ALBERT

Description: Abstract 2610 Background: Acute leukemia, characterized by the presence clonal hematopoietic cells in peripheral blood and bone marrow, comprises approximately 40% of newly diagnosed leukemias. First line treatment for acute leukemias with multi-agent cytotoxic chemotherapy is usually associated with significant toxicity. Advances in therapy have been slow, and nearly all effective therapies lead to prolonged marrow suppression and toxicities associated with subsequent cytopenias. Herein, we describe the biological and pharmacokinetic properties of TGR-1202, a novel small molecule PI3Kδ inhibitor with scope to be developed as a safe and effective therapy for acute myeloid (AML) and lymphoblastic (ALL) leukemia. Material & Methods: Activity of TGR-1202 against individual isoforms of the PI3K enzyme was determined via enzyme, cellular, and whole blood based assays. Potency of the compound was confirmed via leukemic cell viability and Annexin V/PI staining besides testing for inhibition of pAkt, a downstream kinase regulating cell survival and growth. These assays were conducted with cell lines (CCRF-CEM, HL-60, and MOLT-4) and patient derived cells. Anti-tumor efficacy of the compound was studied in vivo with the subcutaneous MOLT-4 xenograft model. Lastly, ADME and pharmacokinetic properties of the molecule were determined. Results: TGR-1202 demonstrated significant potency against PI3Kδ (22.2 nM) with several fold selectivity over the α (〉10000), β (〉50), and γ (〉48) isoforms. Additionally, the compound inhibited B-cell proliferation (24.3 nM) and FcεR1 induced CD63 expression in human whole blood basophils (68.2 nM) indicating specificity towards the delta isoform. Viability testing demonstrated that the compound caused a dose-dependent inhibition in growth of immortalized as well as patient-derived AML and ALL cells. Reduction in viability was accompanied by a reduction in pAKT (〉50% @ 0.3–1 μM) along with a significant induction in apoptosis in both cell lines (CCRF-CEM, HL-60, and MOLT-4) and patient samples. In tumor xenografts, oral administration of 150 mg/kg RP5264 salt over a 25-day period resulted in significant inhibition (〉50%) of MOLT-4 tumor growth in mice. Pharmacokinetic studies across species indicated good oral absorption (〉40% bioavailability for mice, rat, and dog) with favorable plasma concentrations (3–10 μM @ 20 mg/kg for mice, rat, and dog) relevant for efficacy. In addition, early toxicological evaluation of the molecule indicated a MTD 〉 500 mg/kg over a 14-day treatment period in Balb/c mice. Conclusions: TGR-1202, primarily, through its activity at the δ isoform of PI3K, has activity in both myeloid and lymphoid acute leukemia cell lines and primary patient tumors. Further evaluation of this molecule in the treatment of AML and ALL is justified, and current testing of TGR-1202 in various leukemia cell lines and within a variety of primary leukemias is ongoing. Disclosures: Vakkalanka: Rhizen Pharmaceuticals S A: Employment, Equity Ownership. Viswanadha:Incozen Therapeutics: Employment. Niecestro:TG Therapeutics, Inc.: Consultancy, Equity Ownership. Sportelli:TG Therapeutics, Inc.: Employment, Equity Ownership.

Description: Introduction: Ublituximab (UTX) is a novel chimeric mAb targeting a unique epitope on the CD20 antigen, glycoengineered to enhance affinity to FcγRIIIa receptors, thereby demonstrating significantly greater ADCC than rituximab. UTX monotherapy in patients (pts) with rituximab relapsed/refractory NHL and CLL has reported a 43% ORR (ASCO 2014). TGR-1202 is a next generation, once daily, oral PI3Kδ inhibitor which notably lacks the hepatotoxicity associated with other PI3Kδ inhibitors, and is active in pts with relapsed and refractory hematologic malignancies (EHA 2014). UTX and TGR-1202 have shown synergistic activity in-vitroin various lymphoid cell lines (Lugano 2013). This Phase 1 