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NKG2D ligands are widely expressed in solid and hematologic malignancies but absent or poorly expressed on healthy tissues. We conducted a phase I dose-escalation study to evaluate the safety and feasibility of a single infusion of NKG2D-chimeric antigen receptor (CAR) T cells, without lymphodepleting conditioning in subjects with acute myeloid leukemia/myelodysplastic syndrome or relapsed/refractory multiple myeloma. Autologous T cells were transfected with a γ-retroviral vector encoding a CAR fusing human NKG2D with the CD3ζ signaling domain. Four dose levels (1 × 106–3 × 107 total viable T cells) were evaluated. Twelve subjects were infused [7 acute myeloid leukemia (AML) and 5 multiple myeloma]. NKG2D-CAR products demonstrated a median 75% vector-driven NKG2D expression on CD3+ T cells. No dose-limiting toxicities, cytokine release syndrome, or CAR T cell–related neurotoxicity was observed. No significant autoimmune reactions were noted, and none of the ≥ grade 3 adverse events were attributable to NKG2D-CAR T cells. At the single injection of low cell doses used in this trial, no objective tumor responses were observed. However, hematologic parameters transiently improved in one subject with AML at the highest dose, and cases of disease stability without further therapy or on subsequent treatments were noted. At 24 hours, the cytokine RANTES increased a median of 1.9-fold among all subjects and 5.8-fold among six AML patients. Consistent with preclinical studies, NKG2D-CAR T cell–expansion and persistence were limited. Manufactured NKG2D-CAR T cells exhibited functional activity against autologous tumor cells in vitro, but modifications to enhance CAR T-cell expansion and target density may be needed to boost clinical activity.

Introduction: Patients (pts) with newly diagnosed multiple myeloma (MM) are commonly treated with the standard of care combination of lenalidomide (Len), bortezomib (Bz), and dexamethasone (Dex), also known as RVD. A recent randomized phase 3 study found that the addition of Bz to Len and Dex significantly increased median overall and progression free survival as well as response rate (Durie et al. Lancet 2017). Mild to moderate peripheral neuropathy (PN) is commonly reported with Bz use, although lower rates of PN have been reported with subcutaneous (SC) administration of single agent Bz compared with IV Bz (Moreau et al. Lancet Oncol 2011). Here we present preliminary results of a multi-center, open-label, single arm phase II trial of Len, SC Bz, and Dex in pts with newly diagnosed MM. Maintenance was risk-stratified, with high risk patients (defined as those with high risk cytogenetics (del17p, t(4:14), t(14;16)) or ISS stage II or III) receiving Bz in addition to Len. Primary endpoints included 1) overall response rate (ORR) after 4 induction cycles, 2) best response to induction therapy, and 3) rate and severity of PN during induction therapy. Methods: Patients enrolled in this study were newly diagnosed with active MM as defined by the revised IMWG criteria (Rajkumar et al. Lancet Oncol 2014). Protocol specified induction treatment consisted of 21-day cycles with Len 25 mg on days 1-14, SQ Bz 1.3 mg/m2 days 1, 4, 8, and 11, and Dex 20 mg on days 1, 2, 4, 5, 8, 9, 11, and 12. Stem cell mobilization followed induction cycle 4 and patients subsequently proceeded to either high dose melphalan and autologous stem cell transplant (ASCT) or 4 additional cycles of induction therapy based on patient preference with provider input. Following ASCT or completion of the 8th induction cycle pts proceeded to risk-stratified maintenance therapy. Maintenance consisted of 28-day cycles of therapy with Len on days 1-21 for all patients, while those pts defined as high-risk also received SC bortezomib Bz on days 1 and 15. Patients remained on maintenance therapy until progression, unacceptable toxicity, or withdrawal from protocol-directed treatment. Response was based on the IMWG uniform criteria (Rajkumar et al. Lancet Oncol 2011) and toxicities were graded based on the NCI-CTCAE V4. Correlative samples of blood and bone marrow for genomics and proteomics were collected from baseline and then throughout the study, and are currently being analyzed. Results: Forty-five pts were enrolled across 8 US sites between December 2015 and June 2017. Median age at enrollment was 61 years (range: 43 to 79) and 60% of the patients were male, 40% female. FISH cytogenetics found del 17p in 8% of pts tested, t(14;16) in 9%, and t(4;14) in 14%. At baseline, 60% of pts were ISS II/III. High risk pts comprised 62% of the study population overall. 