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Oncology biosimilars on the rise

Key clinical development insights

As researchers and physicians make strides in the fight against cancer, biosimilars are increasingly playing an important role in the oncology space. Although new innovations in treatment, particularly biologics, have helped innumerable cancer patients, the price tag on these therapies is often high. Biosimilars, which are designed to closely emulate reference biologics with patents that have expired, offer a more affordable alternative for what is effectively the same treatment.

Oncology biosimilars also represent a significant opportunity for sponsors. Although biosimilars are typically priced lower than reference biologics, they also cost less to develop, with a preestablished mechanism of action and an abbreviated clinical trial process. Additionally, in some cases oncology biosimilars have earned a significant percentage of the market share and have overtaken the reference product — for example, in Q3 of 2024, biosimilars made up 90% of the market for the multi-cancer drug bevacizumab.1 For sponsors entering the oncology biosimilar space, there are several distinguishing considerations for clinical development, including the clinical pathway, study design and patient selection and recruitment.

Understanding a unique clinical pathway

In the European Union (EU) and the United States (US), biosimilars have different clinical development requirements than novel biologics. Because the reference biologic has already proven its benefit to patients and established safe and effective dosages, it would be redundant for a biosimilar sponsor to conduct clinical trials the same way. Instead, clinical evidence for a biosimilar must primarily establish its comparability with the reference product, illustrating effective biosimilar interchangeability.

The typical process includes the following components:

  • Analytical studies, which assess factors such as structure and manufacturing process, and demonstrate that a biosimilar’s characterisation is highly similar to that of the reference product
  • Preclinical studies, which focus on pharmacokinetic (PK), pharmacodynamic (PD) and toxicology data, primarily in vitro
  • Pharmacokinetic sub-studies, which collect in-human PK/PD profiling and safety data
  • Comparative clinical studies, which assess the biosimilar’s efficacy and immunogenicity
  • Post-market safety monitoring, which gathers information about adverse events over long-term usage of a therapy

Notably, some regulatory bodies, including those in the US and EU, have begun reevaluating whether all of these components are necessary in all cases. In particular, the value of comparative clinical studies has been called into question. Specifically, regulators point out that the extensive analytical and PK/PD requirements can often demonstrate biosimilarity with high confidence, reducing the need — and ethical burden — of large patient trials2.

Creating an appropriate study design

Designing clinical studies for oncology biosimilars takes a distinct approach from novel biologics. This becomes evident in endpoint selection. Typically, oncology clinical trials select survival as an endpoint; however, confounding factors — such as tumour burden, disease status, or previous therapy — may make survival an inappropriate endpoint for biosimilars.3 Instead, oncology biosimilar studies should consider response rate endpoints, which measure the activity of the product, or even include novel endpoints that may contribute to establishing comparability with the reference biologic.

Additionally, for comparative clinical studies, parameters should be constructed specifically to demonstrate that there are no clinically meaningful differences between the biosimilar and its reference product. This means showing an equivalency of clinical effect within a margin of error, or similarity margin, which is based on an estimate of the treatment effect size of the reference product in terms of the comparative study’s primary endpoint.4 Isolating the effect of the reference product may be challenging for oncology drugs — which are often given in combination with other therapies — especially in cases in which a product has few publicly available historical randomised studies.

Anticipating patient selection and recruiting challenges

There are several unique challenges that oncology biosimilars face as they enter clinical trials. One of these is participant selection. For example, PK studies typically enrol healthy volunteers, and the relative homogeneity of this group is typically considered preferable for early in-human studies. However, in the case of oncology, healthy subjects may not reflect certain qualities that influence the results of PK/PD studies, such as the binding of a drug to its pharmacological target site (also referred to as target-mediated drug disposition). And, if the comparability is still in question after studying healthy volunteers, it may be necessary to conduct randomised trials with oncology patients to demonstrate tumour response.

Recruiting patients can also be difficult. In areas where the reference biologic has already been approved, there can be little incentive for cancer patients to participate in clinical trials for biosimilars. Furthermore, if patients are not familiar with the concept of biosimilars, such treatments might be viewed as risky — particularly in the case of a life-threatening illness such as cancer. As a result, it may be beneficial for clinical trial recruitment to focus on regions in which the reference biologic is difficult to access, for example due to a lack of reimbursement.

Preparing for biosimilar development

Oncology biosimilars present unique potential and distinct challenges to sponsors. The specific needs of oncology clinical trials, alongside the distinct clinical pathway for biosimilars, mean that developing these treatments must be approached very differently from novel biologic development. Knowing what to expect from the development process enables preparation and, ultimately, a greater likelihood of success. 

The field of oncology biosimilars is rapidly evolving across multiple axes, requiring a forward-looking perspective. To explore the future of oncology biosimilars, including the patent and market landscape; current regulatory requirements and likely regulatory shifts; and considerations for drug modalities and post-market monitoring, read 91黑料’s whitepaper, “The future of oncology biosimilars: Considerations for development through 2040.”

Sources:

1“Biosimilars Drive Cost Savings and Achieve 53% Market Share Across Treatment Areas.” Center for Biosimilars, 16 Jan. 2025, .

2Reflection Paper on a Tailored Clinical Approach in Biosimilar Development | European Medicines Agency (EMA). 1 Apr. 2025,

3Socinski, Mark A., et al. “Clinical Considerations for the Development of Biosimilars in Oncology.” MAbs, vol. 7, no. 2, Jan. 2015, pp. 286–93, .

4He, Kun, et al. “Statistical Considerations in Evaluating a Biosimilar Product in an Oncology Clinical Study.” Clinical Cancer Research, vol. 22, no. 21, Nov. 2016, pp. 5167–70, .

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