How similar are biosimilars?

Biosimilars are designed to be an almost exact copy of an original biotherapeutic manufactured elsewhere. These molecules are intended to have the same physiological effect as a previously licensed biotherapeutic. To gain license themselves they have to be able to prove that they are identical within the clinically active components, with only minor differences in the non-clinical component. Biosimilar versions of approved biological drugs at the end of their patent life are expected to cost less but be as safe and effective for licensed clinical uses. As more biotherapeutics are used and begin to come off-license, a substantial market exists for biosimilar drugs that can potentially be made more cheaply than branded versions, creating a saving for both patients and healthcare providers.

A study from four different labs, published in Nature Biotechnology, compared four versions of the biotherapeutic drug methionyl Granulocyte-Colony Stimulating Factor (met-G-CSF) by 2D-NMR. G-CSF is a 175 amino acid protein that stimulates the bone marrow to produce neutrophils. It is used as a biotherapeutic to increase neutrophil count and ward off infections and anaemia in cancer patients. This study demonstrates the ability of 2D-NMR to reliably analyse the structures of biosimilar products and establish the degree of difference. Both companies and regulators could employ this technique to assess biosimilars and determine whether clinical differences exists between them. A precise and unique structural profile for each biological molecule is obtained, yielding the equivalent of a molecular fingerprint.

Analysing 2D-NMR profiles of G-CSF biosimilars can determine the level of similarity in these biotherapeutics.
Analysing 2D-NMR profiles of G-CSF biosimilars can determine the level of similarity in these biotherapeutics.

Unlike chemically synthesized drugs, such as aspirin, biological drugs are composed of large, complex protein molecules, produced by living systems. This makes producing exact duplicates difficult, even from batch to batch in the same biomanufacturing process. For specified health conditions and symptoms, the nearly exact copies that result must be shown to achieve the same clinical effects as the already-licensed biological product.

Using met-G-CSF as an example the four different labs examined one product licensed within the US and three unapproved biosimilar versions, on six different spectrometers, from two different manufacturers, to show that there was very little difference between the four versions of met-G-CSF. The four biosimilars were then re-analysed nine months after the initial assessment to determine changes in the measurements over time. Calibration of the spectrometers was shown to be very important along with solution conditions, such as pH or ionic strength, and temperature variations to ensure reproducible results.

Molecular measurements from each of the six instruments were rendered as a pattern of peaks corresponding to signals from hydrogen and nitrogen atoms in the samples. The data were superimposed to determine how tightly the signals were clustered, showing that the measurements hardly varied and all four samples of met-G-CSF were determined to be the same. In addition to reporting on the utility of 2D-NMR for high-precision measurement of the detailed atomic structure of biosimilars, the new paper describes statistical methods used to assess biosimilarity. They include one for rapid analysis of many datasets, which can be generated, for example, when monitoring batch-to-batch variation during production.

In the next phase of this work, researchers from thirty labs across five continents, intend to compare monoclonal antibody measurements using this technique. This will hopefully establish reference materials for the future analysis of these biotherapeutics. Monoclonal antibodies are currently the largest class of approved biotherapeutics and the ability to characterise these molecules via 2D-NMR methods could offer important confirmation of validation and efficacy. Extending both the scale and scope of these experiments will improve the reproducibility and reliability of results and allow NMR spectral analyses to be used by producers of biosimilars and regulatory agencies to offer assurance of drug product quality.