This is a double-blind randomized, parallel group, placebo-controlled dose escalation study (2 cohorts) in patients with sickle cell disease (SCD) and vaso-occlusive crisis (VOC) who are at-risk for development of acute chest syndrome (ACS) based on the combination of VOC, fever (T ≥38.0ºC), and a serum sPLA2 concentration ≥50 ng/mL.