Oxxon Reports Interim Phase II Data at ASCO from Melanoma Trial.

BOSTON, Mass. -- Oxxon Therapeutics, Inc. (Oxxon) today reported interim data from its ongoing Phase II MEL1 immunotherapy study in patients with advanced melanoma. The Company presented the data during a poster session at the American Society for Clinical Oncology (ASCO) annual meeting held in Orlando, Florida.

Oxxon's MEL1 immunotherapy delivers multiple melanoma specific epitopes through the Company's proprietary PrimeBoost approach. In this study, patients received increasing priming doses of plasmid DNA that were then boosted with increasing doses of Modified Vaccinia Ankara (MVA) containing the same epitopes. The MVA doses included the highest administered dose yet in human studies (at 1 x 10e9pfu). The 16-week interim results of the 52-week trial demonstrated that MEL1 was safe and well tolerated, with injection site reactions following first MVA immunization reported as the most common side effect. These reactions were not dose limiting.

In 7/26 (27 percent) patients, melanoma specific immune responses (as measured by ELISPOT and Tetramer assays) were observed. Of these, three showed responses to multiple melanoma epitopes. All three stage III patients showed a confirmed immunological response. The best overall tumor response (as measured by RECIST criteria) showed 2/31 (6 percent) partial responders and 14/31 (45 percent) with stable disease.

"This trial, evaluating the highest dose of MVA administered to date, is encouraging given that 90 percent of these patients have stage IV disease," noted Dr. Robert Hawkins of the Christie Hospital in Manchester, United Kingdom. "Of the three stage III patients, two had clinical responses (one partial and one stable disease) and all three showed immunologic responses. The overall results merit further study, particularly in the stage III patients."

"These preliminary data continue to support PrimeBoost's ability to elicit an immune response and point the way to future clinical studies in stage III patients," said Dr. Deirdre Gillespie, president and chief executive officer at Oxxon. "MEL1 is one of Oxxon's two Phase II immunotherapy programs. The Company also has an ongoing Phase II trial in chronic hepatitis B, for which we anticipate data later in 2005."

Study Details

The 52-week immunotherapy study was conducted at six outpatient study centers in the United Kingdom and Germany. The dose ranging Phase II study was designed to evaluate safety, immunogenicity, and clinical response (by RECIST criteria) in stage III and IV malignant melanoma patients with the HLA-A2 allele. The DNA and MVA viral vectors used contained seven CTL epitopes from five well-characterized human melanoma antigens (Tyrosinase, melan-A, MAGE-1, MAGE-3, NY-ESO-1). Patients received two priming doses of DNA (from 1mg to 2mg) followed by two boosting doses of MVA (from 5 x 10e7pfu to 1 x 10e9pfu). In addition, this protocol allowed continued boosting with MVA at week 16 and week 24 for those patients responding well to therapy at week 16). These data show that the heterologous PrimeBoost immunotherapy stimulated immune responses in 7/26 metastatic melanoma patients. All three stage III patients enrolled showed an immune response and two of the three showed a clinical response (PR greater than 42 weeks and SD 16 weeks). One of these patients in particular, showed that additional MVA boosting given at weeks 18 and 24 increased the patient's immune response.

The principal investigators in the study include: R. E. Hawkins and A. Dangoor of Christie Hospital, Manchester, United Kingdom; U. Keilholz of Charite Hospital, Berlin, Germany; A. Harris of Churchill Hospital, Oxford, United Kingdom; C. Ottensmeier of, Southampton University Hospital, United Kingdom; D. Schadendorf of University of Mannheim, Germany; J. Smyth of University of Edinburgh, United Kingdom; K. Hoffmann of Ruhr-Universitat, Bochum, Germany; and R. Anderson and G. Pearce of Oxxon Therapeutics, Inc.

About Oxxon Therapeutics, Inc.

Oxxon Therapeutics, Inc. (Oxxon) is advancing the next generation of innovative immunotherapies to treat patients with chronic infectious diseases and cancer. To date, the company has built a pipeline through its proprietary PrimeBoost platform, an approach that allows the rapid development of products to selectively stimulate and enhance a potent cellular immune response. The Company has development programs in hepatitis, melanoma and HIV, two of which are in Phase II clinical trials. In addition, the Company is leveraging its enabling platform through partnerships with companies and academic collaborations.

For more information, please visit www.oxti.com.