Differences in the intracellular accumulation of HIV protease inhibitors in vitro and the effect of active transport

Objectives: To investigate the intracellular accumulation of HIV protease i nhibitors (PI) and to assess the effect of active transport on this accumul ation. Methods: CEM cells were incubated with a PI for 18 h and the intracellular concentration determined using cell number and radioactivity. The effect of active transport was investigated using cells expressing P-glycoprotein (C EMVBL) and cells expressing multidrug resistance-associated protein 1 (MRP1 ; CEME1000) Incubations were also carried out at 4 degreesC and in the pres ence of 2-deoxyglucose plus rotenone to examine the effect of inhibiting ac tive transport. Results: Nelfinavir (NFV) accumulated to the greatest extent (> 80-fold) fo llowed by saquinavir (SQV; similar to 30-fold), ritonavir (RTV; 3-7-fold) a nd finally indinavir (IDV; extracellular equivalent to intracellular). In C EMVBL cells there was a significant reduction in the intracellular accumula tion of NFV, SQV and RTV and in CEME1000 cells there was reduced accumulati on of SQV and RTV Inhibition of active transport processes caused a reducti on in SQV and RTV accumulation but had no effect on IDV accumulation in all cell types. NFV accumulation was increased in CEM(VBL)cells as a result of inhibition of active transport. Conclusions: Marked differences can be detected in the intracellular accumu lation of HIV PI drugs in vitro. Both P-glycoprotein and MRP1 may play a ro le in limiting the intracellular concentration of the PI and active influx mechanisms may contribute to drug accumulation. (C) 2001 Lippincott William s & Wilkins.