# Make the biosimilar the default at the pharmacy for trastuzumab, bevacizumab and rituximab

Source: https://onco.cc/ideas/idea-cost-biosimilar-default-substitution/  
OnCo record `idea-cost-biosimilar-default-substitution` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Copies of the big antibody drugs are approved and cheaper, but uptake depends on each prescriber; letting the pharmacy substitute the biosimilar unless the oncologist objects would move most patients within a year.

## Summary

FDA-approved biosimilars of trastuzumab, bevacizumab, rituximab and pegfilgrastim have been on the US market since 2019. IQVIA estimated that biosimilars saved $56 billion over the decade to 2022 and projected $181 billion more over 2023 to 2027. Uptake still varies widely by practice because substitution requires a prescriber decision, a payer preference and a purchasing contract to line up. A default-substitution rule (opt-out rather than opt-in), combined with the flat-fee payment idea, removes the friction. NHS England and several European systems achieved over 90% uptake this way.

## Fields

- Kind: Idea
- Last checked: 2026-09-10
- Hypothesis: Default substitution in a payer's network will lift biosimilar share for the three antibodies above 85% within twelve months, from a baseline that varies between 40% and 80%.
- Rationale: Biosimilars have no clinically meaningful difference by regulatory definition; the remaining barrier is process, not evidence.
- Proposed test: A payer-level stepped rollout across regions with biosimilar share, drug spend and any switch-related adverse events reported quarterly.
- Maturity: being-tested-at-scale
- Actor: payer

## Sources

- IQVIA Institute: Biosimilars in the United States 2023-2027 (January 2023): https://www.iqvia.com/insights/the-iqvia-institute/reports-and-publications/reports/biosimilars-in-the-united-states-2023-2027
- FDA: Biosimilars: https://www.fda.gov/drugs/therapeutic-biologics-applications-bla/biosimilars

## Connected records

- drugs: [Bevacizumab](https://onco.cc/drugs/bevacizumab/), [Rituximab](https://onco.cc/drugs/rituximab/), [Trastuzumab](https://onco.cc/drugs/trastuzumab/), [Trastuzumab biosimilars](https://onco.cc/drugs/trastuzumab-biosimilars/)
- terms: [Biosimilar](https://onco.cc/terms/biosimilar/)
- bottlenecks: [Knowledge reaches practice too slowly](https://onco.cc/bottlenecks/b-knowledge-diffusion/), [Prices and value](https://onco.cc/bottlenecks/b-drug-pricing/)

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