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Oct. 9 (UPI) -- The U.S. Food and Drug Administration has released a series of documents to aid in the development of generic copies of complex drugs applied to a patient's skin. Transdermal and topical delivery systems, known as TDS, require correct medication doses consistently and for the expected length of time under the skin even if exposed to water, humidity and movement.
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"Because of the inherent complexity of delivering a drug through a TDS, making generic copies of these complex drugs can be especially hard," Dr. Scott Gottlieb, the FDA commissioner, said in a press release. "As a result, many branded TDS products like drug patches have not faced timely generic competition."
Gottlieb said the series of guidance documents are designed to advance the development of generic TDS.
"The increased transparency and predictability provided by these and other product-specific recommendations gives applicants seeking to develop generic copies of these complex products a better opportunity to efficiently advance these products and prepare better and more complete submissions," Gottlieb said.
One 12-page guidance provides recommendations for Abbreviated New Drug Application sponsors on the design and conduct of studies to evaluate the in vivo skin irritation and sensitizationpotential of a proposed TDS system.
A revised nine-page draft guidance supersedes a draft from June 2016 that provides recommendations for the design and conduct of studies evaluating the adhesive performance of a TDS.
Also, the FDA is also issuing 25 product-specific guidance documents that include two new and 23 revised guidances that will support industry in identifying appropriate science-based methodologies and evidence for developing generic TDS products.
"In too many cases, there is no generic competition for these costly branded drugs even after they have lost their exclusivity protections," Gottlieb said. "We have made a new commitment to develop product specific guidance documents laying out how to develop a generic copy of a branded medicine for any currently marketed, branded complex medicine in an effort to advance a more efficient and effective framework for developing generic copies of complex drugs."
The pathway for generic drugs was 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," Gottlieb said. "They were generally easy to characterize and evaluate through traditional methods, including traditional bioequivalence studies."
He added 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.
The complex drugs are not necessarily correlated to the amount in blood.
"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," Gottlieb said. "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."
Generic drugs are molecular copies that one company makes of a brand-name drug. Patents last 20 years from the date on which the application was filed in the United States.
In August, the FDA approved the first generic drug under a streamlined process, a treatment for low potassium blood levels in patients on diuretics. The designation was created to expedite the development and review of a generic drug for products that lack competition and have already lost the drugmaker's patent.
Like with brand-name drugs, the FDA reviews manufacturing and packaging facilities for generic drugs. In addition, the FDA has made public a list of drugs that can be made into generics.
Pharma companies have had a close relationship with the FDA, paying paid 75 percent -- or $905 million -- of the agency's scientific review budgets for branded and generic drugs, compared with 27 percent in 1993.
