OXS-1550 is a bispecific scFv recombinant fusion protein-drug conjugate composed of the variable regions of the heavy and light chains of anti-CD19 and anti-CD22 antibodies and a modified form of diphtheria toxin as its cytotoxic drug payload.  CD19 is a membrane glycoprotein present on the surface of all stages of B-lymphocyte development, and is also expressed on most B-cell mature lymphoma cells and leukemia cells.  CD22 is a glycoprotein expressed on B-lineage lymphoid precursors, including precursor acute lymphoblastic leukemia, and often is co-expressed with CD19 on mature B-cell malignancies such as lymphoma.

OXS-1550 targets cancer cells expressing the CD19 receptor or CD22 receptor or both receptors.  When OXS-1550 binds to cancer cells, the cancer cells internalize OXS-1550, and are killed due to the action of drug’s cytotoxic diphtheria toxin payload.  OXS-1550 has demonstrated success in a Phase 1 human clinical trial in patients with relapsed/refractory B-cell lymphoma or leukemia.

The initial phase 1 study enrolled 25 patients with mature or precursor B-cell lymphoid malignancies expressing the CD19 receptor or CD22 receptor or both receptors.  All 25 patients received at least a single course of therapy. The treatment at the higher doses produced objective tumor responses with one patient in continuous partial remission and the second in complete remission. A phase 2 trial of OXS-1550 is underway in patients with ALL/NHL. The FDA-approved clinical trial is being conducted at the University of Minnesota's Masonic Cancer Center. There are currently 18 patients enrolled in this clinical trial.  Patients in this trial are given an approved increased dosage and schedule of OXS-1550.

We began enrolling patients in phase 2 trial of OXS-1550 during the first quarter of 2017 at the University of Minnesota’s Masonic Cancer Center. The first patient began dosing in April 2017. We are currently considering the addition of clinical sites to assist with recruitment for this trial and to be involved in future OXS-1550 studies.