Early Circulating Tumor DNA Dynamics and Efficacy of Lorlatinib in Patients With Treatment-Naive, Advanced, ALK-Positive NSCLC.

INTRODUCTION: Circulating tumor DNA (ctDNA) has been used as a biomarker for prognostication and response to treatment. Here, we evaluate ctDNA as a potential biomarker for response to lorlatinib, a third-generation ALK tyrosine kinase inhibitor in patients with treatment-naive, advanced, ALK-positive NSCLC in the ongoing phase 3 CROWN study (NCT03052608). METHODS: Molecular responses were calculated using mean variant allele frequency (VAF), longitudinal mean change in VAF (dVAF), and ratio to baseline. Efficacy assessments (progression-free survival [PFS] and objective response rate) were paired with individual patient ctDNA and analyzed for association. RESULTS: Compared with baseline, mean VAF at week 4 was decreased in both treatment arms. Considering all detected somatic variants, a reduction in dVAF (≤0) was associated with a longer PFS in the lorlatinib arm. The hazard ratio (HR) for a dVAF less than or equal to 0 versus more than 0 was 0.50 (95% confidence interval [CI]: 0.23-1.12) in the lorlatinib arm. A similar association was not observed for crizotinib (HR = 1.00, 95% CI: 0.49-2.03). Comparing molecular responders with nonresponders, patients treated with lorlatinib who had a molecular response had longer PFS (HR = 0.37, 95% CI: 0.16-0.85); patients treated with crizotinib who had a molecular response had similar PFS as those without a molecular response (HR = 1.48, 95% CI: 0.67-3.30). CONCLUSIONS: In patients with treatment-naive, advanced, ALK-positive NSCLC, early ctDNA dynamics predicted better outcome with lorlatinib but not with crizotinib. These results suggest that ctDNA may be used to monitor and potentially predict efficacy of lorlatinib treatment.

Asian Subgroup Analysis of the Randomized Phase 3 CROWN Study of First-Line Lorlatinib Versus Crizotinib in Advanced ALK-Positive NSCLC.

Introduction: Lorlatinib is a potent, third-generation inhibitor of ALK. In the planned interim analysis of the ongoing, phase 3, randomized, global CROWN trial (NCT03052608), lorlatinib resulted in significantly longer progression-free survival than crizotinib in patients with previously untreated, advanced, ALK-positive NSCLC. Here, we present a subgroup analysis of Asian patients in the CROWN study. Methods: Patients received lorlatinib 100 mg once daily or crizotinib 250 mg twice daily. The primary end point was progression-free survival assessed by blinded independent central review. Objective response rate (ORR), intracranial ORR, safety, and select biomarkers were secondary end points. Results: At data cutoff (September 20, 2021), 120 patients were included in the Asian intention-to-treat subgroup (lorlatinib n = 59; crizotinib n = 61). At 36 months, 61% (95% confidence interval [CI]: 47-72) and 25% (95% CI: 12-41) of patients in the lorlatinib and crizotinib groups, respectively, were alive without disease progression (hazard ratio for disease progression by blinded independent central review or death: 0.40; 95% CI: 0.23-0.71). ORR was 78% (95% CI: 65-88) versus 57% (95% CI: 44-70) for patients treated with lorlatinib and crizotinib, respectively. In patients with measurable, nonmeasurable, or both measurable and nonmeasurable brain metastases at baseline, intracranial ORR was 73% (95% CI: 39-94) versus 20% (95% CI: 4-48) for patients treated with lorlatinib and crizotinib, respectively. The definition of nonmeasurable brain metastases is: a brain lesion less than 10 mm in MRI scan is defined as nonmeasurable brain metastasi based on RECIST criteria (Clinical trial evaluation criteria). Hypercholesterolemia, hypertriglyceridemia, and edema were the most frequently reported adverse events with lorlatinib. Conclusions: Lorlatinib efficacy and safety in the Asian subgroup of CROWN were consistent with those in the overall population.

Plain language summary of the CROWN study comparing lorlatinib with crizotinib for people with untreated non-small cell lung cancer.

