Abstract: Background: PNK-007 is an allogeneic, off the shelf cell therapy enriched for CD56+/CD3- NK cells expanded from placental CD34+ cells. PNK-007 exhibit cytotoxicity against various cancer cell types, including multiple myeloma (MM), and secrete cytokines during co-culture with cancer cells. This is a Phase I study of single infusion PNK-007 after autologous stem cell transplant (ASCT) in MM. Methods: Placental CD34+ cells were cultivated in the presence of cytokines for 35 days to generate PNK-007 under cGMP standards followed by release testing. HLA matching and KIR mismatching were not used. Four treatment arms were evaluated on eligible patients (pts) following ASCT: 10 million (M) cells/kg Day (D) 14 with or without rhIL-2, 30M cells/kg D14 with rhIL-2 or 30M cells/kg D7 with rhIL-2. rhIL-2 was administered subcutaneously at 6M units every other day for up to 6 doses to facilitate PNK-007 expansion. Pts received variable pre-ASCT induction therapy. Maintenance therapy was permitted after the Day 90-100 visit (D90). Enrollment is complete, and all pts have completed the D90 visit as of the cutoff date Oct 26, 2018. Results: 15 pts who received PNK-007 (12 of whom received rhIL-2) were evaluated for clinical response at D90. Pts aged 44-69 yrs included 12 newly diagnosed (ND)MM and 3 relapsed/refractory (RR)MM. The 3 RRMM received 1, 2 or 5 prior lines of therapy, with 2 pts having previous ASCT. All pts had been exposed to IMiDs and PIs. No dose-limiting toxicity, GvHD, graft failure or graft rejection were observed. No serious adverse events (AEs) were attributable to PNK-007 and the reported AEs were consistent with AEs related to ASCT. Based on physician assessed responses by International Myeloma Working Group pre-ASCT, 10/15 pts achieved VGPR or better (1 CR and 9 VGPR), and by D90, 12/15 pts achieved VGPR or better (5 CR or sCR and 7 VGPR). Using a validated Euro-flow minimal residual disease (MRD) assay by bone marrow aspirate (BMA), pre-ASCT, 4/15 pts were MRD negative (MRD-), and by D90, 10/15 pts were MRD-. At one-year post-ASCT, 4/6 pts were MRD-, with 1 converting to MRD-, 1 inadequate sample, and 1 remaining MRD+. PNK-007 did not interfere with immune reconstitution kinetics. Administration of rhIL-2 coincided with a transient increase in circulating regulatory T cell levels. Host NK cells reached a maximum level between 21-28 days post-ASCT followed by contraction independent of rhIL-2 administration. Conclusion: PNK-007 is the first fully allogeneic, off the shelf CD34+ derived NK cell product in MM clinical trials. A single infusion of PNK-007 up to 30M cells/kg with and without rhIL-2 was well tolerated in the post-ASCT setting. We established the feasibility of infusing PNK-007 as early as 7 days post-ASCT without negative impact on blood count recovery. Attainment of BMA MRD- status was observed in 10/15 pts at D90. These clinical data are encouraging and warrant further evaluation. Citation Format: Sarah A. Holstein, Sarah A. Cooley, Parameswaran Hari, Sundar Jagannath, Catherine R. Balint, William van der Touw, Michele L. Donato, Philip L. McCarthy, Paul K. Wallace, Xiaokui Zhang, Robert J. Hariri, Mohamad A. Hussein, Ravi Vij. A Phase I study of PNK-007, allogeneic, off the shelf NK cell, post autologous transplant in multiple myeloma (NCT02955550) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT108.