trial evaluates safety and efficacy of the combination of a glycoengineered anti-CD20 (UTX) and a PI3Kδ inhibitor (TGR-1202) in pts with heavily pre-treated relapsed or refractory CLL and NHL. Methods: Eligible pts have relapsed/refractory CLL or NHL with an ECOG PS ≤ 2. A 3+3 design evaluates cohorts of CLL and NHL pts independently with UTX dosed on Days 1, 8, 15 of Cycles 1 & 2 followed by maintenance therapy. UTX starts at 600 mg in Cohort 1 and increases to 900 mg for pts with CLL and is fixed at 900 mg for pts with NHL. TGR-1202 starts at 800 mg QD in Cohort 1 and is increased in subsequent cohorts. An amendment in July 2014 was introduced to include an improved micronized formulation of TGR-1202, starting at 400 mg once daily and increasing in subsequent cohorts. There are no limits on prior therapy, and patients with Richter’s Transformation or who are refractory to prior PI3Kδ inhibitors or BTK inhibitors are eligible. Primary endpoints: Safety and Dose Limiting Toxicities (DLT). Secondary endpoints: Efficacy (ORR, CR rate). Results: As of August 2014, 21 pts have been enrolled: 8 CLL/SLL, 7 DLBCL, 5 Follicular Lymphoma, and 1 patient with Richter’s Transformation. Median age is 64 years (range 35-82); 12 male/9 female. Median prior Tx = 3 (range 1-9); median ECOG PS = 1. All pts are evaluable for safety. Adverse events have been manageable with no safety concerns noted. Day 1 infusion related reactions (IRR) were the most common treatment related adverse event (48%), with all but one event Grade 1 or 2 in severity, followed by neutropenia (38%), diarrhea (29%), and nausea (29%). Notably, no events of TGR-1202 related hepatotoxicity have been reported to date. All IRR and neutropenia events have been manageable with dose delays. One neutropenia related dose delay in a CLL patient at UTX 600 mg + TGR 800 mg met the criteria for a DLT, necessitating enrollment of additional pts into this cohort. No other DLTs have been reported, including at higher dose levels. Fifteen pts were evaluable for efficacy with 6 pts too early for response assessment. Among evaluable pts, 80% displayed a reduction in tumor burden at first efficacy assessment, despite pts exhibiting a number of high-risk characteristics, including 3/5 CLL pts having 17p/11q deletion and a median of 6 prior lines of therapy amongst pts with FL. Objective responses are summarized below: Table TypePts (n)PRn (%)ORRn (%)PD(n)% pts ≥ SD for 12 wksMedian Prior Rx CLL/SLL54 (80%)4 (80%)-5 (100%)2 (1 – 3) Richter’s1---1 (100%)1 FL4---4 (100%)6 (3 – 8) DLBCL52 (40%)2 (40%)14 (80%)3 (1 – 6) Total156 (40%)6 (40%)114 (93%)3 (1 – 8) Amongst pts with CLL, 2/2 pts with normal cytogenetics achieved a PR including a patient with prior treatment with a BTK inhibitor, while 2/3 pts with presence of 17p/11q deletion achieved a PR, with the remaining patient having SD with a 44% nodal reduction at first assessment. Conclusions: Preliminary data suggests the combination of UTX + TGR-1202 is well tolerated with early signs of clinical activity in heavily pre-treated and high-risk patient subsets. Enrollment is ongoing with at least 30 patients anticipated. Disclosures Lunning: Onyx: Consultancy; Alexion: Consultancy; Gilead: Consultancy; Spectrum Pharmaceuticals: Consultancy. Schreeder:TG Therapeutics, Inc.: Research Funding. Pauli:TG Therapeutics, Inc.: Consultancy. Miskin:TG Therapeutics, Inc.: Employment, Equity Ownership. Sportelli:TG Therapeutics: Employment, Equity Ownership. Weiss:TG Therapeutics, Inc.: Employment, Equity Ownership. Vakkalanka:Rhizen: Employment, Equity Ownership. Viswanadha:Incozen: Employment. O'Brien:Amgen, Celgene, GSK: Consultancy; CLL Global Research Foundation: Membership on an entity's Board of Directors or advisory committees; Emergent, Genentech, Gilead, Infinity, Pharmacyclics, Spectrum: Consultancy, Research Funding; MorphoSys, Acerta, TG Therapeutics: Research Funding.

