What about the assays, then? The GCSB Vancouver meeting features talks from representatives of the two companies whose RUO assays are in widespread use, followed by talks from in-vitro diagnostics companies. Pankaj Oberoi spoke for Meso Scale Diagnostics (MSD), a company that sells a chemiluminescence-based multiplex test mostly to industry and to a select few academic labs that can afford the $100K reader (most bemoan that they cannot). In June 2012, MSD released Aβ42 and tau kits that have been analytically validated in a multiyear collaboration with Soares and others at BMS.
In particular, Oberoi’s group worked to reduce the nagging problem of dilution linearity, where measurement values don’t drop as expected when the operator dilutes the CSF sample. This problem dogs all current assays and, incidentally, was difficult to overcome for cholesterol tests, too. It is blamed on the so-called matrix effect, whereby other proteins in CSF form a web of interactions that changes with each dilution step and, hence, sequesters more or less free Aβ. “We have removed the interference associated with the protein matrix,” Oberoi claimed. At the AAIC conference, Oberoi and colleagues presented posters describing the performance of these assays in vitro and in an initial clinical study of 50 control, 50 MCI, and 50 AD cases. A multisite clinical validation with the University of Gothenburg; Edith Cowan University in Perth, Australia; and other groups is underway.
Oberoi said that MSD recently became certified by the International Organization of Standards. He noted that his company trains local scientists and technicians, and is the only manufacturer to provide on-the-ground support, though some scientists privately quibbled that this support for what they perceive to be an expensive platform could be improved.
For Innogenetics, the manufacturers of the most widely used RUO CSF assays for Aβ and tau, Manu Vandijck said that the purchase last year of his company by the Japanese diagnostics company Fujirebio had not watered down Innogenetics’ commitment to AD or its freedom to operate. He acknowledged the matrix effect, and said Innogenetics researchers were developing new, automated chemiluminescent enzyme immuno assays on an integrated platform called LUMIPULSE®.
Next up were representatives of two large in-vitro diagnostics companies, each presenting similar results of their ongoing work to develop what is called a companion diagnostic. This concept received a widely noticed endorsement when the FDA issued a guidance in July 2011. The guidance encourages the twin development of a drug with a diagnostic that can identify the type of patient the drug will benefit. This is part of a trendy concept referred to as "stratified medicine." Ideally, the diagnostic should be ready for approval concurrently with the drug. Recently, several cancer drugs have been approved together with a molecular diagnostic test that identifies in which subgroups of patients they are likely to work.
Toward that end, Salvatore Salamone from the companion diagnostics company Saladax Biomedical gave an update on a joint project with Ortho-Clinical Diagnostics and BMS to develop automated Aβ and tau assays for a machine called the Vitros ECiQ analyzer. “These should be easy to use in every lab around the world,” Salamone said. Claiming precision of better than 2 percent, Salamone rattled off data points about detection limits and the stability of the assays’ reagents. He noted that adding certain (non-disclosed) dilutants rendered the assays’ linearity “near-perfect,” but acknowledged that “getting past these matrix elements was a tough nut to crack.” According to Salamone, both assays are now in design lock and their reagents in process development at an Ortho-Clinical Diagnostics production facility in the UK.
The next speaker was Tobias Bittner for Roche Diagnostics, who told much the same story. That company is part of the overall Roche Group, whose other division includes Roche Pharma, Genentech, and Chugai in Japan. Bittner develops immunoassays that run on a platform called Cobas E601. The 25,000 machines of this type that are placed in labs around the world each run automated, 18-minute-long tests at a capacity of 180 samples per hour, Bittner said.
The group develops individual sandwich ELISAs for Aβ42 and tau. They are meant to enable identification of prodromal AD patients for treatment with the antibody gantenerumab (see Alzforum interview with Luca Santarelli), and also to work as a stand-alone diagnostic. The Aβ assay—a work in progress—currently achieves a precision of 1.5 to 3 percent, and variation due to dilution linearity is below 4 percent, Bittner said, noting that the tau assay is not ready to show data.
At the GCSB meeting, Diane Stephenson of the Coalition Against Major Diseases, Phoenix, Arizona, said that in a February 2012 advice meeting with the FDA about the status of AD fluid markers, regulators recommended that CAMD help the field rise above the current scientific literature. Specifically, the FDA wants to see precision-based assays with data showing how the test relates to the level of cognitive impairment. The FDA also seeks precise definition of the assay performance characteristics, as well as analyses of individual patient level data. CAMD is a precompetitive initiative to help CSF biomarkers achieve qualification with the FDA. CAMD combines industry and academic experts with representatives of patient advocacy groups and government agencies who work collaboratively toward improving success of therapeutic trials in patients with mild cognitive impairment (see ARF related news story).
“It is gratifying to see the advancement of all the assays. We have struggled with these issues for a long time. As academics and pharma scientists, we would usually go back to our own silo and struggle alone. Without this group, this would not have happened,” said Zetterberg.
See Part 2 of this series for news on how the international certification institutions are weighing in on CSF tests for Alzheimer’s.—Gabrielle Strobel.
This is Part 1 of a two-part series. See also Part 2.