Peripheral expression of brain-penetrant progranulin rescues pathologies in mouse models of frontotemporal lobar degeneration.

Progranulin (PGRN) haploinsufficiency is a major risk factor for frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43) pathology (FTLD-). Multiple therapeutic strategies are in clinical development to restore PGRN in the CNS, including gene therapy. However, a limitation of current gene therapy approaches aimed to alleviate FTLD-associated pathologies may be their inefficient brain exposure and biodistribution.

CD98hc is a target for brain delivery of biotherapeutics.

Brain exposure of systemically administered biotherapeutics is highly restricted by the blood-brain barrier (BBB). Here, we report the engineering and characterization of a BBB transport vehicle targeting the CD98 heavy chain (CD98hc or SLC3A2) of heterodimeric amino acid transporters (TV). The pharmacokinetic and biodistribution properties of a CD98hc antibody transport vehicle (ATV) are assessed in humanized CD98hc knock-in mice and cynomolgus monkeys.

Molecular architecture determines brain delivery of a transferrin receptor-targeted lysosomal enzyme.

Delivery of biotherapeutics across the blood-brain barrier (BBB) is a challenge. Many approaches fuse biotherapeutics to platforms that bind the transferrin receptor (TfR), a brain endothelial cell target, to facilitate receptor-mediated transcytosis across the BBB. Here, we characterized the pharmacological behavior of two distinct TfR-targeted platforms fused to iduronate 2-sulfatase (IDS), a lysosomal enzyme deficient in mucopolysaccharidosis type II (MPS II), and compared the relative brain exposures and functional activities of both approaches in mouse models.

Rescue of a lysosomal storage disorder caused by Grn loss of function with a brain penetrant progranulin biologic.

GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found that Grn mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine.

Neutralization of PD-L2 is Essential for Overcoming Immune Checkpoint Blockade Resistance in Ovarian Cancer.

Purpose: Ovarian cancer represents a major clinical hurdle for immune checkpoint blockade (ICB), with reported low patient response rates. We found that the immune checkpoint ligand PD-L2 is robustly expressed in patient samples of ovarian cancers and other malignancies exhibiting suboptimal response to ICB but not in cancers that are ICB sensitive. Therefore, we hypothesize that PD-L2 can facilitate immune escape from ICB through incomplete blockade of the PD-1 signaling pathway.

Brain delivery of therapeutic proteins using an Fc fragment blood-brain barrier transport vehicle in mice and monkeys.

Effective delivery of protein therapeutics to the central nervous system (CNS) has been greatly restricted by the blood-brain barrier (BBB). We describe the development of a BBB transport vehicle (TV) comprising an engineered Fc fragment that exploits receptor-mediated transcytosis for CNS delivery of biotherapeutics by binding a highly expressed brain endothelial cell target. TVs were engineered using directed evolution to bind the apical domain of the human transferrin receptor (hTfR) without the use of amino acid insertions, deletions, or unnatural appendages.

Brain delivery and activity of a lysosomal enzyme using a blood-brain barrier transport vehicle in mice.

Most lysosomal storage diseases (LSDs) involve progressive central nervous system (CNS) impairment, resulting from deficiency of a lysosomal enzyme. Treatment of neuronopathic LSDs remains a considerable challenge, as approved intravenously administered enzyme therapies are ineffective in modifying CNS disease because they do not effectively cross the blood-brain barrier (BBB). We describe a therapeutic platform for increasing the brain exposure of enzyme replacement therapies.

Reprogramming the immunological microenvironment through radiation and targeting Axl.

Increasing evidence suggests that ionizing radiation therapy (RT) in combination with checkpoint immunotherapy is highly effective in treating a subset of cancers. To better understand the limited responses to this combination we analysed the genetic, microenvironmental, and immune factors in tumours derived from a transgenic breast cancer model. We identified two tumours with similar growth characteristics but different RT responses primarily due to an antitumour immune response.

Engineering High Affinity Protein-Protein Interactions Using a High-Throughput Microcapillary Array Platform.

Affinity maturation of protein-protein interactions requires iterative rounds of protein library generation and high-throughput screening to identify variants that bind with increased affinity to a target of interest. We recently developed a multipurpose protein engineering platform, termed μSCALE (Microcapillary Single Cell Analysis and Laser Extraction). This technology enables high-throughput screening of libraries of millions of cell-expressing protein variants based on their binding properties or functional activity.

Inhibition of the GAS6/AXL pathway augments the efficacy of chemotherapies.

The AXL receptor and its activating ligand, growth arrest-specific 6 (GAS6), are important drivers of metastasis and therapeutic resistance in human cancers. Given the critical roles that GAS6 and AXL play in refractory disease, this signaling axis represents an attractive target for therapeutic intervention. However, the strong picomolar binding affinity between GAS6 and AXL and the promiscuity of small molecule inhibitors represent important challenges faced by current anti-AXL therapeutics.

An engineered Axl 'decoy receptor' effectively silences the Gas6-Axl signaling axis.

Aberrant signaling through the Axl receptor tyrosine kinase has been associated with a myriad of human diseases, most notably metastatic cancer, identifying Axl and its ligand Gas6 as important therapeutic targets. Using rational and combinatorial approaches, we engineered an Axl 'decoy receptor' that binds Gas6 with high affinity and inhibits its function, offering an alternative approach from drug discovery efforts that directly target Axl. Four mutations within this high-affinity Axl variant caused structural alterations in side chains across the Gas6-Axl binding interface, stabilizing a conformational change on Gas6.

Direct regulation of GAS6/AXL signaling by HIF promotes renal metastasis through SRC and MET.

Dysregulation of the von Hippel-Lindau/hypoxia-inducible transcription factor (HIF) signaling pathway promotes clear cell renal cell carcinoma (ccRCC) progression and metastasis. The protein kinase GAS6/AXL signaling pathway has recently been implicated as an essential mediator of metastasis and receptor tyrosine kinase crosstalk in cancer. Here we establish a molecular link between HIF stabilization and induction of AXL receptor expression in metastatic ccRCC.

Beyond antibodies: using biological principles to guide the development of next-generation protein therapeutics.

Protein-based biologics, which leverage the inherent affinity and specificity of protein-protein interactions, offer an effective strategy for targeting and modulating disease pathways. Despite the broad diversity of the proteome, monoclonal antibodies have been the major focus of such drug discovery efforts. While antibodies have shown great clinical value, the breadth and complexity of human disease highlight the need for alternatives that expand the therapeutic repertoire beyond this single class of proteins.

Cystine-knot peptides engineered with specificities for α(IIb)β(3) or α(IIb)β(3) and α(v)β(3) integrins are potent inhibitors of platelet aggregation.

A truncated form of the Agouti-related protein (AgRP), a member of the cystine-knot family, has shown promise as a scaffold for engineering novel peptides with new molecular recognition properties. In this study, we replaced a constrained six amino acid loop in AgRP with a nine amino acid loop containing an Arg-Gly-Asp integrin recognition motif, and randomized the neighboring residues to create a library of approximately 20 million AgRP variants. We displayed the AgRP mutants as fusions on the surface of yeast and used high-throughput fluorescence-activated cell sorting (FACS) to isolate peptides that bound specifically to the platelet integrin α(IIb)β(3), a clinically important target for the prevention and treatment of thrombosis.