ALBERT

Description: Triplet regimens combining an immunomodulatory agent, a proteasome inhibitor (PI), and a steroid are used to treat newly diagnosed and relapsed multiple myeloma (MM). Although ixazomib (Ix), an oral PI with single agent activity, can be combined with lenalidomide (LEN), patients (pts) with relapsed/refractory (R/R) MM are often LEN-refractory. Pomalidomide (POM) has single agent activity in LEN-refractory disease, and both POM and Ix also show activity in poor cytogenetic risk pts. Methods: Primary objectives: 1) determine the maximum tolerated dose (MTD) of Ix in combination with standard dose POM and dexamethasone (DEX), and 2) evaluate the anti-tumor activity of the triplet. The treatment regimen included two dose levels (3 mg and 4 mg) of Ix on days 1, 8, 15; POM 4 mg days 1-21; and DEX 40 mg days 1, 8, 15, 22, of a 28 day cycle. Eligibility: R/R MM after 〉1 prior therapy, LEN-refractory, and ≤ grade(gr) 1 peripheral neuropathy (PN). Pts were treated until progression or unacceptable toxicity. Design: Phase I study utilizing a standard 3+3 design; dose limiting toxicities (DLTs) defined during cycle 1. Results: 32 pts treated, 31 evaluable for toxicity and response. Pts received a median 4 cycles (range 1-13); median follow-up is 5.5 months (range 1.8-21.1). Six pts treated on DL1, 25 treated on DL2, the MTD/Phase II dose (P2D). Median age: 62 years (range 38-84); median time from diagnosis: 3.7 years (range 1.0-8.9); median number prior therapies: 3 (range 1-5); prior transplant: n = 23 (74%); double (LEN/Bortezomib[BOR]) or triple (LEN/BOR/Carfilzomib[CFZ]) refractory: 19 (61%). Phase I: DL1 expanded to n=6 after 1/3 pts experienced DLT (gr3 lung infection); no further DLT seen on DL 1 or 2. Adverse events (AEs) related to POM and/or Ix: ANC decrease Gr1/2 n=11 (35%), Gr3/4 n=10 (32%), platelet decrease Gr1/2 n=9 (29%), lymphocyte decrease Gr1/2 n=8 (26%), Gr3/4 n=11 (35%), PN Gr1/2 n=9 (29%), no Gr3/4. Response: Phase I and II, n=31 pts treated. ORR: 45% (6 VGPR, 8 PR); Clinical Benefit Rate (CBR): 81% (6 VGPR, 8 PR, 3 MR, 8 SD). In the pts with high risk cytogenetics (7[23%] 1q, 3[10%] 17p, 2[6%] t(4;14)) an ORR of 58% (3 VGPR, 4 PR) was seen, and the CBR was 83%. In the double or triple refractory pts, an ORR of 26% and CBR of 79% (1 VGPR, 4 PR, 3 MR, 7 SD) were observed. Conclusions: Ix/POM/DEX is a well-tolerated oral combination therapy, and responses were seen even at DL1 and in high risk patients, including those with poor-risk cytogenetics or advanced refractory disease. Disclosures Kapoor: Celgene: Research Funding; Amgen: Research Funding; Takeda: Research Funding. Kumar:Millennium: Consultancy, Research Funding; AbbVie: Research Funding; Glycomimetics: Consultancy; Sanofi: Consultancy, Research Funding; Noxxon Pharma: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; BMS: Consultancy; Kesios: Consultancy; Onyx: Consultancy, Research Funding; Skyline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Research Funding; Array BioPharma: Consultancy, Research Funding. Lonial:Novartis: Consultancy; BMS: Consultancy; Janssen: Consultancy; Merck: Consultancy; Celgene: Consultancy; Onyx: Consultancy; Novartis: Consultancy; BMS: Consultancy; Celgene: Consultancy; Millenium: Consultancy; Janssen: Consultancy; Onyx: Consultancy. Nathwani:Carevive Systems, Inc.: Research Funding. Forman:Mustang Therpapeutics: Other: Construct licensed by City of Hope. Berdeja:Abbvie, Acetylon, Amgen, Bluebird, BMS, Calithera, Celgene, Constellation, Curis, Epizyme, Janssen, Karyopharm, Kesios, Novartis, Onyx, Takeda, Tragara: Research Funding.

