Pseudomonas aeruginosa is an opportunistic pathogen that rarely causes disease in healthy people, but is a significant problem for critically ill or immunocompromised individuals. Experts estimate that there are greater than 100,000 patients in the United States, Europe and Japan where Pseudomonas pneumonia occurs. Patients with Pseudomonas pneumonia currently represent only about 20% of the patients in the hospital who get Pseudomonas infections.

This trial will evaluate KB001 in patients in the intensive care setting who are receiving ventilator therapy and who have Pseudomonas infections. They will receive either placebo, or one of two dose levels of KB001, a Humaneered™, high-affinity antibody fragment that KaloBios is developing for the treatment of Pseudomonas aeruginosa (Pa) infections. This trial will evaluate the ability of KB001 to protect host epithelium and immune cells, and evaluate reduction of pulmonary Pa burden.

Inclusion Criteria:

• Provision of written informed consent obtained from patient or patient's surrogate if unconscious or altered sensorium
• Age >18 years
• On mechanical ventilation and expected to remain mechanically ventilated for at least 3 days
• Documented pulmonary Pa colonization

Exclusion Criteria:

• Patients with known chronic pulmonary infection with Pa (i.e., patients with cystic fibrosis)
• Patient currently diagnosed with Pa VAP
• Change in systemic antibiotic therapy active against Gram negative bacteria within 72 hours
• Use of an investigational medication within 4 weeks prior to randomization