Abstract: Background: PNK-007 is an allogeneic, off the shelf cell therapy product enriched for CD56+/CD3- NK cells expanded from placental CD34+ cells. PNK-007 cells exhibit cytotoxicity against various cancer cell types, including multiple myeloma (MM), and secrete cytokines during co-culture with cancer cells. This is a Phase I study of single infusion PNK-007 after autologous stem cell transplant (ASCT) in MM. Methods: Placental CD34+ cells were cultivated in the presence of cytokines for 35 days to generate PNK-007 under cGMP standards followed by release testing. HLA matching and KIR mismatching were not used. Four treatment arms were evaluated on patients (pts) following ASCT: 10 million (M) cells/kg Day (D) 14 with or without recombinant human IL-2 (rhIL-2), 30M cells/kg D14 with rhIL-2, or 30M cells/kg D7 with rhIL-2. rhIL-2 was administered subcutaneously at 6M units every other day for up to 6 doses to facilitate PNK-007 expansion. Pts received variable pre-ASCT induction therapy. Maintenance therapy was permitted after the Day 90-100 visit (D90). Subjects were followed for up to 1-year. Results: 15 pts who received PNK-007 (12 of whom received rhIL-2) were followed on this study. Pts aged 44-69 yrs included 12 newly diagnosed (ND)MM and 3 relapsed/refractory (RR)MM. The 3 RRMM pts had received 1, 2 or 5 prior lines of therapy, with 2 pts having previous ASCT. All pts had been exposed to immunomodulatory drug (IMiDs) and proteasome inhibitors (PIs). No serious adverse events (AEs) were attributable to PNK-007 and no dose-limiting toxicity, GvHD, graft failure or graft rejection were observed. 12/15 pts started maintenance therapy following the transplant while participating in this study, at the physician's discretion. Based on physician assessed responses by International Myeloma Working Group pre-ASCT, of the NDMM pts 10/12 achieved VGPR or better (1 CR and 9 VGPR), 1/12 achieved PR and 1/12 was not assessed during pre-ASCT induction. By D90 10/12 pts achieved VGPR or better (5 CR or sCR and 5 VGPR), 1/12 maintained PR and 1/12 stable disease. At 1-year 9/11 achieved VGPR or better (4 CR or sCR and 5 VGPR), 2/11 were not assessed and 1 was removed from the study prior to 1 year due to failure to respond to ASCT. Of the RRMM pts 2/3 achieved PR and 1/3 was not assessed during pre-ASCT induction, by D90 2/3 achieved VGPR and the pt that had not been assessed pre-ASCT achieved PR. At 1-year, 1 pt maintained VGPR, 1 pt was not assessed and 1 pt did not continue to the 1-year visit. Using a validated Euro-flow minimal residual disease (MRD) assay of bone marrow aspirate (BMA) samples, of the NDMM pts 4/12 were MRD negative (MRD-) pre-ASCT; by D90 9/12 were MRD-. At 1-year 6/12 were MRD-, 2/12 had insufficient BMA to perform testing, 2/12 refused BMA procedure, 1/12 did not convert to MRD-, and 1 was removed from the study prior to 1-year due to failure to respond to ASCT. Of the RRMM pts 0/3 were MRD- pre-ASCT with 1/3 having insufficient BMA to perform testing; by D90 1/3 were MRD-. At 1-year 1/3 was MRD-, 1/3 did not convert to MRD- and 1 pt did not continue to the 1-year visit. PNK-007 infusion did not interfere with immune reconstitution kinetics. Platelet, neutrophil, and absolute lymphocyte counts recovered by day 28 post-ASCT in 12/15 patients. All pts' sera tested negative for the presence of anti-HLA antibodies at all timepoints indicating the absence of humoral immunity and alloantibodies to PNK-007. Conclusion: PNK-007 is the first fully allogeneic, off the shelf CD34+ derived NK cell product in MM clinical trials. A single infusion of PNK-007 up to 30M cells/kg with and without rhIL-2 was well tolerated in the post-ASCT setting. We established the feasibility of infusing PNK-007 as early as 7 days post-ASCT without negative impact on blood count recovery or successful engraftment. BMA MRD- status was observed in 7/9 MRD evaluable pts at 1-year post ASCT. These clinical data are encouraging and warrant further evaluation. Disclosures Holstein: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees; Sorrento: Consultancy; GSK: Consultancy; Genentech: Membership on an entity's Board of Directors or advisory committees. Cooley:Fate Therapeutics, Inc: Employment, Equity Ownership. Hari:Cell Vault: Equity Ownership; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Research Funding; Janssen: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Amgen: Research Funding; Spectrum: Consultancy, Research Funding; Sanofi: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria. Jagannath:BMS: Consultancy; Merck: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Medicom: Speakers Bureau; Multiple Myeloma Research Foundation: Speakers Bureau. Balint:Celgene: Equity Ownership; Celularity, Inc: Employment. Van Der Touw:Celularity, Inc: Employment. Zhang:Celularity Inc: Employment. Hariri:Celularity Inc: Employment. Vij:Bristol-Myers Squibb: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Genentech: Honoraria; Janssen: Honoraria; Karyopharm: Honoraria; Sanofi: Honoraria; Takeda: Honoraria, Research Funding.

