KaloBios Pharmaceuticals, Inc. announced top-line data from the randomized, double-blind, placebo-controlled Phase 2 study of KB001-A, an anti-PcrV monoclonal antibody (mAb) fragment, to treat Pseudomonas aeruginosa (Pa) lung infections in subjects with cystic fibrosis (CF). While the data from this study showed KB001-A was generally safe and well-tolerated, the primary endpoint of increased time to need for antibiotics for worsening respiratory tract signs and symptoms (an indicator of reduction of the risk to develop pulmonary exacerbations) was not met. The company also evaluated time to need for antibiotics in a number of pre-specified subgroup analyses known to be associated with such risk and none demonstrated an improvement for KB001-A versus placebo.

In addition, secondary endpoints such as improvements in FEV1 and subject-reported outcomes as measured by Cystic Fibrosis Respiratory Symptom Diary (CFRSD) did not show an advantage with KB001-A treatment. The Phase 2 clinical study of KB001-A in CF subjects with Pa lung infections was a randomized, double-blind, placebo controlled study in which 182 subjects were randomized one to one between treatment with KB001-A or placebo. Eligible subjects were identified as CF patients whose lungs were colonized with Pa at the time of entry into the study, and who had been compliant in taking their antibiotics for at least the preceding two cycles.

Subjects enrolled in the 16 week study were allowed to continue on their antibiotics in the first four weeks of the study, after which antibiotics were withdrawn for the remainder of their time on the study. Throughout the 16 week study duration, subjects received either placebo or KB001-A dosed at 10 mg/kg every four weeks via intravenous administration with one additional loading dose at Week 2. The primary endpoint of the study was the time to need for antibiotics for respiratory signs and symptoms and was analytically expressed as a hazard ratio.