ALBERT

Description: Abstract 352 Background: Autologous stem cell transplantation (ASCT) for MM leads to complete responses in ∼20–40% of patients but rare cures. Patients with rapid recovery of T cells post ASCT may have improved outcomes suggesting possible immune mediated tumor control. We have shown that adoptive T-cell transfers after ASCT for MM using vaccine-primed and ex-vivo costimulated autologous T-cells in combination with pre- and post-transplant immunizations using a tumor antigen vaccine (+ GM-CSF and montanide) led to vaccine-directed T-cell responses in about 1/3 of patients and enhanced recovery of polyclonal T and B cell counts and function. We hypothesized that addition of Poly-ICLC (Hiltonol®) – a TLR-3 agonistic vaccine adjuvant could increase tumor antigen vaccine responses through better priming and boosting. Methods: We report interim results of a Phase II clinical trial (NCT01245673) evaluating safety and activity of autologous T cells primed in-vivo with a MAGE-A3 multipeptide vaccine (Orphan Drug Designation: GL-0817) mixed with GM-CSF and Poly-ICLC (Hiltonol®) +/− montanide. Inclusion criteria included measurable disease or high-risk cytogenetics. MAGE-A3 is expressed in ∼50% MM cases and more frequently in relapsed/extramedullary/proliferative disease. The MAGE-A3 vaccine has 2 HLA-A2-restricted class I peptides and 1 promiscuous class II peptide linked to an HIV-1-TAT membrane translocation sequence (Trojan peptide) to enhance peptide presentation. Vaccine-primed T cells were collected by leukapheresis, costimulated and expanded ex-vivo using anti-CD3/anti-CD28 mAb conjugated beads. T-cells were infused at day +2 after ASCT followed by booster immunizations at days 14, 42, 90, 120 and 150 post-transplant. Lenalidomide maintenance was started at day +100. Patients were evaluated for MM responses in accordance with IMWG criteria at days 60, 100, 180 post-transplant and Q3 months thereafter. T-cell and B-cell responses to the vaccine were evaluated by IFN-g or IL-2 cytokine production (all patients), dextramer binding to CD8 cells (HLA-A2 positive patients) and ELISA antibody assays at days 14, 60, 100 and 180 post-transplant. Results: 25 patients were transplanted on study. At a median followup of 6 months (range 2–18 months), 24 patients are surviving while 1 patient relapsed at about day +60 and died. Four additional patients have relapsed at 7,9,18 and 18 months post-transplant, yielding a 1-year Kaplan-Meier EFS of 77%. Of the 16 patients evaluable for response at day 100, 7/16 (44%) had CR/nCR using the study enrollment (post-induction) myeloma markers as a baseline while at day 180, 7/13 (53%) had CR/nCR. T-cell infusions were well-tolerated with no probable/definite grade 3 or higher toxicities. Vaccinations were associated with 〉 50 mm injection site reactions (redness, induration or both) after 1 or more immunizations in the majority of patients. Two patients developed large and prolonged inflammatory reactions which evolved into sterile abscesses. These resolved over 2–3 months with conservative management but as a result montanide was eliminated from the vaccine formulation for patients 11–25. Thereafter vaccine reactogenicity was decreased with no additional sterile abscesses. Of 16 patients tested for immune responses to date, 2 patients were unevaluable due to poor sample viability. Dextramer staining demonstrated MAGE-A3-specific CD8 T-cells in 4/4 (100%) of evaluable HLA-A2+ patients. Cytokine production in response to MAGE-A3 stimulation was seen in 11/14 (79%) patients; responses usually peaked at day 100 or day 180. Robust MAGE-A3 antibody responses were detected in 7/9 patients who received montanide in the vaccine formulation but in 0/7 patients who did not. Conclusions: Combination immunotherapy using a MAGE-A3 multipeptide tumor antigen vaccine plus vaccine-primed and costimulated autologous T-cells after ASCT for MM is well-tolerated and associated with encouraging early clinical responses. The addition of Poly-ICLC (Hiltonol®) to the vaccine formulation was associated with a high frequency of post-ASCT T-cell functional responses. The combination of Poly-ICLC +GM-CSF + Montanide led to robust injection site reactions that were occasionally severe and prolonged. Elimination of the montanide reduced injection site reactogenicity but may also have compromised the B-cell responses to the tumor antigen vaccine. Disclosures: Rapoport: Gliknik, Inc: Research Funding. Stadtmauer:Celgene: Consultancy, Speakers Bureau; Millenium: Consultancy, Speakers Bureau. Vogl:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium/Takeda: Consultancy, Research Funding; Otsuka: Consultancy; Acetylon: Research Funding. Strome:Gliknik, Inc: Equity Ownership, Patents & Royalties, Research Funding. Salazar:Oncovir, Inc: Employment. Levine:TxCell: Consultancy, Membership on an entity's Board of Directors or advisory committees; University of Pennsylvania: financial interest due to intellectual property and patents in the field of cell and gene therapy. Conflict of interest is managed in accordance with University of Pennsylvania policy and oversight, financial interest due to intellectual property and patents in the field of cell and gene therapy. Conflict of interest is managed in accordance with University of Pennsylvania policy and oversight Patents & Royalties. June:Novartis: Research Funding, entitled to receive royalties from patents licensed to Novartis, entitled to receive royalties from patents licensed to Novartis Patents & Royalties.

