ArQule Initiates Phase 2 Clinical Development of ARQ 501 for Pancreatic Cancer.

WOBURN, Mass. -- ArQule, Inc. (NASDAQ: ARQL) today announced the enrollment and successful dosing of the first patient in a Phase 2 clinical trial of ARQ 501 in combination with gemcitabine to treat pancreatic cancer.

The Company expects to enroll approximately 60 to 70 patients with treatment-naive, unresectable pancreatic adenocarcinoma in this single-arm, open-label trial, which will be conducted at multiple investigator sites in the U.S. and abroad. The primary endpoint of the trial is the Objective Response Rate (ORR), as measured by RECIST (Response Evaluation Criteria in Solid Tumors) criteria.

Patients will receive 800 milligrams per meter squared (mg/m2) of gemcitabine and 400 mg/m2 of ARQ 501 once weekly, administered as separate intravenous infusions over four-week cycles of therapy. Evaluation of anti-tumor activity will be performed at eight-week intervals until progression is determined.

"With the dosing of the first patient in this combination therapy trial, we now are actively enrolling patients in two Phase 2 studies with ARQ 501," said Dr. Stephen A. Hill, president and chief executive officer of ArQule. "The first trial is an open label, monotherapy study of this compound as second-line treatment for persistent, recurrent or metastatic leiomyosarcoma.

"In addition, we are continuing to select sites for a monotherapy trial with ARQ 501 in head and neck cancer, and we are planning for a combination study with ARQ 501 and a taxane in ovarian cancer to begin in the second half of this year," said Dr. Hill. "We believe patients with these cancers could be particularly responsive to ARQ 501 based on Phase 1 data and preclinical scientific findings."

About ARQ 501

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

The Company's Phase 2 clinical program with ARQ 501 will consist of four separate trials, including two monotherapy trials, in leiomyosarcoma and head and neck cancer, and two combination therapy trials, one with gemcitabine in pancreatic cancer and one with a taxane in ovarian cancer.

About Checkpoint Activation

In a normal cell, checkpoint mechanisms serve to monitor genetic (DNA) damage. If damage is detected, the cell attempts to repair the damage. If such repair is not possible, checkpoint functions cause the damaged cell to undergo cell death, or apoptosis. Cancer cells have multiple abnormalities, including DNA damage, but they are able to survive and proliferate because key checkpoints and apoptotic pathways are disabled as the cancer develops. As a result, cancer cells undergo cell division in an uncontrolled way and pass their genetic damage on to their daughter cells.

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 direct activation of DNA damage response/checkpoint pathways. ArQule's lead ACT program, based on the E2F pathway, is partnered with Roche. For more information, please visit www.arqule.com.

This press release contains forward-looking statements regarding the Company's Phase 2 combination therapy and monotherapy clinical trials with ARQ 501. 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 early stage clinical trial results does not ensure that later stage or larger scale clinical trials will be successful. For example, ARQ 501 may not demonstrate promising therapeutic effect; in addition, it may not demonstrate an appropriate safety profile in ongoing or later stage or larger scale clinical trials as a result of known or as yet unidentified side effects. The results achieved in later stage trials may not be sufficient to meet applicable regulatory standards. Problems or delays may arise during clinical trials or in the course of developing, testing or manufacturing ARQ 501 that could lead the company or its partner to discontinue development. Even if later stage clinical trials are successful, the risk exists that unexpected concerns may arise from analysis of data or from additional data or that obstacles may arise or issues be identified in connection with review of clinical data with regulatory authorities or that 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 of clinical trials and the duration and conclusion of such trials for ARQ 501 are subject to the ability of the company to enroll patients, enter into agreements with clinical trial sites and investigators, and other technical hurdles and issues 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. 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.