Abstract: The standard conditioning regimen for multiple myeloma patients undergoing autologous hematopoietic stem cell transplant (HSCT) is intravenous melphalan dosed at 200mg/m 2 (mel200). Prior retrospective studies indicated that dose reduction to melphalan 140 mg/m 2 (mel140) confers similar progression-free (PFS) and overall survival (OS), leading to increased use of mel140 in patients with comorbidities or advanced age. A recent single-center retrospective study (Sharma et al, Leukemia Lymphoma 2023) identified an OS advantage yet similar PFS for mel200 vs mel140, suggesting that certain patient cohorts may benefit from mel200. These findings require confirmation and better understanding of the risks and benefits to different dosing strategies. We performed a single-center retrospective study of mel dosing and transplant outcomes at the University of Nebraska Medical Center between 2008-2018. Three hundred and sixty-two patients underwent a first autologous HSCT with mel conditioning; 95 received mel140 while 267 received mel200. Nearly all patients received maintenance therapy (n= 357, 99%). Patient demographic and disease factors were largely comparable between mel140 and mel200 cohorts including sex, response prior to HSCT (both 73% for very good partial response or better), and presence of high-risk cytogenetics (t(4;14), t(14;16), t(14;20), del17p; 15% vs 14%). The mel140 group was older (65.1 years vs 59.7 years), had higher hematopoietic cell transplantation-specific comorbidity index (HCT-CI) scores (64% vs 40% at ³3), and International Staging System (ISS) stages (40% vs 22% at stage III) than the mel200 group. Average creatinine clearance at transplant was 71 vs 91 mL/min/m 2 in the mel140 vs mel200 cohorts, respectively. OS favored mel200 with a median survival time of 94.4 vs 69.1 months (mel200 vs mel140, Figure 1, p = 0.002). There was no statistical difference in PFS between mel200 vs mel140 (median PFS 73.0 vs 60.5 months, p = 0.43, respectively). With Cox proportional hazards regression, we performed a multivariate analysis of risk factors on PFS and OS. For OS, age ( p = 0.02) retained statistical significance within the model. Mel dosing and high-risk cytogenetics (both p = 0.09) did not retain significance. HCT-CI may have an effect ( p = 0.04), but due to missing data on n= 125/362 subjects this could not be well evaluated. Response prior to HSCT, creatine clearance at transplant, and ISS stage were not statistically significant. Given the multiple variables assessed and missing data for HCT-CI we separately analyzed mel dosing together with the most significant variable in the model, age. In this subset OS model, mel200 was associated with an improved OS (hazard ratio (HR) 0.64, p = 0.03) while age was associated with an adverse effect (HR 1.11 per 5-year increase, p = 0.06). For the multivariate PFS model, only high-risk cytogenetics (HR 1.82 yes vs no, p = 0.004) retained statistical significance. Median engraftment was faster in mel200 cohort (67% vs 92% engraftment starting at ³D+12, p & lt;0.001). We next examined the impact of mel dosing on the rate of exceptional response (Paquin et al, Blood Cancer Journal 2020), defined as alive and progression-free for 8 or more years. Twenty-nine of 362 patients (8%) met the requirements for exceptional response. Two (7%) received mel140 while 27 (93%) received mel200. Exceptional responders were younger and split evenly between male and female. The majority had at least a very good partial response prior to HSCT (79%). Only 2 exhibited high-risk cytogenetics; one received bortezomib and lenalidomide maintenance, the other only bortezomib. On multivariate analysis, only two factors contributed to exceptional response: mel dose (mel200 odds ratio (OR) 5.22, Table 1, p = 0.01) and HCT-CI (OR 0.66 for increasing score, Table 1, p = 0.02. High-risk cytogenetics was not associated with exceptional responders (OR 0.43 yes vs no, p = 0.38) which may be due to low sample size. We conclude that mel dosing impacts OS but not PFS in our cohort, though this effect is confounded by increasing age and potentially comorbidity. We report for the first time that mel200 dosing increases the rate of exceptional response compared to mel140. Overall, these data support recent conclusions by Sharma et al and challenge the previous reports of similar OS outcomes between mel200 and mel140 dosing.

