Co-administration of CAB causes a slight change in the systemic concentration of MTX. However, the concentration change is not clinically significant, hence, does not warrant dosing adjustment of MTX.
CAB Vs. MTX
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Study Design
A mechanistic PBPK model of CAB in the adult population was built using the Simcyp® v17.1 simulator by incorporating physico-chemical properties, in vitro clearance mechanisms, and in vivo data and validated as per regulatory specifications. The CAB PBPK model was validated through comparison with available clinical PK data following oral CAB 30mg administration in healthy volunteers. The simulator was qualified for predicting observed OAT1 and/
or OAT3 inhibition based DDIs. DDI simulations were performed to evaluate the effect of CAB oral doses on the exposure of OAT1/OAT3 substrates (methotrexate, tenofovir, ciprofloxacin, cidofovir, cefuroxime, oseltamivir carboxylate, baricitinib, and S44121)
Study Results
DDI simulations predicted a mean change in systemic exposure for tested OAT1/OAT3 substrates of <25% after co-administration with CAB at steady state
Study Conclusions
OAT1/OAT3 substrate drugs such as tenofovir, cidofovir, methotrexate were predicted to have a minimal risk of DDIs when administered with CAB. Similar CAB concentrations following oral and LA administration suggest that these results would apply to CAB LA. The predicted lack of interactions supports co- administration with OAT1/OAT3 substrates without dose adjustments.
References
Patel, A, Cozens, S, Ford, S, Spreen, W, Baker, M, Patel, P. Prediction of renal oat1 and oat3 inhibition by cabotegravir using pbpk modelling. Conference On Retroviruses And Opportunistic Infections. 2019; : .
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