Tumors can be eradicated by stimulating the "antigen-presenting cells” that capture tumor antigens and trigger tumor-specific CD8+ "killer" T cells. To test if the UltraLigands were capable of inducing anti-tumor immunity, tumors in mice were allowed to grow to > 4 mm in diameter and then treated with 5 injections of UltraLigand™ DNA into the tumor. Despite these arbitrarily stringent conditions, treatments were found that cured mice of two standard but difficult tumors - A20 lymphoma and B16-F10 melanoma.
Lymphoma treatment using UltraCD40L™ or UltraGITRL™
A simple protocol of intratumoral injections of plasmid DNA encoding multimeric soluble UltraCD40L™ (SP-D-CD40L) led to tumor eradication and long-term, tumor-free survival in 80% of mice. Because these tumors are infiltrated with immunosuppressive CD4+ CD25+ regulatory T cells (“Tregs”) and because GITRL turns off Treg immunosuppression (published in Clinical and Vaccine Immunology 13:1223-1230, 2006), multimeric soluble UltraGITRL™ (SP-D-GITRL) is another effective treatment for this lymphoma.
Melanoma treatment using a combination of UltraCD40L™ and other immunostimulants
B16F10 melanoma is a mouse tumor model that is extremely difficult to treat and is therefore used to qualify cancer immunotherapy ideas for subsequent testing in humans. For example, Yervoy™ (ipilimumab) was shown to double survival in B16F10 melanoma. Although Yervoy™ did not cure any mice of B16F10 melanoma, it still became a licensed treatment for melanoma in humans.
Multimeric has found that injections of UltraCD40L™ DNA (pSP-D-CD40L-NST, a 2nd generation version of this molecule) combined with two Toll-like receptor (TLR) agonists (CpG DNA for TLR9 and poly(I:C) for TLR3) plus extracellular ATP (ATPe) cures about 50% of mice without inducing autoimmunity (i.e., there was no loss of melanin pigment or "vitiligo"). When used without CD40L, CpG + poly(I:C) + ATPe did not cure any of the mice, demonstrating a requirement for UltraCD40L™ in this combination. Clinical trials of both of these TLR agonists and ATPe have shown that they can be safely used in humans, setting the stage for a clinical trial of this immunostimulatory combination. In addtion, the delivery of UltraCD40L™ DNA via nanoparticles was recently shown to be a highly effective way to deliver this novel immunostimulatory agent (published in PLOS One 4(10): e7334, 2009).