The Food and Drug Administration has proposed a regulatory path for biosimilar biologics that are interchangeable with the reference product, paving the way for a new generation of less-expensive versions of these unique drugs.

But bringing an interchangeable biosimilar to market won’t be easy. The bar for interchangeability will be high, requiring that manufacturers prove switching between the new and older products is safe. And clinicians, while cautiously optimistic, aren’t thrilled with the industry payoff that could come with the designation: freedom for insurance companies and pharmacies to switch products at the dispensing level without requiring a new prescription.

The draft FDA guidance for industry, “Considerations in Demonstrating Interchangeability With a Reference Product,” arises from the Biologics Price Competition and Innovation Act of 2009. That section of the Affordable Care Act provides for abbreviated approval pathways for biological products that are demonstrated to be “highly similar” (biosimilar) to or “interchangeable” with an FDA-approved biological product.

The difference between these appellations is subtle but critical to the regulatory process – and perhaps to patient safety. Regulators recognize that the structure of these large, highly complex molecules can never precisely replicate the reference product. But to be labeled a “biosimilar,” developers must prove that the new product functions essentially the same; there can be no clinically meaningful differences in terms of safety, purity, and potency. Unlike a generic medication, a biosimilar can’t be substituted for its reference product at the pharmacy level. If a physician wants the patient on that biosimilar, the script must specify it.

Interchangeables jump a higher regulatory bar

An “interchangeable biosimilar,” though, would have to jump a higher regulatory bar. Not only must it produce the same clinical result as the reference product, it also must be benignly interchangeable with it, conferring no additional risk if a patient switches from the reference to the biosimilar and back again. A pharmacist could, if permitted by state law, substitute an interchangeable product for the reference product without going through the prescriber.

Like biosimilars, interchangeable products need not be tested in every disease for which the reference drug is approved, according to the document. Once they are proved safe for one indication, those data can be extrapolated to allow approval for the other indications as well. Nor do biosimilars need to prove efficacy per se, as their molecular similarity to the reference product ensures that they bind to the same receptor and exert the same therapeutic effect.

The biosimilar/interchangeable market has been slow to take off in the United States. There are no approved interchangeable biosimilars, and only four biosimilars – three of which were approved in 2016:

• Sandoz’ filgrastim-sndz (Zarxio).

• Pfizer’s and Celltrion’s infliximab-dyyb (Inflectra).

• Sandoz’ etanercept-szzs (Erelzi).

• Amgen’s adalimumab-atto (Amjevita).

Switching studies is the key to achieving the interchangeable designation, according to the FDA document. They must include at least two full switches between the candidate product and the reference product, which must be licensed in the United States.

But because these products are so structurally diverse, the FDA isn’t imposing a one-size-fits-all process on them. Instead, the molecular complexity and immunogenicity of each product will dictate its approval requirements.

Those with relatively low structural complexity, high molecular similarity to the reference product, and a low incidence of immunogenic adverse events may only need a single switching study to achieve the “interchangeability” designation.

The bar will be higher for a product with high structural complexity that is not as similar to the reference product, or which has been associated with immunogenic adverse events. For this product, FDA might also require extensive safety postmarketing data for the product as a licensed biosimilar, as well as a switching study.

Pharmacokinetics, pharmacodynamics, immunogenicity, and safety will be the primary endpoints of a switching study. Efficacy data are not necessary but can be used as supportive endpoints. Any safety signals in a switching study would raise regulatory eyebrows whether they came from the candidate product or the reference product. Since the study replicates what could happen if the two were used sequentially, it makes little difference from which product the event might arise.

“If an apparent difference in immune response or adverse events is noticed between the switching and nonswitching arms of the study ... it would raise concerns as to whether the proposed interchangeable product is interchangeable, regardless of whether the proposed interchangeable product or the reference product or the switching of the two products actually caused the event,” the document notes.

The E.U. vs. U.S. experience

The United States is only now getting a taste of what has become common fare in the European Union, said Angus Worthing, MD, chair of the American College of Rheumatology’s Government Affairs Committee. The European Medicines Agency approved its first biosimilar in 2006. Since then, 23 such drugs have come on the market, at an average price of about 30% less than the reference drug. Prices for some drugs have dropped as much as 70% in countries in which national health care systems abandoned the reference product in favor of the competing biosimilar, Dr. Worthing said in an interview.

“But the U.S. doesn’t have a national health care system, so it won’t work like that here.” In fact, he noted, brand-new data show that Medicare actually paid 22% more for the infliximab biosimilar Inflectra than it did for Remicade in the last quarter of 2016.

It’s not immediately apparent why this is the case, but it’s probably related to company discounts and rebates on these very expensive drugs. According to the report in Inside Health Policy, Janssen Biotech may have increased its discount on the drug to compete with Inflectra’s launch price of 15% below Remicade’s wholesale cost. Prices won’t moderate as much in the United States as in the European Union until several biosimilars of the same class appear, Dr. Worthing said.

There have already been allegations that big pharma manipulates international and national pricing to reduce biosimilar competition.

