Ligand Announces Partner TG Therapeutics Shows Positive Pre-Clinical Data on IRAK4 Compounds

Ligand Pharmaceuticals Incorporated

partner TG Therapeutics, Inc.

today announced the first presentation of preclinical data demonstrating single agent and combination activity of two of TG Therapeutics' IRAK4 inhibitor compounds under development. This pre-clinical data was presented yesterday at the 106th Annual Meeting of the American Association for Cancer Research (AACR), held in Philadelphia, PA. Highlights and conclusions of the study include: * Both compounds are potent inhibitors of IRAK4 with single-digit nanomolar potency. * Data demonstrated IRAK4 inhibitors inhibited cell proliferation and induced apoptosis as single agents in various B-cell lymphoma cell lines, potentially elucidating the mechanism of action of and clinical rationale for IRAK4 inhibition. * Compounds demonstrated marked synergy when combined with the novel targeted kinase inhibitors TGR-1202, TG Therapeutics' proprietary PI3K delta inhibitor, and the BTK inhibitor, ibrutinib. "We entered into our IRAK-4 partnership with TG Therapeutics last year knowing the promise of IRAK-4 as a target in both oncology and inflammation, as well as the opportunities for treatment synergies between IRAK-4 inhibitors and TG's other best-in-class clinical-stage programs," commented Matt Foehr, President and Chief Operating Officer of Ligand Pharmaceuticals. "These studies now further illustrate that potential, and we congratulate our partners at TG on their progress as they continue to quickly advance the IRAK-4 program toward the clinic." A copy of the presentation is available on the Events page, located within the Investors & Media section of TG Therapeutics' website at www.tgtherapeutics.com.