Description: Introduction: The optimal clinical setting and cell product characteristics for chimeric antigen receptor (CAR) T cell therapy in multiple myeloma (MM) are uncertain. In CLL patients treated with anti-CD19 CAR T cells (CART19), prevalence of an early memory (early-mem) T cell phenotype (CD27+ CD45RO- CD8+) at time of leukapheresis was predictive of clinical response independently of other patient- or disease-specific factors and was associated with enhanced capacity for in vitro T cell expansion and CD19-responsive activation (Fraietta et al. Nat Med 2018). T cell fitness is therefore a major determinant of response to CAR T cell therapy. In an accompanying abstract (Cohen et al.), we report that higher percentage of early-mem T cells and CD4/CD8 ratio within the leukapheresis product are associated with favorable clinical response to anti-BCMA CAR T cells (CART-BCMA) in relapsed/refractory MM. Here, we compare leukapheresis samples from MM patients obtained at completion of induction therapy (post-ind) with those obtained in relapsed/refractory (rel/ref) patients for frequency of early-mem T cells, CD4/CD8 ratio, and in vitro T cell expansion. Methods: Cryopreserved leukapheresis samples were analyzed for the percentage of early-mem T cells and CD4/CD8 ratio by flow cytometry and in vitro expansion kinetics during anti-CD3/anti-CD28 bead stimulation. Post-ind samples were obtained between 2007 and 2014 from previously reported MM trials in which ex-vivo-expanded autologous T cells were infused post-ASCT to facilitate immune reconstitution (NCT01245673, NCT01426828, NCT00046852); rel/ref samples were from MM patients treated in a phase-one study of CART-BCMA (NCT02546167). Results: The post-ind cohort includes 38 patients with median age 55y (range 41-68) and prior exposure to lenalidomide (22), bortezomib (21), dexamethasone (38), cyclophosphamide (8), vincristine (2), thalidomide (8), and doxorubicin (4); median time from first systemic therapy to leukapheresis was 152 days (range 53-1886) with a median of 1 prior line of therapy (range 1-4). The rel/ref cohort included 25 patients with median age 58y (range 44-75), median 7 prior lines of therapy (range 3-13), and previously exposed to lenalidomide (25), bortezomib (25), pomalidomide (23), carfilzomib/oprozomib (24), daratumumab (19), cyclophosphamide (25), autologous SCT (23), allogeneic SCT (1), and anti-PD1 (7). Median marrow plasma cell content at leukapheresis was lower in the post-ind cohort (12.5%, range 0-80, n=37) compared to the rel/ref cohort (65%, range 0-95%). Percentage of early-mem T cells was higher in the post-ind vs rel/ref cohort (median 43.9% vs 29.0%, p=0.001, left figure). Likewise, CD4/CD8 ratio was higher in the post-ind vs rel/ref cohort (median 2.6 vs 0.87, p2 lines of therapy prior to apheresis (n=3) compared to the rest of the cohort (n=35). Conclusion: In MM patients, frequency of the early-mem T cell phenotype, a functionally validated biomarker of fitness for CAR T cell manufacturing, was significantly higher in leukapheresis products obtained after induction therapy compared to the relapsed/refractory setting, as was CD4/CD8 ratio and magnitude of in vitro T cell expansion. This result suggests that CAR T cells for MM would yield better clinical responses at early points in the disease course, at periods of relatively low disease burden and before exposure to multiple lines of therapy. Figure. Figure. Disclosures Garfall: Novartis: Research Funding; Kite Pharma: Consultancy; Amgen: Research Funding; Bioinvent: Research Funding. Cohen:GlaxoSmithKline: Consultancy, Research Funding; Kite Pharma: Consultancy; Oncopeptides: Consultancy; Celgene: Consultancy; Novartis: Research Funding; Poseida Therapeutics, Inc.: Research Funding; Bristol Meyers Squibb: Consultancy, Research Funding; Janssen: Consultancy; Seattle Genetics: Consultancy. Fraietta:Novartis: Patents & Royalties: WO/2015/157252, WO/2016/164580, WO/2017/049166. Davis:Novartis Institutes for Biomedical Research, Inc.: Patents & Royalties. Levine:CRC Oncology: Consultancy; Brammer Bio: Consultancy; Cure Genetics: Consultancy; Incysus: Consultancy; Novartis: