Comparison of a genomic and a multiplex cell imaging approach for the detection of phospholipidosis

Phospholipidosis (PLD) is a topic of concern in drug development because it may be associated with toxicological consequences. The aim of the study was to determine the best method to screen proprietary compounds with regard to their potential to induce PLD. Two in vitro approaches, a genomic method previously evaluated in our laboratory and a fluorescent cell based approach to detect PLD were compared using HepG2 cells. The same set of reference compounds (15 PLD inducing, 7 non-PLD inducing and 4 additional compounds) were used to compare both approaches. The same sensitivity (15/15) and similar specificity (7/7 versus, 6/7 for the genomic approach) were obtained. In addition, 11 proprietary compounds were tested in 4-day exploratory rat toxicity studies as well as in both in vitro approaches. Two of the 11 compounds induced alveolar foamy macrophages and lung vacuolization in vivo and were considered as PLD inducers. Sensitivity (2/2) and specificity (7/9) were better with the fluorescent method than with the genomic approach (1/2 and 3/9, respectively). In conclusion, compared to the genomic approach, the fluorescent method is the test of choice for screening compounds at an early stage of drug development. Indeed, the fluorescent method is more adapted to medium throughput, detects the positive reference compounds at lower (8/15) or equal (7/15) concentrations, allows multiplexing and is associated with higher sensitivity and specificity to predict lung foamy macrophages and vacuolization in vivo. Nevertheless, to confirm our conclusion, it would be necessary to compare the predictivity of both in vitro approaches by using a wide range of reference and proprietary compounds, with information on their potential to induce PLD under in vivo conditions.