Placebo-Controlled Trial of Antibiotic Therapy in Adults With Suspect Lower Respiratory Tract Infection (LRTI) and a Procalcitonin Level

This is a randomized, double-blinded, placebo-controlled, non-inferiority multicenter clinical trial of azithromycin vs. placebo in adults presenting as outpatients with suspect Lower Respiratory Tract Infection (LRTI) and a Procalcitonin (PCT) level of \< / = 0.25 ng/mL, as a strategy for reducing antibiotic prescriptions. The study is designed to compare the efficacy of azithromycin versus placebo on Day 5 (i.e., after 4 days of treatment) in subjects with suspect LRTI and PCT levels of \< / = 0.25 ng/mL at enrollment using a non-inferiority approach. The study will recruit potential subjects 18 years of age or older who are suspected to have LRTI. The enrollment cap will be 840 participants, for the goal of approximately 674 randomized participants who will be randomized 1:1 to receive oral azithromycin or placebo for five days. Randomized subjects will have efficacy measured from the time of the first dose of study drug (Day 1) through approximately Day 28. The primary objective is to compare the efficacy of azithromycin versus placebo on Day 5 (i.e., after 4 days of treatment) in subjects with suspect LRTI and PCT levels of \< / = 0.25 ng/mL at enrollment using a non-inferiority approach. The secondary objectives are to compare:1) groups receiving azithromycin versus placebo with regard to all antibiotic use by Days 11 and 28; 2) groups receiving azithromycin versus placebo with regard to return visits to a physician's office or urgent care by Days 11 and 28; 3) groups receiving azithromycin versus placebo with regard to emergency department visits by Days 11 and 28; 4) groups receiving azithromycin versus placebo with regard to hospitalization by Days 11 and 28 if not hospitalized at the enrollment and randomization visit; 5) groups receiving azithromycin versus placebo with regard to improvement in presenting symptoms by Days 11 and 28; 6) the efficacy of azithromycin versus placebo on Day 11 in subjects with suspect LRTI and PCT levels of \< / = 0.25 ng/mL at enrollment using a non-inferiority approach; 7) the efficacy of azithromycin versus placebo on Day 28 in subjects with suspect LRTI and PCT levels of \< / = 0.25 ng/mL at enrollment using a non-inferiority approach; 8) the efficacy of azithromycin versus placebo in subjects with suspected LRTI and PCT levels of \< / = 0.25 ng/mL at Day 5 using a superiority approach, employing the "Response Adjusted for Days of Antibiotic Risk (RADAR)" methodology; 9) groups receiving azithromycin versus placebo in regard to solicited events by Day 5; 10) groups receiving azithromycin versus placebo in regard to hospitalization or visits to an Emergency Department (ED), outpatient clinic, or urgent care center for worsening or persistent LRTI after randomization by Day 5; 11) groups receiving azithromycin versus placebo in regard to improvement in vital sign abnormalities or symptoms present at enrollment, on Day 5; 12) groups receiving azithromycin versus placebo in regard to new vital sign abnormalities or symptoms on Day 5, or deterioration in symptoms relative to the enrollment visit on Day 5.