A new monoclonal antibody (MAb) is being added to the biosimilar toolbox as a standard to evaluate the precision and accuracy of several analytical methods used to develop the follow-ons. The "anchor molecule" also may lead to more tools to improve the analytics that are foundational to characterizing a biosimilar and moving it from cell line to market.

The goal is to advance analytical technologies to the point that they will be able to provide absolute certainty that a follow-on is the same as its reference biologic within certain limits, said Michael Tarlov, chief of the U.S. National Institute of Standards and Technology (NIST) and director of the agency's program in biomanufacturing. When that day arrives, clinical trials will no longer be necessary for biosimilars, he predicted.

Given the complexity of the molecules and a production process that can span weeks to months, therapeutic MAbs, whether innovative or biosimilar, must undergo repeated rounds of testing and analysis to ensure that their identity, potency and purity remain within accepted bounds and that they can be reliably manufactured. Since the testing methods themselves can vary over time, manufacturers and regulators are left to wonder whether a variance is in the method or the molecule, Tarlov told BioWorld Today.

Answering that question can be challenging because of the number and diversity of molecules being developed and the assays in use. Because of these variances, FDA reviewers faced with data from many molecules may have a hard time reconciling why they're seeing differences from batch to batch of a novel biologic or from a biosimilar to its reference product, Tarlov explained.

"Developing an assay is not a trivial thing," he said, as a company must demonstrate to the FDA that the assay is referencing what the sponsor thinks it is and that the assay is working properly.

Using mass spectrometry as an example, Tarlov noted that differences in the hardware and software of spectrometers can yield varying results when analyzing molecules. Using a single, well-characterized MAb as a standard, regulators and sponsors can examine that MAb with each device to understand the differences in results from one spectrometer to another. That data can then be used to shed light on the results for a specific novel biologic or biosimilar.

That's where NIST's anchor molecule, NIST RM 8671, comes in. MedImmune, part of London-based Astrazeneca plc, donated a large batch of the MAb to NIST, which thoroughly characterized it with help from its international counterparts, producing data comparable with that found in a BLA. Because of that exhaustive characterization, RM 8671 can serve as a benchmark to ensure assays and other analytical tools used in producing novel biologics and biosimilars are functioning properly.

Consisting of more than 20,000 atoms, the publicly available MAb comes in vials of 800 microliters at a concentration of 10 mg/ml and is accompanied by the results of NIST measurements that provide a thorough profile, including details on size, concentration, composition, structure, purity, stability and other attributes.

Because it's derived from a mouse cell line, the standard molecule won't be the end-all of development and optimization of assays for biologics, as some assays are dependent on cell origin. But the NIST MAb will be useful across the board in assays measuring attributes such as size, concentration and primary amino acids, Tarlov said.

The anchor molecule also could be useful in developing other tools and studies that would increase understanding of variances in biologics. For instance, Tarlov said it would be great to have an anchor molecule like RM 8671, at a concentration of 100 mg/ml, for research into protein aggregation and the formation of protein particles that naturally occur when the molecules unfold and stick to each other. Researchers suspect that these naturally occurring particles, which can number up to 5,000 per vial, can affect immunogenicity.

Although NIST has a reserve of RM 8671 at the higher concentration, it would need to gauge the sponsor demand for the product before it could make the MAb available for research. The agency has a large but limited supply of the MAb that cannot be reproduced because of batch variances. The supply should be enough to meet demand for the foreseeable future, Tarlov said, but stability issues could rise over time.

Meanwhile, NIST is developing a second reference material to test and calibrate assays used to measure the size and quantity of particles in biologics.