WALTHAM, Mass.--March 11, 2004--Praecis Pharmaceuticals Inc., today announced that the Company has been advised during discussions with the United States Food and Drug Administration (FDA) that its Phase I clinical trial of PPI-2458 in non-Hodgkin's lymphoma has been placed on clinical hold until questions relating to a finding in a recently completed animal safety study have been satisfactorily resolved. In discussions, the FDA indicated that the Company will need to submit a detailed plan to address this finding. The Company expects to receive a letter from the FDA confirming the clinical hold, and providing details of the actions that will be required prior to proceeding with the clinical trial.

In support of its Investigational New Drug application, the Company had completed and submitted to the FDA results from preclinical studies evaluating the safety of PPI-2458 through 28-days of treatment. These studies showed no evidence of any unexpected safety issues. The FDA's decision was related to a preliminary finding in a recently completed three-month animal safety study. The findings of this study were not available at the time that the clinical study was initiated. The finding consisted of a neuropathological abnormality in some of the animals tested, similar to findings reported in connection with other approved products. The Company will further explore this finding, with input from leading experts as appropriate, to assess its potential implications and prepare a plan for the FDA.

"We remain committed to the development of PPI-2458 for non-Hodgkin's lymphoma, as well as additional evaluation of its activity in other cancers, and will work diligently with the FDA to agree upon an acceptable path forward that will optimize the safest possible use of this novel therapeutic agent," said Marc B. Garnick, M.D., Executive Vice President and Chief Medical Officer of PRAECIS.

Source: Praecis Pharmaceuticals Inc.