Reximmune-C® - Tumor-Targeted Injectable Cancer Vaccine
About Reximmune-C®
Reximmune-C is currently being developed as a targeted and individualized vaccination of patients against their specific cancers. It combines the tumor-targeting vector platform for efficient gene delivery in vivo (in the body) with a powerful immune-stimulating factor, called a cytokine. The targeted, injectable vector bearing the immune response gene works together with the patient’s own immune system to recruit the body's professional antigen-presenting cells to the site(s) of the residual cancer. Reximmune-C is designed to support tumor eradication by providing patients with a customized cancer vaccination that will evoke heightened anti-tumor immune responses and prevent cancer recurrence.
Technically, Reximmune-C is a matrix-targeted nanoparticle that seeks out the biochemical hallmarks of pathology (pathotropic targeting), accumulates in residual tumors, and delivers a copy of the human GM-CSF gene (granulocyte/macrophage colony stimulating factor) directly to remaining tumor cells. Rather than killing the residual cancer cells outright (as Rexin-G does), the expression of the GM-CSF protein in the tumor recruits the patients immune cells into this compartment and enhances their recognition of the tumor neo-antigens. In addition to assisting in the eradication of the residual tumors, and the cleaning up of residual tumor debris, the professional antigen-presenting cells are the very elements needed to help engender an anti-tumor immunity. To ensure that the GM-CSF-expressing tumor cells are eliminated after their therapeutic ‘utility’ is completed, a suicide gene is also incorporated into the expression cassette (as a fail-safe device) to enable the physician to control the vaccination time with pharmacological precision (a prodrug), which adds to the safety of the vaccine.
How Reximmune-C® is Delivered
Reximmune-C is administered by simple intravenous infusion. As the therapeutic nanoparticles are distributed by the general circulation, the exquisite targeting function serves to partition the genetic medicine into the tumors, thereby removing it from the blood stream. While the half-life of the active nanoparticle is rather limited (hours), the therapeutic gene that is efficiently delivered to the cancer cells acts over the next 24 hours to produce the immune-stimulating cytokine in the proximity of the tumor itself. Initial clinical studies in humans have demonstrated that localized immune responses are activated without raising the blood levels of the cytokine, thereby avoiding the problems associated with systemic toxicity. Reximmune-C can be used in strategic combination with Rexin-G (which kills tumor cells) to provide an abundance of tumor antigens for the activated immune cells to ‘recognize’ and respond to.
Clinical Development
Initial clinical findings are extremely promising (ASCO, 2008). Clinical trials are currently underway in the Philippines to establish the optimal doses, number of vaccine pulses, and the sequence and timing of the vaccinations needed to produce lasting remissions.
