Prima Biomed Final Phase IIa Results for Ovarian Cancer Treatment Exceeded Expectations

Announced that the final results of its Phase IIa trial of CVacTM in ovarian cancer exceeded the expectations of the trial, as set by the company’s Scientific Advisory Panel in conjunction with the Principal Investigating Oncologist, Assoc Prof Paul Mitchell, Director of Cancer Services at Austin Hospital. The primary objective of the trial was to determine if CVacTM would reduce or stabilise the blood marker CA125 in at least 15% of patients.

MELBOURNE, Australia | Mar 14, 2007 | 
Prima BioMed Limited (ASX:PRR) today announced that the final results of its Phase IIa trial of CVacTM in ovarian cancer exceeded the expectations of the trial, as set by the company’s Scientific Advisory Panel in conjunction with the Principal Investigating Oncologist, Assoc Prof Paul Mitchell, Director of Cancer Services at Austin Hospital. The primary objective of the trial was to determine if CVacTM would reduce or stabilise the blood marker CA125 in at least 15% of patients.

Twenty-one late stage patients with progressive disease, demonstrated by rising CA125, were eligible to participate in the clinical efficacy evaluation. CVacTM demonstrated a positive clinical response or stabilisation of disease in four of the twenty-one patients (19%; CI 5.4 - 41.9%) based on changes in CA125.

Clinical responses have been assigned into three categories based on standard criteria:

# Major Response required >50% reduction in CA125 levels, responses needed to be confirmed by a second reading at least 21 days later;

# Minor Response required a >25% reduction in CA125 levels, responses needed to be confirmed by a second reading at least 21 days later;

# Stabilisation was defined as +/- <25% change in CA125 that had to last at least 3 months.

Two of the four patients experienced a major response. The duration of major response for Patient One persisted for 42 weeks, remained a major response at the end of the study and the patient has continued to receive CVacTM under the Special Access Scheme (SAS) for the past three months. Patient Two experienced disease stabilisation for a total duration of 44 weeks during which the patient also experienced a minor response for 20 weeks, which in turn included a major response for 10 weeks. This patient remained stable at the end of the treatment.

One patient demonstrated a minor response with duration of 10 weeks during a 34 week period of disease stabilisation. This patient was stable at the end of treatment. The fourth patient demonstrated disease stabilisation for 27 weeks.

Further to the results above, a fifth patient had >25% reduction in CA125 which did not qualify fully as a minor response as it was not supported by a confirmatory reading 21 days later.

“These results demonstrate clear benefit in patients with progressive ovarian cancer. It suggests that CVacTM is a promising new approach for ovarian cancer and warrants further clinical investigation” said Assoc Prof Paul Mitchell. “The enrolled patients had incurable advanced ovarian cancer and most had received extensive prior therapy such that responses to standard chemotherapy would not be expected.”

The trial enrolled a total of twenty-eight patients. Seven patients withdrew prior to receiving the third injection of CVacTM due to rapidly progressing disease and were not eligible for clinical efficacy analysis but were eligible for safety analysis. There were no serious adverse events that were definitely or probably related to CVacTM treatment. There was one patient who experienced two serious adverse events (flu-like symptoms and abdominal pain) that were assessed as possibly related to CVacTM treatment.

Assoc. Prof Bruce Loveland, Chief Scientific Officer of Prima BioMed, stated “these results indicate the potential of dendritic cell therapy and the CVacTM approach to harness the immune system to intervene in tumour growth, even in patients with advanced disease. In addition, the targeting of Mucin-1 is again validated for cancer therapies.”

This concludes the second clinical trial of CVacTM. The company has initiated planning for the next stage of clinical development, forecasted to be a controlled phase IIb clinical trial in 100-200 patients. The trial will be aligned to international regulatory requirements for the development of dendritic cell therapies for cancer and is anticipated to commence within 12 months.

FOR FURTHER INFORMATION:

Company Contacts:

Company Enquiries Eugene Kopp 03 9854 5700

Media Enquiries Daniella Goldberg 02 9237 2803 / 0416 211 067

About Prima BioMed Ltd

Prima BioMed (ASX: PRR) is a biotechnology company based in Melbourne, Australia. The company is focused on technologies in the fields of immunology and cancer immunotherapy, in particular on development of a dendritic-cell based immunotherapy targeting tumours expressing the Mucin-1 tumour antigen. Prima’s lead product, CVac™ has completed Phase IIa clinical development in ovarian cancer.

About CVacTM

CVac™ is an experimental therapy consisting of a patient’s own dendritic cells primed with a tumour antigen (Mucin-1) and an adjuvant, Mannan Fusion Protein (M-FP), currently being investigated in clinical trials.

There are currently no clinical trials of CVacTM open to recruitment. Timeframes for commencement of further clinical trials of CVacTM are still to be finalised. Further clinical trials will be announced on the company’s website once approval to conduct such trials is received.

M-FP refers to the form in which the target protein of the CVac™ immunotherapy is presented to the immune system. The mannan used is a chain of mannose molecules that is oxidised and linked to the cancer protein (Mucin-1). Mannan stimulates the immune system and it is the mannan that results in rapid uptake of Mucin-1 into the dendritic cells of the immune system via the mannose receptor on the cell surface. Once the M-FP is inside the dendritic cell, enzymes digest the Mucin-1 and fragments of Mucin-1 are presented on the dendritic cell surface. This presentation results in the stimulation of certain cells of the immune system to target Mucin-1 on the surface of cancer cells.

Design of the CVacTM Phase IIa

Trial Name: CAN-002 A Phase II trial of cellular immunotherapy with M-FP cancer vaccine in patients with epithelial ovarian carcinoma.

Trial Status: Non-randomised, open label, exploratory study.

Treatment: Three injections of CVacTM at one-monthly intervals, followed by up to 4 injections of CVacTM at 10-weekly intervals, a total of seven injections.

Number of Patients: 28 patients recruited

Drop-out Rate: 7 patients did not receive the required 3 injections of CVac to be eligible for analysis of the primary endpoint.

Eligibility Criteria:

# Epithelial adenocarcinoma of ovarian or fallopian tube origin or primary peritoneal carcinoma

# No options for curative therapy;

# A rising CA125 level defined by an increase of at least 25% from a baseline reading within one month and confirmed by a repeat test. CA125 is an ovarian cancer tumour marker detected in the blood of patients. Increases in CA125 levels indicate disease progression; and

# A life expectancy of at least 6 months.

Control Group: None

Primary Endpoint: To determine whether cellular immunotherapy with DC/M-FP cancer vaccine can lead to clinical responses or stabilisation of disease, as determined by a change in the serum CA125 in patients with adenocarcinoma of the ovary. Patients were classed as major or minor responders or as having disease stabilisation or disease progression.

Secondary endpoints: Safety, survival without progression of disease, and immune responses to CVacTM.

SOURCE: Prima BioMed Limited

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