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Tin-117m is an isotope that emits both a photon that can be imaged with a standard gamma camera, and therapeutic conversion electrons that deposit their energy completely out to ~300μm in tissue.  This unique conversion electron energy has several distinct advantages over traditional radiation therapy including an ideal two week half-life and an unprecedented safety profile which allows shipping with minimal handling procedures.  Tin-117m is manufactured at-will in the United States and is available to other investigators for research purposes.  Manufacturing under cGMP for pre-clinical and clinical studies as well as for the commercial products is available.  There are no other isotopes identified that have the unique characteristics of tin-117m which make it ideal for these medical applications.

Proprietary Homogeneous Tin-117m Colloid is consistently manufactured to a specific, reproducible size.  This particle size is large enough to allow the tin-117m colloid to remain >99% within the joint, and yet is small enough to be readily engulfed by synovial macrophages, as seen in this autoradiogram showing colloid particles dispersed throughout the synovium of a joint (arrow head).

Radiosynoviorthesis is the process whereby a radioisotope, typically in colloidal form, is injected into the joint space of an inflamed joint.  Radiosynoviorthesis decreases the pain associated with the inflammatory condition.  The procedure has been used in humans for decades to treat osteoarthritis, rheumatoid arthritis and other conditions, outside of the United States using β particle-emitting radioisotopes.  Although these treatments are generally successful, the radioisotopes used can have negative consequences when their energy is deposited beyond the tissues of the joint space.  This is not an unusual outcome for the colloids associated with these radioisotopes which may become distributed systemically causing additional irradiation outside of the tissue of interest.  

Other Serene Development Projects–Serene has several active, advanced tin-117m-based projects:

  • Cardiovascular–Vulnerable plaque is the primary target for a tin-117m-linked biologic molecule.  The first indication, which has successfully completed a Phase 1/2 human trial, is for the treatment of symptomatic, inoperable high-grade carotid artery stenosis.
  • Oncology–For the treatment of cancer indications, several therapeutic molecules and devices are being developed including a Phase 2 clinical trial for bone metastases which has been successfully completed using a systemically delivered tin-117m-labelled molecule.  Several tin-117m-labelled molecules for other oncologic indications are also in the pipeline.  Additionally, tin-117m electroplated devices for cancer treatment and palliation are in development.
  • Rheumatoid arthritis–Mannosyl-dextran specifically targets the CD206 mannose receptor expressed on macrophages that are activated in many disease processes. By attaching tin-117m to mannosyl-dextran, this allows the opportunity to precisely target the intended region for therapeutic treatment with coincidental imaging to confirm correct accumulation of product.

Tin-117m Based Product Development Pipeline

For partnering opportunities, please contact Nigel Stevenson, PhD, at .

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