CYTEL BEGINS PHASE II CLINICAL TRIALS IN INFANTS UNDERGOING HEART SURGERY.

SAN DIEGO--(BUSINESS WIRE)--Feb. 18, 1997--Cytel Corporation (Nasdaq:CYTL) today announced that researchers at the Harvard Medical School have begun studying the Company's drug candidate Cylexin(TM) as an aid to improving the post operative course of surgery to correct congenital heart defects in newborn infants. Cylexin is being evaluated in this Phase II clinical trial for its ability to mitigate reperfusion injury that frequently follows cardiopulmonary bypass used during surgery. Approximately 20,000 infants undergo this surgery annually in North America at an estimated cost of $45,000 per procedure. Successful intervention would reduce morbidity, shorten recovery time, and materially impact the cost of therapy.

The clinical trials are being conducted at Children's Hospital, Boston, the largest pediatric medical center in the United States and a teaching hospital of the Harvard Medical School. The Cardiovascular Program at Children's Hospital has an international reputation for excellence in clinical care and clinical research advances. Trials are being conducted under the direction of Jane Newburger, M.D., M.P.H., Associate Professor of Pediatrics, Harvard Medical School, Associate Cardiologist in Chief at Children's Hospital and Director of the Clinical Research Service in the Cardiovascular Program, and Dr. John Mayer, Professor of Surgery at Harvard Medical School and Senior Associate in Cardiac Surgery at Children's Hospital, Boston. In preclinical studies Dr. Mayer and colleagues administered Cylexin into the coronary arteries of the hearts of lambs before arresting the circulation of the heart. Dr. Mayer reported, "The hearts treated with Cylexin showed much better recovery of contractile function than control hearts that did not receive the drug. In additional experiments, Cylexin was administered to the entire circulation of newborn lambs undergoing open heart surgery under conditions similar to those used during cardiac surgery in humans. Compared to control animals, the lambs treated with Cylexin had dramatically better recovery of heart and lung function. These experiments suggest that Cylexin may be effective in reducing injury to blood vessels and tissues that follows open heart surgery in infants and children undergoing repair of serious congenital heart defects."

Two trials are planned. An initial dose ranging trial, which is expected to take approximately 6 months, will evaluate the safety and pharmacokinetics of several different doses of Cylexin, and will provide pilot efficacy data. Immediately following this trial, a single dose regimen will be selected for a double blind placebo controlled trial involving 60 infants. Clinical efficacy endpoints will include indices of cardiac, pulmonary and neurological function.

"The predictive data from the preclinical research conducted at Harvard, and the positive clinical data from an earlier Phase II trial in adults undergoing cardiopulmonary bypass during surgery to remove chronic blood clots from the lung, cause us to have high expectations for Cylexin in this indication," stated Robert L. Roe, M.D., Cytel's Executive Vice President and Chief Operating Officer.

Cytel Corporation is a leader in the discovery, design and development of immunotherapeutics, drugs which the company believes will be more selective and have fewer side effects than drugs currently on the market. Cytel's core technology platforms consist of the Immune Stimulation Program under which the company is developing therapeutic vaccines for infectious diseases and cancers, the Immune Suppression Program which is based on anti-inflammatory cell adhesion inhibitors, and Glycotechnology--its proprietary SNC Technology enabling the manufacture of large quantities of complex carbohydrates at commercially viable prices.

Except for the historical information contained herein, this discussion contains forward-looking statements that involve risks and uncertainties. The Company's actual results could differ materially from those discussed in this press release. Factors that could cause or contribute to such differences include, but are not limited to, successful and timely clinical development of products and the ability to manufacture those products cost effectively, as well as those discussed in the Company's most recent Form 10-K and Form 10-Qs.

CONTACT: Cytel Corporation, San Diego

Karin Eastham, Vice President and Chief Financial

Officer, 619/552-3000