[ Visit Client Website ]

Before you can access ASH's online program, you must agree to the following:
  • Abstracts submitted to the ASH Annual Meeting are considered embargoed from the time of submission.
  • The media, companies and institutions issuing press releases, and others are required to abide by the embargo policies governing the Society’s annual meeting. Read ASH’s embargo policy for more information.
-Author name in bold denotes the presenting author
-Asterisk * with author name denotes a Non-ASH member
Clinically Relevant Abstract denotes an abstract that is clinically relevant.

PhD Trainee denotes that this is a recommended PHD Trainee Session .

3725 Novel PI3K Inhibitors Demonstrated Marked Cytotoxicity in T Cell Lymphoma Models, Caused Apoptosis and Were Synergistic with A Novel Anti-CD20 Monoclonal Antibody Ublituximab in B Cell Lymphoma Models

Program: Oral and Poster Abstracts
Session: 625. Lymphoma - Pre-Clinical - Chemotherapy and Biologic Agents: Poster III
Monday, December 10, 2012, 6:00 PM-8:00 PM
Hall B1-B2, Level 1, Building B (Georgia World Congress Center)

Changchun Deng, MD, PHD1, Peter Sportelli2*, Richard Rodriguez1*, Hari Miskin2*, Swaroop Vakkalanka3*, Srikant Viswanadha4* and Owen A. O'Connor, MD, PhD1*

1Center for Lymphoid Malignancies, Department of Medicine, Columbia University Medical Center, New York, NY
2TG Therapeutics, Inc., New York, NY
3Rhizen Pharmaceuticals SA, La Chaux de Fonds, Switzerland
4Incozen Therapeutics Pvt. Ltd., Hyderabad, India

Background: Activation of PI3K has been shown to be required for the proliferation and survival of cancer cells.  A selective PI3K-delta inhibitor, GS-1101/CAL-101, has produced promising results in the treatment of lymphoid malignancies.  More recently, new chemical entities targeting PI3K have been developed, with pharmacologic and pharmacodynamic features distinct from CAL-101.  We sought to determine the activities of two structurally related PI3K inhibitors, TGR-1202 and TGR-5237, in B- and T cell lymphoma models. 

Methods: The activity of TGR-1202 on individual PI3K isoforms was determined in a cell free system using the PI3K HTRF Assay Kit, and in a cell based assay using the Flow2CAST kit that measures the induction of CD63 surface expression on human whole blood basophils as a marker for PI3K-delta signaling. The cytotoxicity of TGR-1202 and TGR-5237 was studied in 4 mantle cell lymphoma (MCL) cell lines, 1 T-cell acute lymphoblastic leukemia (T-ALL) cell line (P12), and 1 cutaneous T cell lymphoma (CTCL) cell line (H9).  Growth inhibition was determined using the ATP-based Cell Titer Glo assay, and apoptosis was determined by flow cytometry using the Alexa Fluo kit.  The potency of ublituximab was determined in antigen recognition studies using the Human Whole Blood B-cell depletion assay. Cell cycle progression was evaluated using a Guava cell cycle assay kit in 4 lymphoma cell lines, including Daudi, Raji, U266B1, and DB.  

Results: In the enzyme based assay, TGR-1202 demonstrated marked potency against PI3K-delta, with a half maximal effective concentration (EC50) at 22 nM. TGR-1202 was 48- to 10,000-fold more selective for the PI3K-delta relative to the alpha, beta, and gamma isoforms.  In the cell based assay, the EC50 of TGR-1202 for PI3K-delta was 67 nM, compared with 92 nM with CAL-101.  In the cytotoxicity assay of TGR-5237, the concentration required to inhibit growth by 50% (IC50) ranged from 10 uM to 50 uM for the 4 MCL cells and the T-ALL cell P12.  Surprisingly, the CTCL cell line H9, was exquisitely sensitive to TGR-5237, with IC50 below 0.1 uM (Figure 1).  TGR-5237 induced concentration-dependent apoptosis in WSU-NHL, with its potency comparable to CAL-101 (Figure 2).  TGR-1202 caused a concentration-dependent accumulation of cells in the G2-M phase in Raji, Daudi, U266B1, and DB.  While TGR-1202 was not cytotoxic to CD20+ B-cells at the 1 uM concentration, combination of 1 uM TGR-1202 with ublituximab increased CD20+ cell depletion by 20% at the 0.1-10 ng/ml concentrations.  Last, the combination of TGR-1202 and ublitiximab markedly increased the percentage of cells in sub-G0 phase in Daudi and Raji cells, indicative of their synergy in causing apoptosis (Figure 3).

Conclusion: Two novel PI3K-delta inhibitors, TGR-1202 and TGR-5237, disrupted cell cycle progression, induced apoptosis, and inhibited cell growth and proliferation in B- and T cell lymphoma models. TGR-1202 enhanced the activity of a novel CD20 monoclonal antibody, ublituximab, in CD20 positive lymphoma cells.

Disclosures: Sportelli: TG Therapeutics, Inc.: Employment, Equity Ownership. Miskin: TG Therapeutics, Inc.: Employment, Equity Ownership. Vakkalanka: Rhizen Pharmaceuticals: Employment, Equity Ownership. Viswanadha: Incozen Therapeutics: Employment. O'Connor: Millenium Pharmaceuticals, Inc: Membership on an entity’s Board of Directors or advisory committees; TG Therapeutics, Inc: Consultancy; Seattle Genetics, Inc: Membership on an entity’s Board of Directors or advisory committees; Allos Therapeutics, Inc: Consultancy.

<< Previous Abstract | Next Abstract

*signifies non-member of ASH