Phase II PK/PD Driven Dose Finding Trial of Praziquantel in Children Under Four

Over 200 million individuals worldwide are infected with one of three predominant species of schistosomes, with over half of infections occurring in children.1 Recent studies have highlighted the fact that many children experience their first infections before the age of two, with the prevalence of infection among children under four mirroring the prevalence of older children and adults from the same community.2 Importantly, schistosomiasis has been implicated as a cause of linear growth stunting, undernutrition, anemia, and deficits in neurodevelopment among children over the age of four, representing a significant proportion of the global burden of disease due to schistosomiasis.3 Little is known with respect to the impact of schistosomiasis on key morbidities among the highly vulnerable group of children under four.

In the 1980s, Praziquantel (PZQ) was approved for the treatment of schistosomiasis among adults and children ages four and older, and remains FDA approved only for this age group. In 2008, the WHO funded studies to address the safety and parasitologic efficacy of PZQ in the context of S. haematobium and S. mansoni in young children. Based on these and other studies, the WHO in 2011 issued a report recommending that pre-school age children be treated as part of "regular health services."4 This recommendation was based on studies that did not a) evaluate pharmaco-kinetics/dynamics (PK-PD) in this age group, b) evaluate parasitologic efficacy in S. japonicum or c) evaluate the impact of treatment on key schistosomiasis-related morbidities. Since that time, co-PI Bustinduy led the first study of the PK-PD of PZQ at both 40 and 60 mg/kg dosing among children ages 3-8. Results from that study, albeit small, showed that higher doses are likely needed, particularly for younger children. Authors urged further study of higher doses in this age group, the causes of the significant inter-subject variability in PK-PD, better PD indices linking drug exposure to treatment effects, and enantiomer activity across all three species before introduction of monoenantiomeric formulations.5

Thus, significant lacunae remain with respect to treatment of pre-school age children, which contribute to the persistent exclusion of this vulnerable age group from preventive chemotherapy campaigns, with none of the 28 schistosomiasis endemic African nations or The Philippines currently including children under the age of four in control programs.2 In this application, we propose a trial to investigate the off label use of PZQ in children under the age of four. The trial will be conducted at two sites, with high prevalence of intestinal schistosomiasis due to S. mansoni (Uganda) and S. japonicum (The Philippines) employing a two arm single blind, placebo controlled modified cross-over trial design among N=600 children ages 1-4. Children who are infected with schistosomiasis will be randomized at baseline to receive 40 or 80 mg/kg of PZQ. At six months, we will re-randomize half of each baseline group to receive a treatment at the same dose or placebo. This will allow us to evaluate the impact of 6 versus 12 month treatment intervals on key measures of morbidity which, importantly, will inform frequency of treatment needed in this young age group. Successful execution of the following specific aims for this trial will address the significant aforementioned gaps:

SA1 To assess the PK/PD of PZQ administered at different dose regimens. SA1a To measure drug efficacy as per standard parasitological endpoints (Cure Rate and Egg Reduction Rate) at 4 +/- 1 weeks post-PZQ.

SA1b To expand PD endpoints for drug efficacy to include state-of-the art antigen tests to accurately capture residual worm burden (Circulating Cathodic and Anodic Antigens (CCA and CAA)).