First and Only Anti-Cancer siRNA Drug Candidate Currently Undergoing Human Clinical Trials

Calando Pharmaceuticals, Inc., a majority-owned subsidiary of Arrowhead Research Corporation, announced today the issuance of U.S. Patent No. 7,427,605, entitled, "Inhibitors of ribonucleotide reductase subunit 2 and uses thereof."

The patent contains claims directed to inhibitory nucleic acid sequences targeting the Ribonucleotide Reductase Subunit 2 ("R2") gene, as well as pharmaceutical compositions and methods for inhibiting tumor growth utilizing the sequences. R2 is the gene targeted by Calando’s lead siRNA-containing nanoparticle therapeutic, CALAA-01, which is currently in a Phase I clinical trial for patients with non-resectable or metastatic solid tumors. CALAA-01 is the only RNAi therapeutic for cancer to have reached the clinic.

"The issuance of this patent is an important milestone for Calando," said Dr. Jeremy Heidel, Ph.D., Calando’s Chief Scientific Officer for Nucleic Acid Delivery. "It provides a significant addition to the strong patent portfolio that Calando maintains for its CALAA-01 product."