Chemicals & raw materials USP Novel Excipients survey


The results of US Pharmacopoeia’s 2019 survey of 264 drug formulation experts on the use of novel excipients did not make comfortable reading for either the FDA or the pharmaceutical industry it regulates. The overwhelming majority of respondents (96%) agreed that excipients are at least very important in advancing a formulation through drug development. At the same time, around 40% of them reported that they had been forced to reformulate drug products for the US market because of the limitations of approved excipients, a process which typically takes between one and five years. Of those respondents, 28% discontinued development programmes because of similar issues. More than three-quarters of respondents also noted that they had faced challenges in using novel excipients in the US market. Regulatory issues represented the most frequently cited challenges, followed distantly by


safety concerns. Source: USP


are food ingredients and they’re making their way into very complex types of parenteral drugs,” explains Sheehan. “We need to have an understanding of whether there are better excipients out there that will provide a better function in these new therapies. We shouldn’t keep using the same ones over and over just because they are safe in the context of an approved drug that’s already on the market.” As Shoichet puts it, “On the one hand, you’d like to see more innovation in excipients, and on the other hand, you’d like them to be looked at with the same molecular and safety toolbox that we apply to drugs”.


“We need to have an understanding of whether there are better excipients out there that will provide a better function in these new therapies.”


Catherine Sheehan


Is every excipient truly inactive? In fact, an unwillingness to innovate can create its own risks. Not only might ‘established’ be somewhat less than ‘good’, it might not even equate to ‘safe’. In 2017, with FDA funding, Shoichet and his colleagues, along with a team headed by Laszlo Urban at the Novartis Institutes for BioMedical Research (NIBR), began investigating the FDA’s inactive ingredients database (IID), to find out more about how excipients worked. “We wanted to focus on: how do you get these molecules? If you want to do research on them, where can you buy them from? How pure are they? And where have they been used?” Shoichet explains. “There are a lot of excipients in that database that are officially approved as excipients, but no one’s used them in 30 years.” The team even found some drug ingredients that had been added by mistake. Shoichet and his fellow investigators were not convinced that every excipient listed was inactive. Almost all the excipients listed were “grandfathered in under looser rules that have since become much


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stricter, stalling further development,” says Shoichet. “Some had a long history of use and were just accepted as safe, by precedence alone. Others had gross animal toxicity studies and monographs for purity and conditions of use. These were also grandfathered in.” When the FDA started to regulate excipients more rigorously, these “had such a long history that everybody just agreed – see no evil – that they were fine,” he adds. Shoichet’s team created their own database and began investigating the excipients more thoroughly: “We have this method for taking the chemical structure of a molecule like an excipient, which we had designed for drugs, and saying, ‘What molecular targets in the body like enzymes, receptors, transporters, might this molecule be active on?’” After screening 3,296 excipients in the IID, Shoichet and his fellow researchers identified 38 excipient molecules that interact with 134 important human enzymes and receptors. “There was a substantial number that were active in vitro, so not necessarily in an animal or a human, but were clearly active on a target that is in animals and humans,” he says. Some were as potent as most drugs. “If they do get exposed, they’ll certainly have an effect and it’s just a question of knowing whether they’ll get exposed or not,” continues Shoichet. The probability is that most of them don’t, but under certain circumstances, such as in an individual with a leaky gut or where a patient is taking multiple drugs, there might be cause for concern. “The ones that there is most immediate worry about are the injected ones, because most orally dosed excipients don’t get out of the gut,” says Shoichet. This includes thimerosal, an excipient used in some vaccines. Shoichet’s research demonstrates just how much need there is for more innovation in the development of excipients. The good news is that in December 2019, the FDA announced a pilot programme to carry out a separate regulatory process for them. Giving manufacturers the opportunity to introduce new excipients outside of the drug application pathway will, believes Sheehan, bring “greater flexibility” to identify unforeseen issues in the early stages of the formulation process. It would also provide publicly available information about quality and safety so that formulators “have a common understanding and common starting point on the name, the definition and the chemical information description”.


An update on the pilot is expected in the summer of 2021. For Sheehan, who joined USP 20 years ago with the hope that an independent pathway for excipient regulation would be developed, it’s great – if surprising – news. “This has been percolating for four decades,” she says. “The launch of the pilot was a major milestone and for FDA to say that by this summer they will have an update on where they are with it is fantastic.” ●


World Pharmaceutical Frontiers / www.worldpharmaceuticals.net


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