The translation elongation factor eEF1A promotes protein synthesis. Its methylation by METTL13 increases its activity, supporting tumor growth. However, in some cancers, a high abundance of eEF1A isoforms is associated with a good prognosis. Here, we found that eEF1A2 exhibited oncogenic or tumor-suppressor functions depending on its interaction with METTL13 or the phosphatase PTEN, respectively. METTL13 and PTEN competed for interaction with eEF1A2 in the same structural domain. PTEN-bound eEF1A2 promoted the ubiquitination and degradation of the mitosis-promoting Aurora kinase A in the S and G2 phases of the cell cycle. eEF1A2 bridged the interactions between the SKP1-CUL1-FBXW7 (SCF) ubiquitin ligase complex, the kinase GSK3β, and Aurora-A, thereby facilitating the phosphorylation of Aurora-A in a degron site that was recognized by FBXW7. Genetic ablation of Eef1a2 or Pten in mice resulted in a greater abundance of Aurora-A and increased cell cycling in mammary tumors, which was corroborated in breast cancer tissues from patients. Reactivating this pathway using fimepinostat, which relieves inhibitory signaling directed at PTEN and increases FBXW7 expression, combined with inhibiting Aurora-A with alisertib, suppressed breast cancer cell proliferation in culture and tumor growth in vivo. The findings demonstrate a therapeutically exploitable, tumor-suppressive role for eEF1A2 in breast cancer.

BACKGROUND:Risk of recurrence and progression of ductal carcinoma in situ (DCIS) to invasive cancer remains uncertain, emphasizing the need for developing predictive biomarkers of aggressive DCIS. METHODS:Human cell lines and mouse models of disease progression were analyzed for candidate risk predictive biomarkers identified and validated in two independent DCIS cohorts. RESULTS:RNA profiling of normal mammary and DCIS tissues (n = 48) revealed that elevated SOX11 expression correlates with MKI67, EZH2, and DCIS recurrence score. The 21T human cell line model of DCIS progression to invasive cancer and two mouse models developing mammary intraepithelial neoplasia confirmed the findings. AKT activation correlated with chromatin accessibility and EZH2 enrichment upregulating SOX11 expression. AKT and HER2 inhibitors decreased SOX11 expression along with diminished mammosphere formation. SOX11 was upregulated in HER2+ and basal-like subtypes (P < 0.001). Longitudinal DCIS cohort (n = 194) revealed shorter recurrence-free survival in SOX11+ than SOX11- patients (P = 0.0056 in all DCIS; P < 0.0001 in HER2+ subtype) associated with increased risk of ipsilateral breast event/IBE (HR = 1.9, 95%CI = 1.2-2.9; P = 0.003). DISCUSSION:Epigenetic activation of SOX11 drives recurrence of DCIS and progression to invasive cancer, suggesting SOX11 as a predictive biomarker of IBE.

Knockout of p53 in HCT116 colon cancer cells treated with KW-2450.

Topic: 19. Aggressive Non-Hodgkin lymphoma - Clinical Background: Despite recent progress in treating LBCL, approximately 50% to 60% of pts will either not achieve a complete response (CR) or will relapse with current first- or second-line treatments and require additional therapy. With their unmatched efficacy, autologous anti-CD19 chimeric antigen receptor (CAR) T cells have revolutionized the care of patients whose disease progresses following standard therapies; however, patient-specific manufacturing processes and long wait times to treatment initiation prevent broader and more equitable use of these agents. In contrast, allogeneic (healthy-donor-derived), off-the-shelf CAR T cells promise to provide more patients with rapid access to one-dose treatment with curative intent. ALLO-501/501A is a pre-manufactured, allogeneic, CD52-knock-out/TCRα-knock-out, anti-CD19 CAR T cell product that uses Cellectis’ technologies. Conditioning with a regimen of fludarabine (F)/cyclophosphamide (C)/ALLO-647 (A, a humanized anti-CD52 monoclonal IgG1) targets host CD52+ immune cells for elimination while allowing subsequently infused CD52-knock-out ALLO-501/501A cells to persist. TCR-knock-out prevents the host immune system from recognizing MHC disparities between donor and host cells, and greatly reduces the risk of graft-versus-host disease (GvHD). Initial phase 1 data for the anti-CD19 AlloCAR T™ products ALLO-501 (NCT03939026) and successor ALLO-501A (NCT04416984) demonstrated a manageable safety profile with no dose-limiting toxicities (DLTs); efficacy outcomes were comparable to published results for autologous CAR T therapy in pts with r/r LBCL. Aims: This update provides data on the durability of response with the optimized AlloCAR T regimen (ALLO-501/501A following conditioning with ALLO-647 in FCA) that will be evaluated further in phase 2 trials. Methods: In these two multicenter, single-arm, open-label phase 1 trials, autologous CAR T-naïve pts with r/r LBCL underwent 3-day lymphodepletion (LD) followed by a single dose of ALLO-501/501A to identify the optimal regimen. FCA90 conditioning (F 30 mg/m2/day; C 300 mg/m2/day; A 30 mg/day [total dose: 90 mg]) followed by a single dose (120 X 106 CAR+ cells) of ALLO-501 or ALLO-501A produced by the Alloy manufacturing process was selected as the optimal regimen for development. Results: As of the Jan 26, 2023, cutoff, 12 pts received the FCA90 LD regimen and AlloCAR T therapy; 100% received the product per specifications with a median time of 3 days from enrollment to LD. Median follow-up time was 7.1 months (range: 1.4, 36.0). No DLTs were observed nor were any events of severe (Gr3+) cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS); no GvHD events occurred. In this cohort of 12 pts, the overall response rate was 66.7% with 58.3% achieving a best overall response of CR. Among pts with the opportunity to be followed for 6 months, 5 of 8 (62.5%) achieved CR and 4 of 8 (50.0%) maintained CR through 6 months with the longest CR ongoing at 36 months; median duration of response (DOR) was 23.1 months. Summary/Conclusion: A single dose of AlloCAR T therapy following FCA90 conditioning provided durable responses with a manageable safety profile in autologous CAR T-naïve pts with r/r LBCL. Among 8 pts who received FCA90 and ALLO-501/501A and had the opportunity to be evaluated for 6 months, 50% maintained that response for at least 6 months, with a median DOR of 23.1 months. These findings support broader evaluation of ALLO-501A/ALLO-647 in the ongoing, first potentially pivotal phase 2 trial (ALPHA2) of AlloCAR T therapy. Keywords: CAR-T, Allogeneic, Clinical trial, Diffuse large B cell lymphoma