Description: Key Points NFKB2 GOF mutations are associated with CID without endocrine or ectodermal manifestations. As most autosomal-dominant primary immunodeficiencies, NFKB2 GOF changes have incomplete penetrance and variable expressivity.

Description: Key Points GATA2 deficiency-associated bone marrow disorder can present with features that overlap with idiopathic aplastic anemia. GATA2 marrows have severely decreased hematogones, monocytes, NK cells, and B cells; variable dysplasia; and clonal cytogenetic abnormalities.

Description: Pathogenic gain-of-function variants in the genes encoding phosphoinositide 3-kinase δ (PI3Kδ) lead to accumulation of transitional B cells and senescent T cells, lymphadenopathy, and immune deficiency (activated PI3Kδ syndrome [APDS]). Knowing the genetic etiology of APDS afforded us the opportunity to explore PI3Kδ inhibition as a precision-medicine therapy. Here, we report in vitro and in vivo effects of inhibiting PI3Kδ in APDS. Treatment with leniolisib (CDZ173), a selective PI3Kδ inhibitor, caused dose-dependent suppression of PI3Kδ pathway hyperactivation (measured as phosphorylation of AKT/S6) in cell lines ectopically expressing APDS-causative p110δ variants and in T-cell blasts derived from patients. A clinical trial with 6 APDS patients was conducted as a 12-week, open-label, multisite, within-subject, dose-escalation study of oral leniolisib to assess safety, pharmacokinetics, and effects on lymphoproliferation and immune dysregulation. Oral leniolisib led to a dose-dependent reduction in PI3K/AKT pathway activity assessed ex vivo and improved immune dysregulation. We observed normalization of circulating transitional and naive B cells, reduction in PD-1+CD4+ and senescent CD57+CD4− T cells, and decreases in elevated serum immunoglobulin M and inflammatory markers including interferon γ, tumor necrosis factor, CXCL13, and CXCL10 with leniolisib therapy. After 12 weeks of treatment, all patients showed amelioration of lymphoproliferation with lymph node sizes and spleen volumes reduced by 39% (mean; range, 26%-57%) and 40% (mean; range, 13%-65%), respectively. Thus, leniolisib was well tolerated and improved laboratory and clinical parameters in APDS, supporting the specific inhibition of PI3Kδ as a promising new targeted therapy in APDS and other diseases characterized by overactivation of the PI3Kδ pathway. This trial was registered at www.clinicaltrials.gov as #NCT02435173.

Description: The production of placental growth factor (PlGF) increases during normal third trimester pregnancy, a point at which women are at an increased risk of morbid viral infections (e.g. an 8-fold increased risk of mortality during the 2009 H1N1 influenza pandemic). Pathologic increases in PlGF have also been detected in sickle cell disease patients and are associated with similarly increased morbidity (hospitalizations and acute chest syndrome). While treatment of normal donor mononuclear cells with exogenous PlGF reportedly increases cytokine transcripts (including tumor necrosis factor-alpha [TNF]), whether TNF mRNA is translated is unclear, as are: (a) the comparative activity of PlGF isoforms, (b) the scope of inflammatory cytokines involved, (c) the TNF-dependency of other induced cytokines, (d) and the potential effects of PlGF when combined with toll-like receptor (TLR) pathway activators. Consequently, we sought to test the hypothesis that PlGF could enhance pro-inflammatory responses of peripheral blood monocytes to TLR-stimulation and focused on endosomal TLRs which would be expected to be activated by the types of viral infections (ssRNA) for which pregnant women and sickle cell anemia patients are at risk. Normal primary peripheral blood CD14+ cells were exposed to the PlGF isoforms (PlGF-1, -2, -3). None induced TNF secretion. However, when CD14+ cells were exposed to both PlGF-1 (250 ng/ml) and the TLR-7/8 ligand R848 (3 μM), production of TNF mRNA (qRT-PCR) at 4-6 hours (mean 2.52-fold, p=0.05, 10 separate experiments) and TNF protein (ELISA) at 24-hours (mean 2.15-fold, p=0.0007, 24 separate experiments) was significantly