A randomized, controlled trial of Panax quinquefolius extract (CVT-E002) to reduce respiratory infection in patients with chronic lymphocytic leukemia.

Background: Chronic lymphocytic leukemia (CLL) patients are at high risk for acute respiratory illness (ARI).

Objective: We evaluated the safety and efficacy of a proprietary extract of Panax quinquefolius, CVT-E002, in reducing ARI.

Methods: This was a double-blind, placebo-controlled, randomized trial of 293 subjects with early-stage, untreated CLL conducted January-March 2009.

Results: ARI was common, occurring on about 10% of days during the study period. There were no significant differences of the 2 a priori primary end points: ARI days (8.5 ± 17.2 for CVT-E002 vs 6.8 ± 13.3 for placebo) and severe ARI days (2.9 ± 9.5 for CVT-E002 vs 2.6 ± 9.8 for placebo). However, 51% of CVT-E002 vs 56% of placebo recipients experienced at least 1 ARI (difference, -5%; 95% confidence interval [CI], -16% to 7%); more intense ARI occurred in 32% of CVT-E002 vs 39% of placebo recipients (difference, -7%; 95% CI, -18% to 4%), and symptom-specific evaluation showed reduced moderate to severe sore throat (P = .004) and a lower rate of grade ≥3 toxicities (P = .02) in CVT-E002 recipients. Greater seroconversion (4-fold increases in antibody titer) vs 9 common viral pathogens was documented in CVT-E002 recipients (16% vs 7%, P = .04).

Limitations: Serologic evaluation of antibody titers was not tied to a specific illness, but covered the entire study period.

Conclusion: CVT-E002 was well tolerated. It did not reduce the number of ARI days or antibiotic use; however, there was a trend toward reduced rates of moderate to severe ARI and significantly less sore throat, suggesting that the increased rate of seroconversion most likely reflects CVT-E002-enhanced antibody responses.