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STRO-001 is a site-specific, predominantly single-species, fully human, aglycosylated anti-CD74 antibody-drug conjugate incorporating a non-cleavable linker-maytansinoid warhead with a drug-antibody ratio of 2 which was produced by a novel cell-free antibody synthesis platform. We examined the potential pharmacodynamics and anti-tumor effects of STRO-001 in multiple myeloma (MM). CD74 expression was assessed in MM cell lines and primary bone marrow (BM) MM biopsies. CD74 mRNA was detectable in CD138+ enriched plasma cells from 100% (892/892) of patients with newly diagnosed MM. Immunohistochemistry confirmed CD74 expression in 35/36 BM biopsies from patients with newly diagnosed and relapsed/refractory MM. Cytotoxicity assays demonstrated nanomolar STRO-001 potency in 4/6 MM cell lines. In ARP-1 and MM.1S tumor-bearing mice, repeat STRO-001 dosing provided significant antitumor activity with eradication of malignant hCD138+ BM plasma cells and prolonged survival. In a luciferase-expressing MM.1S xenograft model, dose-dependent STRO-001 efficacy was confirmed using bioluminescent imaging and BM tumor burden quantification. Consistent with the intended pharmacodynamic effect, STRO-001 induced dose-responsive, reversible B-cell and monocyte depletion in cynomolgus monkeys, up to a maximum tolerated 10 mg/kg, with no evidence of off-target toxicity. Collectively, these data suggest that STRO-001 is a promising therapeutic agent for the treatment of MM.

Folding within the crowded cellular milieu often requires assistance from molecular chaperones that prevent inappropriate interactions leading to aggregation and toxicity. The contribution of individual chaperones to folding the proteome remains elusive. Here we demonstrate that the eukaryotic chaperonin TRiC/CCT (TCP1-ring complex or chaperonin containing TCP1) has broad binding specificity in vitro, similar to the prokaryotic chaperonin GroEL. However, in vivo, TRiC substrate selection is not based solely on intrinsic determinants; instead, specificity is dictated by factors present during protein biogenesis. The identification of cellular substrates revealed that TRiC interacts with folding intermediates of a subset of structurally and functionally diverse polypeptides. Bioinformatics analysis revealed an enrichment in multidomain proteins and regions of beta-strand propensity that are predicted to be slow folding and aggregation prone. Thus, TRiC may have evolved to protect complex protein topologies within its central cavity during biosynthesis and folding.

On our initial discovery that prion protein (PrP)-derived peptides were capable of capturing the pathogenic prion protein [Prp.sup.Sc]), we have been interested in how these peptides interact with [PrP.sup.Sc]. After screening peptides from the entire human PrP sequence, we found two peptides ([PrP.sub.19-30] and [PrP.sub.100-111]) capable of binding full-length [PrP.sup.Sc] in plasma, a medium containing a complex mixture of other proteins including a vast excess of the normal prion protein ([Prp.sup.C]). The limit of detection for captured [PrP.sup.Sc] was calculated to be 8 amol from a [approximately equal to] 105-fold dilution of 10% (wt/vol) human variant Creutzfeldt-Jakob disease brain homogenate, with >3,800-fold binding specificity to [PrP.sup.Sc] over [PrP.sup.C]. Through extensive analyses, we show that positively charged amino acids play an important, but not exclusive, role in the interaction between the peptides and [PrP.sup.Sc]. Neither hydrophobic nor polar interactions appear to correlate with binding activity. The peptide-[PrP.sup.Sc] interaction was not sequence-specific, but amino acid composition affected binding. Binding occurs through a conformational domain that is only present in [PrP.sup.Sc], is species-independent, and is not affected by proteinase K digestion. These and other findings suggest a mechanism by which cationic domains of [PrP.sup.C] may play a role in the recruitment of [PrP.sup.C] to [PrP.sup.Ssc]. plasma | Creutzfeldt--Jakob disease | detection | cationic interaction | diagnostic

Alzheimer's Disease (AD) is the most prevalent form of dementia worldwide, yet the development of therapeutics has been hampered by the absence of suitable biomarkers to diagnose the disease in its early stages prior to the formation of amyloid plaques and the occurrence of irreversible neuronal damage. Since oligomeric Ab species have been implicated in the pathophysiology of AD, we reasoned that they may correlate with the onset of disease. As such, we have developed a novel misfolded protein assay for the detection of soluble oligomers composed of Ab x-40 and x-42 peptide (hereafter Ab40 and Ab42) from cerebrospinal fluid (CSF). Preliminary validation of this assay with 36 clinical samples demonstrated the presence of aggregated Ab40 in the CSF of AD patients. Together with measurements of total Ab42, diagnostic sensitivity and specificity greater than 95% and 90%, respectively, were achieved. Although larger sample populations will be needed to confirm this diagnostic sensitivity, our studies demonstrate a sensitive method of detecting circulating Ab40 oligomers from AD CSF and suggest that these oligomers could be a powerful new biomarker for the early detection of AD. [ABSTRACT FROM AUTHOR]

Background: Prion diseases are fatal neurodegenerative disorders characterized by misfolding and aggregation of the normal prion protein PrPC. Little is known about the details of the structural rearrangement of physiological PrPC into a still-elusive disease-associated conformation termed PrPSc. Increasing evidence suggests that the amino-terminal octapeptide sequences of PrP (huPrP, residues 59-89), though not essential, play a role in modulating prion replication and disease presentation. Methodology/Principal Findings: Here, we report that trypsin digestion of PrPSc from variant and sporadic human CJD results in a disease-specific trypsin-resistant PrPSc fragment including amino acids ,49-231, thus preserving important epitopes such as the octapeptide domain for biochemical examination. Our immunodetection analyses reveal that several epitopes buried in this region of PrPSc are exposed in PrPC. Conclusions/Significance: We conclude that the octapeptide region undergoes a previously unrecognized conformational transition in the formation of PrPSc. This phenomenon may be relevant to the mechanism by which the amino terminus of PrPC participates in PrPSc conversion, and may also be exploited for diagnostic purposes. [ABSTRACT FROM AUTHOR]

