As part of the U.S. Food and Drug Administration’s efforts to promote drug competition and patient access, there are advanced many policies aimed at making it more efficient to bring generic competition to the market. These are drugs that, by nature of their formulation or delivery systems for example, are harder to “genericize” under our traditional approaches. As a result, these drugs often face less competition.
TDS products are applied to a patient’s skin and deliver the drug into and through the skin. These products should deliver the correct medication dose consistently and for the expected length of time. They should adhere consistently and uniformly to the skin, and should withstand variables such as exposure to water, humidity and movement. Because of the inherent complexity of delivering a drug through a TDS, making generic copies of these complex drugs can be especially hard. As a result, many branded TDS products like drug patches have not faced timely generic competition.
The new guidances releasing include the revised draft guidance, Assessing Adhesion with Transdermal and Topical Delivery Systems for ANDAs, which provides updated advice for the design and conduct of studies evaluating the adhesive performance of a proposed generic TDS. A second draft guidance, Assessing the Irritation and Sensitization Potential of Transdermal and Topical Delivery Systems for ANDAs, provides recommendations for the design and conduct of studies to evaluate the in vivo skin irritation and sensitization potential of a proposed generic TDS.
In addition to these documents, the FDA is also issuing 25 product-specific guidance documents. These include two new and 23 revised guidances. These documents will support industry in identifying appropriate science-based methodologies and evidence for developing generic TDS products.
To understand the challenges posed by complex generics, we need to go back to the pathway developed in 1984 under the Hatch-Waxman Amendments. This legislation put into place the framework for generic drug review at a time when most drugs were simpler small molecules requiring simple manufacturing processes. They were generally easy to characterize and evaluate through traditional methods, including traditional bioequivalence studies. In most cases, a drug’s activity correlated directly with how quickly it got into the blood and how long the drug stayed in the blood, so it could have its intended effect on the intended site of action.
In contrast, complex drugs involve cases where the drug is often harder to formulate and manufacture because it has a complex formulation or complex active ingredient. In other cases, the drug acts locally on the tissue rather than through the concentration in the blood.
This includes inhaled drugs that act directly on the lungs, a topical patch that acts directly on the skin, or an eye drop that acts on the surface of the eye. The therapeutic effect of these types of drugs does not necessarily correlate with the amount in the blood and can be more difficult to measure through the blood. They can raise other issues that make the traditional, and often simpler, metrics generally used to evaluate generic drugs and prove sameness difficult to employ. There’s often no easy way to make the demonstrations necessary for generic approval.
These draft guidances are aimed at ensuring that we provide as much scientific and regulatory clarity as possible with respect to complex generic drugs. This focus is critical because, first and foremost, these drug products provide important therapies to patients. These higher value generic business opportunities can help underwrite the costs of other generic applications at a time when we believe the generic industry is facing new economic pressures from rising costs, supply chain consolidation, increased competition and declining reimbursement on many competitive generic medicines.
