Extreme Language: Ultra-High Potency

By David O’Connell, BSc (Hons), Director of Scientific Affairs

The latest generation of small-molecule therapies is redefining containment requirements, pushing far beyond what conventional HPAPIs demand—and prompting a rethink of both industry language and infrastructure. For decades, “high potency” has been the catch-all term for active pharmaceutical ingredients (APIs) requiring specialized handling, stringent engineering controls, and risk-based containment, with the acronym HPAPI embedded in regulatory guidance, production protocols, and outsourced service offerings. Yet as potency continues to escalate, this designation increasingly falls short of describing the extraordinary demands of next-generation molecules.

A growing subset of small-molecule therapies — including targeted protein degraders (TPDs) like PROTACs, SERDs, and molecular glues, as well as certain ADC payloads — exhibit higher potency, narrower therapeutic windows, and more complex toxicology than the legacy compounds that defined the original HPAPI category. Their properties often exceed the capabilities of traditional high-potent facilities, requiring pharma companies and CDMOs to rethink — or even reinvent — risk management strategies. In response, the term “ultra-high potency” has emerged. While not yet formally recognized by regulators, it captures the practical need to differentiate compounds at the extreme end of the potency spectrum.

The takeaway is clear: as pharmacological science advances, existing classifications no longer suffice, and the industry must evolve its terminology, protocols, and infrastructure to keep pace.