Leukemia is a cancer of the bone marrow and blood that accounts for at least 300,000 new cases and 222,000 deaths worldwide each year - a very high death rate. Wilms' Tumor gene 1 (WT1) is highly associated with these types of cancer. Preclinical data from mice showed strong induction of antigen-specific CD8+ T cells and the ability to kill human tumor cells expressing WT1. This is the first study to combine DNA vaccination with electroporation delivery of WT1 antigens with the goal of stimulating high and durable levels of immune responses, in particular T cells, which are considered critical for improving clinical outcomes for this disease.
The principal investigator of this study, Dr. Ottensmeier, said, "These preliminary data show strong vaccine-induced immune responses in vaccinated subjects in the CML arm. We are looking forward to enrolling and testing the vaccine's impact in AML patients, who currently have limited treatment options and a low rate of progression free survival."
In this ongoing phase II trial, all participants initially receive six doses of two DNA vaccines (called p.DOM-WT1-37 and p.DOM-WT1-126) delivered at four week intervals. Vaccine responders may continue with booster vaccinations every three months out to 24 months. An additional 60-75 AML/CML patients are being enrolled across the two arms as non-vaccinated controls for comparison. The primary endpoints are molecular responses to a disease marker called BCR-ABL in CML patients and time to disease progression in AML patients. The study is also monitoring WT1 transcript levels, immune responses to the WT1 antigen, time to progression and overall survival, and two-year survival in the AML group. The trial is taking place at hospitals in Southampton, London and Exeter. Regulatory approval to start this clinical study was provided by the UK Medicines and Healthcare Products Regulatory Authority (MHRA) and Gene Technology Advisory Committee (GTAC).
Inovio's CEO, Dr. J. Joseph Kim, said, "We are encouraged by preliminary phase II data showing the WT1 DNA vaccine's potential, administered with our novel delivery technology, to generate T cells and robust antibodies to treat leukemia. These results follow on our recent scientific breakthrough represented by our human data showing the powerful killing effect of T cells generated by our cervical dysplasia therapeutic vaccine.About Leukemia Leukemia is a malignant disease (cancer) of the bone marrow and blood characterized by the uncontrolled accumulation of blood cells. Leukemia accounts for at least 300,000 new cases and 222,000 deaths worldwide each year. This high ratio of deaths-to-cases (74%) reflects the poor prognosis of leukemia in many parts of the world, where the somewhat complex treatment regimes are not available. Approximately 45,000 new cases of leukemia were diagnosed in 2008 in the US, with 20,000 deaths. This represents 3% of all cancers in the United States, and 30.4% of all blood cancers. It is estimated that approximately $3 billion is spent in the United States each year to treat leukemia. There are five types of leukemia based on rate of development and types of blood cells affected. Two of these are being evaluated in the study discussed in this release: 1) Acute myeloid leukemia (AML), a cancer of the myeloid line of blood cells, is characterized by rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute leukemia affecting adults and its incidence increases with age. Only about one-third of those between ages 18-60 who are diagnosed with AML can be cured. With conventional chemotherapy 70% of the patients in the group under study will relapse within two years and current therapy is devastating in older adults; and 2) Chronic myeloid leukemia (CML) is a type of cancer that causes the body to produce large numbers of immature and mature white blood cells (myelocytes). Approximately 85% of patients with CML are in the chronic phase at the time of diagnosis. Ultimately, in the absence of curative treatment, the disease progresses to an accelerated phase where median survival is around 3-5 years. Chronic myeloid leukemia can occur at any age, but it more commonly affects middle-aged and older people.