The non-inferiority of piperonyl-butoxide Yorkool G3 insecticide-treated nets compared to Olyset®Plus measured by Anopheles arabiensis mortality in experimental huts in Tanzania.

BACKGROUND

Non-inferiority trials are recommended by the World Health Organization (WHO) to demonstrate that health products show comparable efficacy to that of existing standard of care. As part of the WHO Global Malaria Programme (GMP) process of assessment of malaria vector control products, a second-in-class insecticide-treated net (ITN) must be shown to be non-inferior to a first-in-class product based on mosquito mortality. The public health impact of the first-in-class pyrethroid-piperonyl butoxide (PBO) ITN, Olyset Plus, has been demonstrated in epidemiological trials in areas with insecticide-resistant mosquitoes, but there is a need to determine the efficacy of other pyrethroid-PBO nets to ensure timely market availability of nets in order to increase access to ITNs. The non-inferiority of a deltamethrin-PBO ITN Yorkool G3 was evaluated entomologically against Olyset Plus in experimental huts in Tanzania, following WHO guidelines for non-inferiority trials.

METHODS

The trial of the two pyrethroid-PBO ITNs was conducted in experimental huts in Lupiro, Tanzania, using a randomized 7 × 7 Latin square block design. The study ran for 49 nights in 14 huts assessing the mosquito mortality and blood-feeding of wild, free-flying, pyrethroid-resistant Anopheles arabiensis. Using the non-inferiority approach, the comparative efficacy (primary endpoint was mosquito mortality at 24 h and secondary endpoint was blood-feeding) of unwashed and 20 times field-washed pyrethroid-PBO Yorkool G3 ITNs, were compared with the first-in-class product Olyset Plus and against a pyrethroid-only ITN, PermaNet 2.0 ITNs, as a standard comparator.

RESULTS

The experimental hut trial demonstrated non-inferiority and superiority of Yorkool G3 to Olyset Plus based on mosquito mortality [51% vs. 39%, OR 1.68 (95% CI 1.50-1.88)], given that lower 95% CI exceeded 0.74 (delta of 39%) and the margin of no difference (1). Blood-feeding inhibition was high for all treated ITNs (> 90%) and Yorkool® G3 was non-inferior to Olyset® Plus [4% vs. 2%, OR 1.81 (95% CI 1.46-2.39)], given that upper 95% CI was less than 4.85 (delta of 4%). The pyrethroid-PBO ITNs were superior to the pyrethroid-only net, PermaNet 2.0, as determined by both the proportion of mortality and blood-feeding of mosquitoes (p-value < 0.05).

CONCLUSION

Yorkool G3 ITNs demonstrated non-inferiority to the first-in-class Olyset® Plus and superiority over the standard pyrethroid-only ITN, PermaNet 2.0 as measured by mortality and blood-feeding inhibition of wild pyrethroid-resistant An. arabiensis mosquitoes. Yorkool G3 ITNs are potential tools for the control of metabolic insecticide-resistant malaria vectors, and their market availability will contribute to the cost-effective selection of ITNs by malaria control programmes to improve population access to ITNs.