Dose selection for toxicity studies: a protocol for determining the maximum repeatable dose

Area of Science:

• Pharmacology
• Toxicology
• Drug Development

Background:

• Formal regulatory toxicity studies (2-4 weeks) are crucial for new drug development.
• Designing these studies requires accurate dose selection and understanding of toxicokinetics.
• Current methods may lack efficiency in early-stage substance evaluation.

Purpose of the Study:

• To present a novel three-stage protocol for dose-ranging studies.
• To define the maximum repeatable dose (MRD) for new pharmacologically active substances.
• To generate essential toxicokinetic (TK) data for optimizing formal study designs.

Main Methods:

• A three-stage protocol (A, B, C) for dose-ranging and TK data generation.
• Stage A: Provisional MRD determination and basic TK data.
• Stage B: Daily dosing for ≥7 days to substantiate MRD and gather extensive TK data.
• Stage C: Single-dose administration at identified levels to correlate dose with TK data.

Main Results:

• The protocol efficiently determines the maximum repeatable dose (MRD).
• Comprehensive toxicokinetic (TK) data is generated, informing formal study protocols.
• The protocol can be executed with minimal animal use (e.g., 24 rats or 6 dogs).
• Early termination of development is possible for highly toxic substances based on protocol findings.

Conclusions:

• This dose-ranging protocol effectively previews toxicology and establishes the MRD.
• Integrated TK data significantly aids in selecting appropriate dose levels for formal toxicity studies.
• The protocol offers an efficient and resource-conscious approach to early drug development evaluation.