Consultancy, Patents & Royalties, Research Funding; Tmunity Therapeutics: Equity Ownership, Research Funding. Siegel:Novartis: Research Funding. Stadtmauer:Janssen: Consultancy; Amgen: Consultancy; Takeda: Consultancy; Celgene: Consultancy; AbbVie, Inc: Research Funding. Vogl:Karyopharm Therapeutics: Consultancy. Milone:Novartis: Patents & Royalties. June:Tmunity Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Tmunity Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Immune Design: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceutical Corporation: Patents & Royalties, Research Funding; Celldex: Consultancy, Membership on an entity's Board of Directors or advisory committees; Immune Design: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceutical Corporation: Patents & Royalties, Research Funding. Melenhorst:Novartis: Patents & Royalties, Research Funding; Incyte: Research Funding; Tmunity: Research Funding; Shanghai UNICAR Therapy, Inc: Consultancy; CASI Pharmaceuticals: Consultancy.

Description: Neurologic toxicity has been observed with anti-CD19 chimeric antigen receptor (CAR) T cells and the anti-CD19 BiTE blinatumomab. Both focal (e.g., cranial nerve palsy) and global (e.g., generalized seizures) abnormalities have been reported, often associated with systemic cytokine release syndrome (CRS) but also observed after recovery from or in absence of CRS. CART-BCMA consists of expanded autologous T cells transduced with a 4-1BB:CD3-zeta-based CAR specific for B Cell Maturation Antigen. Here, we report clinical features and management of a severe neurotoxicity observed on a phase 1 trial of CART-BCMA for multiple myeloma (MM) (NCT02546167). The subject is a 55-year-old female with high-risk IgA lambda MM. At time of CART-BCMA infusion, her MM manifestations included cytopenias and plasmacytomas of the pleura and paravertebral muscles. Bone marrow (BM) was 〉95% BCMA+ plasma cells. Pre-treatment brain MRI showed pachymeningeal thickening and enhancement over the left cerebral convexity, possibly due to extension of calvarial MM lesions. There was no evidence of CNS MM on a neurologist's exam or by CSF cytology. The subject received 2x108 CART-BCMA cells, 40% of the planned dose, over two consecutive days, without lymphodepleting chemotherapy; a third planned infusion was held due to fevers. Over the next 4 days, fevers persisted, hypoxia and delirium developed, and cytopenias worsened. Brain MRI and lumbar puncture on day 4 showed no new abnormalities. Evaluation for infection was negative. These symptoms coincided with rise in serum IL-6 (nl range

Description: Multiple myeloma (MM) is selectively sensitive to perturbations of protein catabolism. Genetic evidence has identified a link between plasma cell differentiation and upregulation of the unfolded protein response. The effective, selective, cytotoxic effect of proteasome inhibition observed in MM therapy further validates pathways of protein degradation as therapeutic targets in this incurable disease. Upon proteasome inhibition, cancer cells utilize compensatory pathways such as aggresome formation and macroautophagy. Despite a remarkable increase in the granularity of knowledge surrounding autophagy in mammalian cell biology, the role of autophagy in MM cell survival has not been studied. Lysosome-dependent macroautophagy (autophagy) pathway is known to be up-regulated by chemical inhibition of the proteasome. Therefore we theorized that autophagy is a pathway of proteasome inhibitor resistance in MM, and that simultaneous inhibition of both the ubiquitin-proteasome system (UPS) and the autophagy pathway would result in synergistic toxicity in MM cells. We chose to explore this hypothesis utilizing a chemical genetic approach, with the goal of repurposing off-patent autophagy inhibitors for immediate translation in the context of human clinical investigation. We selected for study the combination of the only FDA-approved proteasome inhibitor, bortezomib, and the 4-aminoquinoline autophagy inhibitor, hydroxychloroquine (HCQ). Indeed, HCQ exhibits a dose-dependent cytotoxic effect on cultured human MM cells in vitro. Using high-throughput, high-content