Key Points A novel PI3Kδ inhibitor TGR-1202 synergizes with proteasome inhibitor carfilzomib by silencing c-Myc in preclinical models of lymphoma. The unique activity of TGR-1202 as a single agent and in combination with carfilzomib is driven by an unexpected activity targeting CK1ε.

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Purpose: To evaluate the pharmacologic activity of a novel inhibitor of IkB kinase b (IKK2), LY2409881, in preclinical models of B-and T-cell lymphoma, as a single agent and in combination with histone deacetylase (HDAC) inhibitors.Experimental Design: The in vitro activity of LY2409881 was determined using an ATP-based growth inhibition assay and flow cytometric assay of apoptosis in lymphoma cell lines. The in vivo activity of LY2409881 was determined using SCID-beige xenograft mouse model. The mechanism of action was determined using immunoblotting, immuofluorescence, and electrophoretic mobility shift assay. Synergy of LY2409881 with other drugs active in lymphoma was determined by calculating relative risk ratio (RRR) and combination index (CI).Results: LY2409881 inhibited constitutively activated NF-kB, and caused concentration-and time-dependent growth inhibition and apoptosis in lymphoma cells. In models of diffuse large B-cell lymphoma (DLBCL), the cytotoxicity of LY2409881 correlated with the overall activation status of NF-kB, but not simply in a pattern predicted by the cell-of-origin classification of these cell lines. LY2409881 was safe to mice at three dose levels, 50, 100, and 200 mg/kg, all of which caused significant inhibition of tumor growth. LY2409881 suppressed the activity of the NF-kB subunit p65 in lymphoma cells treated by the HDAC inhibitor romidepsin, underlying a potential mechanism of the marked synergy observed of these two drugs.Conclusion: Collectively, these data strongly suggest that targeting the NF-kB pathway in combination with romidepsin could represent a novel and potent regimen for the treatment of B-and T-cell lymphoma.

402 grew Pseudomonas(Ps.) cepacia. I n 208 c u l t u r e s , i t was t h e s i n g l e i s o l a t e . and i n 194 i t grew together with Staphylococcus aureus andlor Ps. aeruginos a , o r t o g e t h e r w i t h other gram-negative organisms. A t o t a l of 54 p a t i e n t s , (24 t o 22 y e a r s ) , 32 females and 22 males, with mild (2). moderate(l5) and advanced(37) degrees of CF has Ps. cepacia i s o l a t e d from b r o n c h i a l o r sputum c u l t u r e s . Ps. cepacia has been found i n p a t i e n t s who have never been h o s p i t a l i z e d and i n those who r a r e l y used a e r o s o l therapy. I t was recovered c o n s i s t e n t l y f o r 2 t o 3 years from 17 p a t i e n t s . Nine females and 5 males have died from r e s p i r a t o r y f a i l u r e . Premortem c u l t u r e s i n 12 p a t i e n t s grew Ps. cepacia alone o r together with Ps. aeruginosa. I n 10 autopsied c a s e s , the lung c u l t u r e grew Ps. cepacia alone i n 3 and Pa. aeruginosa i n 4. Pa. cepacia is r e s i s t a n t t o almost a l l a n t imicrobials including n a l i d i x i c a c i d and g a n t r i s i n b u t a few a r e s e n s i t i v e t o chloramphenicol. trimethoprim-sulfamethoxazole (TMP-SXT) and kanamycin. Good c l i n i c a l response has been observed i n those t r e a t e d w i t h TMP-SXT o r chloramphenicol. Transient d i sappearance of Ps. cepacia i n post-therapy c u l t u r e s has been achieved i n a few cases. The s i g n i f i c a n c e of t h i s f i n d i n g i s under study. The s u p e r i n f e c t i o n with Ps. cepacia of p a t i e n t s with CF with advanced d i s e a s e has made the a n t i m i c r o b i a l therapy more d i f f i c u l t . TEICHOIC ACID SEROLOGY I N VARIOUS STAPHYLO- COCCAL COAGULASE P O S I T I V E I N F E C T I O N S I N INFANTS AND CHILDREN.C h i n h T. Le a n d Edward B. Lewin ( S p o n . by M a r t i n R. K l e m p e r e r ) . U n i v . o f R o c h e s t e r S c h . o f Med. a n d D e n t . , S t r o n g M e m o r i a l H o s p i t a l , D e p a r t m e n t o f P e d i a t r i c s , R o c h e s t e r . N . Y .C o u n t e r i m m u n o e l e c t r o p h o r e s i s ( C I E ) a n d O u c h t e rl o n y g e l d i f f u s i o n w e r e u s e d f o r t h e d e t e c t i o n a n d t i t r a t i o n o f a n t i c o a g . p o s i t i v e (SC+) i n i n f a n t s a n d c h i l d r e n . Serum s a m p l e s w e r e o b t a i n e d o n a d m i s s i o n , a t 2 w e e k s , a n d up t o 1 2 w e e k s i n t o t h e i l l n e s s .TAA w e r e f o u n d by CIE i n 7 0 % ( 7 1 1 0 ) o f p a t i e n t s w i t h i n v a s i v e SC+ d is e a s e w i t h b a c t e r e m i a ( g r o u p A). 1 4 % ( 1 1 7 ) o f p at i e n t s w i t h SC+ i n f e c t i o n w i t h o u t b a c t e r e m i a ( g r o u p B ) , 0 % ( 0 1 1 9 ) o f p a t i e n t s w i t h b a c t e r e m i a a n d l o r i n v a s i v e i n f e c t i o n s n o t c a u s e d by SC+ ( g r o u p C ) a n d 0 % ( 0 1 1 3 ) o f n o n -i n f e c t e d , h o s p i t a l i z e d p a t i e n t s a n d h e a l t h y c h i l d r e...