Abstract: Multiple myeloma is characterized by the proliferation of malignant plasma cells which secrete large quantities of monoclonal protein (MP). As yet, no therapeutic strategies have been developed which directly target MP secretion. The Rab family of small GTPases plays key roles in intracellular vesicle trafficking. We have demonstrated that agents which impair the geranylgeranylation of Rab proteins induce apoptosis of myeloma cells by disrupting MP secretion, resulting in accumulation of MP within the cells and activation of the unfolded protein response pathway (UPR). Previously identified inhibitors of Rab geranylgeranyl transferase (Rab GGTase), the enzyme responsible for post-translational modification of Rab proteins, lack potency and have limited therapeutic potential. We hypothesized that potent and selective inhibitors of Rab GGTase could be designed based on available crystallographic data which reveals how the isoprenoid substrate interacts with the enzyme’s active site. Families of compounds were therefore designed incorporating three motifs to allow for interaction with key components of the enzyme’s active site: a non-hydrolyzable polar head group, a zinc-binding motif, and an isoprenoid or isoprenoid-like chain. The isoprenoid-based compounds were prepared using a divergent synthetic strategy based on azide-acetylene cycloadditions or “click” chemistry. We have previously demonstrated that direct use of an isoprenoid azide in a click reaction results in a triazole product that is a mixture of olefin isomers, due to an unavoidable [3,3] sigmatropic rearrangement that scrambles the stereochemistry of the first olefin prior to cycloaddition. This problem now has been circumvented by the development of a new synthetic strategy which is based on a regiospecific epoxidation of the C-2 olefin in the isoprenoid alcohol, followed by introduction of the azide and formation of the triazole. After completion of a click reaction the product can be reduced back to the parent olefin with good stereocontrol, to afford isoprenylated triazoles of the same chain length as those prepared directly from isoprenoid azides. Series of compounds were thus prepared in which chain length (including isoprenoid and isoprenoid-like), olefin stereochemistry, and polar head group (including bisphosphonic acids and carboxyphosphonic acids) were varied. All novel agents were subjected to in vitro enzyme assays for Rab GGTase as well as the related enzymes farnesyl transferase (FTase) and geranylgeranyl transferase I (GGTase I) and IC50 values were obtained. The cytotoxic activities of these agents were determined via MTT assays in human myeloma cell lines. Disruption of protein prenylation in myeloma cells was assessed via immunoblot analysis of farnesylated (Ras) and geranylgeranylated (Rap1a and Rab6) proteins. The results from these enzymatic and cell-based assays enabled the determination of a detailed structure-function relationship. These studies reveal that both chain length and olefin stereochemistry have a significant impact on both inhibitor potency and selectivity with respect to the target enzyme and the related prenyltransferases. For example, when the chain length was increased by just one methylene unit (farnesyl to homofarnesyl), the potency against Rab GGTase was enhanced by approximately 4-fold while changing the stereochemistry at the second olefin site from trans to cis diminished the potency by approximately 5-fold. These studies are guiding the design and synthesis of future generations of inhibitors with the ultimate goal of developing a potent and selective Rab GGTase inhibitor which can be utilized as a therapeutic agent for myeloma. Disclosures: No relevant conflicts of interest to declare.