epifluorescence microscopy, we have demonstrated a dose-dependent increase in autophagosome number and average vesicle area in MM cells treated with HCQ consistent with inhibition of late autophagy. These findings were confirmed by electron microscopy. Autophagy inhibition by HCQ was verified by LC3 immunoblot with and without bafilomycin clamp. Gold-standard pulse-chase studies of HCQ verified inhibition of long-lived protein degradation in MM cells. Of note, in vivo studies of HCQ in a bioluminescent orthotopic xenograft model of MM failed to demonstrate a statistically evident disease response or prolongation of survival. Drawing on the aforementioned biological and clinical insights, we predicted that combination autophagy and proteasome inhibition would result in synergistic cytotoxicity. To explore multiple combinations of these classes of therapeutic agents, we devised a high-throughput translational platform for assessing synergy between therapeutic agents. In this model, library plates of compounds are established which may be “crossed” with each other by alternating plate orientation and delivering compounds to experimental assay microtiter plates by robotic pin transfer. Experimental measurements (i.e. cytotoxicity, protein content, post-translational modifications) are then processed in a semi-automated manner employing the median effect principle and illustrative graphical outputs. This platform was validated by modeling known, effective combination therapies in current clinical use or study in MM. We observe potent, synergistic toxicity from the combination of bortezomib and HCQ in both MM1.S and RPMI-8826 MM cell lines. Of note, the combination index observed is

Description: Abstract 74 Background: Carfilzomib, a novel proteasome inhibitor (PI), and pomalidomide, an immunomodulatory agent (IMiD), have both demonstrated promising activity as single agents or in combination with dexamethasone in relapsed/refractory multiple myeloma. IMiD+PI combinations including lenalidomide, bortezomib, dexamethasone and lenalidomide, carfilzomib, dexamethasone have had high response rates and good tolerability. We aimed to combine carfilzomib and pomalidomide with dexamethasone (Car-Pom-d) for the first time and hypothesized that this regimen would be highly active in patients with relapsed/refractory multiple myeloma. Here, we report the first findings from the Phase I dose-escalation and expansion portions of the first phase I/II trial of Car-Pom-d in patients with relapsed/refractory multiple myeloma (NCT01464034). Methods: The primary objectives were to determine the maximum tolerated dose (MTD) and the safety/tolerability of Car-Pom-d. Secondary objectives included determination of overall response rate, time to progression, progression free survival, and time to next therapy. All patients had to be refractory to prior lenalidomide, and must have been relapsed/refractory to their most recent therapy. Treatment consisted of 28-day cycles of oral pomalidomide once daily on days 1–21, intravenous (IV) carfilzomib over 30 minutes on days 1, 2, 8, 9, 15, and 16, and oral or IV dexamethasone 40 mg on days 1, 8, 15, and 22. Dose-escalation of carfilzomib started with 27mg/m2 carfilzomib/4mg pomalidomide/40 mg dexamethasone using a standard 3+3 schema based on dose-limiting toxicities (DLTs) occurring in cycle 1. Carfilzomib was initiated at 20 mg/m2for Cycle 1, days 1–2 at all dose levels. Investigators were permitted to adjust the dose of dexamethasone at any point based on their discretion. Adverse events (AEs) were graded by NCI-CTCAE v4. Response was assessed by the modified International Uniform Response Criteria. Results: In the Phase I dose-escalation portion of the trial, a total of 12 patients were enrolled from 6 centers. The median age was 61 years (range 44–78), 67% were male. The median number of prior regimens was 6 (range 2–15), and median time from diagnosis was 5.1 years. Four (33%) patients had prior stem cell transplant, 11 (92%) had prior bortezomib, and all were lenalidomide-refractory. Cytogenetic abnormalities included 5 patients with del(17p), 2 patients with t(4;14), and 1 