What impact could we expect at a community level from an effective rectal microbicide used by MSM in Peru? HJ Prudden, HC Johnson, AM Foss, J Peinado, J Sanchez, JR Williams, C Celum, PT Vickerman and CH Watts

Background  The HIV epidemic remains concentrated in high-risk groups including men who have sex with men (MSM) in Peru  There is known to be behavioural heterogeneity in anal sex roles, with different MSM behavioural subgroups having different risks of infection  Given the challenges of condom use, interest has been growing in the potential role of a rectal microbicide for MSM who have sex with men (MSM) in Peru Modelling microbicides can give insights into a range of issues:  Potential impact of the widespread distribution of a rectal microbicide  Relative impact associated with different microbicide attributes  Effect of potential condom substitution

Aim and Objectives The aim of this project is to use detailed biological and behavioural data from men who have sex with men (MSM) in Lima, Peru, to model the potential impact of a rectal microbicide on the HIV epidemic in this setting Objectives:  Project model-estimated future HIV epidemic trends among MSM  Estimate the potential impact on the HIV epidemic amongst MSM for a rectal microbicide for different assumptions about the coverage and patterns of use of the microbicide  Explore the effect of possible condom substitution 3

Model Components and Data Sources  A deterministic compartmental model was developed which:  simulates joint transmission dynamics of HIV, Herpes simplex virus type-2 (HSV-2) and Syphilis  incorporates 3 behavioural subgroups of MSM  Parameterised and fitted to setting-specific behavioural and epidemiological data in 2002  Latin Hypercube Sampling was used to obtain parameter sets

Model Features and Identity Groups 5 Identity grouping: population divided into role-based groups Predominantly Insertive Predominantly Receptive Versatile ActivoPasivo Moderno

Prevalence data and model illustrative fit

Key model parameter input estimates for model illustrative fit 7 Based on data collected for the sentinel surveillance 2002 study, supplemented with data from HPTN 039

Preliminary findings from illustrative fit for a microbicide with 60% efficacy: condom use remains the same as before the intervention (70%) 8 Microbicide intervention time frame:

9 Preliminary findings from illustrative fit for a microbicide with 60% efficacy : relative reduction in condom use of 20% Microbicide intervention time frame:

Limitations  Lack of data on sexual mixing patterns between subgroups  The model was fitted to 7 data points but only for one time point  Only one illustrative fit presented here in which the epidemic increases in the absence of microbicide during the intervention timeframe  Key next step to evaluate the uncertainty in the projections by identifying more model fits especially ones in which the epidemic plateaus 10

Key Messages Using mathematical modelling, it can be shown that the introduction of an effective microbicide in Peru could have a measured effect on reducing the percentage of HIV infections in MSM This study also highlights the importance of maintaining the current consistency of condom use following the introduction of a microbicide intervention This study emphasises the importance of pursuing further research and development into the use of rectal microbicides in helping prevent HIV 11

Acknowledgements  Collaborators:  London School of Hygiene & Tropical Medicine, UK  Imperial College London, UK  IMPACTA, Lima, Peru  University of Washington, USA  HIV Prevention Trials Network (HPTN 039), sponsored by the National Institutes of Health, U.S. Department of Health and Human Services  Funders:  Support for this research has been provided by amfAR  Some authors/coauthors are also members of DFID-funded RPC  Microbicides Development Programme (MDP), funded DFID and MRC 12 Advisory Group:  Steven Goodreau  Jerome Galea  Jim Hughes  Scott Rose  Sam Griffith  Cesar Carcamo