Background: Prion diseases are fatal neurodegenerative disorders characterized by misfolding and aggregation of the normal prion protein PrPC. Little is known about the details of the structural rearrangement of physiological PrPC into a still-elusive disease-associated conformation termed PrPSc. Increasing evidence suggests that the amino-terminal octapeptide sequences of PrP (huPrP, residues 59-89), though not essential, play a role in modulating prion replication and disease presentation. Methodology/Principal Findings: Here, we report that trypsin digestion of PrPSc from variant and sporadic human CJD results in a disease-specific trypsin-resistant PrPSc fragment including amino acids ,49-231, thus preserving important epitopes such as the octapeptide domain for biochemical examination. Our immunodetection analyses reveal that several epitopes buried in this region of PrPSc are exposed in PrPC. Conclusions/Significance: We conclude that the octapeptide region undergoes a previously unrecognized conformational transition in the formation of PrPSc. This phenomenon may be relevant to the mechanism by which the amino terminus of PrPC participates in PrPSc conversion, and may also be exploited for diagnostic purposes. [ABSTRACT FROM AUTHOR]

On our initial discovery that prion protein (PrP)-derived peptides were capable of capturing the pathogenic prion protein (PrPSc), we have been interested in how these peptides interact with PrPSc. After screening peptides from the entire human PrP sequence, we found two peptides (PrP19–30 and PrP100–111) capable of binding full-length PrPSc in plasma, a medium containing a complex mixture of other proteins including a vast excess of the normal prion protein (PrPC). The limit of detection for captured PrPSc was calculated to be 8 amol from a ≈105-fold dilution of 10% (wt/vol) human variant Creutzfeldt-Jakob disease brain homogenate, with >3,800- fold binding specificity to PrPSc over PrPC. Through extensive analyses, we show that positively charged amino acids play an important, but not exclusive, role in the interaction between the peptides and PrPSc. Neither hydrophobic nor polar interactions appear to correlate with binding activity. The peptide-PrPSc interaction was not sequence-specific, but amino acid composition affected binding. Binding occurs through a conformational domain that is only present in PrPSc, is species-independent, and is not affected by proteinase K digestion. These and other findings suggest a mechanism by which cationic domains of PrPC may play a role in the recruitment of PrPC to PrPSc. [ABSTRACT FROM AUTHOR]

On our initial discovery that prion protein (PrP)-derived peptides were capable of capturing the pathogenic prion protein (PrPSc), we have been interested in how these peptides interact with PrPSc. After screening peptides from the entire human PrP sequence, we found two peptides (PrP19–30 and PrP100–111) capable of binding full-length PrPSc in plasma, a medium containing a complex mixture of other proteins including a vast excess of the normal prion protein (PrPC). The limit of detection for captured PrPSc was calculated to be 8 amol from a ≈105-fold dilution of 10% (wt/vol) human variant Creutzfeldt-Jakob disease brain homogenate, with >3,800- fold binding specificity to PrPSc over PrPC. Through extensive analyses, we show that positively charged amino acids play an important, but not exclusive, role in the interaction between the peptides and PrPSc. Neither hydrophobic nor polar interactions appear to correlate with binding activity. The peptide-PrPSc interaction was not sequence-specific, but amino acid composition affected binding. Binding occurs through a conformational domain that is only present in PrPSc, is species-independent, and is not affected by proteinase K digestion. These and other findings suggest a mechanism by which cationic domains of PrPC may play a role in the recruitment of PrPC to PrPSc. [ABSTRACT FROM AUTHOR]

STRO-002 is a novel homogeneous folate receptor alpha (FolRα) targeting antibody-drug conjugate (ADC) currently being investigated in the clinic as a treatment for ovarian and endometrial cancers. Here, we describe the discovery, optimization, and antitumor properties of STRO-002. STRO-002 was generated by conjugation of a novel cleavable 3-aminophenyl hemiasterlin linker-warhead (SC239) to the nonnatural amino acid para-azidomethyl-L-phenylalanine incorporated at specific positions within a high affinity anti-FolRα antibody using Sutro's XpressCF+, which resulted in a homogeneous ADC with a drug-antibody ratio (DAR) of 4. STRO-002 binds to FolRα with high affinity, internalizes rapidly into target positive cells, and releases the tubulin-targeting cytotoxin 3-aminophenyl hemiasterlin (SC209). SC209 has reduced potential for drug efflux via P-glycoprotein 1 drug pump compared with other tubulin-targeting payloads. While STRO-002 lacks nonspecific cytotoxicity toward FolRα-negative cell lines, bystander killing of target negative cells was observed when cocultured with target positive cells. STRO-002 is stable in circulation with no change in DAR for up to 21 days and has a half-life of 6.4 days in mice. A single dose of STRO-002 induced significant tumor growth inhibition in FolRα-expressing xenograft models and patient-derived xenograft models. In addition, combination treatment with carboplatin or Avastin further increased STRO-002 efficacy in xenograft models. The potent and specific preclinical efficacy of STRO-002 supports clinical development of STRO-002 for treating patients with FolRα-expressing cancers, including ovarian, endometrial, and non-small cell lung cancer. Phase I dose escalation for STRO-002 is in progress in ovarian cancer and endometrial cancer patients (NCT03748186 and NCT05200364)., (©2022 The Authors; Published by the American Association for Cancer Research.)