patient each with del(13), t(11;14), and t(14;16). In these first 12 patients, drug-related AEs occurring in 〉20% of patients included fatigue (42%), anemia (33%), pneumonia (33%), dyspnea (25%), and thrombocytopenia (25%). Six (50%) patients experienced grade ≥3 AEs including 2 incidence each of neutropenia and febrile neutropenia. The MTD was established as the starting dose level (carfilzomib 20/27 mg/m2, pomalidomide 4mg, dexamethasone 40 mg). At this dose, 1 of 6 patients experienced a protocol-defined DLT of febrile neutropenia. At dose level 2 (carfilzomib 20/36 mg/m2, pomalidomide 4 mg, dexamethasone 40 mg), 2 of 6 patients experienced DLTs, consisting of grade 4 thrombocytopenia and grade 3 rash. All 12 patients were response evaluable with 2 very good partial response (VGPR), 4 partial response (PR), 2 minor response (MR), 2 stable disease (SD), and 2 progressive disease (PD) for a ≥ MR rate of 67%. The 6 month progression free survival was 70% (95% CI: 37 to 90%). Of the 5 patients with del(17p), 1 achieved VGPR, 2 achieved PR, 1 achieved SD. We then enrolled an expansion cohort of 20 patients from 8 centers resulting in a total study population of 32 patients, with 25 still receiving treatment. Three patients have died, all from progressive multiple myeloma. Early response assessments in 27 out of 32 patients show 2 VGPR, 7 PR, 6 MR, 8 SD, and 4 PD for a ≥MR rate of 56%. Conclusions: The Car-Pom-d regimen is well tolerated and achieves a high response rate in a heavily pre-treated, lenalidomide-refractory population with prior bortezomib exposure. Importantly, we have seen responses in patients with poor risk cytogenetics, specifically del (17p). We are beginning enrollment in a larger phase 2 cohort, and updated safety and efficacy data for all patients will be presented at the meeting. Disclosures: Shah: Celgene: Consultancy; Onyx: Consultancy; Novartis: Consultancy; Array: Consultancy. Stadtmauer:Celgene: Consultancy, Speakers Bureau; Millennium: Consultancy, Speakers Bureau. Abonour:Celgene: Honoraria, Speakers Bureau; Millenium: Honoraria, Speakers Bureau. Cohen:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bensinger:Onyx: Research Funding; Celgene: Consultancy, Research Funding, Speakers Bureau. Gasparetto:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kaufman:Millenium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Onyx: Consultancy. Lentzsch:Celgene: Consultancy, Research Funding. Vogl:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium/Takeda: Consultancy, Research Funding; Otsuka: Consultancy; Acetylon: Research Funding. Orlowski:Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Research Funding. Durie:Onyx: Consultancy; Celgene: Consultancy; Millenium: Consultancy; Amgen: Consultancy.

Description: Abstract 1869 BACKGROUND: The aggresome/autophagy pathway is the primary mechanism for disposal of ubiquitinated proteins for cells exposed to proteasome inhibition. Preclinical evidence shows that combining inhibition of the proteasome with bortezomib (Bz) and inhibition of autophagy with the anti-malarial drug hydroxychloroquine (HCQ) leads to enhanced cytotoxicity in myeloma cells. METHODS: Patients with relapsed or refractory myeloma enrolled on a standard 3+3 dose escalation design. Patients received 2-weeks of single-agent oral HCQ, followed by the addition of Bz on days 1, 4, 8, and 11 of 21-day cycles. HCQ and Bz doses were determined by dose level: (1) 200 mg qod / 1.0 mg/m2, (2) 200 qod / 1.3, (3) 200 qd / 1.3, (4) 200 bid / 1.3, (5) 400 bid / 1.3, (6) 600 bid / 1.3. Dose-limiting toxicity (DLT) was defined as grade ≥3 toxicity probably related to study therapy and occurring during the first 5 weeks, with the exception of any anemia or lymphopenia, neutropenia responsive to growth factor, platelets 〉10,000/mm3 not associated with bleeding, or gastrointestinal complaints relieved by symptomatic therapy. We used electron microscopy to characterize changes in autophagic vesicles in serial samples of peripheral blood mononuclear cells and CD138-selected bone marrow plasma cells. RESULTS: We enrolled 25 patients between 1/2008 and 2/2011, of which 21 patients completed