ArQule to Present Phase 1 Monotherapy Data with ARQ 501 at AACR Meeting on April 4, 2006.

WOBURN, Mass. -- ArQule, Inc. (Nasdaq: ARQL) today announced that data from its Phase 1 monotherapy trial with ARQ 501 in patients with advanced solid tumors will be presented in the late breaking session at the 97th Annual Meeting of the American Association for Cancer Research (AACR) in Washington, D.C.

Geoffrey I. Shapiro, M.D., Ph.D., of the Dana-Farber Cancer Institute / Harvard Medical School and a principal investigator of the ARQ 501 trial, will lead the presentation on Tuesday, April 4, 2006, beginning at 8:00 a.m. in Exhibit Hall C of the Washington Convention Center (Late Breaking Poster Session Number 1, Abstract Number LB-142, Cellular and Molecular Biology Section). The poster will be featured from 8:00 a.m. to 12:00 Noon.

ARQ 501, the Company's lead product from its Activated Checkpoint Therapy(SM) (ACT) platform, is being developed under an alliance with Roche. The ACT compounds are designed to selectively and broadly target cancer cells through activation of checkpoint pathways. ARQ 501 directly activates E2F1-mediated checkpoint pathways, resulting in apoptosis (cell suicide) in cancer cells selectively.

Based on data from Phase 1 trials, the Phase 2 development plan for ARQ 501 has been established, which will include monotherapy trials in leiomyosarcoma and head and neck cancer, as well as combination therapy trials with gemcitabine in pancreatic cancer and with paclitaxel in ovarian cancer.

About ArQule

ArQule, Inc. is a biotechnology company engaged in the research and development of next-generation, small-molecule cancer therapeutics. The Company's targeted, broad-spectrum products are designed to affect key biological processes that are central to cancer. ArQule's innovative Activated Checkpoint Therapy(SM) (ACT) platform is generating products designed to improve the way cancer patients are treated by selectively killing cancer cells and sparing normal cells through restoration and activation of cellular checkpoint pathways that are underfunctioning in cancer. ArQule's lead ACT program, the E2F program, is partnered with Roche. For more information, please visit www.arqule.com.

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, which provides a safe harbor for forward-looking statements made by or on behalf of ArQule. ArQule and its representatives may from time to time make written or oral forward-looking statements, including statements contained in this press release. Generally, the words "believe," "expect," "intend," "estimate," "anticipate," "will" and similar expressions identify forward-looking statements. All statements which address operating performance, events or developments that ArQule expects or anticipates will occur in the future, such as projections about its future results of operations or its financial condition, research, development and commercialization of its products and anticipated trends in its business are forward-looking statements within the meaning of the Reform Act. Actual results may differ materially from those projected in the forward-looking statements or historical performance due to numerous risks and uncertainties that exist in ArQule's operations, development efforts and the business environment, including without limitation: the ACT platform or other, proprietary platforms may not improve efficacy or reduce toxicity, and compounds resulting from these platforms may not operate as intended; the current and future clinical studies may encounter enrollment difficulties and unexpected toxicity; the commencement of the anticipated clinical trials may be delayed or the trials may never commence; the preclinical efforts associated with the product pipeline may fail or prove disappointing; the animal xenograft preclinical studies may be unpredictive of human response; collaborators may terminate their agreements with ArQule because ArQule may fail to satisfy the collaborators' needs or for other reasons; and, the risks and uncertainties described in ArQule's filings with the Securities and Exchange Commission. The forward-looking statements contained herein represent the judgment of ArQule as of the date of this report. ArQule disclaims any intent or obligation to update any forward-looking statement except to the extent required by law.