EMA: clinical data may not be needed for topical comparisons

The agency is developing guidelines on alternative ways for topical medicine makers to prove the comparability of their drugs with innovator products.

For topical products, small changes in formulation, dosage form, administration or the manufacturing process can significantly affect safety and efficacy. This makes showing therapeutic equivalence difficult in marketing authorisation applications, before and after approval, the EMA said.

While clinical trials are the benchmark for comparing the safety and efficacy of medicines, other tools may be used.

But these other options are currently very poor, according to the European regulator, which criticised their accuracy, sensitivity, reproducibility, and in vitro-in vivo correlation.

Currently, non-clinical equivalence measures include in vitro ​drug release through an artificial or human skin membrane to measure drug release rates. PK studies can also be used when there is a high level of absorption into the blood stream from the application site.

“The scientific rational[e] as to how these methods may be used to support a claim of therapeutic equivalence needs to be developed, taking account of the site of action of the active substance(s),​” said the EMA.

It called for an exploration of different methods, which should be “fully explored and understood to avoid inappropriate use and claims.​”

Non-clinical tools​

The EMA said it needs to review the way the industry understands and characterises topical drugs, “supported by a robust manufacturing process and control strategy.​”

Under present rules, most topical products cannot prove they are therapeutically equivalent based on pharmaceutical equivalence alone. But the EMA said it may waive this rule for solutions, such as eye drops, nasal spray, and cutaneous solutions.

It may also extend the exception to other dosage forms, if they can show pharmaceutical equivalence combined with another type of equivalence, for instance using in vitro ​or in vivo ​models.

This comparative quality data would include information on the relevant reference drug, qualitative and quantitative data about the product’s physical properties, microstructure, performance, and administration.

As well as the comparator issue, the EMA wants to reform shelf life rules for topicals. Expiry dates will in future incorporate evidence about in vitro ​stability as well as the usual chemical tests to make sure the drugs keep their efficacy throughout storage.

The public has three months to comment on the EMA’s concept paper​ before the agency’s Quality Working Party prepares draft guidelines on topicals.

Topical drugs​

Topical products are drug applied to parts of the body with a physical barrier – such as skin, eyes, and ears. The action of the API may work externally, on the surface of the physiological barrier; internally (around the physiological barrier); or beyond the barrier in adjacent tissues.

Bioavailability of topical drugs is affected by their physical and chemical properties, formulation, and manufacturing process.