enhanced. PlGF-2 and -3 had no effect on TLR-7/8 activated cells. PlGF-1 did not prolong TNF mRNA half-life (Actinomycin D chase results) but did enhance TNF gene transcription. Specifically, in kinetic studies we quantified equivalent increases in both spliced and unspliced TNF mRNA and TNF protein (Figure 1). The same experiments indicated that PlGF-1 prolongs the duration of TNF gene transcription compared to cells treated with R848 alone. The synergistic effect of PlGF with TLR-7/8 was not seen with the TLR-4 activator LPS. VEGF-A exhibited no influence on TLR-7/8 induced TNF gene expression. We sought to identify signaling pathways involved in the PlGF/TLR effect and determined by western blotting (total IKK-α and β, and phospho-IKK-α/β) that PlGF markedly enhanced R848-induced phosphorylation of IKK. Moreover, treatment of primary cells with an IKK inhibitor (BMS 345541; 0.5, 1.5, 5 μM) inhibited the enhancing effect of PlGF on R848-induced TNF production. TNF gene expression was not inhibited by small molecule inhibitors of p38 MAPK, PI3K, MEK-1/2, or ERK-1/2. Gene microarray analysis (Affymetrix HTA 2.0) revealed a PlGF/R848-specific increase in RIPK1 mRNA encoding a known IKK activator. To identify other inflammatory cytokines influenced by PlGF/TLR, and their dependency on TNF, we performed Luminex multiplex cytokine arrays of conditioned culture media from CD14+ cells cultured for 6 and 24-hours with PlGF-1 (250 ng/ml) and R848 (3 μM), and found (n=2 biological replicates) that PlGF enhanced R848-induced protein levels of: TNF, interleukin-6 (IL-6), IL-8, IL-1β, macrophage inflammatory protein 1 alpha (MIP-1α), MIP-1β, monocyte chemoattractant protein-1 (MCP-1), interferon-alpha, G-CSF, and monocyte interferon gamma inducing factor (MIG). To test the idea that the production of these factors was TNF-dependent, CD14+ cells were cultured as above in the presence and absence of soluble TNF receptor (sTNFR) (0.1, 1, 10 μg/ml). Complete inhibition of signal transduction through the TNF receptor had no effect on the production of other inflammatory cytokines (i.e. IL-8). We conclude that PlGF directly contributes to an exaggerated pro-inflammatory response in human mononuclear phagocytes incited by TLR-7/8 activation and suggest that it does so by promoting the expression or activation of an IKK kinase (e.g. RIPK1) and/or suppressing an IKK phosphatase. We also conclude that the production of inflammatory cytokines by PlGF and R848 is independent of autocrine TNF production. Clarification of the effect of PlGF on TLR-pathway hyper-reactivity may lead to the identification of key pathways that can be safely suppressed in individuals with high PlGF levels to achieve the goal of reducing virus related morbidity and mortality. Figure 1. Figure 1. Disclosures Tyner: Constellation Pharmaceuticals: Research Funding; Aptose Biosciences: Research Funding; Array Biopharma: Research Funding; Janssen Pharmaceuticals: Research Funding; Incyte: Research Funding.

Description: Introduction: 18Fluoro-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is one of the most widely used imaging techniques to detect multiple myeloma (MM). Intracellular FDG uptake depicts in vivo metabolic activity, which can be seen in both malignant and non-malignant cells, resulting in limited sensitivity and specificity. Our group showed preclinically that tracing MM dissemination using a CD38-directed human antibody, daratumumab, that is radioconjugated with copper-64 via the chelator DOTA (64Cu-DOTA-Dara), led to improved sensitivity and specificity over that of FDG (Caserta et al, Blood 2018). Herein, we report the results of a Phase 1 trial (NCT#03311828) designed to 1) assess the safety and feasibility of 64Cu-DOTA-Dara PET/CT and 2) to evaluate and characterize the ability of 64Cu-DOTA-Dara to accurately detect or exclude MM lesions compared with FDG PET/CT. Methods: Patients with biopsy-proven MM and/or a plasmacytoma received an FDG PET/CT scan within 60 days of enrollment. On Day 0, patients were infused with unlabeled ("cold") Dara at one of four dose levels (0 mg, 10 mg, 45 mg, 95 mg) to optimize biodistribution of radioconjugated 64Cu-DOTA-Dara, especially in the liver and the spleen. Within 6 hours of unlabeled Dara administration, patients received 64Cu-DOTA-Dara at a dose of 13.63-16.68 mCi (~5 mg). Whole-body PET scans were obtained at 24 hours and at 48 hours (the latter scan encompassing known tumors). 