80% of pts (36/45) collected stem cells and 31% of pts (14/45) continued to ASCT. The median number of CD34+ stem cells collected was 9.67 x 10^6. The median number of induction cycles completed was 8 (1 to 8 cycles) and 43 of 45 pts were evaluable for the primary endpoint of response after 4 induction cycles, with preliminary results indicating an ORR of 91% (39/43). Three pts did not reach the end of cycle 4 and 1 patient had stable disease. ORR at any point up to the beginning of maintenance was 98% (42/43). Any grade PN was reported by 80% of patients, including 38% with grade 1 and 36% with grade 2 PN. There were two cases of Grade 3 PN and one case of Grade 4 PN. Among the three patients with Grade ≥ 3 PN, symptoms improved to Grade ≤ 2 with dose reduction, modification of treatment schedule, or discontinuation of Bz. Importantly, given the higher than expected rate of all and high-grade PN, hydration with IV normal saline 500-1000 ccs prior to Bz administration as part of supportive care in selected patients was instituted and a comprehensive evaluation of the impact of this intervention on PN is in process. Conclusions: The combination of RVD with SC Bz is a highly effective treatment regimen for patients with newly diagnosed MM, including high risk pts. However, rates of all- and high-grade PN were greater than expected despite the use of SC Bz. Prompt dose reduction and/or change in schedule of Bz administration to weekly administration is recommended, with careful attention to supportive care in order to further improve tolerability. Disclosures Rosenblatt: Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Farber:Charles M. Farber, MD, PhD, LLC-Medical legal consulting: Consultancy; Gilead: Honoraria; Genentech: Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Research Funding; ummit Medical Group-MD Anderson Cancer Center: Employment; BeiGene: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Speakers Bureau; Acerta: Research Funding. Ghobrial:Celgene: Consultancy; BMS: Consultancy; Takeda: Consultancy; Janssen: Consultancy. Richardson:Karyopharm: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding.

8002 Background: Elotuzumab (elo) is approved for use in combination with lenalidomide (len) and dexamethasone (dex) for relapsed and refractory multiple myeloma (MM). This phase 2a study evaluated the efficacy and safety of elo in combination with len, subcutaneous bortezomib (bortez), and dex. Methods: The primary objective of this study was to determine the response rate of newly diagnosed, transplant-eligible MM patients (pts) after four cycles of therapy with elo plus len, bortez, and dex. Pts were newly diagnosed with MM by the revised IMWG criteria. Elo was administered days 1, 8, and 15 of the first two 28 day cycles and days 1 and 11 in cycles 3 and 4. Following cycle 4, pts underwent stem cell mobilization and could then proceed with either autologous stem cell transplant (ASCT) or defer transplant and receive four more cycles of induction therapy with elo plus len, bortez, and dex. Following either ASCT or 8 cycles of induction chemotherapy, pts transitioned to risk-adapted maintenance with elo, len, and dex plus every other week bortez (pts with high-risk cytogenetics, ISS stage II or III) or elo, len, dex (all others). Responses were assessed by the modified Uniform Response Criteria and toxicities graded based on NCI-CTCAE V4. Results: 41 patients with a median age of 60 were enrolled and this analysis encompasses response data from 29 patients. The overall response rate (ORR) after four cycles was 100%, with 24% achieving a complete response (CR), 47% achieving a very good partial response (VGPR), and 29% a partial response (PR). The rate of VGPR or better was 71%. The median number of CD34+ stem cells collected was 10.3 x 10^6. The most frequent grade 3 or higher toxicities included thrombocytopenia (15%) and hypophosphatemia (12%). The rate of grade 3 or higher peripheral neuropathy was 2%. Two pts died while on study, one due to complications of septicemia and the other due to respiratory failure. Conclusions: The combination of elo plus len, bortez, and dex was effective in newly diagnosed, ASCT-eligible patients. The rate of high-grade toxicities was low, although there were two grade 5 events (septicemia and respiratory failure). Clinical trial information: NCT02375555.

