Abstract 4591: Biotinylated derivatives of selective high affinity ligand (SHAL) therapeutics as companion diagnostics for prescreening non-Hodgkin's lymphoma patients

Selective High Affinity Ligands (SHALs) are a new class of small molecule targeting agents that can be designed to bind selectively and with high affinity to unique sites located on almost any protein. A series of SHAL-based therapeutics have been developed to target the cell surface antigen HLA-DR10 that is over-expressed on many B-cell derived malignancies. SHALs are created by first identifying subsets of potential ligands, or “recognition elements,” that bind to two or three neighboring unique sites on the surface of the target protein. Bidentate or tridentate SHALs are produced by linking two or three of these recognition ligands together using carbodiimide chemistry and a miniPEG and lysine scaffold. SHAL synthesis is rapid, uses relatively inexpensive, commercially available components, and is very versatile. Multiple forms of the SHAL can be created by combining different recognition elements (ligands) or by attaching a variety of tags (biotin, chelating groups, dyes, inhibitors) to the end of the linker. Using this approach, SH7139 has been developed as a promising therapeutic for treating non-Hodgkin's lymphoma. Previous studies have shown SH7139 to be effective in treating human B-cell lymphoma in a mouse xenograft model at extremely low doses (3.3μg/kg); 70% of the tumors disappeared within 30 days after treatment and did not reoccur during the remainder of the life of the animal. Here we report that a biotinylated derivative of SH7139 can be used as companion diagnostic to prescreen needle aspirates or biopsies from B-cell lymphomas and determine whether or not the tumor is likely to respond to SH7139 therapy. The staining protocol involves detecting the bound biotinylated SHAL using commercially available alkaline phosphatase reagents, and it works equally well with both fixed and unfixed biopsy sections. Biotinylated SH7139 has been used to identify potentially responsive B-cell lymphomas in both canine and human patients. The development of SHAL-based diagnostics in parallel with new SHAL-based therapeutics will help advance individualized therapies and minimize the systemic trauma and valuable time lost by patients given treatments that prove to be ineffective. Our results also suggest this diagnostic may also prove useful in determining whether malignancies over-expressing HLA-DR10 have metastasized and individual lymphoma cells have migrated out of the tumor into surrounding normal tissue. This research was supported, in part, by NIH/NCI