64Cu-DOTA-Dara standardized uptake values (SUV) were evaluated in MM lesions and normal organs, which were then compared with values from standard FDG PET/CT. Biopsies were performed on accessible discordant lesions. Results: A total of 10 Dara-naïve patients were imaged. Patients were treated with 0 (n=3), 10 (n=3), 45 (n=3), or 95 mg (n=1) of unlabeled Dara. Four patients had newly diagnosed disease, one had biochemical relapse, one had a recurrent plasmacytoma by MRI, and four had possible recurrence by standard PET/CT. No significant adverse events were observed from either cold or 64Cu-DOTA-Dara. With the exception of the one patient with a recurrent plasmacytoma, radiolabeled antibody was eliminated from systemic circulation in subjects analyzed at the first three dose levels within 30 min post injection. In the patient with a recurrent plasmacytoma, the radiolabeled antibody was elevated in the blood for over two days. One newly diagnosed patient had extensive disease by FDG PET and had a biopsy-proven target lesion in the sternum, which had an SUVmax of 14.7 on 64Cu-DOTA-Dara PET/CT vs. 3.3 onFDG PET/CT. A second biopsy from the same patient was taken from a discordant iliac crest lesion (positive for 64Cu-DOTA-Dara but negative for FDG PET/CT) that showed 20-30% MM cell infiltration. In another patient, an iliac crest lesion was 64Cu-DOTA-Dara positive and FDG-negative; biopsy revealed 6% plasmacytosis in the bone. A third patient had an FDG PET/CT positive pleural lesion with an SUVmax of 8.98 and negative on 64Cu-DOTA-Dara (Figure 1A). The lesion did not show recurrence upon biopsy. Furthermore, 64Cu-DOTA-Dara PET/CT yielded superior imaging of bone lesions in the calvarium (Figure 1B). Escalating doses of unlabeled Dara decreased liver and spleen uptake by 64Cu-DOTA-Dara. Conclusions: In this ongoing study, 64Cu-DOTA-Dara PET/CT imaging is to date safe and provides whole body imaging of MM. Further dose escalation of cold Dara (145 mg, 195 mg) is planned to optimize background interference. This modality has the potential to improve sensitivity and specificity over FDG PET/CT scanning in early-stage MM as well as in recurrent disease. Disclosures Krishnan: Celgene, Janssen, Sanofi, BMS: Consultancy; Sutro BioPharma, zPredicta: Consultancy; Amgen, Takeda: Speakers Bureau; Celgene, Z Predicta: Other: Stock Ownership; Takeda: Research Funding. Palmer:Gilead Sciences: Consultancy. Rosenzweig:Celgene, Takeda: Speakers Bureau. Wu:ImaginAb, Inc.: Consultancy, Other: Board Member.

Description: Background :Carfilzomib (CFZ) is a novel irreversible proteasome inhibitor (PI) approved for relapsed/refractory multiple myeloma, but its safety and efficacy in AL amyloidosis is not known. We report updated results of an investigator-initiated, multi-center, Phase I/II study of CFZ in AL (NCT01789242), including additional patients (pts) treated in the expansion cohort. Methods: Eligible pts (relapsed or refractory AL after ≥1 prior therapy; Mayo cardiac stage I or II; LVEF ≥40%; CrCl≥30; CFZ-naive) received CFZ over 30 minutes on days 1, 2, 8, 9, 15, 16 every 28 days, for 8 cycles, given at 20 mg/m2 on days 1, 2 of cycle 1, then at 27, 36, or 45 mg/m2 (depending on cohort) thereafter. Pre-CFZ hydration was recommended during cycle 1, but could be modified or omitted at investigator discretion. Responding pts could continue on a day 1, 2, 15, 16 schedule at investigator discretion. Dexamethasone 20mg with each CFZ dose was added if no VGPR after cycle 4. Primary objectives were safety and determination of MTD. A 3+3 dose escalation design was used, with a planned expansion cohort at MTD. Responses were based on updated AL consensus guidelines. Pts completing ≥2 cycles (or progressing before 2 cycles) were evaluable for response; all treated