Single dose of Pain Therapeutics' PTI-188 decreased melanoma tumors: Study

Mar 24 2010

Tumors Stayed Stable or Decreased in Size in Nearly All Melanoma Patients

Phase I Studies Show Median Survival Rate of 13 Months

Corporate Partnership Expected by Year-end

Pain Therapeutics, Inc. (Nasdaq:PTIE) today announced encouraging clinical data with PTI-188, an early-stage drug for metastatic melanoma. Metastatic melanoma is a lethal form of skin cancer in which patients typically have a median survival time of 9 months.

Although efficacy was not a primary endpoint, PTI and its clinical investigators were encouraged by the number of melanoma tumors that had either stabilized or decreased in size after a single dose of PTI-188. In a first Phase I study with PTI-188, most patients (nearly 70%) showed stable disease in target lesions at the conclusion of the six-week study. In a second Phase I study, approximately 40% of patients showed stable disease at week fourteen. Preliminary analysis, combining both clinical studies, indicates a median overall survival time of 13 months>

Pain Therapeutics' PTI-188 is a proprietary, radio-labeled monoclonal antibody. It is designed to locate and bind to melanoma tumors inside the body, and to deliver a powerful dose of radiation to tumor sites. This radiation destroys cancer cells, thus promoting anti-tumor activity. Pain Therapeutics holds exclusive worldwide, commercial rights to PTI-188.

"There is no satisfactory treatment for metastatic melanoma," said Arturo Casadevall, MD, PhD, Professor of Microbiology and Immunology and Medicine, Albert Einstein College of Medicine. "PTI-188 is very promising because its approach to treatment is completely different from current attempts to treat this disease. Its unique activity could significantly improve survival for patients with metastatic melanoma." 

"We are excited by the evidence of tumor targeting seen with PTI-188," said Michal Lotem, MD, Principal Investigator and Head, Center for Melanoma and Cancer Immunotherapy, Hadassah Hebrew University Medical Center. "This experimental treatment may exert its beneficial effects by direct tumor hit and by changing the tumor's microenvironment, including the feeding blood vessels and supportive cells. Further studies with PTI-188 are of the highest priority."

"Our clinical data in melanoma is encouraging and much work remains," said Remi Barbier, Chairman, President & CEO of Pain Therapeutics. "We intend to stick to our strategy to spend carefully but to keep innovation at the top of our agenda. To balance these competing goals, we expect to sign a worldwide R&D and commercial partnership for PTI-188 by year-end."

Phase I Dose-Escalating Studies

Two open-label, dose-escalating Phase I studies were conducted in Israel to assess the safety, pharmacokinetics, dosimetry and anti-tumor activity of PTI-188. A total of 19 patients were enrolled with confirmed Stage IV or unresectable Stage III melanoma, the worst forms of melanoma disease. All patients were treated with a single intravenous dose of PTI-188. Anti-tumor effects were measured by RECIST (Response Evaluation Criteria in Solid Tumors) at baseline, post-treatment at weeks two and six, and monthly thereafter. Among evaluable patients to date, top-line results confirm the preliminary safety and biological activity of PTI-188, within the confines of two Phase I studies:

• Based on the safety profile and dosimetry to normal organs, PTI-188 was well tolerated at all doses, suggesting these studies did not reach the maximum tolerated dose.
• In a first Phase I study with PTI-188, most patients (nearly 70%) met the RECIST criteria for stable disease in target lesions at the conclusion of the six-week study. 
• In a second Phase I study with PTI-188, approximately 40% of patients met the RECIST criteria for stable disease at week 14.
• In the second Phase I study, five of seven patients were still alive an average of 26 months from initial diagnosis of Stage III/IV melanoma through disease progression following a single dose of PTI-188, with a range of 8 to 68 months. Preliminary analysis, combining both clinical studies, indicates a median overall survival of 13 months>
• Target tumors were observed to stay stable or decrease in size in nearly all patients.
• Drug-related adverse events were predominantly mild in severity. No drug-related serious adverse events were observed in these studies.

Source : Pain Therapeutics, Inc.