Mice body weights follow-up during KW-2450 treatment.

SA-beta-gal assay with KW-2450 in TNBC cells.

Knockdown of Mad2 or BubR1 in TNBC cells treated with KW-2450.

Profiles of cell lines used in the present study.

Cell cycle profile in p53-wild breast cancer cells treated with KW-2450.

Knockdown of IGF-IR or InsR in TNBC cells.

2517 Background: Approximately 50% to 60% of pts with r/r LBCL will either not achieve a complete response (CR) or will relapse with current treatments and require additional therapy. Autologous anti-CD19 chimeric antigen receptor T (CAR T) therapies have revolutionized the care of patients whose disease progresses following standard therapies, but patient-specific manufacturing processes and long wait times to treatment present challenges for their broad clinical use. Allogeneic (healthy-donor-derived), off-the-shelf, anti-CD19 (CAR T) treatment promises broader and more rapid access to one-dose treatment with curative intent. Initial phase 1 data for the anti-CD19 AlloCAR T cell product ALLO-501 (NCT03939026) and successor, ALLO-501A (NCT04416984), demonstrated a manageable safety profile with no dose-limiting toxicities (DLTs), and efficacy comparable to autologous CAR T therapy in pts with r/r LBCL who were autologous CAR T-naïve. This update provides additional follow up and a focus on participants who received the conditioning regimen and cells made with an optimized manufacturing process currently under study in the first potentially pivotal trial for an allogeneic CAR T product. Methods: In these two multicenter, single-arm, open-label, phase 1 trials, a cohort of autologous CAR T-naïve pts with r/r LBCL underwent 3-day lymphodepletion (LD) with FCA90, fludarabine (F, 30 mg/m 2 /day), cyclophosphamide (C, 300 mg/m 2 /day), and ALLO-647 (A [anti-CD 52 mAb] 30 mg/day; total dose: 90 mg) followed by a single dose of ALLO-501 or ALLO-501A produced by the Alloy manufacturing process. Results: As of Jan 26, 2023, 12 pts received the FCA90 LD regimen and CAR T therapy with 100% receiving product per specifications with a median time from enrollment to LD of 3 days. Median follow-up time (actual) was 7.1 months (range: 1.4, 36.0). No DLTs, severe (Gr3+) cytokine-release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), or graft-versus-host disease (GvHD) events occurred. An overall response rate and a CR rate of 66.7% and 58.3%, respectively, were observed. Median DOR was 23.1 months. Among 8 pts with the opportunity to be followed for 6 months, 5 (62.5%) had achieved CR and 4 (50.0%) sustained CR through 6 months. Analyses of vector copy number pharmacokinetics at Days 28 and 56 documented substantial and sustained expansion of CAR T cells. Conclusions: A one-time dose of allogeneic CAR T therapy following LD with FCA90 provided durable responses with a manageable safety profile in patients with r/r/ LBCL comparable to those treated with autologous CAR T cells. This treatment enables rapid access to off-the-shelf treatment with a median time from trial enrollment to treatment of 3 days. These findings support broader evaluation of ALLO-501A in the ongoing, first potentially pivotal phase 2 trial (ALPHA2) of off-the-shelf allogeneic CAR T cells. Clinical trial information: NCT03939026 .