pts were evaluated for safety. Cardiac function was monitored in all pts by serial NT-proBNP and echocardiograms. Data cutoff was 6/23/16. Results: From June 2013 - June 2016, 28 eligible pts were enrolled and treated. Median age was 64 (range 43 - 81); 64% were male. Median time from diagnosis was 31 mos., with median of 2 prior regimens (range 1-5), including bortezomib (96%), IMiDs (43%) and stem cell transplant (46%). Thirteen (46%) were refractory to last therapy, and 10 (36%) were PI-refractory (9 bortezomib, 1 ixazomib). Involved organs included kidney (64%), heart (50%), nerve (25%), GI tract (21%), soft tissue (14%), and liver (11%); 13 pts had ≥2 major organs involved. Median baseline NT-proBNP was 542 pg/ml (range 20 - 13571), and median baseline difference in free light chains (dFLC) was 138 mg/L (range 44 - 4709). There were no DLTs at 20/27 and 20/36 mg/m2. At 20/45 mg/m2, there were 2 first-cycle DLTs of grade 3 fatigue ≥7 days, making 20/36 mg/m2 the MTD. Eighteen more pts have enrolled at MTD. Median number of cycles is 6 (range 1-25+), with 10 pts completing the planned 8 cycles (7 continuing on maintenance), 3 ongoing before cycle 8, and 15 stopping early (9 for AE's, 4 for no response, 2 other). Most common drug-related AE's to date are fatigue (36%), increased creatinine (29%), nausea (25%), dyspnea (18%), anemia (18%), diarrhea (14%), pyrexia, chills, and hypertension (11% each). Grade 3/4 AEs (all-cause) occurred in 20 (71%) pts, including several grade 3/4 cardiac or pulmonary AEs: hypoxia (n=1), lung infection (n=2), chest pain (n=1), hypotension (n=1), hypertension (n=3), decreased ejection fraction/CHF (n=3), and symptomatic ventricular tachycardia (n=2, 1 with cardiac arrest requiring defibrillation). There have been no grade 5 AEs. Of 24 response-evaluable pts, 15 (63%) have responded hematologically (3 CR, 8 VGPR, 4 PR), including 6 of 8 evaluable PI-refractory pts (1 CR, 2 VGPR, 3 PR). Responses have occurred at all dose levels (Table). Dex was added in 5 pts, with 3 response upgrades. Five (21%) pts have had organ responses (3 kidney, 1 GI, 1 liver) to date. With median follow-up of 16 mos. (range 0.5 - 32), 9 pts have had hematologic progression, and 2 have died. To date, 11 pts have had NTproBNP increases of ≥30% and ≥300 pg/ml on CFZ. For 5 this correlated with progressive clinical and/or echocardiographic signs of cardiac dysfunction; the other 6 lacked objective signs of worsening cardiac function, with either no symptoms (n=4) or progressive fatigue (n=2). Conclusions: CFZ monotherapy is feasible and effective in relapsed/refractory AL amyloidosis, with MTD identified as 20/36 mg/m2 as a 30-minute infusion. Hematologic response rates are promising in this bortezomib-exposed population, including in PI-refractory pts. Cardiac, pulmonary, and renal toxicities were common, warranting close monitoring and dose reductions as appropriate. Similar to IMiDs, NT-proBNP can increase in pts receiving CFZ, without always correlating with progressive cardiac dysfunction, potentially confounding its use as a marker of cardiac response/progression in this setting. Disclosures Cohen: Bristol-Meyers Squibb: Consultancy, Research Funding; Janssen: Consultancy. Landau:Spectrum Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Prothena: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx/Amgen: Research Funding; Janssen: Consultancy. Scott:Amgen: 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; Incyte: Membership on an entity's Board of Directors or advisory committees. Kaufman:Novartis: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Pharmacyclics: Consultancy; Incyte: Consultancy. Vesole:Janssen: Speakers Bureau; Novartis: Speakers Bureau; Celgene: Speakers Bureau; Takeda: Speakers Bureau; Amgen: Speakers Bureau. Lentzsch:BMS: Consultancy; Celgene: Consultancy, Honoraria. Gomes:Criterium, Inc: Employment. Comenzo:Karyopharm: Research Funding; Janssen: Consultancy, Research Funding; Prothena: Consultancy, Research Funding; Takeda: Consultancy, Research Funding. Durie:Takeda: Consultancy; Janssen: Consultancy; Amgen: Consultancy.