This is a summary of a research study (known as a clinical trial) called CROWN. The study tested two medicines called lorlatinib and crizotinib in participants with untreated non-small cell lung cancer that had spread to other parts of their body. All those who took part had changes in a gene called ALK, which is involved in cell growth. In total, 296 participants from 23 countries took part. Half the participants took lorlatinib and half took crizotinib. After participants started taking lorlatinib or crizotinib, they were checked regularly to see if their tumors had grown or spread to other parts of their body (known as tumor progression) and to monitor any side effects. After 1 year of treatment, the participants who took lorlatinib were twice as likely to be alive with no tumor growth as the participants who took crizotinib. More participants who took lorlatinib had cancer that shrank (76%) compared with the participants who took crizotinib (58%). This was also true of the participants whose cancer had spread to their brain. The most common side effects in participants who took lorlatinib were increases in the amount of cholesterol and triglycerides (a type of fat) in their blood, swelling, weight gain, nerve damage, unclear thoughts, and diarrhea. Among the participants who took crizotinib, the most common side effects were diarrhea, feeling like you want to throw up, sight problems, swelling, vomiting, changes in liver function, and feeling tired. Overall, the CROWN study showed that fewer participants with advanced ALK+ non-small cell lung cancer died or had tumor growth with lorlatinib compared with crizotinib treatment. ClinicalTrials.gov NCT number: NCT03052608.

Prion protein and Abeta-related synaptic toxicity impairment.

Alzheimer's disease (AD), the most common neurodegenerative disorder, goes along with extracellular amyloid-beta (Abeta) deposits. The cognitive decline observed during AD progression correlates with damaged spines, dendrites and synapses in hippocampus and cortex. Numerous studies have shown that Abeta oligomers, both synthetic and derived from cultures and AD brains, potently impair synaptic structure and functions. The cellular prion protein (PrP(C)) was proposed to mediate this effect. We report that ablation or overexpression of PrP(C) had no effect on the impairment of hippocampal synaptic plasticity in a transgenic model of AD. These findings challenge the role of PrP(C) as a mediator of Abeta toxicity.

Unexpected tolerance of alpha-cleavage of the prion protein to sequence variations.

The cellular form of the prion protein, PrP(C), undergoes extensive proteolysis at the alpha site (109K [see text]H110). Expression of non-cleavable PrP(C) mutants in transgenic mice correlates with neurotoxicity, suggesting that alpha-cleavage is important for PrP(C) physiology. To gain insights into the mechanisms of alpha-cleavage, we generated a library of PrP(C) mutants with mutations in the region neighbouring the alpha-cleavage site. The prevalence of C1, the carboxy adduct of alpha-cleavage, was determined for each mutant. In cell lines of disparate origin, C1 prevalence was unaffected by variations in charge and hydrophobicity of the region neighbouring the alpha-cleavage site, and by substitutions of the residues in the palindrome that flanks this site. Instead, alpha-cleavage was size-dependently impaired by deletions within the domain 106-119. Almost no cleavage was observed upon full deletion of this domain. These results suggest that alpha-cleavage is executed by an alpha-PrPase whose activity, despite surprisingly limited sequence specificity, is dependent on the size of the central region of PrP(C).

Prions: protein aggregation and infectious diseases.

Transmissible spongiform encephalopathies (TSEs) are inevitably lethal neurodegenerative diseases that affect humans and a large variety of animals. The infectious agent responsible for TSEs is the prion, an abnormally folded and aggregated protein that propagates itself by imposing its conformation onto the cellular prion protein (PrPC) of the host. PrPC is necessary for prion replication and for prion-induced neurodegeneration, yet the proximal causes of neuronal injury and death are still poorly understood. Prion toxicity may arise from the interference with the normal function of PrPC, and therefore, understanding the physiological role of PrPC may help to clarify the mechanism underlying prion diseases. Here we discuss the evolution of the prion concept and how prion-like mechanisms may apply to other protein aggregation diseases. We describe the clinical and the pathological features of the prion diseases in human and animals, the events occurring during neuroinvasion, and the possible scenarios underlying brain damage. Finally, we discuss potential antiprion therapies and current developments in the realm of prion diagnostics.