Background: While breakthroughs in hematologic malignancies with autologous CAR T-cell therapies have been met with growing clinical interest due to impressive outcomes, limitations in logistics/manufacturing, quality consistency, and product availability persist. Allogeneic CAR T-cell therapies may circumvent such challenges by providing an off-the-shelf therapeutic option derived from healthy donors. For allogeneic CAR T cells to be successful, there must be a safe and effective way to control host lymphocyte rejection of allogeneic CAR T cells (allo-rejection). ALLO-501 and ALLO-501A are allogeneic anti-CD19 CAR T-cell products that use Cellectis technologies' TALEN® gene editing to disrupt both the TCRα constant ( TRAC) and CD52 genes. CD52 disruption specifically permits use of ALLO-647, an anti-CD52 antibody, for the transient and selective depletion of host lymphocytes that enables ALLO-501 and ALLO-501A to proliferate after infusion without rapid allo-rejection. Updated phase 1 data for ALLO-501 (ALPHA; NCT03939026) and ALLO-501A (ALPHA2; NCT04416984) showed that administration of anti-CD19 allogeneic CAR T product following use of lymphodepletion that includes ALLO-647 plus fludarabine and cyclophosphamide provided durable responses and an acceptable safety profile in CAR T-cell-naive pts with r/r large B-cell lymphoma (LBCL; Locke FL, et al. ASCO 2023; #2517). Herein, we provide safety results of ALLO-647 in pts with r/r LBCL and follicular lymphoma (FL). Methods: Pts with r/r LBCL and FL enrolled in ALPHA and ALPHA2 studies received a 3 to 5-day lymphodepletion regimen consisting of fludarabine 30 mg/m 2 and cyclophosphamide 300-500 mg/m 2 (FC) and 39, 60, or 90 mg of ALLO-647 in divided doses. ALLO-501/ALLO-501A were administered after the completion of lymphodepletion. Incidence rates of grade ≥3 cytopenias (neutropenia, thrombocytopenia, anemia and pancytopenia) were assessed at 3 timepoints (Study Day 28, Day 56, and Month 4). Pts underwent weekly cytomegalovirus (CMV) monitoring. Leukocyte reconstitution was evaluated following lymphodepletion and CAR T-cell infusion. Results: As of April 20, 2023, 87 pts with r/r LBCL (n=61) and FL (n=26) were treated with ALLO-647 and included in the analysis (median age, 64 years; median number of prior regimens, 3). In total, 11 (13%), 39 (45%), and 37 (43%) pts received 39, 60, and 90 mg ALLO-647, respectively. Among the LBCL pts, 33 were CAR T-cell-naive and treated with product manufactured using the Phase 2 process. Median follow-up was 29.5 months (range, 6.8-47.5). The most common treatment-emergent adverse events (TEAEs), assessed from the time of first dose of lymphodepletion, included neutropenia (79%), anemia (61%), infusion-related reactions (IRRs, 55%), and thrombocytopenia (53%). The most common grade ≥3 TEAEs included neutropenia (74%), anemia (38%), and thrombocytopenia (38%). The proportion of pts experiencing grade ≥3 cytopenias decreased over time from Day 28 (29%) to Day 56 (20%) to Month 4 (15%), which was consistent across all lymphoma pt subgroups. ALLO-647 IRRs were typically low grade, except for 5 (6%) grade 3 events; all IRRs were managed with supportive care measures. After treatment with ALLO-501/501A, 20 pts (23%) experienced cytokine release syndrome events, which were low grade except for 1 (1%) grade 3 event. No GvHD, grade ≥3 immune effector cell-associated neurotoxicity syndrome events, or progressive multifocal leukoencephalopathy were reported. Any grade and grade ≥3 infections were reported in 50 pts (58%) and 18 pts (21%), respectively. Two pts had (2%) fatal infectious events (COVID-19 pneumonia and pneumonia, n=1 each) as previously reported. The most common infection was CMV reactivation (any grade, n=22 [25%]; grade 3, n=8 [9%]). Following lymphodepletion, the median time to absolute neutrophil count and absolute lymphocyte count recovery to grade <4 was 7 days and 28 days, respectively. T-cell counts exhibited a steady increase over time, with the majority of pts achieving full T-cell recovery (return to baseline levels) by Month 6. Detailed pharmacokinetics and pharmacodynamics data will be presented. Conclusions: These data suggest allogeneic CAR T-cell products administered following lymphodepletion consisting of FC and ALLO-647 can provide a safe and tolerable alternative to autologous CAR T-cell therapy.

Inhibitory activity of KW-2450 against p-IGF-IR in TNBC cells.

