The FDA has granted Fast Track designation to Sanofi Pasteur and KaloBios Pharmaceuticals’ investigational drug KB001A, an antibody fragment intended for protection against bacterial pneumonia caused by Pseudomonas aeruginosa (Pa) in mechanically-ventilated patients.

Sanofi Pasteur has worldwide rights to KaloBios' KB001A technology for all disease indications related to Pa infections, except cystic fibrosis and bronchiectasis, the rights in which were retained by KaloBios, and Sanofi Pasteur has the option to obtain at a later date.

"Sanofi Pasteur is currently targeting the antibody for use in primary prevention of Pa-associated pneumonia in mechanically ventilated patients in hospitals and we are also interested in providing prevention of relapses and improvement of treatment outcomes in patients with an ongoing Pa infection," said Michel DeWilde, Ph.D., senior vice president, R&D, Sanofi Pasteur. "Additional indications may be considered later in the lifecycle of the product."

Most serious Pa infections occur in hospitalized and critically or chronically ill patients—primarily affecting the respiratory system in susceptible individuals—and are a serious clinical problem due to the bacteria's resistance to antibiotics. Sanofi Pasteur, which is responsible for the clinical development under the terms of the agreement with KaloBios, is currently conducting a phase I trial of the monoclonal antibody in the U.S. and has started the planning of a phase IIb study.

KB001A, a Humaneered antibody fragment, is designed to fight Pa by blocking a virulence mechanism (the Type Three Secretion System or TTSS) on the bacterium's external surface that enables Pa to evade human immune defenses by killing white blood cells and epithelial cells, and triggering tissue-damaging inflammation. By blocking Pa's killing mechanism, KB001A is intended to reduce the damage done to the lungs by Pa and potentially enable the patient's own immune system to effectively fight and clear the bacteria from sites of infection. KB001A avoids known mechanisms of antibiotic resistance and does not contribute to broad-spectrum resistance, making it optimal for use as a single agent or in synergy with antibiotics in the preventive or therapeutic setting.

"KB001's novel mechanism of action against Pa may provide a unique means of fighting these infections, which are often resistant to antibiotic therapies,” said David Pritchard, president and CEO of KaloBios. “The FDA Fast Track designation recognizes that this novel biologic could address an important unmet medical need."