We Are Developing a New Class of “Theranostics” to Treat Cancer
What is a
Theranostic?
The Combination of a Therapeutic and a Diagnostic
Theranostics enable the ability to see a specific tumor and then treat it.
Targeted Theranostics Provide the Potential to Improve Efficacy and Minimize Toxicity
Through the use of proprietary, specialized targeting peptides, we are able to diagnose and then deliver our powerful alpha-particle radiotherapy directly to the tumor. Utilizing a radioactive imaging agent, Pb-203, connected to a specific targeting peptide, we have the ability to diagnose the tumor. Following diagnosis, we link our alpha-particle radioactive isotope, Pb-212, to the same targeting peptide to treat and potentially kill the tumor. This two-step, personalized medicine approach offers the ability to understand which patients may respond to our therapy and potentially improve efficacy while minimizing toxicity associated with many other types of cancer treatments.
Targeting Peptides
Our image-guided targeted alpha therapies (TAT) leverage a specialized targeting peptide to deliver our diagnostic Pb-203 and cancer-killing Pb-212 directly to the tumor. Targets are carefully selected to ensure they are overexpressed on cancer cells and minimally expressed on normal healthy cells. When the peptide is radiolabled with our diagnostic Pb-203, the patient can be imaged (i.e., SPECT/CT) to reveal cancer cells in the body. When the peptide is radiolabeled with Pb-212 (alpha-particle emitting radiation) the target-peptide binding delivers powerful, yet locally deposited, cancer-killing alpha-particle radiation directly to cancer cells. This targeting mechanism allows for maximized therapeutic effects while minimizing off-target toxicities.
Pb-203 (Lead-203)
Pb-203 is a gamma-emitting nuclide that acts as the diagnostic in our innovative theranostic approach. Pb-203 has a long enough half-life to facilitate radiopharmaceutical preparation and gamma-ray imaging (e.g., SPECT or planar gamma camera) at time points up to 24 hours, and potentially 48 hours post-administration. The ability to collect data on the biodistribution of Pb-203 over this period allows for a more detailed understanding of tumor and other organ accumulation, retention, and clearance that can be used as part of a treatment planning process for determining appropriate administered radioactivity levels of Pb-212 for alpha-particle therapy.
Pb-212 (Lead-212)
Pb-212 is an alpha-emitting nuclide that acts as the therapeutic in our innovative theranostic approach. The higher linear-energy transfer (LET) of alpha-particles, compared to beta particles, results in an increased incidence of double-strand DNA breaks and improved localized cancer-cell damage. Pb-212 only has a half-life of 10.6 hours, which we believe provides many significant advantages over other radiotherapies, including faster clearance and the potential for reduced off-site toxicity. Its decay chain includes the short-lived isotopes bismuth-212, polonium-212 and thallium-208, which all emit either alpha or beta during decay over about another hour. The end of the decay chain is the stable element lead-208.
Mechanism of Action