Description: Background: TGR-1202 is a novel, next generation PI3Kδ inhibitor which exhibits a differentiated safety profile from other PI3Kδ inhibitors, both approved and in development, and has demonstrated activity in patients (pts) with advanced heme malignancies (ASH 2014). Herein we present updated safety and efficacy results from a Ph I study of TGR-1202 in pts with rel/ref CLL and lymphoma. Methods: TGR-1202 is administered orally once-daily (QD) following a 3+3 dose escalation design. Eligible pts have rel/ref non-Hodgkin lymphoma (NHL), chronic lymphocytic leukemia (CLL), or other B-cell malignancy and an ECOG PS ≤ 2. Endpoints include safety, PK/PD, and efficacy. Results: As of August 2015, 75 pts are evaluable for safety including pts with CLL, FL, Hodgkin's (HL), DLBCL, MCL, and MZL. Patients had a median age of 65 yo (range: 22-85), 67% male, ECOG 0/1/2: 26/47/2, median prior Tx: 3 (range: 1-14), and 49% refractory to prior Tx. No Gr≥3 AEs were observed in ≥10% of pts. AEs (all grades, all causality) in 〉20% of pts were limited to nausea (44%, Gr3/4 0%), diarrhea (36%, Gr3/4 1%), and fatigue (31%, Gr3/4 3%). Notably, general tolerability and the incidence of hepatotoxicity and colitis appear significantly less than that reported with other agents in this class. Expansion cohorts are open at 800 mg, 1000 mg, and 1200 mg QD. Of 16 evaluable CLL pts, 15 (94%) achieved a nodal PR (median nodal ↓ of 76%), of which 10 (63%) achieved a PR per Hallek 2008 criteria. Among the 32 evaluable NHL patients, 10 achieved an objective response, including 3/11 evaluable patients with DLBCL, while responses have been limited in pts with MCL (1/5) and HL (1/9). Of the 16 evaluable indolent NHL (FL & MZL) pts, 14 (88%) have achieved reductions in tumor burden with 6 pts on study for over 12 cycles (and durations upwards of 29+ cycles), with 5/12 FL and 1/4 MZL pts achieving an objective response to date. Notably, a strong exposure-response relationship has been observed. Of the 24 patients starting TGR-1202 at 800 mg or 1200 mg of the micronized formulation, 19 (79%) remain on therapy, with 9/18 (50%) evaluable pts (6 too early to evaluate) achieving an objective response to date (range on study 3 - 49+ weeks). Conclusions: TGR-1202 is well tolerated in pts with rel/ref heme malignancies with a distinct safety and tolerability profile from other PI3K-delta inhibitors (with 43% of pts on study 6+ Cyc) and promising activity in CLL and NHL. Enrollment continues in expansion cohorts and registration directed Phase 3 studies are planned. Disclosures Flinn: Celgene Corporation: Research Funding. Fenske:Millennium/Takeda: Research Funding; Celgene: Honoraria; Seattle Genetics: Honoraria; Pharmacyclics: Honoraria. Deng:TG Therapeutics, Inc.: Honoraria, Research Funding; Seattle Genetics: Research Funding. Kuhn:TG Therapeutics, Inc.: Consultancy; Otsuka American Pharmaceutical: Consultancy; Azaya Therapeutics: Consultancy. Miskin:TG Therapeutics, Inc.: Employment, Equity Ownership. Sportelli:TG Therapeutics, Inc.: Employment, Equity Ownership. Vakkalanka:Rhizen Pharmaceuticals SA: Employment, Equity Ownership.

Description: INTRODUCTION: The phosphatidylinositol 3-kinase (PI3K) pathway is consistently activated in relapsed/refractory Hodgkin lymphoma (HL). Activation of this pathway is critical for transformation and also for the angiogenic switch in malignant cells. Thus, inhibition of PI3K holds the promise of a multistep strategy for tumor inhibition. Expression of the δ and γ isoforms of PI3K is restricted to cells of the hematopoietic system, suggesting that RP6530, a novel PI3K δ/γ Inhibitor, might represent a promising approach in the treatment of lymphomas. The CD30-directed antibody-drug conjugate, Brentuximab Vedotin (BV), has recently been reported to induce a high overall response rate in relapsed/refractory HL, but is associated with limited response duration. Combination therapies aimed at enhancing the anti-tumor activity of BV and eventually reducing its side effects may have significant clinical impact in the treatment of relapsed/refractory HL. Our study aimed at investigating the activity and mechanism(s) of action of RP6530 in combination with BV in preclinical HL models. METHODS: Three HL cell lines, including L-540, KM-H2 and L-428, were used to investigate the effects of RP6530 and BV on cell growth and survival in vitro. Western blotting (WB) was used to assess the effects of RP6530 on both the PI3K/AKT and MAPK pathways. The efficacy and mechanism of action of RP6530/BV combination was finally analyzed in NOD/SCID mice bearing HL cell line xenografts. To analyze tumor vasculature, we performed in vivo biotinylation of vascular endothelial proteins. RESULTS: Inhibition of the PI3K pathway byRP6530 (1.25 - 20 µM) resulted in reduced Akt phosphorylation, decreased cell proliferation (range, 30% to 40%) and induction of apoptosis (range, 30% to 60%) of HL cells. Interestingly, RP6530 treatment also resulted in an early dose-dependent inhibition of ERK1/2 phosphorylation. BV, at clinically achievable concentrations induced a significant growth inhibition (range, 30% to 40%) in all HL