Nitrosylcobalamin (NO-Cbl) is an investigational drug that kills cancer cells through intratumor release of nitric oxide. This study assessed the drug in 4 dogs with various tumors: inoperable thyroid carcinoma, malignant peripheral nerve sheath tumor, apocrine gland adenocarcinoma, and spinal meningioma after surgical resection. he drug was given after surgery or after other therapies had failed. NO-Cbl was administered SC Q 24 H by owners. Tumor response was monitored by physical examinations and ultrasonography or magnetic resonance imaging. All 4 dogs showed a marked response to therapy; tumor reductions ranged from 43% to 77%. In 1 case, complete remission of spinal meningioma occurred after 6 months of therapy. One dog has safely received the drug for 61 months. Routine monitoring of complete blood counts and serum biochemical profiles revealed no signs of toxicity in the dogs.

COMMENTARY:
These investigators are also studying NO-Cbl in a larger group of dogs. The goal is to file an investigational new drug application with the Food and Drug Administration for use in humans. The drug is a vitamin B12 analog and exploits a tumor’s high need for vitamin B12 to divide and proliferate. Cancer cells cannot differentiate between regular B12 and NO-Cbl. When the drug binds to cancer cells, it releases NO, which kills cells via apoptosis.—Karen A. Moriello, DVM, Diplomate ACVD

Anti-tumor effects of nitrosylcobalamin against spontaneous tumors in dogs. Bauer JA, Frye F, Bahr A, et al. INVEST NEW DRUGS 2009; DOI 10.1007/s10637-009-9282-0.