Can Blood Biomarkers Predict Clinical Response to Azithromycin in Cystic Fibrosis Patients?

Although azithromycin can lower pulmonary exacerbation (PEx) risk in patients with cystic fibrosis (CF), it does not help all patients. This study assessed whether any blood protein markers could serve as indicators of clinical response to azithromycin treatment in young CF patients. The study included 188 serum and plasma protein samples from 40 CF patients who were randomized to receive azithromycin in the AZ0004 trial. The researchers applied novel proteomic technologies to the samples and analyzed early changes in blood protein levels from day zero to 28 of treatment in regard to changes in forced expiratory volume in one second (FEV1) percent predicted and weight by days 28 and 168 and to predict PEx risk by day 168. After 28 days of azithromycin treatment, there was an association between early changes in 15 plasma proteins’ levels and FEV1 percent predicted from day zero to 28, but this did not extend to day 168. Early serum calprotectin level changes after 28-day azithromycin treatment predicted PEx risk by day 168 of treatment. Using a calprotectin cutoff to maximize test sensitivity (88%) and specificity (68%), two in five patients whose calprotectin reduction was less than the cutoff sustained at least one PEx versus 8% of patients whose calprotectin reduction was greater than the cutoff. The authors concluded that early changes in blood protein markers after treatment with azithromycin corresponded with short-term lung function changes but not long-term. Early serum calprotectin level changes indicated azithromycin response regarding PEx risk modification. Read more