at least 1 cycle of combined therapy and were evaluable for toxicity. The median duration of study participation was 14 weeks (range 1–77). Reasons for study discontinuation were side effects of therapy (6), lack of response (7), disease progression (11), and non-compliance (1). No protocol-defined dose limiting toxicities occurred, and the maximum tolerated dose was determined to be the top dose level of Bz 1.3 mg/m2 and HCQ 600 mg twice daily. Hematologic abnormalities were generally more attributable to disease progression than to treatment toxicity, but at the top dose level one patient had grade 3 thrombocytopenia and neutropenia after starting with a normal platelet count and ANC, without evidence of progression through therapy. At the top dose level, gastrointestinal toxicities predominated, including 5 out of 6 evaluable patients with some form of grade 3 GI toxicity. Treatment emergent neuropathy occurred in 7 patients but was restricted to grade 1 or 2 and was easily managed with dose reduction of the Velcade. Three patients came off study before receiving the combined regimen and were not evaluable for response. The best responses for the remaining 22 patients included 3 near complete responses (nCR), 3 minor responses (MR), 9 stable disease (SD), and 7 progression (PD). The 3 nCRs occurred in Bz-naïve patients receiving HCQ at 400 mg/d (1 pt) and 1200 mg/d (2 pts). Two patients who had previously progressed while receiving weekly maintenance Bz had MRs on study, including one who maintained a MR for over 7 months. Three additional Bz-refractory patients initially achieved stable disease during study treatment, with on study TTP of 8 weeks (at HCQ 1200 mg/d), 15 weeks (100 mg/d), and 17 weeks (200 mg/d). Preliminary analyses of vesicle counts at HCQ doses up to 800 mg/d identify individual patients with increases in autophagic vesicles in either peripheral blood or bone marrow plasma cells, but these are not consistent, nor is there any evident correlation with response. CONCLUSION: Combined Bz and HCQ is tolerable, with a phase 2 dose of Bz 1.3 mg/m2 and HCQ 1200 mg/d and likely hematologic and gastrointestinal DLTs. There is a suggestion of improved efficacy over Bz alone, with minor responses and long periods of stable disease in Bz-refractory patients. Final analysis of autophagy inhibition in correlative specimens, including the top dose cohort, will be available for the meeting. Disclosures: Vogl: Millennium Pharmaceuticals: Honoraria, Research Funding. Off Label Use: Hydroxychloroquine is FDA approved for treatment of malaria and rheumatoid arthritis. This paper discusses its use in treatment of myeloma. Carroll:Agios Pharmaceuticals: Research Funding; TetraLogic Pharmaceuticals: Research Funding; Sanofi Aventis Corporation: Research Funding; Glaxo Smith Kline, Inc.: Research Funding. Amaravadi:Millennium Pharmaceuticals: Honoraria, Research Funding.

Description: Background: Though CD19 is expressed only rarely on multiple myeloma (MM) plasma cells (PC), rare CD19+ B cells can be identified in MM patients that are clonally related to the MM PC. These clonotypic B cells may exhibit properties of cancer stem cells (enhanced MM-propagating properties and drug resistance compared to MM PC) and thus be a potential therapeutic target in conjunction with therapies that target MM PC. CTL019 consists of autologous T cells transduced via lentiviral vector with an anti-CD19 scFv coupled to CD3-zeta and 4-1BB signaling domains and expanded ex vivo with anti-CD3/CD28-conjugated beads. To target both clonotypic B cells and MM PC, we conducted a pilot clinical trial of CTL019 administered after high-dose melphalan and autologous stem cell transplantation (ASCT) in relapsed/refractory MM patients who had previously undergone first-line ASCT with short progression-free survival (PFS). Methods: Subjects were required to be medically fit for ASCT and have progressed within 1 year of a prior ASCT performed as part of first-line therapy. Study therapy consisted of ASCT with melphalan 140-200 mg/m2 followed by 1-5x107 CTL019 cells 12-14 days later. The primary endpoint was safety and feasibility of CTL019 