The U.S. Patent and Trademark Office has agreed in principle to grant Purple Biotech a patent on the core design of its CAPTN-3 cancer antibody platform. The agency issued a Notice of Allowance — its determination that an application meets patentability requirements, ahead of formal issuance — for an application titled "Precursor Tri-Specific Antibody Constructs and Methods of Use Thereof," the company said in a September 2 press release filed with the SEC.
CAPTN-3 is built around antibodies that do three things at once: bind to a tumor and recruit both T cells and NK cells to attack it. Most approved cancer antibodies engage only one type of immune cell. The allowed claims cover constructs with dual tumor-targeting binders — the antibody grabs the tumor in two places simultaneously — alongside other features of the platform, according to the release.
The platform also uses what the company calls capping technology, designed to confine immune activation to the area immediately around the tumor. The goal is to avoid the system-wide immune reactions that have limited conventional T-cell engager drugs, a class of cancer therapy that pulls immune cells toward tumors but can trigger dangerous inflammation elsewhere in the body.
Shares closed 19.28% higher at $1.9800 after the announcement, on dollar volume of about $178 million.
What the patent most directly protects is the platform's modular architecture. Rather than designing each new antibody candidate from scratch, CAPTN-3 is structured so the tumor-targeting component can be swapped in and out while the rest of the design stays the same. "This allows us to rapidly develop new multispecific antibody candidates by incorporating different targeting domains and functional components," CEO Gil Efron said in the release.
The platform's lead candidate, IM1240, is advancing toward the clinic, according to the release. A second candidate, IM1305, is in preclinical development. The company gave no timeline for either.
A Notice of Allowance is not a granted patent. The USPTO still requires payment of issue fees before the patent formally issues, and the protection it confers does not take effect until then.