cells. Remarkably, when RP6530 was combined with BV at minimal, or mildly inhibitory concentrations, a highly synergistic inhibition in all HL cells was observed. Following a 48 hour exposure, RP6530 (5 μM) and BV (10 ng/ml) synergistically inhibited the mean (±SEM) growth of HL cells (RP6530: 9 ± 3%; BV: 12 ± 3%; RP6530/BV: 26 ± 3%). While single agents induced only 20% HL cell death, combination of RP6530 and BV caused remarkable induction of apoptosis (90%), with Combination Index (CI) as low as 0.003. Consistent with the lack of vascular CD30 expression, caspase-3 staining of L-540 tumor sections failed to detect apoptotic Tumor Endothelial Cells (TECs) in BV-treated tumors while a marked apoptosis of TECs was detected in mice receiving RP6530 alone or the combination therapy. Additionally, a significant increase of tumor necrosis (2-fold increase, P ≤ 0.0001) was detected in mice receiving RP6530/BV as compared to single agents. Apoptosis of TECs resulted also in a significant reduction of tumor vessel density with a 90% decrease of vessel density over controls being observed in mice receiving RP6530 alone. This finding was paralleled by histological observation of severe disruption of the tumor vasculature, which was deficient in capillaries and lacked most of its branches and sprouts. In keeping with the lack of apoptosis in TECs, treatment with BV alone failed to affect L-540 tumor vessel density and vasculature morphology. Furthermore, the combined RP6530 (100 mg/kg/BID/3 weeks) and BV (0.5 mg/kg/q4x4d) treatment significantly reduced the growth of L-540 and KM-H2 nodules, resulting in a mean tumor growth inhibition of 50% (P ≤.0001), compared to single agents. No mice experienced any apparent treatment-related toxicity. CONCLUSIONS: The novel PI3K δ/γ inhibitor RP6530 synergistically enhances the anti-tumor activity of BV by increasing drug-induced cell death and inhibiting tumor angiogenesis in HL cell line xenografts. These data provide a strong rationale for clinical studies using RP6530/BV in combination in refractory/relapsed HL patients and warrants clinical evaluation. Disclosures Viswanadha: Incozen: Employment. Vakkalanka:Rhizen Pharmaceuticals SA: Employment, Equity Ownership.

Description: INTRODUCTION: The phosphatidylinositol 3-kinase (PI3K) pathway is consistently activated in relapsed/refractory Hodgkin lymphoma (HL), suggesting that TGR-1202, a novel inhibitor of the δ isoform of PI3K (PI3K-δ) in clinical development for a variety of hematologic malignancies, might represent an attractive therapeutic option. The anti-CD30 monoclonal antibody, Brentuximab Vedotin (BV), a conjugate of Brentuximab and the microtubule-disrupting agent, monomethyl auristatin E (MMAE), induced a 75% objective response rate with limited duration of response in relapsed/refractory HL. Combination therapies aimed at enhancing the anti-tumor activity of BV may have the potential for significant clinical impact in the treatment of relapsed/refractory HL. Therefore, the present study was aimed at investigating the activity and mechanism(s) of action of the PI3K-δ inhibitor TGR-1202 in combination with BV. METHODS: Three HL cell lines, including L-540, KM-H2 and L-428, were used to investigate in vitro cell growth and cell survival. The activity of TGR-1202 and BV, each as single agents and in combination, on tubulin polymerisation and microtubule distribution across cell membrane was investigated by means of a tubulin polymerisation assay and a three-dimensional volume rendering technique. The efficacy of TGR-1202/BV in combination was finally analyzed in NOD/SCID mice with HL cell line xenografts. RESULTS: As compared to single agents, exposure of L-540, KM-H2, and L-428 cell lines to the TGR-1202 (10 µM) and BV (10 ng/ml) combination resulted in a synergistic inhibition of mean (±SEM) cell growth (TGR-1202: 40 ± 4%; BV: 30 ± 2%; TGR-1202/BV: 85 ± 1%, P ≤.0001) and a marked increase of cells in G2/M phase (TGR-1202/BV: 72 ± 3%). This finding was paralleled by a 3-fold reduction of cells in S phase (TGR-1202: 25 ± 1%; BV: 23 ± 1%; TGR-1202/BV: 9 ± 1%) and a marked Cyclin B1 and p21 overexpression. Upon TGR-1202/BV exposure, HL cell lines showed a 3-fold increase in apoptosis over that observed with single agents (TGR-1202: 27 ± 2%; BV: 27 ± 2%; TGR-1202/BV: 75 ± 2%, P ≤.0001). Activation of caspase-8, -9, -3, and cleavage of PARP were reversed by the pan-caspase inhibitor Z-VADfmk, supporting a caspase-dependent apoptosis. Analysis of α-tubulin by immunofluorescence showed a synergistic microtubule disruption induced by TGR-1202/BV treatment with a strong α-tubulin inhibition (40%, P ≤.0001) and a low diffuse staining with irregular microtubule fragments throughout the cytosol. In addition, TGR-1202/BV in combination strongly inhibited tubulin polymerization in a time-dependent manner, suggesting that TGR-1202/BV treatment abrogates microtubule assembly and disrupts microtubules. In NOD/SCID mice bearing human HL xenografts, TGR-1202 (150 mg/Kg) and BV (0.5 mg/Kg) combined treatment significantly reduced the growth of L-540 and L-428 nodules, resulting in an average 50% tumor growth inhibition (P ≤.0001) compared to