Abstract Background: Screening mammography has dramatically increased incidental detection of Ductal Carcinoma in situ (DCIS), a non-obligate precursor of breast cancer. Approximately 10-50% of DCIS progress to the invasive disease and the risk of developing recurrence or progression after surgery is still not well defined based on clinical and pathological characteristics. Our study investigated the genetic and epigenetic mechanisms associated with recurrence and progression of DCIS to invasive cancer. Methods: To identify genes associated with recurrence and progression of DCIS to invasive cancer, we performed Nanostring nCounter analysis (MDACC, n = 40) and RNA-sequencing (Sloane study, n = 183) in two independent prospective primary DCIS cohorts. Mammary epithelial-specific Pten knockout mouse model developed in our lab was used to interrogate the genetic pathway deregulated during development of mammary intraepithelial neoplasia to adenocarcinoma. ATAC-seq and ChIP-qPCR were performed to assess chromatin accessibility in the genome and validate binding of histone-modifying enzymes on target promoters. Histopathological analyses were performed to determine DCIS grades, subtypes, and protein expression profiles. Results: RNA expression profiles of normal mammary and primary DCIS tissues (n = 40) identified 10 gene transcripts that were significantly and differentially expressed between normal and high-grade DCIS. Only SOX11 expression was significantly and progressively correlated with KI67 and the DCIS recurrence score as described by Solin (JNCI 2013). Mammary intraepithelial neoplasia in Pten knockout mice and 21T DCIS to IDC progression cell line model also revealed SOX11 upregulation compared to controls. Since PTEN/PI3K/AKT pathway is known to regulate global active histone marks and open accessible chromatin, we investigated the role of AKT on SOX11 expression. Results demonstrated that inhibition of AKT altered enrichment of histone-modifying enzymes KDM5A and EZH2 on the promoter accompanying downregulated SOX11 expression in DCIS cell lines. SOX11 and EZH2 expression profiles revealed significant correlation in DCIS tissue samples. In two independent DCIS cohorts, SOX11 was found significantly upregulated in HER2+ and basal-like DCIS subtypes (P < 0.001). RNA sequencing in 183 longitudinal DCIS cases of the Sloane study (median follow-up of 96 months) revealed significantly shorter recurrence-free survival in SOX11+ than SOX11- patients (P < 0.02 in all subtypes; P = 0.002 in HER2+ subtype). Based on COX proportional hazards model, SOX11 alone was significantly associated with the risk of developing recurrence and invasive breast cancer (HR = 1.7, 95% CI = 1.1 to 2.6; P < 0.02). Conclusions: Epigenetic activation of SOX11 is associated with recurrence and progression of DCIS to invasive breast cancer. SOX11 and its epigenetic regulators can be developed as prognostic markers for DCIS patients with recurrence risk independent of traditional clinical and pathologic characteristics. Citation Format: Warapen Treekitkarnmongkol, Vandna Shah, Kazuharu Kai, Hiroshi Katayama, Justin W. Wong, Farah A Ladha, Brian Menegaz, Sarah E. Pinder, Wei Lu, Fei Yang, Ximing Tang, Savitri Krishnamurthy, Ignacio I. Wistuba, Elinor J. Sawyer, Alastair M. Thompson, Subrata Sen. Epigenetic activation of SOX11 is associated with recurrence and progression of DCIS to invasive breast cancer [abstract]. In: Proceedings of the AACR Special Conference on Rethinking DCIS: An Opportunity for Prevention?; 2022 Sep 8-11; Philadelphia, PA. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_1): Abstract nr A017.

NKTR-255 is an investigational polyethylene glycol-modified recombinant human IL-15 (rhIL-15) receptor agonist, designed to improve the immunotherapeutic and anti-cancer benefit observed with rhIL-15 while circumventing the toxicities associated with this therapy. In preclinical studies, NKTR-255 has demonstrated enhanced proliferation and function of CD8+ T cells and natural killer cells, as well as enhanced anti-tumor activity and survival both as monotherapy and in combination with monoclonal antibodies in multiple cancer models. Here, we describe the rationale and design of the first-in-human Phase I, dose-escalation and dose-expansion study of NKTR-255 alone and in combination with daratumumab or rituximab in adults with relapsed/refractory multiple myeloma or non-Hodgkin's lymphoma that will determine the maximum tolerated dose and recommended Phase II dose for NKTR-255.

Background: Autologous T cells engineered to express a CD19 or BCMA-specific chimeric antigen receptor (CAR) have shown high overall response rates in treatment-refractory B-cell non-Hodgkin lymphoma (NHL) and BCMA + multiple myeloma (MM), respectively. However, most patients will eventually relapse, and thus strategies are needed to further improve the efficacy and durability of CAR-T cell products. NKTR-255 is an investigational polyethylene glycol-modified recombinant human IL-15 (rhIL-15) receptor agonist designed to engage the IL-15 pathway to stimulate and expand natural killer (NK) cells and promote the survival and expansion of memory CD8 + T cells. Preclinical data in B-cell lymphoma xenograft models have shown that NKTR-255 enhanced expansion, survival, and anti-tumor activity of human CD19 CAR-T cells. Furthermore, clinical studies have validated that IL-15 augments anti-tumor activity and promotes a stem-cell memory subset in tumor-specific T cells. Here we report pharmacodynamic (PD) analysis of CAR-T cells from relapsed/refractory (R/R) NHL or MM patients who had prior CAR-T therapy and were subsequently enrolled in an ongoing Phase 1 study of NKTR-255.