Introduction: c-Myc is a master transcription factor and one of the most frequently altered genes across a vast array of human cancers including diffuse large B-cell lymphoma (DLBCL), and is thus an attractive therapeutic target . However, no direct inhibitor of c-Myc has been successfully developed for the treatment of any cancer. The c-Myc protein has a short half-life of less than 30 minutes , and the complex secondary structures in the 5' untranslated region (UTR) of MYC mRNA make its translation highly dependent on the eukaryotic translation initiation factor 4F (eIF4F) . eIF4F exists as a complex comprised of the eIF4E, eIF4A, and eIF4G subunits. eIF4E can be sequestered by 4E-BP1, which acts as a "brake" for initiation of mRNA translation . Hyper-phosphorylation of 4E-BP1, caused by upstream signals such as mTORC1, leads to release of eIF4E from 4E-BP1, assembly of the eIF4F complex, and robust mRNA translation. Surprisingly, neither FDA approved mTORC1 inhibitors nor the investigational mTORC1/mTORC2 inhibitor MLN0128 has demonstrated adequate activity in aggressive lymphoma. The therapeutic effects of mTOR inhibition in c-Myc driven aggressive lymphoma remain poorly understood. Recognizing phosphoinositide 3-kinase (PI3K) and the proteasome pathway are both involved in activating mTOR, we hypothesized that co-targeting the PI3K and proteasome pathways might synergistically inhibit translation of c-Myc. Since both PI3K and proteasome are proven drug targets in blood cancer, such co-targeting strategy may be expeditiously studied in clinical trials for c-Myc driven aggressive lymphoma. Methods: Cytotoxicity was studied in lymphoma cell lines and primary lymphoma cells using Cell TiterGlo (Promega®). The Bliss additivism model was used to determine the expected inhibition of cell growth and the excess over Bliss (EOB) values. EOB values above 0 indicate synergy, with higher values indicating higher levels of synergy. Expression of c-Myc was investigated at the translation and transcription levels, using a combination of Western blot, qPCR, and a bi-cistronic luciferase reporter we developed to study cap dependent translation. Gene expression profiling (GEP) studies were conducted using RNAseq, and analyzed by the Fisher t-test and running enrichment score (RES) between different treatment groups. Mechanisms of synergy were determined through interrogating the effects of small molecule inhibitors and shRNA targeting regulators of various regulators of 4E-BP1. Structural studies of TGR-1202 were performed by in silico docking, and validated by synthesis of novel analogs of TGR-1202. Activity of TGR-1202 on CK1 epsilon was studied by kinome profiling (Reaction Biology®), cell free kinase assay of CK1e (Promega®), and cell based assay of CK1e autophosphorylation. Results: We found that a novel PI3K delta isoform inhibitor TGR-1202, but not the approved PI3Kd inhibitor idelalisib, was highly synergistic with the proteasome inhibitor carfilzomib in lymphoma, leukemia, and myeloma cell lines and primary lymphoma and leukemia cells (Figure 1). TGR-1202 and carfilzomib (TC) synergistically inhibited phosphorylation of eIF4E-binding protein 1 (4E-BP1), leading to suppression of c-Myc translation and silencing of c-Myc dependent transcription (Figure 2). Furthermore, the synergistic cytotoxicity of TC was rescued by overexpression of eIF4E or c-Myc. TGR-1202, but not other PI3Kd inhibitors, was active against casein kinase-1 (CK1) epsilon (Figure 3). Targeting CK1e using a selective chemical inhibitor or shRNA complements the effects of idelalisib, as a single agent or in combination with carfilzomib, in repressing phosphorylation of 4E-BP1 and the protein level of c-Myc. Conclusion: These results suggest that TGR-1202 is a first-in-class dual PI3Kd/CK1e inhibitor, which may in part explain the preliminary clinical activity of TGR-1202 in aggressive lymphoma not found with idelalisib. Targeting CK1e should become an integral part of therapeutic strategies targeting translation of oncogenes such as c-Myc. Disclosures Lentzsch: BMS: Consultancy; Foundation One: Consultancy; Celgene: Consultancy, Honoraria. O'Connor:Seattle Genetics: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Research Funding; Spectrum: Research Funding; Spectrum: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; TG Therapeutics: Research Funding; Bristol Myers Squibb: Research Funding; Bristol Myers Squibb: Research Funding; Celgene: Research Funding; Celgene: Research Funding.

