Biosimilars & Switching

Biosimilars are near-copies of complex biologic medicines that treat inflammatory bowel disease. In the United States, the Food and Drug Administration (FDA) confirms that approved biosimilars are as safe and effective as their reference products. An extra US-only legal label, interchangeability, allows pharmacist substitution under state law. This guide explains what those terms mean, what the evidence shows, and how switching is planned. (fda.gov)

Key takeaways

• FDA-approved biosimilars match the reference biologic in safety and effectiveness. (fda.gov)

• Interchangeability is a legal status for pharmacy substitution, not a higher clinical standard. (fda.gov)

• Randomized and real-world studies show switching is safe and effective for IBD. (pubmed.ncbi.nlm.nih.gov)

• Antidrug antibodies to a biologic usually cross-react with its biosimilar, so switching within the same molecule rarely fixes immune-mediated loss of response. (pubmed.ncbi.nlm.nih.gov)

• Good communication reduces nocebo concerns after non-medical switches. Plan simple monitoring after the switch. (pubmed.ncbi.nlm.nih.gov)

What are biosimilars

A biosimilar is a biologic medicine that is highly similar to a previously approved biologic, the reference product. There are no clinically meaningful differences in safety, purity, or potency. Dosing, route, and strength are the same. The FDA reviews analytical, clinical, and manufacturing data before approval. (fda.gov)

In the US, biologics use a core nonproprietary name plus a four‑letter suffix without meaning, for clear tracking. Example: infliximab‑dyyb. This naming helps safety reporting. (fda.gov)

The FDA’s Purple Book lists all licensed biologics, including which biosimilars have interchangeability. That list changes over time. (fda.gov)

What does “interchangeable” mean

Interchangeability is a US legal category. An interchangeable biosimilar may be substituted at the pharmacy for its reference product without contacting the prescriber, as allowed by state law. It is not a higher clinical standard, and it does not mean the product works better than a non‑interchangeable biosimilar. Clinically, both are expected to perform the same. (fda.gov)

The FDA has proposed dropping routine “switching studies” to grant interchangeability, reflecting growing evidence that switching does not add risk. This proposal aims to improve access and may speed future decisions. (reuters.com)

What does the evidence say about switching in IBD

• In NOR‑SWITCH, adults stable on originator infliximab were randomized to continue the originator or switch to biosimilar CT‑P13. After 52 weeks, switching was non‑inferior for disease worsening, with similar safety. The extension study showed no differences after longer follow‑up. (pubmed.ncbi.nlm.nih.gov)

• For adalimumab, the VOLTAIRE‑X randomized trial tested multiple back‑and‑forth switches between Humira and its biosimilar. Pharmacokinetics, efficacy, safety, and immunogenicity were similar to continuous treatment. These data supported FDA interchangeability. (pubmed.ncbi.nlm.nih.gov)

• Real‑world IBD cohorts show stable remission rates, drug levels, and biomarkers after mandated switches, though some people report nocebo symptoms early that usually settle with support. (pubmed.ncbi.nlm.nih.gov)

Professional societies in Europe support switching from originator infliximab to its biosimilar in IBD, with attention to traceability and communication. (academic.oup.com)

Types of switching

State rules for notification vary. The Purple Book confirms which products have interchangeability. (fda.gov)

When is switching within the same molecule unhelpful

If antidrug antibodies have formed against a biologic, they usually cross‑react with its biosimilar of the same molecule. In that situation, switching from originator infliximab to infliximab biosimilar, or vice versa, rarely restores response. Consider switching to a different drug or class, guided by therapeutic drug monitoring. (pubmed.ncbi.nlm.nih.gov)

How a planned switch usually works

1) Confirm the goal. Clarify whether the reason is medical or non‑medical. Align on keeping dose and schedule the same at first. (fda.gov)
2) Choose timing. Switch at the next scheduled infusion or injection to avoid gaps. Record the exact product name and four‑letter suffix for tracking. (fda.gov)
3) Prepare and teach. Devices, needles, and excipients can differ slightly across products. A quick training on the new pen or syringe helps. (fda.gov)
4) Monitor simply. Plan a symptom check and, when relevant, CRP or fecal calprotectin about 8 to 12 weeks after the switch. Check drug levels if there are concerns about response. (pubmed.ncbi.nlm.nih.gov)
5) Address expectations. Explain that outcomes match the original medicine. This reduces the chance of a nocebo response. (fda.gov)

Common questions about US interchangeability and substitution

• Is a biosimilar the same as a generic
  No. Biologics are made in living cells, so exact copies are not possible. Biosimilars must meet strict standards to show no meaningful clinical differences. Generics are identical chemical copies. (fda.gov)

• Can a pharmacist substitute a biosimilar automatically
  Only if the biosimilar has the FDA’s interchangeable designation, and state law permits substitution. The prescriber can also write the biosimilar by name without interchangeability. (fda.gov)

• Where can the current interchangeability status be checked
  In the FDA’s online Purple Book, which is updated as products gain or change status. (fda.gov)

• Are multiple switches safe
  Trials and real‑world data show similar outcomes after one or more switches within the same molecule. Communication and routine monitoring are key. (pubmed.ncbi.nlm.nih.gov)

• What if symptoms worsen soon after a mandated switch
  Short‑term nocebo effects can occur, even when inflammation markers remain stable. Reassurance, device coaching, and follow‑up usually help. If objective inflammation rises, manage as a true flare. (pubmed.ncbi.nlm.nih.gov)

Bottom line

Biosimilars expand access to effective IBD care. Interchangeability governs pharmacy substitution, not clinical performance. With a clear plan, good communication, and simple follow‑up, switching is routine and safe for most people living with IBD. (fda.gov)