Abstract: Introduction: DARA is approved for NDMM and previously treated MM. In the primary analysis of the phase 2 GRIFFIN trial (NCT02874742) in autologous stem cell transplant (ASCT)-eligible NDMM pts (median follow-up, 13.5 mo), DARA plus RVd (D-RVd) improved the rate of stringent complete response (sCR) by the end of post-ASCT consolidation versus RVd (42.4% vs 32.0%, 1-sided P=0.068) (Voorhees PM, et al. Blood. 2020). With longer follow-up (median, 27.4 mo), responses deepened and were improved for D-RVd versus RVd (sCR rate: 63.6% vs 47.4%, 2-sided P=0.0253), as did the MRD-negativity (10 -5) rate (62.5% vs 27.2%, P & lt;0.0001) (Kaufman JL, et al. Blood. 2020). Here, we present updated efficacy and safety results after 24 months of maintenance therapy or treatment discontinuation (median follow-up, 38.6 mo). Methods: Pts with NDMM eligible for high-dose therapy (HDT) and ASCT were randomized 1:1 to receive RVd or D-RVd, stratified by ISS disease stage (I, II, or III) and creatinine clearance (30-50 or & gt;50 mL/min). Pts received 4 RVd or D-RVd induction cycles, HDT, ASCT, 2 RVd or D-RVd consolidation cycles, and maintenance with lenalidomide (R) alone or with DARA (D-R) for 24 months. During induction and consolidation (21-day cycles), pts received R (25 mg PO on Days 1-14), bortezomib (1.3 mg/m 2 SC on Days 1, 4, 8, and 11), and dexamethasone (40 mg PO QW) ± DARA (16 mg/kg IV on Days 1, 8, and 15 of Cycles 1-4 and Day 1 of Cycles 5-6). During maintenance (Cycles 7-32; 28-day cycles), pts received R (10 mg PO on Days 1-21; if tolerated, 15 mg in Cycle 10+) ± DARA (16 mg/kg IV) Q8W (or Q4W per pt decision after protocol amendment 2) until disease progression or up to 24 months. The primary endpoint was sCR rate by the end of post-ASCT consolidation (tested at 1-sided α of 0.10). Responses were assessed per IMWG criteria by a validated computer algorithm. Key secondary endpoints included progression-free survival (PFS) and MRD negativity assessed by NGS at the minimum sensitivity threshold of 10 -5, at suspected complete response or better (≥CR), at the end of induction and consolidation, and after 12 and 24 months of maintenance, regardless of response. Secondary analyses were evaluated using 2-sided α of 0.05, not adjusted for multiplicity. Results: In total, 207 pts were randomized (D-RVd, n=104; RVd, n=103); baseline characteristics were well balanced. After 24 months of D-R or R maintenance therapy, the rate of sCR favored D-RVd versus RVd in the response-evaluable population (66.0% [66/100] vs 47.4% [46/97] , 2-sided P=0.0096; Figure). In the intent-to-treat (ITT) population, MRD-negativity (10 -5) rates also remained higher for D-RVd versus RVd (64.4% [67/104] vs 30.1% [31/103] , P & lt;0.0001), as well as among pts who achieved ≥CR (78.0% [64/82] vs 47.5% [28/59] , P=0.0003). Similarly, MRD-negativity (10 -6) rates favored D-RVd versus RVd in the ITT population (35.6% vs 14.6%, P=0.0007; Figure), as well as among pts who achieved ≥CR (42.7% vs 22.0%, P=0.0121). The rate of sustained MRD negativity (10 -5) lasting ≥12 months in the ITT population was & gt;3-fold higher for D-RVd versus RVd (44.2% vs 12.6%, P & lt;0.0001). With 38.6 months follow-up, median PFS was not reached in either arm but trended towards favoring D-RVd versus RVd (hazard ratio, 0.46; 95% CI, 0.21-1.01; Figure). The estimated 36-month PFS rate was 88.9% for D-RVd and 81.2% for RVd. In total, 14 pts died (D-RVd, n=7; RVd, n=7), 9 from progressive disease (D-RVd, n=5; RVd, n=4). No new safety concerns were observed with extended follow-up. In total, 86.9% (86/99) of D-RVd pts and 79.4% (81/102) of RVd pts developed grade 3/4 treatment-emergent adverse events (TEAEs). Serious TEAEs occurred in 46.5% of D-RVd pts and 52.0% of RVd pts. TEAEs led to discontinuation of study treatment at the same rate (D-RVd, 34.3%; RVd, 34.3%). One pt in each group died due to TEAEs, neither related to study treatment. Conclusion: After 24 months of maintenance therapy, the addition of DARA to RVd induction and consolidation in conjunction with ASCT, followed by DARA plus R maintenance, continued to demonstrate deep and durable responses in pts with transplant-eligible NDMM, including sCR and MRD-negativity (10 -5 and 10 -6) rates. While this study was not powered for PFS, there is a positive trend towards improved PFS in the D-RVd group. No new safety concerns were observed with longer