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.

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Background Targeting the epigenetic apparatus has become a successful treatment paradigm for the treatment of T-cell lymphomas (TCL), as demonstrated by the FDA approval of two histone deacetylase (HDAC) inhibitors, romidepsin and vorinostat. Romidepsin and vorinostat are pan-HDAC inhibitors, and their lack of enzyme specificity may be associated with toxicities that limit their clinical application. There is emerging evidence that the 11 classical HDAC isoforms, HDAC1-11, play different roles in oncogenesis, depending on the disease context. For example, HDAC3 has been strongly implicated in the survival of diffuse large B cell lymphoma, by interacting with STAT3. In T cells, HDAC1 and HDAC2 suppress lymphomagenesis in a dosage dependent manner, and are required to maintain the survival of TCL. Our hypothesis is that if different HDAC isoforms are involved in distinct cellular functions, then isoform selective HDAC inhibitors may be active in select subtypes of lymphoma, and that unique combinations of isofrom selective inhibitors could be used to more precisely target the relevant biology. Methods Cytotoxicity of isoform selective and nonselective HDAC inhibitors was determined in a panel of T cell lymphoma cell lines using a High Throughput Screening approach. Growth inhibition was determined using Cell TiterGlo that measures ATP produced by live and proliferating cells. The concentrations required to reach 50% of inhibition (IC50) were calculated from cells treated for 48 hours, using the CalcuSyn software. Cell death was determined by flow cytometry, using both Annexin V and propidium iodide as the probes. Finally, drug : drug synergy was determined by calculating relative risk ratio (RRR), as published previously. Values below 1 indicates synergy, and the smaller the RRR values the higher the level of synergy. Results Isoform selective HDAC inhibitors as a rule were much less potent than nonselective HDAC inhibitors in their ability to inhibit the growth of TCL cells (Table 1). However, two HDAC1/2 selective inhibitors, BRD2283 and BRD6597, demonstrated IC50 values comparable to vorinostat in the H9 cell line, but not in any other cell lines. This may be due to unique epigenetic features in H9 that are sufficiently sensitive to the inhibition of only HDAC1 and 2. In contrast, other cell lines may have complex epigenetic abnormalities that are not sensitive to the inhibition of only HDAC1 and 2, but were nevertheless sensitive to inhibition of a broader spectrum of HDAC isoforms. To further confirm that inhibiting a broader array of HDAC enzymes may lead to more efficient growth inhibition, we investigated the effect of combining the HDAC1/2 inhibitor BRD2283 and the selective HDAC3 inhibitor repligen-136 on TCL cell growth. Figure 1 demonstrates that repligen-136 at the concentration of 4uM produced only 30% growth inhibition at 48-hour exposure. BRD2283 as a single agent produced 20, 30, and 65% of growth inhibition at the concentration of 0.5, 1, and 2uM, respectively. BRD2283 at these concentrations, combined with the mildly active repligen-136 at 4uM, produced 80, 90, and 95% of growth inhibition, respectively. The calculated RRR values were 0.35, 0.20, and 0.13, respectively, highly significant for synergistic drug : drug interaction. These results serve as a proof of principle that inhibition of a narrow spectrum of isoform specific HDAC enzymes may be sufficient to inhibit select lymphoma characterized by 'uncomplicated' epigenetic apparatus. In contrast, lymphoma with 'complicated' epigenetic abnormalities may require simultaneous inhibition of multiple HDAC isoforms, which may be achieved by combining HDAC inhibitors that target different HDAC enzymes. The combination approach, as compared to a single, non-selective HDAC inhibitor, may allow for more opportunity of personalized cancer treatment based on improved understanding of the precise epigenetic abnormalities in the lymphoma. We have begun a broader combinatorial screening approach to explore what specific set of isoform selective inhibitors recapitulate, or perhaps even improve upon, the activity seen with the pan HDAC inhibitors. C-: Negative control Rep: Repligen-136 2283: BRD2283 RRR: Relative risk ratio Disclosures: No relevant conflicts of interest to declare.