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: 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: Autologous hematopoietic stem cell transplantation (AHSCT) after melphalan (Mel) conditioning has been shown to improve outcomes in patients (pts) with multiple myeloma (MM), including complete response (CR), progression free (PFS) and overall survival (OS). Successful stem cell rescue with adequate number of CD34+ stem cells is thought to be important in achieving these goals post-AHSCT, including reduced platelet (plt) transfusion need, neutrophil engraftment time and previously noted effect on lower cumulative incidence of relapse (CIR). However, there has been some discordance regarding the optimal CD34+ transplantation dose and the effects on outcomes. A retrospective analysis of 508 consecutive MM patients (pts) who underwent AHSCT between 1994-2017 at a single institution was performed to determine the relationship between OS and PFS/CIR at two different CD34+ stem cell infusion dose cutoffs ( 〈 2.5 vs ≥ 2.5 x 106 (mill) CD34+ cells/kg, or 〈 5.0 vs ≥ 5.0 mill CD34+), an age cutoff ( 〈 65 vs ≥ 65) and a Mel conditioning dose cutoff of 140 mg/m2 vs 200 mg/m2. Multivariate analysis considered high risk MM, defined as either having one of the high risk fluorescent in situ hybridization probes [del17p, t(4;14), t(14;16), t(14;20), gain1q, del1p] or having a complex karyotype (standard risk MM did not contain either), international staging system (ISS) stages I, II and III, and immunomodulatory drug (IMiD)-containing induction (yes/no). Fisher's exact test and the Mann-Whitney test were used to look at the association of CD34+ cutoff groups and patient characteristics. OS was defined as the time from infusion to death from any cause, and was determined by the Kaplan-Meier method; comparisons of survival curves was done using the log-rank test. The CIR was determined using cumulative incidence methods that considered death as a competing event. Gray's test was used to compare CIR curves. Linear regression and Cox regression were used for multivariable analysis. P 〈 0.05 was considered statistically significant. Overall, CD34+ dichotomized at 2.5 or 5.0 mill was not associated with PFS (p=0.25, HR 1.19, CI 0.88-1.62; p=0.99, HR 1.00, CI 0.74-1.35) or OS (p=0.50, HR 1.11, CI 0.82-1.51; p=0.27, HR 0.85, CI 0.63-1.41). When analyzing OS by either age ( 〈 65 vs ≥ 65), Mel conditioning (140 mg/m2 vs 200 mg/m2) or CD34+ infusion cutoffs ( 〈 2.5 vs ≥ 2.5, or 〈 5.0 vs ≥ 5.0 mill), there was no statistically significant difference. On univariate analysis, the CIR was not statistically different for Mel 140 mg/m2 vs 200 mg/m2 patients at 2.5 mill CD34+ cutoff (p=0.62), but was approaching significance at 5.0 mill cutoff (p=0.054). On univariate analysis, the CIR was not statistically different for patients aged 〈 65 vs ≥ 65 at 2.5 mill CD34+ cutoff (p=0.92), or 5.0 mill cutoff (p=0.11). On univariate analysis, the CIR was statistically different for CD34+ at 5.0 mill cutoff for patients age ≥ 65 (p=0.01, Figure 1A) and for CD34+ at 5.0 mill cutoff for pts who received Mel140 mg/m2 conditioning (p=0.01, Figure 1B). However, after adjusting for the ISS stage and MM risk in both groups, no difference in CIR was noted (respectively p=0.095, HR: 2.00; 95% CI 0.88, 4.53; p=0.21, HR: 1.77; 95% CI 0.73, 4.29). In a subset analysis for pts ≥ 65 years at the CD34+ 5.0 mill cutoff, mean time in days to neutrophil engraftment on multivariate analysis was shorter for pts who received CD34+ ≥ 5.0 mill compared to 〈 5.0 mill after adjusting for Mel dose (140 mg/m2 vs 200 mg/m2), ISS stage (I,II vs III), MM risk (standard vs high) and IMiD induction (yes vs no): 11.1 days vs. 12.1 days (p 〈 0.0001). Mean time in days to last platelet infusion on multivariate