follow-up. These results support the use of D-RVd induction/consolidation and D-R maintenance in transplant-eligible NDMM pts. Figure 1 Figure 1. Disclosures Kaufman: Sutro, Takeda: Research Funding; Incyte, TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Research Funding; Amgen: Research Funding; Tecnofarma SAS, AbbVie: Honoraria; Janssen: Honoraria; Fortis Therapeutics: Research Funding; Novartis: Research Funding; Incyte, celgene: Consultancy; Heidelberg Pharma: Research Funding; Roche/Genetech, Tecnopharma: Consultancy, Honoraria; Genentech, AbbVie, Janssen: Consultancy, Research Funding. Sborov: Sanofi: Consultancy; SkylineDx: Consultancy; GlaxoSmithKline: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees. Reeves: Bristol-Myers Squibb: Speakers Bureau; Incyte Corporation: Honoraria; Takeda: Honoraria; Pharma Essentia: Consultancy, Honoraria. Rodriguez: Janssen: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Karyopharm: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Oncopeptides: Consultancy, Honoraria. Chari: Oncopeptides: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Membership on an entity's Board of Directors or advisory committees; Shattuck Labs: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Secura Bio: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi Genzyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Research Funding; Antengene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millenium/Takeda: Consultancy, Research Funding; Janssen Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; BMS/Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Silbermann: Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Sanofi Genzyme: Membership on an entity's Board of Directors or advisory committees, Research Funding. Costa: Pfizer: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Anderson: Celgene, BMS, Janssen, GSK, Karyopharm, Oncopeptides, Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Shah: GSK: Consultancy; Nektar: Research Funding; Kite: Consultancy; CareDx: Consultancy; CSL Behring: Consultancy; Indapta Therapeutics: Consultancy; Janssen: Research Funding; Poseida: Research Funding; Karyopharm: Consultancy; BMS/Celgene: Research Funding; Bluebird Bio: Research Funding; Oncopeptides: Consultancy; Teneobio: Research Funding; Sanofi: Consultancy; Precision Biosciences: Research Funding; Sutro Biopharma: Research Funding; Amgen: Consultancy. Bumma: Janssen: Membership on an entity's Board of Directors or advisory committees; Amgen: Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Holstein: Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech, GSK, Janssen, Secura Bio, Sorrento: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees, Research Funding. Jakubowiak: Abbvie: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Gracell: Membership on an entity's Board of Directors or advisory committees. Wildes: Carevive: Consultancy; Seattle Genetics: Consultancy; Sanofi: Consultancy; Janssen: Consultancy. Orlowski: Asylia Therapeutics, Inc., BioTheryX, Inc., and Heidelberg Pharma, AG.: Other: Laboratory research funding; CARsgen Therapeutics, Celgene, Exelixis, Janssen Biotech, Sanofi-Aventis, Takeda Pharmaceuticals North America, Inc.: Other: Clinical research funding; Asylia Therapeutics, Inc.: Current holder of individual stocks in a privately-held company, Patents & Royalties; Amgen, Inc., BioTheryX, Inc., Bristol-Myers Squibb, Celgene, Forma Therapeutics, Genzyme, GSK Biologicals, Janssen Biotech, Juno Therapeutics, Karyopharm Therapeutics, Inc., Kite Pharma, Neoleukin Corporation, Oncopeptides AB, Regeneron Pharmaceuticals, I: Membership on an entity's Board of Directors or advisory committees; Amgen, Inc., BioTheryX, Inc., Bristol-Myers Squibb, Celgene, EcoR1 Capital LLC, Genzyme, GSK Biologicals, Janssen Biotech, Karyopharm Therapeutics, Inc., Neoleukin Corporation, Oncopeptides AB, Regeneron Pharmaceuticals, Inc., Sanofi-Aventis, and Takeda P: Consultancy, Honoraria. Shain: AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi Genzyme: Consultancy, Speakers Bureau; GlaxoSmithLine, LLC: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Adaptive Biotechnologies Corporation: Consultancy, Speakers Bureau; Janssen oncology: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Karyopharm Therapeutics Inc.: Honoraria, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy. Cowan: BMS: Research