manufacturing and administration in this clinical setting. Secondary endpoints included assessments of CTL019 in vivo persistence and activity against normal B cells, plasma cell immunophenotype as a response biomarker, and PFS after ASCT + CTL019 in comparison to PFS after initial ASCT. Results: Twelve subjects enrolled, and 10 received study therapy; autologous T cells failed to expand ex vivo in one enrolled subject, and one enrolled subject elected to pursue off-study therapy. Median age was 61 (range 48-68). Median prior lines of therapy was 6 (range 2-10). Poor-prognosis features were present in 8/10 subjects (6/10 with poor-prognosis cytogenetics, 2/10 with BRAF V600E mutations, 1/10 with secondary plasma cell leukemia). Median PFS after first-line ASCT was 258 days (range 100-342). In pre-ASCT bone marrow (BM), the dominant MM PC population was CD19-negative by flow cytometry in 9/9 evaluable subjects, though 7/9 exhibited rare CD19+ subsets comprising 0.05-1.5% of MM PC. Melphalan dose was 140 (N=7) or 200 (N=3) mg/m2. All subjects infused received the maximum target dose of 5x107 CTL019 cells. Adverse events (AE) consisted mostly of expected ASCT toxicities. Grade ³3 AE that were at least possibly related to CTL019 included grade 3 autologous GVHD (N=1, resolved with corticosteroids) and oral mucositis (N=1). Grade 1 cytokine release syndrome occurred in 1 subject. There was no ASCT-related mortality. After infusion, CTL019 cells were detectable in peripheral blood (PB) of all subjects and persisted for median of 44 days (range 14-156). Presence of PB CTL019 cells was associated with absence of PB B cells. Notably, CTL019 cells were detected in BM in 9/10 subjects at day 42 and/or 100 post-ASCT. Median PFS after ASCT + CTL019 was 185 days (range 42-479); all subjects have progressed. The peak BM CTL019 frequency correlated significantly with favorable PFS (SpearmanÕs rho=0.77, P=0.009). There was no association between PFS and peak frequency of CTL019 or duration of CTL019 persistence in PB. In 3/10 subjects, PFS after ASCT + CTL019 met or exceeded PFS after first-line ASCT (Figure). For comparison, in a historical cohort of 18 patients who received first-line and salvage ASCT at our institution since 2008, no patients exhibited longer PFS after salvage ASCT. Conclusion: CTL019 manufacturing and administration post-ASCT is safe and feasible in patients with advanced MM. Correlation of PFS with CTL019 frequency in BM and prolonged PFS in 3 subjects is suggestive of clinical efficacy. A phase-two study of CTL019 using a 10-fold higher dose after first-line ASCT in high-risk MM patients is ongoing. Figure. Figure. Disclosures Garfall: Medimmune: Consultancy; Bioinvent: Research Funding; Novartis: Consultancy, Research Funding. Stadtmauer:Novartis: Consultancy; Takada: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Teva: Consultancy; Celgene: Consultancy. Maus:Novartis: Patents & Royalties: related to CTL019, Research Funding. Hwang:Novartis: Research Funding. Vogl:Takeda: Consultancy, Research Funding; GSK: Research Funding; Calithera: Research Funding; Teva: Consultancy; Constellation: Research Funding; Celgene: Consultancy; Acetylon: Research Funding; Karyopharm: Consultancy. Cohen:Bristol-Meyers Squibb: Consultancy, Research Funding; Janssen: Consultancy. Weiss:Novartis: Consultancy. Porter:Genentech: Employment; Novartis: Patents & Royalties, Research Funding. Frey:Novartis: Research Funding; Amgen: Consultancy. Milone:Novartis: Patents & Royalties, Research Funding. Mangan:Novartis: Speakers Bureau. Lacey:Novartis: Research Funding. Melenhorst:Novartis: Patents & Royalties: Novartis, Research Funding. Ambrose:Novartis: Research Funding. Chen:Novartis: Research Funding. Kulikovskaya:Novartis: Research Funding. Levine:Novartis: Patents & Royalties, Research Funding; GE Healthcare Bio-Sciences: Consultancy. June:Johnson & Johnson: Honoraria; Tmunity Therapeutics: Equity Ownership; Novartis: Honoraria, Patents & Royalties, Research Funding; Immune Design: Consultancy, Equity Ownership; Celldex: Consultancy, Equity Ownership; Novartis: Honoraria, Patents & Royalties, Research Funding; Pfizer: Honoraria.