Background : Selinexor (SEL) is a novel, first-in-class oral selective inhibitor of nuclear export (SINE) which blocks XPO1, forcing the nuclear retention and activation of tumor suppressor proteins, ultimately causing cell death in cancer cells. SEL 80 mg and dexamethasone (dex) 20 mg, both twice weekly (BIW), received accelerated approval from the FDA for patients (pts) with relapsed refractory multiple myeloma (RRMM). SEL continues to be evaluated in earlier lines of therapy with once weekly administration and in combination regimens. The SVd regimen with once weekly (QW) oral SEL (100 mg), dexamethasone (dex) and QW bortezomib (BOR) had significantly increased progression free survival (PFS) and overall response rate (ORR) with significantly reduced peripheral neuropathy as compared to standard BIW BOR/dex (Vd) in the phase III BOSTON study. The combination of lenalidomide (LEN) and dex (Rd) is an approved regimen in RRMM and newly diagnosed MM (NDMM) with an ORR of 70-76% in RRMM but a low complete response rate. SEL showed synergistic antitumor activity with LEN in a MM xenograft model. Therefore, we hypothesized that the all oral combination of weekly SEL with standard Rd (i.e., SRd) could improve the efficacy compared with Rd in pts with RRMM and NDMM with acceptable toxicity profile. Methods: STOMP is a phase 1b/2 multicenter, open-label, clinical trial with the goals of determining the maximum tolerated dose, the recommended phase 2 dose (RP2D), efficacy and safety of SRd in pts with RRMM or NDMM. For RRMM, SEL was dose escalated in two regimens QW (starting at SEL 80 mg) or BIW (starting at 60 mg), LEN 25 mg PO daily and DEX 20 mg BIW or 40 mg QW. Results: As of June 1, 2020, 24 pts (13 male, 11 female) with RRMM were enrolled. The median age was 67 years (range, 49-84) and the median number of prior lines of therapy was 1.5 (range, 1 - 8). In the 60 mg BIW dosing, 4 pts experienced dose limiting toxicities (DLTs) out of 5 pts dosed (2 thrombocytopenia, 1 anorexia, 1 >25% missed dose due to unrelated QT interval prolongation). In the 80 mg QW dosing, 2 pts experienced DLTs out of 6 pts (both grade 4 thrombocytopenia). In the 60 mg QW dosing, no DLTs were observed. Based on these data, the RP2D of SRd was determined to be: SEL 60 mg QW, LEN 25 mg QD and DEX 40 mg QW. Common treatment related adverse events (TRAEs) (All Grades, ≥3) were thrombocytopenia (71%, 63%), neutropenia (63%, 63%), nausea (58%, 4%), fatigue (54%, 17%), decreased appetite (50%, 8%), and weight loss (42%, 8%). Amongst the 20 pts with RRMM where efficacy was evaluable, previously treated/documented refractory rates were: bortezomib (100%, 45%), LEN (40%, 25%), daratumumab (20%, 20%), and pomalidomide (20%, 20%). Amongst the LEN naïve pts (n=12), the ORR was 92% including 1 stringent complete response [sCR], 4 very good partial responses [VGPR] and 6 partial responses [PR, 2 unconfirmed]). PFS in LEN naïve pts has not been reached with a median follow-up period of 7.8 months. In the pts with prior LEN treatment (n=8), the ORR was 13%. Based on the high levels of activity of SRd in LEN naïve pts, 8 pts (4 males and 4 females) with NDMM were enrolled at the RP2D. The median age was 74 (range: 51-86) years. No DLTs were observed in 5 DLT evaluable pts. Common TRAEs (All Grades, ≥3) were thrombocytopenia (63%, 38%), neutropenia (75%, 75%), fatigue (63%, 50%), nausea (50%, 0%), weight loss (63%, 0%), and decreased appetite (13%, 13%). All 7 efficacy evaluable pts achieved a response, an ORR of 100%, including 1 CR, 4 VGPR, and 2 PR. With a median follow-up of 10.2 months, median PFS has not been reached. Out of these 7 pts, three pts withdrew consent to transit to successful autologous stem cell collection and transplantation. Conclusions: The all oral combination of SRd with once weekly SEL 60 mg, LEN 25 mg QD and DEX 40 mg QW was established as the RP2D for pts with RRMM or NDMM. The safety profile was similar in both settings. All TRAEs were manageable with adequate supportive care and/or dose modification. The all oral combination of SRd has demonstrated ORR of 92% in pts with LEN naïve RRMM and ORR of 100% in pts with NDMM, warranting further investigation of SRd with or without additional anti-MM agents for the treatment of pts with NDMM. Disclosures White: Sanofi: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Karyopharm: Honoraria; Antengene: Honoraria; GSK: Honoraria. LeBlanc:Celgene: Research Funding; Celgene Canada; Janssen Inc.; Amgen Canada; Takeda Canada: Membership on an entity's