single agent treatments. No systemic toxicity was observed in mice receiving the combination therapy. Interestingly, a significant increase of microtubule disruption resulting in a marked tumor necrosis (5-fold increase, P ≤.0001) detected in mice receiving TGR-1202/BV combination as compared to mice receiving single agents. Finally, TGR-1202/BV was found to interfere with the mitotic spindle integrity, which may suggest that the cytotoxicity of the combined TGR-1202/BV treatment primarily arises from the inhibition of tubulin polymerization. CONCLUSIONS: The novel PI3K-δ inhibitor TGR-1202 synergistically enhances the anti-tumor activity of BV by increasing drug-induced cell death and tubulin disruption in HL cell line xenografts. These data provide a strong rationale for clinical studies using TGR-1202/BV in combination in refractory/relapsed HL patients. A Phase I study of the combination of TGR-1202 and BV is ongoing in patients with relapsed/refractory HL. Disclosures Viswanadha: Incozen: Employment. Sportelli:TG Therapeutics: Employment, Equity Ownership. Vakkalanka:Rhizen: Employment, Equity Ownership.

Description: Introduction: Phosphoinositide-3-kinases (PI3Ks) are pivotal in cell proliferation and survival, cell differentiation, intracellular trafficking and immunity. The delta (δ) and gamma (γ) isoforms of PI3K are often dysregulated in various hematologic malignancies and therefore key targets for the treatment of lymphomas/ leukemia. RP6530 is a novel, highly specific dual PI3K δ/γ inhibitor with nanomolar inhibitory potency that effectively inhibits AKT phosphorylation and induces apoptosis in lymphoma/leukemic cell lines. We herein present results from an ongoing Phase I, first-in-human, dose escalation study of RP6530 (NCT02017613). Methods: The dose escalation will determine the maximum tolerated dose (MTD) of RP6530 using a standard 3+3 design. Patients (pts) with a confirmed diagnosis of hematological malignancy and at least one prior therapy are eligible. Additional eligibility criteria include an ECOG performance status ≤ 2, measurable/evaluable disease, and life expectancy of at least 12 weeks. Primary endpoints are safety and pharmacokinetic (PK) and are supported by secondary endpoints such as pharmacodynamic and efficacy parameters (overall and complete response rates) and correlative biomarkers. RP6530 is given orally twice daily in 28-day cycles until disease progression, unacceptable toxicity, or withdrawal from study. The study is designed to enroll up to 120 pts in the dose-escalation and expansion phase. Adverse events (AE) are assessed using the CTCAE v4.0/IWCLL guidelines as applicable. Efficacy evaluations are conducted every 8 wks. Results: Twenty six pts were enrolled to date across various dose levels: BID 25mg, 50mg, 100mg, 200mg, 400mg, 600mg and 800mg. Sixteen were males; ECOG score was 0/1/2 in 20/3/3 pts, respectively, with a mean age of 59 yrs (range 20-83). Pts had a median of 5 (range: 1-11) prior treatment regimens, and 19 were refractory to prior treatments. Malignancy categories included HL (9), TCL (4), DLBCL (4), MCL (3), CLL/SLL (2), FL (1), MZL (1), WM (1), and MM (1). Majority of them were considered as "high tumor burden patients" as per different prognostic scores. Sixteen patients were discontinued mainly due to disease progression. RP6530 was well tolerated with no DLT reported to date. Majority of AEs were mild and resolved with/without concomitant medication. None of Grade III/IV AEs or SAEs were deemed related to RP6530. No drug related increase in ALT/AST, colitis, pneumonia, or neutropenia was observed to date. Dose escalation is currently ongoing at 800 mg BID. Single agent activity, manifested by a reduction in tumor size by CT or PET scan, was noticed at ≥ 200 mg BID. The efficacy observations are mostly in indications, that are difficult-to-treat or with minimal therapeutic options. The ORR is 20 % [CR 2 (10 %) + PR 2 (10%)] with disease control rate of 65%. The responders are HL (2), PTCL (1) and DLBCL (1). The CLL/SLL patients, known to be the best responders to selective PI3K inhibitors, were not included in dose-cohorts ≥ 200 mg BID. Clinical response was associated with a significant reduction in pAKT expression. Dose-proportional increase in plasma concentrations were observed upon oral administration of RP6530. Conclusions: To date, RP6530 has been well tolerated in pts with heavily pre-treated relapsed/refractory hematologic malignancies. Reported toxicities were manageable with no DLTs. Single agent activity was evident in difficult-to-treat patients at ≥ 200 mg BID. Enrolment continues at higher dose cohorts. Updated safety, efficacy, PK, and PD data will be presented at the annual meeting. Disclosures Barde: Rhizen Pharmaceuticals SA: Employment. Kumar:Rhizen Pharmaceuticals SA: Employment. Viswanadha:Incozen: Employment. Vakkalanka:Rhizen Pharmaceuticals SA: Employment, Equity Ownership. Ghia:Adaptive: Consultancy; GSK: Research Funding; Acerta Pharma BV: Research Funding; Roche: Consultancy, Research Funding; Pharmacyclics: Consultancy; AbbVie: Consultancy; Janssen: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau.

