3:07 PM
Mar 17, 2017
 |  BioCentury  |  Tools & Techniques

Calibrating PD-L1

How Flagship hopes to obviate the need to run different PD-L1 assays for every drug

Flagship Biosciences Inc.’s Computational Tissue Analysis platform won’t provide a common cutoff point across the five major assays used to measure PD-L1 expression. But it could calibrate the output so that results from one assay can be used to predict the scores the other assays would produce for the same sample.

That would allow oncologists to make decisions about using any marketed PD-1 or PD-L1 therapy without necessarily having to order the corresponding assay.

At the American Association for Cancer Research (AACR) meeting in April, Flagship will present data from a pilot study that demonstrates the approach is feasible.

There are three FDA-approved PD-L1 assays. Each uses a different anti-PD-L1 antibody clone to stain biopsy tissue, and each was developed for use with a specific therapy: PD-L1 IHC 22C3 pharmDx assay was developed for Keytruda pembrolizumab from Merck & Co. Inc.; PD-L1 IHC 28-8 pharmDx assay was developed for Bristol-Myers Squibb Co.’s Opdivo nivolumab; and PD-L1 (SP142) assay was developed for Tecentriq atezolizumab from the Genentech Inc. unit of Roche.

Two other tests are still investigational: PD-L1 (SP263) assay, which is being developed for use with AstraZeneca plc’s durvalumab, and the PD-L1 E1L3N XP assay from Cell Signaling Technology Inc., which is a laboratory-developed test (LDT) currently used for research.

The pharmDx assays are from the Dako A/S unit of Agilent Technologies Inc. The SP142 and SP263 assays are from Roche’s Ventana Medical Systems Inc. unit.

The challenge for pathologists and oncologists is that because each assay was developed based on clinical data for a specific therapeutic, the reagents, scoring algorithms and resulting interpretations are different. As a result, each diagnostic can be used only with its corresponding therapy (see “Differential Staining”).

“They’ve had to really simplify the scoring paradigms on these diagnostics to match the level of human ability.”

Joseph Krueger, Flagship...

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