Exosomes Shown to Be Involved in Spread of Amyloid Beta in Alzheimer’s

Another obstacle to discovering new PPI inhibitors is the lack of libraries designed to hunt for them, points out Philippe Roche, PhD, senior scientist at the Integrative Structural and Chemical Biology team at the Cancer Research Center of Marseilles, France. “If you screen PPIs using libraries that were designed for kinases or GPCRs, that’s why you don’t get a lot of good results,” he says. To that end, his group began assembling a library focused on orthosteric inhibitors of PPIs. The result was 2P2Idb, a hand-curated, structural database cataloguing orthosteric inhibitors of PPIs for which the interface had been 3D characterized. From analyzing these known PPI inhibitors, and what structures they had in common, Roche and his colleagues developed a model to predict whether compounds would likely inhibit PPIs. Using this method, 2P2Idb creates an enriched screening library that dramatically increases the hit rate compared to standard libraries. Having proven their success with a small library of 1600 compounds, they are in the process of expanding the library to 10,000 compounds. Once that’s published, “the idea is to make this library available to labs around the world,” Roche says. “We will provide the library free of charge for people to be able to screen PPI targets.”

A crucial question often addressed during preclinical development focuses on the in vivo stability of therapeutic antibodies. Increasing the half-life of a therapeutic antibody has several benefits ranging from higher treatment efficacy to increased advantages for the patients who will have a fewer number of therapy sessions and a reduced cost. Given these compelling benefits, following the identification of therapeutic antibodies with the desired specificity, developers usually subject them to a refinement step to increase their stability. This process is often hindered by the lack of reliable experimental tools to predict the half-life of antibodies in patients. The major hurdle of using mouse models to predict antibody stability in the serum lies in the way immunoglobulin proteins are processed by the organism. In mammals, most proteins circulating in the serum undergo constant uptake by endothelial cells and are routed through the endosomes to the lysosomal compartment for degradation. In the endosomes, immunoglobulin G (IgG) proteins are recognized and bound by a transmembrane protein, called the neonatal Fc receptor (FcRn), which mediates their recycling to the plasma membrane and subsequent release back into the serum. As a result, the half-life of IgGs are significantly extended by this mechanism. Since most therapeutic antibodies belong to the IgG class, this recycling system is very relevant for their relative stability in the body. Remarkably, the relative affinity between IgGs and FcRn is extremely disparate between different species, with the mouse receptor showing a much higher affinity than its human counterpart.

The performance of MK-6240 appears to be driven largely by differences in biologic binding characteristics, said Pascoal, who is also a behavioral neurologist at the University of Pittsburgh School of Medicine. “The main driver is biological affinity: MK-6240 binds tau tangles with roughly sixfold higher affinity than flortaucipir, as demonstrated in post-mortem tissue,” he explained. “This translates into a stronger signal-to-noise ratio in vivo, allowing detection of the sparse, early tangle deposits in medial temporal regions that flortaucipir tends to miss.” However, access to this newer tau PET tracer remains limited, he acknowledged. “Availability remains a real barrier,” Pascoal said. “MK-6240 is currently produced at a limited number of academic and trial-affiliated PET centers and is not yet approved as a routine clinical test.” The new agent received FDA Fast Track designation in 2025. The agency is expected to issue a decision on the manufacturer Lantheus’ new drug application expected in August, the company reported in a statement . The study provides evidence supporting sensitive approaches to tau detection, said Stephen Salloway, MD, director of Neurology and the Memory and Aging Program at Butler Hospital in Providence, Rhode Island, who was not part of the research. “Early detection of AD pathology will be critical for testing new interventions to slow or prevent cognitive decline in individuals at risk for AD,” and MK-6240 is better at detecting early stages of tau pathology than the currently available tracer, Salloway told Medscape Medical News . However, he cautioned that broader clinical implementation will require additional work to standardize interpretation and staging. “Better molecular staging of AD is needed to improve diagnostic accuracy and to identify individuals most likely to benefit from treatment,” he said. “Nuclear medicine specialists, radiologists, and dementia experts need experience and training to interpret tau PET scans.” The study was funded by the National Institute on Aging. Disclosure information for study authors is available in the original study publication. Salloway reported having no relevant financial disclosures.