Description: Background The constitutively activated PI3K/AKT/mTOR pathway plays a key role in the proliferation and survival of cancer cells. Specific inhibitors of the delta isoform of PI3K, such GS-1101 (idelalisib), have shown promising activity in the treatment of B-cell lymphoma. In contrast, some data from models of T-cell lymphoma (TCL) have suggested that these diseases may require inhibition of both PI3Kdelta and PI3Kgamma for optimal cytotoxicity. Proteasome inhibitors, such as carfilzomib, potently inhibit the activation of NF-kappaB (NF-kB) by preventing degradation of the NF-kB inhibitor IkB. We hypothesize that inhibition of this pathway at both the proximal (PI3K) and distal (NF-kB) aspects, using both inhibitors of PI3K and proteasome, could lead to a synergistic cyototoxic effect in models of lymphoma. Methods Cytotoxicity of TGR-1202 and carfilzomib was studied in a panel of B and T-cell lymphoma cell lines. Growth inhibition was determined using Cell TiterGlo that measures ATP produced by live and proliferating cells. Cell death was determined by flow cytometry, using the probes Annexin V and propidium iodide. Drug: drug synergy was determined by calculating relative risk ratio (RRR). Values below 1 indicate synergy, with smaller RRR values corresponding to higher levels of synergy. Results TGR-1202 as a single agent active against a panel of diverse B- and T-lymphomas. By the Cell TiterGlo assay, the concentration required to inhibit growth by 50% (IC50) following 48-hour exposure ranged from 10 uM to 15 uM in most of the cell lines. Maver and H9, representing mantle cell lymphoma (MCL) and TCL respectively, were more resistant to TGR-1202. Carfilzomib, on the other hand, is a potent inhibitor of B- and T cell lymphomas, with an IC50 in the range of 2-8 nM most lymphomas (Table 1). Remarkably, when TGR-1202 is combined with carfilzomib at minimally, or mildly inhibitory concentrations, there was a highly synergistic inhibition in both B and T-cell lymphomas. Following a 24 hour exposure, carfilzomib alone achieved only 20% growth inhibition of the MCL cell line Jeko-1, while TGR-1202 at concentrations ranging from 2.5 to 15 uM did not produce any growth inhibition (Figure 1). However, the combination of carfilzomib and TGR-1202 markedly inhibited growth of Jeko-1, with a synergy index, RRR, as low as 0.10. In contrast, the synergy of carfilzomib and TGR-1202 in the TCL cell line H9 following a 48-hour exposure, as shown in Figure 2, demonstrated remarkable synergy with a RRR as low as 0.02. To further confirm the synergy of these two drugs in lymphoma, apoptosis was determined in H9 cells treated either with each drug as a single agent or together in combination. Figure 4 illustrates that the combination of these two drugs at marginally active concentrations caused apoptosis in as many as 90% of the H9 cells. The synergy of TGR-1202 and carfilzomib stood out among the combinations tested, as being among one of the most synergistic combinations explored. Table 2 contains a summary of the synergy seen with TGR-1202 and carfilzomib, in contrast to the effects seen with other drug: drug combinations. In conclusion, the combination of the PI3K delta inhibitor TGR-1202 and the proteasome inhibitor carfilzomib remarkably and distinctively synergize to kill both B and T-cell lymphoma cells, and represents a promising therapeutic strategy in the treatment of these diseases. C-: Negative control CFZ: carfilzomib TG: TGR-1202 RRR: Relative risk ratio. Values below 1 indicate synergy. C-: Negative control CFZ: carfilzomib TG: TGR-1202 RRR: Relative risk ratio. Values below 1 indicate synergy. NR: IC50 was not reached at the highest tested concentrations of 32 nM. DLBCL: Diffuse large B cell lymphoma MCL: Mantle cell lymphoma CTCL: Cutaneous T cell lymphoma Disclosures: Sportelli: TG Therapeutics, Inc. : Employment, Equity Ownership. Miskin:TG Therapeutics, Inc.: Employment, Equity Ownership. Vakkalanka:3Rhizen Pharmaceuticals: Employment, Equity Ownership. Viswanadha:Incozen Therapeutics Pvt. Ltd.: Employment, Equity Ownership.

