Exhibit 99.1

For Immediate Release:

ARQULE, INC. ANNOUNCES APPOINTMENT OF DR. SUSAN KELLEY

TO BOARD OF DIRECTORS

Woburn, MA, April 28, 2011 — ArQule, Inc. (Nasdaq: ARQL) today announced the appointment of Susan L. Kelley, M.D. to its board of directors, effective April 27, 2011.

Dr. Kelley is currently an independent consultant to the pharmaceutical and biotechnology industries in the field of oncology drug development and strategy.  From 2008 to 2011, she was Chief Medical Officer of the Multiple Myeloma Research Consortium and its sister organization, the Multiple Myeloma Research Foundation, where her responsibilities spanned the continuum of clinical drug development from translational research and clinical trials to FDA regulatory compliance.

From 2001 to 2008, Dr. Kelley was employed by Bayer Healthcare Pharmaceuticals and Bayer-Schering Pharma as Vice President, Global Clinical Development and Therapeutic Area Head — Oncology.  Dr. Kelley worked at Bristol-Myers Squibb Company from 1987 to 2001, most recently as Executive Director, Oncology Clinical Research, at the Bristol-Myers Squibb Pharmaceutical Research Institute.

Dr. Kelley received her M.D. from Duke University School of Medicine and an A.B. in biology, magna cum laude, from Colgate University.  She was a Fellow in Medical Oncology and Clinical Fellow in Medicine at Dana-Farber Cancer Institute, Harvard Medical School, and a Fellow in Medical Oncology and Pharmacology at Yale University School of Medicine, where she also served as a Clinical Assistant Professor of Medicine.

“Dr. Kelley brings strong clinical development skills and regulatory experience to the ArQule board of directors as the Company’s lead product, tivantinib, progresses in its Phase 3 trial in non-small cell lung cancer,” said Patrick J. Zenner, chairman of the board of ArQule.  “We welcome her to the board and look forward to her contributions to the advancement of tivantinib and other pipeline products that are directed toward promising therapeutic targets in oncology.”

About ArQule

ArQule is a biotechnology company engaged in the research and development of next-generation, small-molecule cancer therapeutics.  The Company’s targeted, broad-spectrum products and research programs are focused on key biological processes that are central to

human cancers.  ArQule’s lead product, in Phase 2 and Phase 3 clinical development, is tivantinib (ARQ 197), an inhibitor of the c-Met receptor tyrosine kinase.  The Company has also initiated Phase 1 clinical testing with ARQ 621, designed to inhibit the Eg5 kinesin motor protein, and with ARQ 736, designed to inhibit the RAF kinases. ArQule’s current discovery efforts, which are based on the ArQule Kinase Inhibitor Platform (AKIP™), are focused on the identification of novel kinase inhibitors that are potent, selective and do not compete with ATP (adenosine triphosphate) for binding to the kinase.

This press release contains forward-looking statements regarding the Company’s clinical trials with tivantinib (ARQ 197) and other candidate compounds in earlier stages of development.  These statements are based on the Company’s current beliefs and expectations, and are subject to risks and uncertainties that could cause actual results to differ materially.  Positive information about pre-clinical and early stage clinical trial results does not ensure that later stage or larger scale clinical trials will be successful. For example, tivantinib and the Company’s earlier-stage compounds may not demonstrate promising therapeutic effects; in addition, they may not demonstrate appropriate safety profiles in current or later stage or larger scale clinical trials as a result of known or as yet unanticipated side effects. The results achieved in later stage trials may not be sufficient to meet applicable regulatory standards or to justify further development. Problems or delays may arise during clinical trials or in the course of developing, testing or manufacturing these compounds that could lead the Company or its partners to discontinue development.  Even if later stage clinical trials are successful, unexpected concerns may arise from analysis of data or from additional data. Obstacles may arise or issues may be identified in connection with review of clinical data with regulatory authorities and regulatory authorities may disagree with the Company’s view of the data or require additional data or information or additional studies.  In addition, the planned timing of initiation and completion of clinical trials for tivantinib are subject to the ability of the Company or Daiichi Sankyo, Inc., its partner, and Kyowa Hakko Kirin, a licensee of tivantinib, to enroll patients, enter into agreements with clinical trial sites and investigators, and overcome other technical hurdles and issues related to the conduct of the trials for which each of them is responsible that may not be resolved.  Drug development involves a high degree of risk. Only a small number of research and development programs result in the commercialization of a product.  Positive pre-clinical data may not be supported in later stages of development.  Furthermore, ArQule may not have the financial or human resources to successfully pursue drug discovery in the future.  Moreover, Daiichi Sankyo has certain rights to unilaterally terminate the tivantinib license, co-development and co-commercialization agreement.  If it were to do so, the Company might not be able to complete development and commercialization of tivantinib on its own. For more detailed information on the risks and uncertainties associated with the Company’s drug development and other activities, see the Company’s periodic reports filed with the Securities and Exchange Commission. The Company does not undertake any obligation to publicly update any forward-looking statements.

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