Background: Administration of recombinant human thrombopoietin (rhTPO) with G-CSF for stem cell mobilization is associated with high CD34+ stem cell yield, rapid neutrophil recovery following autologus transplantation (ASCT), and decreased red blood cell (rbc) and platelet (plt) transfusions (Solomo, G. et al. Blood 1999). However, clinical development of rhTPO was complicated by the formation of neutralizing anti-TPO antibodies (Li, J. et al. Blood 2001), prompting discontinuation of further clinical development of recombinant TPO. Eltrombopag (Elt) is an orally bioavailable small molecule thrombopoietin receptor (TPO-R) agonist approved by the FDA for treatment of chronic immune thrombocytopenic purpura (ITP). In vitro studies have demonstrated that Elt promotes megakaryocyte proliferation and differentiation of CD34+ bone marrow progenitor cells (Erickson-Miller CL Stem Cells 2009), suggesting that Elt might be a surrogate for rhTPO for stem cell mobilization. In this pilot trial, we evaluated the combination of Elt plus standard G-CSF and cyclophosphamide (C) for stem cell mobilization in patients (pts) with multiple myeloma (MM), a disease for which ASCT remains a standard of care (Blade et al. Blood 2010). Methods: Primary objectives included determination of the median number of CD34+ cells/kg mobilized and the maximum tolerated dose (MTD) of Elt. Pts had MM that was stable or responsive to at least two cycles of chemotherapy with plans for stem cell mobilization and ASCT. Four pts were to be enrolled in each of four dose escalation arms in which they received 0 (Arm D), 50 (Arm A), 100 (Arm B), or 150 mg (Arm C) of eltrombopag in combination with standard C + G-CSF. Adverse events (AEs) were graded by NCI-CTCAE v4. Results: 17 pts have been screened and enrolled to date. Two patients withdrew consent prior to receiving Elt and were excluded from statistical analysis. 15 patients have completed participation in the study to date and two patients remain to be enrolled in Arm C. The first subject in Arm A experienced delayed engraftment that was determined to be unrelated to ELT; rather, the event was attributed to administration of a one-time high dose of corticosteroid for management of a severe hypersensitivity reaction to DMSO that occurred during stem cell infusion. A second subject in Arm A had undergone mobilization with Elt prior to the previously described delayed engraftment event, and to ensure safety underwent a second mobilization with G-CSF and plerixafor. During ASCT, this patient received cells from the second mobilization procedure. While neither event met criteria for a dose-limiting toxicity, the protocol was amended such that three additional patients enrolled in Arm A underwent two rounds of mobilization - the first with Elt plus C and G-CSF and a second with G-CSF plus plerixafor - and received as part of ASCT cells mobilized with Elt. Each of these patients engrafted successfully. The median number of CD34+ cells/kg collected during the first collection day of apheresis in Arms D, A, B, and C was 8.0, 11.0, 15.3, and 26.4. The median total number of CD34+ stem cells collected following mobilization with Elt plus C and G-CSF in Arms D, A, B, and C was 13.2, 12.7, 15.4, and 26.4. The percentage of patients in Arms D, A, B, and C who achieved a target collection of 8 x 10^6 CD34+ stem cells in one collection day was 50, 60, 75, and 100%. There have been no severe adverse events related to Elt . Conclusions: Administration of Elt in combination with C plus G-CSF for stem cell mobilization in pts with MM undergoing ASCT was safe and well tolerated, with no DLTs or severe AEs attributable to Elt. The small size of this pilot study precludes formal statistical comparison of outcomes across treatment Arms, but there appears to be a trend toward increase in yield of CD34+ cells and decrease in apheresis procedures required with increasing doses of Elt. Disclosures Richardson: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Introduction: Conventional CAR-T cells express a single chain antibody variable fragment that restricts recognition to one tumor antigen and a limited set of cancers. This study employs a novel CAR fusing full-length human NKG2D with the CD3z signaling domain. In autologous transduced CM-CS1 T cells, NKG2D CAR receives endogenous costimulation via DAP10 to target multiple NKG2D-ligands that are upregulated in solid and hematologic malignancies but absent or poorly expressed on healthy tissues. Methods: A phase 1 dose-escalation study to establish safety and feasibility