pts remained on POM Tx for a median of 7.4 mos (range, 0.9-17.7 mos) and on DARA Tx for a median of 7.5 mos (range, 0.9-18.6 mos). CONCLUSIONS LEN-refractory pts with RRMM are in need of effective Tx options. MM-014 is the first prospective clinical trial to investigate a POM-based doublet or triplet regimen immediately after LEN-based Tx failure. In the context of a relatively short follow-up, the 9-mo PFS rate (86.3%) is promising. The ORR (77.7%) was higher than that previously reported with this triplet combination in heavily pre-treated pts with RRMM (≥ 2 prior lines [median, 4]; ORR, 60%), and the rate of grade 3/4 neutropenia in the present study was lower (61.6% vs 77%). These updated res ults from cohort B continue to demonstrate that POM + LoDEX + DARA is safe and effective following first- or second-line LEN-based Tx failure and further support earlier use of POM-based Tx in pts with RRMM Disclosures Siegel: Takeda: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Merck: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau. Schiller:Pharmacyclics: Research Funding; Celator/Jazz Pharmaceuticals: Research Funding. Sebag:Amgen Canada: Membership on an entity's Board of Directors or advisory committees; Takeda Canada: Membership on an entity's Board of Directors or advisory committees; Janssen Inc.: Membership on an entity's Board of Directors or advisory committees; Celgene Canada: Membership on an entity's Board of Directors or advisory committees. Berdeja:Bluebird: Research Funding; Janssen: Research Funding; Sanofi: Research Funding; Takeda: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Bristol-Myers Squibb: Research Funding; Glenmark: Research Funding; Genentech: Research Funding; Amgen: Research Funding; Teva: Research Funding; Poseida Therapeutics, Inc.: Research Funding. Ganguly:Janssen: Consultancy; Seattle Genetics: Speakers Bureau; Amgen: Consultancy; Daiichi Sankyo: Research Funding. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Bar:Celgene: Consultancy. Quick:CTI BioPharma: Research Funding. Fonseca:Celgene: Speakers Bureau. Reece:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Merck: Honoraria, Research Funding; Otsuka: Research Funding. Agarwal:Celgene Corporation: Employment, Equity Ownership. Chung:Celgene Corporation: Employment, Equity Ownership. Zafar:Celgene: Employment. Bahlis:Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding.

Abstract: Introduction: Lenalidomide (LEN), a standard of care for newly diagnosed multiple myeloma, is routinely administered until disease progression. However, patients with disease that has relapsed after or become refractory to LEN have been poorly represented in recent trials investigating triplet regimens after ≤ 3 prior treatment (Tx) lines. Consequently, patients who have exhausted the benefits of LEN in early relapse are a clinically relevant population in need of proven Tx options. The trial that led to approval of pomalidomide (POM) + dexamethasone (DEX) + daratumumab (DARA) evaluated patients with heavily pretreated (median of 4 prior lines of therapy) relapsed refractory multiple myeloma (RRMM; Chari et al. Blood 2017). The phase 2 MM-014 trial (NCT01946477), which is composed of 3 cohorts, was specifically designed to investigate the outcomes of sequencing POM-based therapy immediately after first- or second-line LEN-based Tx failure in patients with RRMM. In an earlier report from cohort B of MM-014, POM + DEX + DARA demonstrated promising efficacy and safety results: the overall response rate (ORR) was 77.7%, and the 1-year progression-free survival (PFS) rate was 75.1% at a median follow-up of 17.2 months (Siegel et al. Leukemia 2020). Updated efficacy and safety results from cohort B are reported here. Methods: Patients with RRMM treated with 1-2 prior Tx lines, LEN-based Tx as their most recent regimen, and progressive disease during/after their last line of Tx received POM + DEX + DARA. POM 4 mg/day was given orally on days 1-21; DEX 40 mg/day (20 mg/day in patients aged & gt; 75 years) was given orally on days 1, 8, 15, and 22; and DARA 16 mg/kg was given intravenously on days 1, 8, 15, and 22 of cycles 1 and 2, days 1 and 15 for cycles 3-6, and day 1 for cycles 7+. ORR was the primary endpoint; secondary endpoints included PFS and safety. Results: In the intention-to-treat (ITT) population of 112 patients, the median age was 66.5 years, all patients had prior LEN, and 77.7% had prior bortezomib. Overall, 84 patients (75%) had LEN-refractory MM and 28 (25%) had MM that relapsed after prior LEN Tx; most patients (70 [62.5%]) received 1 vs 2 (42 [37.5%] ) prior Tx lines. As of March 24, 2020, 31 patients (27.7%) were still on treatment; median follow-up was 28.4 months. The most common reasons for discontinuation in 81 patients (72.3%) were progressive disease (46 patients [56.8%]), withdrawal