Description: Introduction: Despite significant progress in the treatment of multiple myeloma (MM), the disease remains incurable and typically follows a pattern of multiple responses and relapses. In the relapsed/refractory MM setting (RRMM), outcomes for patients may be particularly discouraging. New treatments that are safe and effective are therefore of urgent need for this population. Since its FDA approval in 1998 for the treatment of rheumatoid arthritis, leflunomide has been used in over 300,000 patients worldwide. Leflunomide is hepatically cleared and has a favorable toxicity profile even when given over long periods. Its primary mechanism of action is inhibition of pyrimidine synthesis by targeting dihydroorotate dehydrogenase, thus achieving anti-proliferative effects on B and T lymphocytes. The anti-neoplastic potential of this agent has been studied in a number of pre-clinical tumor models. Leflunomide's immunoregulatory action may be related to functional inhibition of CD4+ effector T cells, including Th17 cells as well as dysregulation of T regulatory cells (Tregs). We found that leflunomide-treated C57BL/KaLwRij mice engrafted with 5TGM1 cells had more robust expansion of CD8+ cytotoxic T cells and subsequent decrease of CD4+ Tregs compared to untreated mice. We have also noted that leflunomide impairs growth of MM cells at least partly through inhibition of PIM kinases and c-Myc signaling. We present here final results from a phase 1 study of leflunomide in patients with RRMM. Methods: This single center, single agent, phase 1 dose-escalation trial was designed to determine the maximum tolerated dose of leflunomide in patients with RRMM. The trial implemented a modified rolling six phase 1 dose escalation design. The primary objectives were as follows: 1) to determine the maximum tolerated dose and recommended phase 2 dose of leflunomide; 2) to assess the safety and tolerably of leflunomide at each dose level by evaluation of toxicities. Leflunomide was administered at a loading dose of 100 mg daily for the first three days, then daily in 28-day cycles. The starting dose of daily leflunomide was 20 mg daily, with dose escalation in increments of 20 mg/day, up to 60 mg/day. Dose de-escalation in decrements of 10mg/day was planned. Results: A total of 12 patients have been enrolled starting in December 2015 and treated. The median age is 68 (range 48 - 85), and the median number of prior therapies is 5 (range: 3 - 14). Nine patients had prior autologous stem cell transplant. Double refractory (lenalidomide/bortezomib) disease was noted in 9 patients. High-risk cytogenetics were observed in 5 patients including 2 patients with del17p. All 12 subjects were evaluable for toxicity. One subject was not evaluable for response because of non-compliance. Of the eleven patients evaluable for response, the median number of cycles was 3 (range 1- 15). The median follow up was 177 days (range: 42 - 602). Three patients were treated on DL 1 (20 mg) and three on DL3 (40 mg) without incidence of DLT. At DL5 (60 mg), one patient had a DLT with grade III elevation of alanine aminotransferase; an additional three patients were enrolled at this dose level without further DLTs. One out of 12 subjects remains on treatment, 8 patients were removed from study due to disease progression, two due to adverse events (bacteremia at 60 mg, possibly related to study drug and angioedema at 40 mg, not related to study drug) and one from noncompliance. The most common toxicities were hematologic. There were 4 patients with grade 1 or 2 neutropenia on the 20 and 40 mg dose levels and 1 patient with grade 4 lymphopenia on the 40 mg dose. Except for the DLT, all non-hematologic toxicities were ≤ grade 2. Response: Although not all patients were treated at the 60 mg dose, a clinical benefit rate of 90% has been seen, with 9/10 achieving stable disease (SD). The median duration of SD among 9 patients thus far is 56 days (range: 27-401). In the five evaluable patients with high risk cytogenetics, four of them achieved a clinical benefit. Two subjects had SD lasting nearly one year or longer. In this small cohort, no association between dose and benefit was observed. Conclusion: Leflunomide is a safe and well-tolerated oral option for patients with RRMM, with a clinical benefit from single agent dosing. On the basis of our preclinical work showing synergistic inhibition of MM using leflunomide, pomalidomide, and dexamethasone, we plan clinical testing of this drug combination. Disclosures Rosenzweig: Celgene: Speakers Bureau. Krishnan:Janssen: Consultancy, Speakers Bureau; Sutro: Speakers Bureau; Onyx: Speakers Bureau; Takeda: Speakers Bureau; Celgene: Consultancy, Equity Ownership, Speakers Bureau. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding.

Description: Key Points AD STAT1 GOF is the most common genetic cause of inherited CMC and is not restricted to a specific age or ethnic group. STAT1 GOF underlies a variety of infectious and autoimmune features, as well as carcinomas and aneurysms associated with a poor outcome.