In June, Russian biotech company Biocad filed a lawsuit in New York charging Roche/Genentech with price fixing. The suit alleges that the companies cut the cost of three cancer drugs (Avastin, Herceptin, and Rituxan/MabThera) in Russia, where Biocad markets biosimilars for each. At the same time, Biocad alleges, the companies raised U.S. prices on those drugs to make up for the money they were losing on the Russian market.

It’s also unclear who would actually reap the financial rewards of a burgeoning biosimilar market in this country, said Jonathan Krant, MD, chief of rheumatology and chairman of the department of medicine at Adirondack Health Systems in Saranac Lake, N.Y.

“I think most of the cost benefits will accrue to insurance plans and pharmacy managers, but maybe not to the patients themselves,” he said in an interview. “The most important beneficiaries may not see a single penny of benefit.”

It may be difficult to extrapolate the European economic experience into the U.S. health care market, but the safety record of its biosimilar armamentarium is solid. None of the biosimilars approved in the E.U. have ever been recalled or removed from the European market because of regulatory or safety concerns.

Nonmedical switching raises concerns

Academic medical societies and clinicians interviewed for this article view the proposed approval pathway with cautious optimism. While acknowledging the potential benefit of reducing the costs of prohibitively expensive drugs, they uniformly insist that patient safety – not economic pressure – should be the driving force here.

“I was initially skeptical, and I do believe that we need very close pharmacovigilance in monitoring these for safety,” said Gideon Smith, MD, PhD, a dermatologist at Massachusetts General Hospital, Boston. “But there has been huge uptake of these products in the E.U., and the data are so extensive that we can be reasonably confident these drugs are effective, and no good reason to believe the safety will be any different.”

He is not as comfortable with the prospect of pharmacy-level substitution of an interchangeable biosimilar with the reference product – a feeling that other clinicians echoed.

“I think this is a fundamental issue that should have been dealt with on a federal level. Physicians should always be involved in the decision,” said Dr. Smith, who spoke at an FDA advisory committee meeting last summer on behalf of the American Academy of Dermatology (AAD).

The prospect of switching between products makes gastroenterologist Stephen Hanauer, MD, nervous.

“In general, the GI field is OK with the idea of starting someone on a new prescription [of an interchangeable biosimilar], but not so much with the idea of switching around,” said Dr. Hanauer, who is the Clifford Joseph Barborka Professor of Gastroenterology at Northwestern University, Chicago. “In these biologic compounds, very small differences can be amplified” and alter therapeutic response.

The possibility of switching from the reference to the biosimilar and maybe back again worries him. He hearkened back to the approval of Remicade, when patients who had taken it during clinical trials only were finally able to obtain it on the market. Dr. Hanauer explained that, “20% of them developed serum sickness reactions after the reexposure.”

He also expressed some concern about quality control in international manufacturing plants, citing a 2005 epidemic of immune-mediated pure red cell anemia in patients who received an epoetin alfa biosimilar manufactured in Thailand. The prefilled syringes had an uncoated rubber stopper that apparently reacted with polysorbate 60 in the solution – an interaction that increased immunogenicity when the drug was administered subcutaneously.

Dr. Smith concurred. “We know that some patients produce antibodies to biologics if they come on and off, and so we discourage that. The concern is that switching may lead to an increased rate of medication failure, if you have to switch back. This is especially troubling in the case of a hard-to-control patient with severe flares. If they’re being well controlled on a medication, the last thing you want to do is change it for no good clinical reason. And we may well be forced to do that.”

Neither the AAD nor the American College of Gastroenterology has a published stand on the FDA’s proposed guidance for interchangeable biosimilars. The preliminary view of the American College of Rheumatology is a positive one, Dr. Worthing said. However, ACR feels pharmacy-level switching should be a joint, not unilateral, decision.

“Our position statement on biosimilars has been that if it’s legal for a pharmacy to make that switch then we want the doctor and the patient to know, so we can track for safety signals.”

Bringing any biosimilar to market, though, takes a lot of money and a lot of time. And while companies are growing cell lines and producing new molecules that mimic existing drugs, science marches on, said Dr. Smith.

“If we keep dragging our feet on this issue, it might end up being a moot point,” he said. Newer drugs are achieving better results, raising the bar for therapeutic success. An example is the monoclonal antibody secukinumab (Cosentyx), an inhibitor of interleukin 17A. In October 2016, late-breaking data released at the annual meeting of the European Academy of Dermatology and Venereology impressed the dermatology community. In psoriasis patients, the drug maintained 90% skin clearance for 4 years in 66% of patients, and 100% clearance for 4 years in 43%.

Not only does this kind of efficacy provide symptomatic relief, it also prevents the expensive long-term morbidity associated with psoriasis, Dr. Smith said.

“Even if these new medications are considerably more expensive upfront than a biosimilar for an older drug, they may end up being less expensive in the long run.”

Dr. Krant and Dr. Worthing had no financial disclosures. Dr. Smith has received grants from Allergan and Cipher Pharmaceuticals. Dr. Hanauer has received grants from numerous pharmaceutical companies that manufacture biologics.

*This article was updated 1/31/2017.

msullivan@frontlinemedcom.com

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FDA opens abbreviated approval pathway for interchangeable biosimilars