Description: Abstract 3914 Background: The PI3K pathway is a central pro-survival mechanism in chronic lymphocytic leukemia (CLL). Expression of the delta isoform of PI3K is largely restricted to lymphocytes. Inhibition of PI3K activity in vitro induces CLL cell apoptosis and death. Clinical evaluation of PI3K-d inhibitors, such as GS-1101, has been promising, with responses seen in relapsed and/or refractory CLL patients. TGR-1202 is a novel PI3K-d specific inhibitor previously demonstrated to inhibit Akt phosphorylation and induce apoptosis in B-cell lymphoma cell lines. Given the efficacy of other PI3K-d inhibitors observed in CLL, we assessed the ability of TGR-1202 to induce cytotoxicity and apoptosis, and inhibit Akt phosphorylation in primary CLL lymphocytes. Methods: We collected blood from CLL patients seen at the Duke Center for CLL and enrolled in IRB approved protocols at the Duke University and Durham VA Medical Centers. CLL lymphocytes were isolated using negative selection yielding greater than 95% purity of CLL lymphocytes. Primary CLL cells were incubated with serial dilutions of TGR-1202 or GS-1101 for 48 hours and tested for apoptosis by activated caspase-3 and 7AAD staining measured by flow cytometry. After 72 hours of incubation with either compound, CLL cells were evaluated for cytotoxicity using the colorimetric MTS reagent. Phosphorylated Akt (S473) was measured by flow cytometry after one hour of incubation of either compound and ten minutes of incubation with anti-IgM or anti-IgD. Akt phosphorylation was quantified by median fluorescent intensity (MFI). Results: We evaluated TGR-1202 and GS-1101 in CLL lymphocytes collected from seven patients. Five had mutated IGHV, five had 13q deletion or normal cytogenetics determined by fluorescent in situ hybridization, three were ZAP-70 negative, and seven were CD38 negative. IgM expression ranged between 13% and 90%, whereas IgD expression was uniformly elevated. Both TGR-1202 and GS-1101 significantly induced apoptosis (caspase-3+/7AAD+) and cytotoxicity in a dose-dependent manner in concentrations between 0.1 and 25.6 μM (p 〈 0.05 in pairwise Wilcoxon signed rank tests). There was no significant difference observed between the compounds in terms of induction of apoptosis or cytotoxicity at any of the tested concentrations tested (0.1 – 25.6 μM) except 0.4 μM, where GS-1101 induced more apoptosis and cytotoxicity (median of 18.6 vs. 13.7% caspase-3+/7AAD+; median of 55.2 vs. 48.6% cytotoxicity, p = 0.03 for both, Wilcoxon signed rank test). Incubation with anti-surface immunoglobulin significantly induced Akt phosphorylation compared to media alone (median MFI 1011.5 and 369, respectively, p = 0.03, Wilcoxon rank sum test). The addition of either TGR-1202 or GS-1101 significantly abrogated this effect (p = 0.03 for 0.1, 0.4, and 1.6 uM, Wilcoxon rank sum test) and returned Akt phosphorylation to baseline (p 〉 0.05 comparing drug treatment to media control, Wilcoxon rank sum test). Conclusions: TGR-1202 is a potent PI3K-δ inhibitor that suppresses Akt phosphorylation and induces apoptosis-dependent cytotoxicity in primary CLL lymphocytes. These effects are comparable to those seen with GS-1101, another PI3K-δ inhibitor that has demonstrated efficacy in CLL clinical trials. Differences seen at the 0.4 μM concentration were not observed at higher or lower concentrations. Evaluating additional CLL patients' cells would help clarify these findings. Given the improved selectivity for the delta isoform of PI3K seen with TGR-1202 compared to GS-1101, these results suggest that TGR-1202 may have benefit in treating CLL, while inducing fewer off-target effects and toxicities. These findings provide the rationale for future clinical trials evaluating TGR-1202 in CLL. Disclosures: Friedman: Rhizen Pharmaceuticals: Research Funding. Miskin:TG Therapeutics: Employment, Equity Ownership. Viswanadha:Incozen Therapeutics: Employment. Vakkalanka:Rhizen Pharmaceuticals: Employment, Equity Ownership.

