Sonoval is developing protein-based anticancer drug candidates including SON-211 and others, each engineered to minimize potential side-effects and manufactured using proprietary expression technology
SON-211 is a protein-based anticancer agent comprising the cytokine human interleukin 2 (IL-2) fused to modified portions of diphtheria toxin. It binds to, and kills, T lymphocytes that bear the IL-2 receptor, CD25. These include certain T cell lymphomas as well as T regulatory cells (Tregs).
Previous IL-2 diphtheria toxin fusion proteins had good clinical efficacy, but suffered from high levels of aggregated protein and contaminants. They also caused a major side effect called "vascular leak syndrome" (VLS) in some patients. VLS causes fluid retention and peripheral edema, sometimes leading to fatal pulmonary and cardiovascular failure.
SON-211 is a second generation version of this class of drug that retains the same high potency as its predecessors, but is manufactured as a fully monomeric compound without aggregates and is genetically modified to substantially reduce the potential for vascular leak syndrome.
SON-211 is being developed to treat two distinct forms of cancer:
Subclasses of non-Hodgkin lymphoma, including peripheral T cell lymphoma (PTCL) and cutaneous T cell lymphoma (CTCL) where the cancer cells express CD25 and are directly targeted and killed by SON-211. Current therapies are often not effective, with frequent relapses, particularly in more aggressive forms of these diseases. There is a major unmet need for more effective treatments.
Solid tumors, including melanoma, renal cell carcinoma, non small cell lung cancer, pancreatic, ovarian and breast cancers. In these diseases, SON-211 is designed to activate the patient's own antitumor immune system by killing Tregs which suppress the innate immune response. Patients with these diseases often fail chemotherapy regimens, while other treatments such as targeted drugs or checkpoint inhibitors (see below) are effective in only a subset of individuals. New treatment options are critically needed.
Recent studies have shown that SON-211 dramatically increases the efficacy of checkpoint inhibitors, another class of drug that activates the antitumor response, but by a different mechanism than SON-211. Sonoval plans to test SON-211 as a sequential combination therapy with checkpoint inhibitors for the treatment of solid tumors.