analysis was also shorter after adjusting for the Mel dose, ISS stage, MM risk and IMiD induction: 7.3 days vs. 10.6 days (p=0.0083). After adjusting for the same variables in multivariate analysis, depth of response at day+100 (CR vs partial response) was not statistically different. Hospitalization duration in days was not significantly affected by either Mel dosing or CD34+ dose. Our single institution experience suggests that there is no significant association between CD34+ stem cell infusion dose at either 2.5 mill or 5.0 mill cutoffs and post-AHSCT outcomes with either Mel dose once controlled for relevant disease specific factors. However, our results do suggest that in pts ≥ 65 years of age, infusing ≥ 5.0 mill CD34+ cells shortens time to neutrophil engraftment and reduces plt transfusion requirements during AHSCT. Disclosures 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; Sorrento: Consultancy; GSK: Consultancy; Genentech: Membership on an entity's Board of Directors or advisory committees. Lunning:Curis: Research Funding; Janssen Scientific Affairs, LLC: Consultancy, Research Funding; Juno Therapeutics: Consultancy, Research Funding; MiRagen: Research Funding; TG Therapeutics: Consultancy, Research Funding; AbbVie: Consultancy; Bayer: Consultancy; DAVA: Consultancy; Gilead Sciences, Inc.: Consultancy; Kite: Consultancy; Novartis: Consultancy; OncLive: Consultancy; Portola: Consultancy; Seattle Genetics: Consultancy; Spectrum: Consultancy; VANIUM: Consultancy; Verastem: Consultancy. Armitage:Oncology Analytics: Consultancy; Partner Therapeutics: Consultancy; Samus Therapeutics: Consultancy; Ascentage: Consultancy; Union Pacific: Consultancy; Tesaro bio: Membership on an entity's Board of Directors or advisory committees. Al-Kadhimi:Seattle Genetics: Other: Stocks; Celldex Biotech: Other: Stocks. Vose:Celgene Corporation: Research Funding; Incyte Corporation: Research Funding; Kite Pharma: Honoraria, Other: Grants, Research Funding; Novartis: Research Funding; Seattle Genetics: Research Funding; AbbVie: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria; Legend Pharmaceuticals: Honoraria; Acerta Pharma: Honoraria, Other: Grants, Research Funding; Bristol-Meyers Squibb Company: Research Funding. Baljevic:Karyopharm: Other: Internal Review Committee participant; Cardinal Health Specialty Solutions: Consultancy; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Abstract: Patients with multiple myeloma are at increased risk of vascular thromboembolic events (VTEs). This post hoc analysis evaluated VTEs in the randomised phase 2 GRIFFIN study ( ClinicalTrials.gov Identifier: NCT02874742) that investigated lenalidomide/bortezomib/dexamethasone (RVd) ± daratumumab (D). Patients with newly diagnosed multiple myeloma who were eligible for autologous stem cell transplantation (ASCT) received D‐RVd/RVd induction, high‐dose therapy and ASCT, D‐RVd/RVd consolidation and up to 2 years of lenalidomide maintenance therapy ± D. VTE prophylaxis was recommended (at least aspirin, ≥162 mg daily) in accordance with International Myeloma Working Group guidelines. In the safety population (D‐RVd, n  = 99; RVd, n  = 102), VTEs occurred in 10.1% of D‐RVd patients and 15.7% of RVd patients; grade 2–4 VTEs occurred in 9.1% and 14.7%, respectively. Median time to the first onset of VTE was longer for D‐RVd versus RVd patients (305 days vs 119 days). Anti‐thrombosis prophylaxis use was similar between arms (D‐RVd, 84.8% vs RVd, 83.3%); among patients with VTEs, prophylaxis use at time of first VTE onset was 60.0% for D‐RVd and 68.8% for RVd. In summary, the addition of daratumumab to RVd did not increase the incidence of VTEs, but the cumulative VTE incidence was relatively high in this cohort and anti‐thrombotic prophylaxis use was suboptimal.