Description: Introduction: Phosphoinositide-3-kinases (PI3Ks) are pivotal in various cellular functions including cell proliferation and survival, cell differentiation, intracellular trafficking and immunity. The delta (δ) and gamma (γ) isoforms of PI3K are highly expressed in cells of hematopoietic origin, and often dysregulated in various hematologic malignancies. Because these isoforms contribute to the development, maintenance, transformation, and proliferation of immune cells, dual targeting of PI3K δ and γ represents a promising approach in the treatment of lymphomas. RP6530 is a novel, highly specific dual PI3K δ/γ inhibitor with nanomolar inhibitory potency at the enzyme and cellular level. Besides, RP6530 was effective in inhibiting Akt phosphorylation and inducing apoptosis in various lymphoma and leukemic cell lines. Herein we present preliminary results of a Phase I, first in human, open label study of an oral PI3K δ/ γ inhibitor, RP6530. (NCT02017613). Methods: The dose escalation will determine the maximum tolerated dose (MTD) of RP6530 using a standard 3+3 design. Patients (pts) with a confirmed diagnosis of B-cell non-Hodgkin lymphoma, peripheral T-cell lymphoma, chronic lymphocytic leukemia, Acute lymphoblastic leukemia (CLL), Primary central nervous system lymphomas or Multiple myeloma who have at least one prior therapy are eligible. Additional eligibility criteria include ECOG performance status ≤ 2, and measurable/evaluable disease with a life expectancy of at least 12 weeks. Primary endpoints are safety and pharmacokinetic (PK) parameters; secondary endpoints include pharmacodynamic and drug activity (overall and complete response rates). Correlative biomarker samples including quantitative/qualitative measurements of cytokines, chemokines and aberrations indicative of PI3K function and RP6530 efficacy will be analyzed. RP6530 is given orally twice daily in 28-day cycles until disease progression, unacceptable toxicity, or withdrawal from treatment. The study is designed to enroll up to 30 pts in the dose-escalation phase with up to an additional 42 pts in the cohort expansion phase. Efficacy evaluations are planned every 8 weeks. Adverse events (AE) are assessed using the CTCAE v4.0/ IWCLL guidelines as applicable. Results: Nine pts were enrolled to date across 3 dose levels: BID 25mg, 50mg and 100mg. Five pts were males; ECOG score was 0/1/2 in 5/1/3 pts, respectively, with mean age of 74 yrs (range: 54-82). Pts had median 5 (range: 1-11) prior treatment regimens, and 6 were refractory to prior treatments. Lymphoma categories included DLBCL (2 pts), Mantle Cell Lymphoma (2 pts), follicular lymphoma (1 pt), Marginal Zone Lymphoma (1 pt); and CLL/SLL (2 pts); one pt had multiple myeloma. All nine pts are evaluable for DLT assessment. Of the 9 evaluable pts, 6 are currently on study; 1 patient discontinued treatment due to disease progression. Pts tolerated the treatment well. To date, there have been no DLTs. One pt experienced G4 neutropenia that was unrelated to RP6530. No other G3/4 related hematologic or non-hematologic toxicities were observed. Of the six pts who completed 2 cycles of treatment (8 wks) at 50 mg daily dosing or less, 5 showed stable disease while 1 had disease progression. Three pts did not reach the first response assessment. Mean PK parameters determined on Day 1 of Cycle 1(C1D1) are: median Tmax of 1 hrs (range 0.5-2.0hrs), harmonic mean t1/2 of 2 (± 0.47) hr, and CL/F of 39.55 (± 19.3) L/hr. A linear relationship exists between dose and both AUC (r2 = 0.97) and Cmax (r2 = 0.97). The average accumulation index represented by Cmin on Cycle 2 day 1 is 1.12 (± 0.1). PK data from the first 3 cohorts on C1D1 is summarized below. Table 1.Dose25 mg (n=3)50 mg (n=3)100 mg (n=3)Cmax (µg/mL)0.356 (± 0.08)0.563 (± 0.12)1.329 (± 0.55)AUC (µg*hr/mL)0.775 (± 0.32)1.619 (± 0.67)2.482 (± 1.18) Conclusions: To date, RP6530 has been well tolerated in pts with heavily pre-treated relapsed/refractory hematologic malignancies. There were no DLTs and toxicities were minimal. Enrollment continues at higher dose cohorts. Updated safety, efficacy, PK, and PD data will be presented. Disclosures Scarfò: Rhizen Pharmaceuticals SA: Research Funding. Barde:Rhizen Pharmaceutical SA: Employment. Fazi:Rhizen Pharmaceuticals SA: Research Funding. Kumar:Rhizen Pharmaceuticals SA: Employment. Viswanadha:Incozen: Employment. Vakkalanka:Rhizen Pharmaceuticals SA: Employment, Equity Ownership. Ghia:Rhizen Pharmaceuticals SA: Research Funding. Ferreri:Rhizen Pharmaceuticals SA: Research Funding.