A Highly Potent Active Pharmaceutical Ingredient (HPAPI) is usually defined as an API with an occupational exposure limit (OEL) at or below 10 μg/m3 of air as an 8-h time-weighted average.
Cytotoxics are a subcategory of HPAPIs; cytotoxic drugs are highly potent but not all highly potent drugs are cytotoxic.
Early chemotherapy drugs (such as alkylating agents, anti-metabolites and topoisomerase inhibitors) interfered with the structure or function of DNA. The generalized cell-killing action of these compounds led to them being labelled as ‘cytotoxic’.
HPAPIs are usually classified in Occupational Exposure Bands (OEB), representing different level of toxicity and requiring different levels of containment. The lower and upper toxicity limits of each band is associated with a maximum and minimum Occupational Exposure Level (OEL).
The classification of a compound is based on the evaluation of qualitative and quantitative toxicity data available such as the mechanism of action, the therapeutic dose, the OEL, etc. In the absence of toxicity data, the classification can be made by default, based on the chemical structure of the compound by analogy with other compounds.
Various OEB banding systems are used by the industry and it is important to specify the system used and the actual OEL when sharing information on a compound.
Novasep usually refers to the 4 band Safebridge approach:
Many HPAPIs are in the oncology field, but HPAPIs may also be found in other therapeutic areas (e.g. respiratory).