Board of Directors or advisory committees. Baljevic:NCCN Hematologic Malignancies Congress: Honoraria; MediCom Myeloma CME: Honoraria; Amgen: Research Funding; Exelixis: Research Funding; Celgene Corporation / BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cardinal Health: Consultancy, Membership on an entity's Board of Directors or advisory committees; Putnam Associates: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gerson Lehrman Group: Consultancy, Membership on an entity's Board of Directors or advisory committees; AlphaSights: Consultancy, Membership on an entity's Board of Directors or advisory committees; Coleman: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm Therapeutics Inc.: Honoraria. Bahlis:Karyopharm Therapeutics: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; BMS/Celgene and Janssen: Consultancy, Honoraria, Other: Travel, Accomodations, Research Funding; Sanofi: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Lentzsch:Celularity: Consultancy; Sorrento: Consultancy; Janssen: Consultancy; Caelum Biosciences: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Mesoblast: Divested equity in a private or publicly-traded company in the past 24 months; Sanofi: Research Funding; Magenta: Current equity holder in private company; Karyopharm: Research Funding. Venner:Celgene, Amgen: Research Funding; Janssen, BMS/Celgene, Sanofi, Takeda, Amgen: Honoraria. Chen:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Research Funding. Lipe:Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Tuchman:Roche: Research Funding; Oncopeptides: Consultancy; Janssen: Research Funding; Amgen: Research Funding; Sanofi: Honoraria, Research Funding; Caelum: Honoraria; Karyopharm: Honoraria, Research Funding; Celgene: Honoraria, Research Funding, Speakers Bureau. Sutherland:Janssen: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Celgene: Consultancy; Amgen: Consultancy. Kotb:Merck: Honoraria, Research Funding; Karyopharm: Current equity holder in publicly-traded company; Takeda: Honoraria; Celgene: Honoraria; Sanofi: Research Funding; Amgen: Honoraria; Janssen: Honoraria. Sebag:Amgen: Honoraria; Janssen: Honoraria, Research Funding; Celgene: Honoraria; Takeda: Honoraria. Callander:Cellectar: Research Funding; University of Wisconsin: Current Employment. Bensinger:BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; GSK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Regeneron: Consultancy, Honoraria, Research Funding, Speakers Bureau. Rossi:Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Sheehan:Karyopharm Therapeutics Inc: Current Employment. Van Domelen:Karyopharm Therapeutics Inc: Current Employment, Current equity holder in publicly-traded company. Zhou:Karyopharm Therapeutics Inc.: Current Employment, Current equity holder in publicly-traded company. Kazuharu:Karyopharm Therapeutics Inc.: Current Employment. Shah:Karyopharm Therapeutics Inc: Current Employment, Current equity holder in publicly-traded company. Shacham:Karyopharm: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: (8999996, 9079865, 9714226, PCT/US12/048319, and I574957) on hydrazide containing nuclear transport modulators and uses, and pending patents PCT/US12/048319, 499/2012, PI20102724, and 2012000928) . Kauffman:Karyopharm Therapeutics Inc: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Schiller:Ariad: Research Funding; Actinium: Research Funding; Jazz Pharmaceuticals: Research Funding; Johnson & Johnson: Current equity holder in publicly-traded company; Kaiser Permanente: Consultancy; Trovagene: Research Funding; Tolero: Research Funding; Sangamo: Research Funding; Samus: Research Funding; Regimmune: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; Karyopharm: Research Funding; Kite Pharma: Research Funding; Mateon: Research Funding; MedImmune: Research Funding; Onconova: Research Funding; Cyclacel: Research Funding; Daiichi Sankyo: Research Funding; Deciphera: Research Funding; Astellas Pharma: Honoraria, Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Celator: Research Funding; Abbvie: Research Funding; Constellation: Research Funding; Ono Pharma: Consultancy; Novartis: Consultancy, Research Funding; Stemline: Speakers Bureau; Incyte: Consultancy, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Gilead: Speakers Bureau; Sanofi: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; DeltaFly: Research Funding; Forma: Research Funding; Gamida: Research Funding; FujiFilm: Research Funding; Genentech-Roche: Research Funding; Geron: Research Funding.