of a single infusion of CM-CS1 T cells without lymphodepleting conditioning enrolled subjects with AML/MDS-RAEB or relapsed/refractory progressive multiple myeloma (MM) without standard therapy options (NCT02203825). Eligibility criteria included suitable organ function, no CNS disease, no prior allogeneic SCT or adoptive T-cell therapy, no therapy within 3 weeks prior to infusion, no immune suppression, and no uncontrolled infection. Dose-escalation spanned 4 cohorts [half-log increments from 1x106 to 3x107 CM-CS1 T cells] according to a 3+3 design. DLTs included ≥ Grade 3 non-hematologic toxicity or ≥ Grade 2 autoimmune toxicity related to CAR T cells. Initial assessment was at 28 days. At least 1 AML/MDS and 1 MM subject were mandated in each dose level. Manufacturing included PBMC stimulation with OKT3 and IL-2 followed by 2 rounds of retroviral transduction at DFCI's Cell Manipulation Core Facility. Vector copy number (VCN) and replication-competent retrovirus (RCR) testing were performed on whole blood and PBMCs, respectively, using quantitative PCR. Results: From April 2015 to July 2016, 11 subjects were infused, and 10 completed the DLT period. Eight of 11 were male, 6 had AML/MDS, and median age was 70 (range 44 to 79) (Panel A). Median WBC was 2.3 (range 0.7 to 7.2 K/uL); median ALC was 0.74 (range 0.09-2.37 K/uL). Five had cells manufactured from peripheral blood; 6 underwent apheresis. Median percentage of blasts in bone marrow for AML/MDS patients was 50% (range 4-68%). All myeloma patients had undergone ≥ 5 therapies including ≥1 autologous SCT. Four of the 6 AML/MDS patients had secondary disease, 3 had complex cytogenetics, 3 had p53 mutations, and 1 had a FLT3-ITD mutation. Dose-escalation proceeded from 1x106 to 3x107 CM-CS1 T cells. All 11 products passed release criteria, and there were no infusion reactions. Products consisted of median 97.2% CD3+ cells and 31.0% CD8+ cells, with vector-specific NKG2D expression on median 74.6% of CD3+ and 66.3% of CD8+ cells (Panel B). The first 10 subjects completed their 28 day evaluation period without DLTs. There were no cases of cytokine release syndrome, cell-related neurotoxicity, auto-immunity, or CAR T-related death. SAEs included a Grade 4 intracochlear bleed and an episode each of grade 4 neutropenia and thrombocytopenia deemed related to disease progression. Forty percent of patients experienced some Grade 3 toxicity, all related to underlying disease or a complication thereof (Panel C). At these initial cell doses, no patient to date has had objective tumor response at the 28 day evaluation mark. Nine initiated subsequent therapies; there have been 4 deaths secondary to disease or complications of subsequent therapies. However, cases of unexpected survival without further therapy and responses to subsequent treatments were noted. For example a patient with p53-mutated AML survived 4 months despite 50% blasts at infusion, and another entered PR at 6+months after cells on an IDH-1 inhibitor with Conclusion: In the first 3+ dose-escalation cohorts of patients with AML/MDS and myeloma, a single dose of CM-CS1 T cells without lymphodepletion was feasible and well-tolerated, with no DLTs. CAR T cells generally have not persisted beyond 1 week, consistent with pre-clinical models. Correlative analyses including post-infusion immunophenotyping are in process. Future studies of multiple infusions of NKG2D CAR T cells in both hematologic malignancies and solid tumors at the higher cell doses associated with efficacy in pre-clinical models are in planning. Table Table. Disclosures Murad: Celdara Medical, LLC: Employment. Reder:Celdara Medical, LLC: Employment. Sentman:Celdara Medical, LLC: Membership on an entity's Board of Directors or advisory committees, Other: Holds patents on this technology. Wade:Celdara Medical, LLC: Employment. Schmucker:Celdara Medical, LLC: Employment. Lehmann:Celyad, SA: Employment. Snykers:Celyad, SA: Employment. Allen:Celyad, SA: Employment. Stone:Celator: Consultancy; Jansen: Consultancy; Novartis: Consultancy; Merck: Consultancy; ONO: Consultancy; Sunesis Pharmaceuticals: Consultancy; Roche: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Consultancy; Xenetic Biosciences: Consultancy; Agios: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Pfizer: Consultancy; Karyopharm: Consultancy; Amgen: Consultancy. Soiffer:Kiadis: Membership on an entity's Board of Directors or advisory committees; Juno: Consultancy. Dranoff:Novartis: Employment. Ritz:Kiadis: Membership on an entity's Board of Directors or advisory committees.