Combined with Clofarabine, Thiarabine achieves High Cure Rate
in a Colorectal Cancer Model

DALLAS, TX, June 4, 2009,

ACCESS PHARMACEUTICALS, INC. (OTCBB: ACCP), announced today that new Thiarabine preclinical efficacy data will shortly be published demonstrating that thiarabine combined with clofarabine provides much greater antitumor activity than achieved by either agent alone. In one colorectal cancer model, 66% of mice were cured of their tumors. The publication which will appear in the journal Cancer Chemotherapy and Pharmacology, was based on work conducted by Access’ collaborators at the Southern Research Institute. The paper is entitled Enhancement of the in vivo antitumor activity of clofarabine by 1-beta-D-[4-thio-arabinofuranosyl]-cytosine (thiarabine). A preprint of the paper is currently available for download from the journal’s website.

“Thiarabine is a next generation nucleoside analogue, licensed by Access from Southern Research Institute ,” stated Jeffrey Davis, President & CEO. “Thiarabine has been in two Phase 1/2 solid tumor trials and was shown to have significant anti-tumor activity. Access is working with leukemia and lymphoma specialists at M.D. Anderson Cancer Center in Houston to initiate additional Phase 2 clinical trials in acute myeloid leukemia (AML) , acute lymphocytic leukemia (ALL) and other indications. Additionally, we are actively seeking co-development partners, and believe that thiarabine could have applications in certain solid tumors as well,” he continued.

In the study, thiarabine, clofarabine, and their combinations were tested in five tumor models. “In all cases, thiarabine demonstrated superior tumor growth inhibition than clofarabine when the agents were used alone” commented David P Nowotnik, Ph.D., Access Pharmaceuticals’ Senior Vice President, Research and Development. “But, in the combination of these two agents, efficacy was dramatically superior to the use of either agent alone. Tumor regression and cures were observed in several models including colorectal cancer and leukemia. The combination of agents proved to be effective even when used at low doses, indicating a potential for effective treatment with a reduced side-effect profile.”

Prior clinical studies have shown that the effectiveness of cytarabine, or Ara-C, (a close structural analog of thiarabine which is widely used in treating leukemia patients) can be improved by combining it with clofarabine in the treatment of leukemia patients. The Southern Research paper showed that thiarabine/clofarabine combinations have significantly superior efficacy to cytarabine/clofarabine combinations in the xenograft models. Thiarabine has previously been shown to have much better solid tumor efficacy than cytarabine in preclinical models.