by patient (19 patients [23.5%] ), and adverse events (AEs; 7 patients [8.6%]). The efficacy-evaluable (EE) population comprised 109 patients who received ≥ 1 dose of study Tx and had ≥ 1 post-baseline assessment and was used for supportive efficacy analyses. ORR was 77.7% (≥ very good partial response [VGPR] , 52.7%) and 79.8% (≥ VGPR, 54.1%) in the ITT and EE populations, respectively. ORR was similar in patients with LEN-relapsed and LEN-refractory disease (82.1% and 76.2%, respectively). The median PFS was reached: 30.8 months in both the ITT and EE populations (Figure). Overall, 97.3% of patients had ≥ 1 grade 3/4 AE, with neutropenia (64.3%; febrile 9.8%) being the most common grade 3/4 hematologic Tx-emergent AE, followed by anemia (17.9%) and thrombocytopenia (14.3%). Grade 3/4 infections were noted in 36.6% of patients, including 16.1% with grade 3/4 pneumonia. Conclusions: POM + DEX + DARA administered in early-line Tx immediately after LEN failure continues to show a high response rate and a consistent safety profile, demonstrating the benefit of maintaining continuous immunomodulation with POM following LEN. These updated results continue to demonstrate the efficacy and safety of POM-based therapy as early as second line in patients with RRMM, even immediately after LEN failure, indicating that switching from the immunomodulatory agent class is not necessary. Furthermore, these findings support the use of POM + DEX as the foundation of novel combinations in MM. Figure 1 Disclosures Siegel: Karyopharma: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Merck: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau; Celulatiry: Consultancy. Schiller:Forma: Research Funding; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; Deciphera: Research Funding; DeltaFly: Research Funding; Regimmune: Research Funding; Samus: Research Funding; Sangamo: Research Funding; Tolero: Research Funding; Trovagene: Research Funding; Kaiser Permanente: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; FujiFilm: Research Funding; Mateon: Research Funding; Kite Pharma: Research Funding; Karyopharm: Research Funding; Celator: Research Funding; Constellation: Research Funding; Cyclacel: Research Funding; Jazz Pharmaceuticals: Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; Incyte: Consultancy, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding; Ono Pharma: Consultancy; Celgene: Research Funding, Speakers Bureau; Sanofi: Speakers Bureau; Gilead: Speakers Bureau; Astellas Pharma: Honoraria, Research Funding; Ariad: Research Funding; Actinium: Research Funding; Abbvie: Research Funding; Stemline: Speakers Bureau; Pfizer: Current equity holder in publicly-traded company, Research Funding; MedImmune: Research Funding; Onconova: Research Funding; Daiichi Sankyo: Research Funding; Geron: Research Funding; Genentech-Roche: Research Funding; Gamida: Research Funding. Sebag:Celgene: Honoraria; Takeda: Honoraria; Amgen: Honoraria; Janssen: Honoraria, Research Funding. Berdeja:CRISPR Therapeutics: Consultancy, Research Funding; Cellularity: Research Funding; Celgene: Consultancy, Research Funding; Servier: Consultancy; Teva: Research Funding; Prothena: Consultancy; BMS: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Bioclinica: Consultancy; Bluebird: Research Funding; Vivolux: Research Funding; Abbvie: Research Funding; Amgen: Consultancy, Research Funding; Acetylon: Research Funding; Poseida: Research Funding; CURIS: Research Funding; EMD Sorono: Research Funding; Genentech, Inc.: Research Funding; Glenmark: Research Funding; Janssen: Consultancy, Research Funding; Karyopharm: Consultancy; Kesios: Research Funding; Kite Pharma: Consultancy; Legend: Consultancy; Lilly: Research Funding; Novartis: Research Funding; Constellation: Research Funding. Ganguly:KITE Pharma: Speakers Bureau; Settle Genetics: Speakers Bureau; Kadmon: Other: Ad Board. Matous:Bristol-Myers Squibb Company: Consultancy, Honoraria, Speakers Bureau. Song:Celgene: Research Funding; Celgene, Janssen, Amgen, Takeda: Honoraria. Bar:Bristol-Myers Squibb Company: Consultancy. Anz:AbbVie: Other: Investigator in AbbVie-sponsored clinical trials. Fonseca:Bristol-Myers Squibb Company: Speakers Bureau. Reece:Janssen, Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Research Funding; Otsuka: Research Funding; Janssen, Bristol-Myers Squibb, Amgen, Takeda: Consultancy, Honoraria. Lee:Bristol-Myers Squibb Company: Current Employment, Current equity holder in publicly-traded company. Agarwal:Bristol-Myers Squibb Company: Current Employment, Current equity holder in publicly-traded company. Bahlis:BMS/Celgene and Janssen: Consultancy, Honoraria, Other: Travel, Accomodations, Research Funding; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Karyopharm Therapeutics: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria.