Price quotes for Sibutramine from multiple providers

OSI Pharmaceuticals, Inc. (Nasdaq: OSIP) announced today that it
has initiated the first-in-human clinical study of its development
compound PSN602. Discovered by OSI’s diabetes and obesity team, PSN602
is an oral dual serotonin and norepinephrine reuptake inhibitor and
5-HT1A agonist, being developed for the treatment of obesity. PSN602
is the first clinical candidate to emerge from the Company’s research
efforts in obesity.

“Our research efforts are focused on designing innovative,
next-generation, small molecule compounds to provide safer or more
effective options for the treatment of type 2 diabetes and obesity,”
stated Anker Lundemose, M.D., Ph.D., President of (OSI) Prosidion. “We
believe that not only does PSN602 have the potential to have a
favorable side-effect profile relative to current therapies for
obesity, but also the potential to provide greater efficacy.”

The double-blind, placebo-controlled, ascending, single and
multiple, oral dose study is designed to provide preliminary
information on the safety, tolerability and pharmacokinetics of PSN602
in healthy lean and overweight/obese subjects, as well as on the
effects of PSN602 on appetite and food intake in healthy
overweight/obese subjects.

Background

OSI’s research showed, in preclinical in vivo models, that PSN602
was at least as effective at reducing body weight as a high dose of
the anti-obesity agent sibutramine, with a more favorable
cardiovascular profile, supporting the hypothesis that the 5-HT1A
agonism component of PSN602 could potentially counterbalance the
undesirable cardiovascular activity seen with sibutramine.

About Obesity

Obesity is a state of excess body fat. The World Health
Organization expresses the prevalence of obesity by using body mass
index (BMI), a simple index of weight-for-height that classifies
underweight, overweight and obesity in adults. Obesity has reached
epidemic proportions globally with more than 1 billion adults
overweight, of which at least 300 million are clinically obese. Excess
weight and obesity lead to adverse metabolic effects on blood
pressure, lipid levels and insulin resistance and thus pose a major
risk for serious chronic diseases, including hypertension, type 2
diabetes and cardiovascular disease. In addition, obesity increases
the risk of respiratory difficulties, chronic musculoskeletal
problems, infertility, gall bladder disease and certain forms of
cancer.

About OSI Pharmaceuticals

OSI Pharmaceuticals is committed to “shaping medicine and changing
lives” by discovering, developing and commercializing high-quality and
novel pharmaceutical products designed to extend life and/or improve
the quality of life for patients with cancer and diabetes/obesity. The
Company’s oncology programs are focused on developing molecular
targeted therapies designed to change the paradigm of cancer care.
OSI’s diabetes/obesity efforts are committed to the generation of
novel, targeted therapies for the treatment of type 2 diabetes and
obesity. OSI’s flagship product, Tarceva(R) (erlotinib), is the first
drug discovered and developed by OSI to obtain FDA approval and the
only EGFR inhibitor to have demonstrated the ability to improve
survival in both non-small cell lung cancer and pancreatic cancer
patients in certain settings. OSI markets Tarceva through partnerships
with Genentech, Inc. in the United States and with Roche throughout
the rest of the world. For additional information about OSI, please
visit http://www.osip.com.

This news release contains forward-looking statements. These
statements are subject to known and unknown risks and uncertainties
that may cause actual future experience and results to differ
materially from the statements made. Factors that might cause such a
difference include, among others, the completion of clinical trials,
the FDA review process and other governmental regulation, OSI’s and
its collaborators’ abilities to successfully develop and commercialize
drug candidates, competition from other pharmaceutical companies, the
ability to effectively market products, and other factors described in
OSI Pharmaceuticals’ filings with the Securities and Exchange
Commission.