Memo to the FDA and ICH: appeal for in vivo drug target identification and target pharmacokinetics Recommendations for improved procedures and requirements.

This memorandum is addressed to members of regulatory agencies, as well as managers of pharmaceutical companies. Pharmacokineticists and toxicologists may consider this proposal, weigh its merits, and provide input for implementation. Experience from academic research and ADME experiments during drug development has prompted this appeal for improved drug target recognition. Similar demands have been made repeatedly in the literature. Such efforts are not new, but a renewed urgency has come from comparing results obtained with methods of different resolution and sensitivity, namely high-resolution receptor microscopic autoradiography compared and viewed in parallel to conventional low-resolution 'cut-and-count' radioassays and whole body autoradiography. Conflicting results reveal astounding deficiencies of current ADME approaches. False negatives and false positives of favored 'expedient' procedures allow drugs to reach the market with misleading and inaccurate information about the total drug effect.