Background : Selinexor (SEL) is a novel, first-in-class oral selective inhibitor of nuclear export (SINE) which blocks exportin 1 (XPO1), forcing the nuclear retention and activation of tumor suppressor proteins that cause cell cycle arrest and apoptosis in cancer cells. The combination of SEL with dexamethasone (dex), each administered twice weekly (BIW), received accelerated approval from the FDA in relapsed refractory multiple myeloma (RRMM). Subsequent evaluations of combination regimens have utilized once weekly (QW) SEL. The addition of oral SEL 100 mg QW to bortezomib also QW with dex (SVd) showed superior PFS and ORR with reduced peripheral neuropathy compared with standard BIW bortezomib plus dex (Dimopoulos et al. JCO 2020). SEL sensitized the activity of carfilzomib (CAR) in PI-resistant MM cell lines in vitro and ex vivo in PI-refractory MM cells derived from bone marrow aspirates of patients (pts) with RRMM. SEL and CAR also showed synergistic anti-tumor activity in a NOD-SCID mice xenograft model in vivo. Furthermore, a phase I trial in RRMM pts demonstrated that the combination of SEL and CAR both administered BIW with DEX showed high overall response rates (ORR) in pts with MM refractory to CAR. Carfilzomib QW was recently approved and we hypothesized that the addition of SEL QW to CAR QW plus dex (SKd) would be synergistic and convenient with an acceptable adverse event (AE) profile. Methods: STOMP is a phase 1b/2 multicenter, open-label, clinical trial with the goals of determining the maximum tolerated dose (MTD), the recommended phase 2 dose (RP2D) and the ORR according to the International Myeloma Working Group (IMWG) criteria. The starting SEL dose was 100 mg QW with 20/56 mg/m2 QW CAR (20 mg/m2 only on C1D1 and 56 mg/m2 thereafter, dosed Day 1, 8, and 15, 28 days cycle) with 40 mg QW DEX (Table 1). Eligible pts had MM progressing on study entry that was not refractory to CAR, were ≥ 18 years old, with Eastern Cooperative Oncology Group (ECOG) score of 0-2, WBC ≥ 1,500/mm3,Hb ≥ 8.0 g/dL, and platelet count ≥ 75,000/mm3. Results: The MTD was 20/56 mg/m2 CAR + 80 mg SEL + 40 mg DEX, all given QW. As of May 1, 2020, a total of 24 pts enrolled, of which 17 received the MTD. Median age was 70.5 (range, 50-76) years, 62.5% male, median number of prior therapies 3 (range, 1-8). Median years from initial diagnosis 5.0 (range, 2.7-11.3) years. Prior therapies in the 24 pts included bortezomib 24 pts (100%), lenalidomide 23 pts (95.8%), pomalidomide 15 pts (62.5%), daratumumab 14 pts (58.3%) and 19 (79.2%) stem cell transplantation. Common hematopoietic treatment-related AEs (TRAEs) were thrombocytopenia (70.8% all grades, 54.2% grades 3/4) and anemia (54.2%, 20.8%). Common non-hematological TRAEs were nausea (66.7%, 0%), fatigue (54.2%, 8.3%), anorexia (45.8%, 4.2%), weight loss (37.5%, 0%), and dysgeusia (37.5%, 0%). All TRAEs were expected and manageable with appropriate supportive care (eg, TPO receptor agonists for thrombocytopenia) and/or dose modifications; long term cumulative toxicities have not been observed. ORR was 75.0% including 4 CR (16.7%), 7 VGPR (29.2%) and 7 PR (29.2%). There was 1 MR yielding a clinical benefit rate of 79.2%. Amongst the 14 pts previously treated with daratumumab, 8 pts (57.1%) achieved ≥PR, 9 pts (64.3%) achieved ≥MR. Median time to the first response (≥PR) was 28 days (range, 27-98 days). Median progression free survival has not been reached with a median follow-up of 4.4 months. Conclusions: Weekly SKd (20/56 mg/m2 CAR + 80 mg SEL QW + 40 mg DEX QW) is active with an ORR of 75.0% and deep responses (CR 16.7%, VGPR 29.2%) in pts who had a median of 3 prior lines of therapy including bortezomib and lenalidomide. The ORR of 57.1% in patients previously treated with daratumumab warrants further investigation of this once weekly regimen in 1st or 2nd relapse including among patients with prior daratumumab. Disclosures Lipe: Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Tuchman:Roche: Research Funding; Oncopeptides: Consultancy; Janssen: Research Funding; Amgen: Research Funding; Sanofi: Honoraria, Research Funding; Caelum: Honoraria; Karyopharm: Honoraria, Research Funding; Celgene: Honoraria, Research Funding, Speakers Bureau. Callander:University of Wisconsin: Current Employment; Cellectar: Research Funding. Lentzsch:Sanofi: Research Funding; Mesoblast: Divested equity in a private or publicly-traded company in the past 24 months; Celularity: Consultancy; Sorrento: Consultancy; Janssen: Consultancy; Caelum Biosciences: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Magenta: Current equity holder in private company; Karyopharm: Research Funding. Baljevic:NCCN Hematologic Malignancies Congress: Honoraria; Cardinal Health: Consultancy, Membership on an entity's Board of Directors or advisory committees; Putnam Associates: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gerson Lehrman Group: Consultancy, Membership on an entity's Board of Directors or advisory committees; AlphaSights: Consultancy, Membership on an entity's Board of Directors or advisory committees; Coleman: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm Therapeutics Inc.: Honoraria; Celgene Corporation / BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Exelixis: Research Funding; MediCom Myeloma CME: Honoraria. Rossi:BMS: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Bahlis:Sanofi: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Karyopharm Therapeutics: Consultancy, Honoraria; BMS/Celgene and Janssen: Consultancy, Honoraria, Other: Travel, Accomodations, Research Funding. White:Sanofi: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Karyopharm: Honoraria; Antengene: Honoraria; GSK: Honoraria; Celgene: Honoraria; Janssen: Honoraria. Chen:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Research Funding. Sutherland:Janssen: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Celgene: Consultancy; Amgen: Consultancy. Kotb:Karyopharm: Current equity holder in publicly-traded company; Merck: Honoraria, Research Funding; Celgene: Honoraria; Janssen: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Sanofi: Research Funding. LeBlanc:Celgene: Research Funding; Celgene Canada; Janssen Inc.; Amgen Canada; Takeda Canada: Membership on an entity's Board of Directors or advisory committees. Sebag:Celgene: Honoraria; Takeda: Honoraria; Amgen: Honoraria; Janssen: Honoraria, Research Funding. Venner:Janssen, BMS/Celgene, Sanofi, Takeda, Amgen: Honoraria; Celgene, Amgen: Research Funding. Bensinger:BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; GSK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Regeneron: Consultancy, Honoraria, Research Funding, Speakers Bureau. Sheehan:Karyopharm Therapeutics Inc: Current Employment. Van Domelen:Karyopharm Therapeutics Inc: Current Employment, Current equity holder in publicly-traded company. Kazuharu:Karyopharm Therapeutics Inc.: Current Employment. Schiller:MedImmune: Research Funding; Onconova: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; Regimmune: Research Funding; Samus: Research Funding; Sangamo: Research Funding; Tolero: Research Funding; Trovagene: Research Funding; Kaiser Permanente: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Ariad: Research Funding; Actinium: Research Funding; Abbvie: Research Funding; Stemline: Speakers Bureau; Gilead: Speakers Bureau; Sanofi: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Agios: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Incyte: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding; Ono Pharma: Consultancy; Mateon: Research Funding; Kite Pharma: Research Funding; Karyopharm: Research Funding; Jazz Pharmaceuticals: Research Funding; Geron: Research Funding; Genentech-Roche: Research Funding; Gamida: Research Funding; FujiFilm: Research Funding; Forma: Research Funding; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; DeltaFly: Research Funding; Deciphera: Research Funding; Daiichi Sankyo: Research Funding; Cyclacel: Research Funding; Constellation: Research Funding; Celator: Research Funding; Astellas Pharma: Honoraria, Research Funding.