Funding; Secura Bio: Consultancy; GSK: Consultancy; Harpoon: Research Funding; Cellectar: Consultancy; Sanofi: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Nektar: Research Funding. Pei: Janssen: Current Employment, Current equity holder in publicly-traded company. Cortoos: Janssen: Current Employment, Current equity holder in publicly-traded company. Patel: Janssen: Current Employment. Bartlett: Janssen: Current Employment. Vermeulen: Janssen: Current Employment, Current equity holder in publicly-traded company. Lin: Janssen: Current Employment. Richardson: Sanofi: Consultancy; Secura Bio: Consultancy; Regeneron: Consultancy; Karyopharm: Consultancy, Research Funding; Janssen: Consultancy; Protocol Intelligence: Consultancy; Celgene/BMS: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; AstraZeneca: Consultancy; Oncopeptides: Consultancy, Research Funding; AbbVie: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding. Voorhees: Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Secura Bio: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: 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. OffLabel Disclosure: The specific regimen combination is not yet approved, but individual components are.

Abstract: Background: Immunoglobulin light-chain (AL) amyloidosis is a rare disease caused by plasma cell secretion of misfolded light chains that assemble as amyloid fibrils and deposit on vital organs including the heart and kidneys, causing organ dysfunction. Plasma cell directed therapeutics, aimed at preferentially eliminating the clonal population of amyloidogenic cells in bone marrow are expected to reduce production of toxic light chain and alleviate deposition of amyloid thereby restoring healthy organ function. Melphalan flufenamide ethyl ester, melflufen, is a peptidase potentiated alkylating agent with potent toxicity in myeloma cells. Melflufen is highly lipophilic, permitting rapid cellular uptake, and is subsequently enzymatically cleaved by aminopeptidases within cells resulting in augmented intracellular concentrations of toxic molecules, providing a more targeted and localized treatment. Previous data demonstrating multiple myeloma plasma cell sensitivity for melflufen suggests that the drug might be useful to directly eliminate amyloidogenic plasma cells, thereby reducing the amyloid load in patients. Furthermore, the increased intracellular concentrations of melflufen in myeloma cells indicates a potential reduction in systemic toxicity in patients, an important factor in the fragile amyloidosis patient population. To assess potential efficacy in amyloidosis patients and to explore the mechanism of action, we examined effects of melflufen on amyloidogenic plasma cells invitro and invivo. Methods: Cellular toxicity and apoptosis were measured in response to either melflufen or melphalan in multiple malignant human plasma cell lines, including the amyloidosis patient derived light chain secreting ALMC-1 and ALMC-2 cells, as well as primary bone marrow cells from AL amyloidosis patients, using annexin V and live/dead cell staining by multicolor flow cytometry, and measurement of cleaved caspases. Lambda light chain was measured in supernatant by ELISA, and intracellular levels were detected by flow cytometry. To assess efficacy of melflufen in vivo, the light chain secreting human myeloma cell line, JJN3, was transduced with luciferase and adoptively transferred into NSG mice. Cell death in response to melflufen or melphalan was measured by in vivo bioluminescence, and serum light chain was monitored. Results: Melflufen demonstrated increased potency against multiple myeloma cell lines compared to melphalan, inducing malignant plasma cell death at lower doses on established light chain secreting plasma cell lines. While ALMC-1 cells were sensitive to both melphalan and melflufen, the IC50 for melphalan at 960 nM was approximately 3-fold higher than melflufen (334 nM). However, ALMC-2 cells were relatively insensitive to melphalan (12600 nM), but maintained a 100-fold increase in sensitivity to melflufen (121 nM). Furthermore, while 40% of primary CD138+ plasma cells from patients with diagnosed AL amyloidosis responded to melflufen treatment in vitro, only 20% responded to melphalan with consistently superior IC50 values for melflufen (Figure 1). Light chain secreting cell lines and AL amyloidosis patient samples were further analyzed