B-cell lymphoma is cancer of B-lymphocytes and accounts for more than 20,000 deaths in the U.S. each year. While many patients respond to currently available therapy, there is a high rate of cancer relapse and inability for the patients o tolerate chemotherapy. Thus, there is a significant need to make available to these patients newer therapies that are more effective and better tolerated than the drugs that are currently used. Actinobac Biomed, Inc. is developing a natural biologic therapy that seeks out and kills a subset of white blood cells (WBCs). This therapy, Leukothera(R) (LtxA; leukotoxin), is a native protein derived from an oral bacterium. LtxA binds specifically to the active form of lymphocyte function associated antigen- 1 (LFA-1) and causes cell death. LFA-1 is found exclusively on WBCs, and malignant WBCs overexpress the molecule, making them ideal targets for the drug. During the phase I stage of this STTR application, we showed that 1) LtxA kills malignant B-cells using a unique mechanism of action, which involves Fas death receptor and caspase 8; 2) lymph node tissue samples from B-cell lymphoma patients express high levels of LFA-1; 3) LtxA causes complete regression of tumors in a humanized mouse model for B-cell lymphoma and results in long-term survival; 4) the drug is well-tolerated, highly active, and does not cause a neutralizing immune response in healthy dogs or a dog with naturally-occurring lymphoma, and 5) we have initiated expression and production of recombinant LtxA in a cGMP drug manufacturing facility in preparation for Investigational New Drug (IND)-enabling studies and clinical trials. Important pharmaceutical properties of LtxA include: 1) the drug works rapidly in vivo, within minutes or less; 2) doses as low as 0.5 g/kg have been shown to be highly active in animals; 3) neutralizing antibody to LtxA is not generated in healthy or diseased animals, even after repeat dosing; and 4) the high specificity of the drug allows targeting of a subset of WBCs and complete depletion of WBCs has never been observed with LtxA treatment. During this STTR phase II proposal, Actinobac will carry out IND-enabling studies that will be included in the IND application to the FDA.
B-cell lymphomas kill thousands of people each year. We are developing a biotherapeutic agent (Leukothera(R)) that has targeted specificity for malignant white blood cells. This phase II application will accomplish studies that are required for FDA approval to start testing in human patients with B-cell lymphoma.