8510 Background: Selinexor is a first-in-class oral Selective Inhibitor of Nuclear Export (SINE) compound that binds and inactivates exportin 1 (XPO1). Selinexor in combination with low dose dexamethasone (Sel-dex) was approved by the FDA, based on data from the STORM study, wherein Sel-dex induced an overall response rate (ORR) of 26.2% in patients (pts) with relapsed/refractory MM (RRMM). Single agent daratumumab has demonstrated an ORR of 29% in MM reftactory to proteasome inhibitors (PIs)/immunomodulatory drug (IMiDs). We evaluated the safety, tolerability and preliminary efficacy of the combination of Sel-dex and daratumumab (SDd) in pts with MM refractory to PIs/IMiDs. Methods: This is a multicenter, open-label, phase 1b/2 dose escalation and expansion study. Pts were eligible if they had received ≥ 3 prior lines of therapy, including a PI and an IMiD, or whose MM was refractory to a PI and an IMiD. In the expansion phase, pts were required to be anti-CD38 monoclonal antibody-naïve. One dose level was tested at each schedule: selinexor once-weekly (QW at 100 mg) or twice-weekly (BIW at 60 mg) with dexamethasone 40 mg. Daratumumab 16 mg/kg IV was administered per label. Primary objective was to determine the maximum tolerated dose and recommended phase 2 dose (RP2D), and assess safety, tolerability and efficacy of SDd in pts with RRMM. Results: A total of 34 pts were enrolled; 3 in the 60 mg BIW and 31 in the 100 mg QW cohorts. Median age was 69 and median number of prior treatment regimens was 3 (range, 1–10). Out of 34 pts, 62% and 65% were refractory to bortezomib and lenalidomide respectively. Common treatment related adverse events (all grades, grades 3/4) included: thrombocytopenia (71%, 47%), fatigue (62%, 18%), nausea (71%, 9%), anemia (62%, 32%) and neutropenia (50%, 26%). Two dose limiting toxicities (DLTs) were reported in the 60 mg BIW cohort: Grade 3 thrombocytopenia and Grade 2 fatigue requiring dose reduction in selinexor to 100 mg QW. In the 100 mg QW escalation cohort (n = 6), no DLTs occured. 32 patients were evaluable for efficacy. The ORR was 73% (11 VGPR, 11 PR) for 30 daratumumab-naïve pts. Median progression-free survival was 12.5 months in both groups. Conclusions: Based on tolerability and efficacy, the RP2D of SDd is selinexor 100 mg, daratumumab 16 mg/kg and dexamethasone 40 mg, administered QW. In pts with PI and IMiD refractory MM, weekly SDd demonstrated promising activity with an ORR of 73% in daratumumab-naïve pts and a median PFS of 12.5 months. This supports further development of a novel non-PI, non-IMiD backbone in earlier lines of therapy. Clinical trial information: NCT02343042 .