by single cell sequencing. We further examined differential effects on apoptosis and the unfolded protein response in vitro in response to either melflufen or melphalan. This is of particular interest in amyloidosis, where malignant antibody producing plasma cells possess an increased requirement for mechanisms to cope with the amplified load of unfolded protein and associated ER stress. As AL amyloidosis is ultimately a disease mediated by secretion of toxic immunoglobulin, we assessed the effects of melflufen on the production of light chain invitro, measuring a decrease in production of light chain in response to melflufen treatment. Finally, we took advantage of a recently described adoptive transfer mouse model of amyloidosis to assess the efficacy of melflufen and melphalan in eliminating amyloidogenic clones and reducing the levels of toxic serum light chain in vivo. Conclusions: These findings provide evidence that melflufen mediated toxicity, previously described in myeloma cells, extends to amyloidogenic plasma cells and further affects the ability of these cells to produce and secrete toxic light chain. This data supports the rationale for the evaluation of melflufen in patients with AL amyloidosis. Figure 1 Disclosures Flanagan: Oncopeptides AB: Employment. Slipicevic:Oncopeptides AB: Employment. Holstein:Celgene: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Genentech: Membership on an entity's Board of Directors or advisory committees; Sorrento: Consultancy. Lehmann:Oncopeptides AB: Employment. Nupponen:Oncopeptides AB: Employment. Heckman:Celgene: Research Funding; Novartis: Research Funding; Oncopeptides: Research Funding; Orion Pharma: Research Funding.

Abstract: Lenalidomide, bortezomib, and dexamethasone (RVd) followed by autologous stem cell transplantation (ASCT) is standard frontline therapy for transplant-eligible patients with newly diagnosed multiple myeloma (NDMM). The addition of daratumumab (D) to RVd (D-RVd) in transplant-eligible NDMM patients was evaluated. Patients (N = 207) were randomized 1:1 to D-RVd or RVd induction (4 cycles), ASCT, D-RVd or RVd consolidation (2 cycles), and lenalidomide or lenalidomide plus D maintenance (26 cycles). The primary end point, stringent complete response (sCR) rate by the end of post-ASCT consolidation, favored D-RVd vs RVd (42.4% vs 32.0%; odds ratio, 1.57; 95% confidence interval, 0.87-2.82; 1-sided P = .068) and met the prespecified 1-sided α of 0.10. With longer follow-up (median, 22.1 months), responses deepened; sCR rates improved for D-RVd vs RVd (62.6% vs 45.4%; P = .0177), as did minimal residual disease (MRD) negativity (10−5 threshold) rates in the intent-to-treat population (51.0% vs 20.4%; P & lt; .0001). Four patients (3.8%) in the D-RVd group and 7 patients (6.8%) in the RVd group progressed; respective 24-month progression-free survival rates were 95.8% and 89.8%. Grade 3/4 hematologic adverse events were more common with D-RVd. More infections occurred with D-RVd, but grade 3/4 infection rates were similar. Median CD34+ cell yield was 8.2 × 106/kg for D-RVd and 9.4 × 106/kg for RVd, although plerixafor use was more common with D-RVd. Median times to neutrophil and platelet engraftment were comparable. Daratumumab with RVd induction and consolidation improved depth of response in patients with transplant-eligible NDMM, with no new safety concerns. This trial was registered at www.clinicaltrials.gov as #NCT02874742.

Abstract: The development of chimeric antigen receptor (CAR) T‐cell therapy for select hematological malignancies represents one of the most remarkable therapeutic advances in the past decade. Currently, CD19‐targeted CAR T‐cell therapy is approved for relapsed/refractory diffuse large B‐cell lymphoma and acute lymphoblastic leukemia. However, there is significant interest in the application of CAR T‐cell therapy to other hematological malignancies, including multiple myeloma, where the current focus is on the development of B‐cell maturation antigen‐directed CAR T‐cell therapy. Despite the successes achieved to date, there remain significant challenges associated with CAR T‐cell therapy and substantial research efforts are underway to develop new targets and approaches. Here, we provide an overview of the rapidly evolving landscape of CAR T‐cell therapy in hematological malignancies and look ahead at the advances that will shape the future of this field.