The comprehensive native interactome of a fully functional tagged prion protein.

The enumeration of the interaction partners of the cellular prion protein, PrP(C), may help clarifying its elusive molecular function. Here we added a carboxy proximal myc epitope tag to PrP(C). When expressed in transgenic mice, PrP(myc) carried a GPI anchor, was targeted to lipid rafts, and was glycosylated similarly to PrP(C). PrP(myc) antagonized the toxicity of truncated PrP, restored prion infectibility of PrP(C)-deficient mice, and was physically incorporated into PrP(Sc) aggregates, indicating that it possessed all functional characteristics of genuine PrP(C). We then immunopurified myc epitope-containing protein complexes from PrP(myc) transgenic mouse brains. Gentle differential elution with epitope-mimetic decapeptides, or a scrambled version thereof, yielded 96 specifically released proteins. Quantitative mass spectrometry with isotope-coded tags identified seven proteins which co-eluted equimolarly with PrP(C) and may represent component of a multiprotein complex. Selected PrP(C) interactors were validated using independent methods. Several of these proteins appear to exert functions in axomyelinic maintenance.

Prion depletion and preservation of biological activity by preparative chaotrope ultracentrifugation.

Prions are characterized by unusual physicochemical properties, such as insolubility and resistance to proteases, and maintain infectivity after contact with disinfectants and decontamination procedures active against conventional pathogens. To date, most methods for prion inactivation are either incomplete or unacceptably harsh for the purification of fragile biotherapeutics. Here we describe a simple prion removal procedure that takes advantage of differential sedimentation and denaturation of prions. Prion-spiked fluids were layered onto an intermediate sucrose cushion and an 8M urea solution, and subjected to single-step ultracentrifugation. Due to their insolubility, prions rapidly traveled through the sucrose cushion into the urea solution. Prion infectivity in the upper phase was reduced by at least 3.2 logs, or up to 6 logs or more. Very little soluble protein was lost from the input sample and a proof-of-principle experiment demonstrated only marginally reduced biological activity of spiked enzyme after ultracentrifugation. This procedure is likely to synergize with nanofiltration and other prion removal steps in the treatment of batches of raw and semifinal biopharmaceutical materials.

Neurotrophin/Trk receptor signaling mediates C/EBPalpha, -beta and NeuroD recruitment to immediate-early gene promoters in neuronal cells and requires C/EBPs to induce immediate-early gene transcription.

BACKGROUND: Extracellular signaling through receptors for neurotrophins mediates diverse neuronal functions, including survival, migration and differentiation in the central nervous system, but the transcriptional targets and regulators that mediate these diverse neurotrophin functions are not well understood. RESULTS: We have identified the immediate-early (IE) genes Fos, Egr1 and Egr2 as transcriptional targets of brain derived neurotrophic factor (BDNF)/TrkB signaling in primary cortical neurons, and show that the Fos serum response element area responds to BDNF/TrkB in a manner dependent on a combined C/EBP-Ebox element. The Egr1 and Egr2 promoters contain homologous regulatory elements. We found that C/EBPalpha/beta and NeuroD formed complexes in vitro and in vivo, and were recruited to all three homologous promoter regions. C/EBPalpha and NeuroD co-operatively activated the Fos promoter in transfection assays. Genetic depletion of Trk receptors led to impaired recruitment of C/EBPs and NeuroD in vivo, and elimination of Cebpa and Cebpb alleles reduced BDNF induction of Fos, Egr1 and Egr2 in primary neurons. Finally, defective differentiation of cortical dendrites, as measured by MAP2 staining, was observed in both compound Cebp and Ntrk knockout mice. CONCLUSION: We here identify three IE genes as targets for BDNF/TrkB signaling, show that C/EBPalpha and -beta are recruited along with NeuroD to target promoters, and that C/EBPs are essential mediators of Trk signaling in cortical neurons. We show also that C/EBPs and Trks are required for cortical dendrite differentiation, consistent with Trks regulating dendritic differentiation via a C/EBP-dependent mechanism. Finally, this study indicates that BDNF induction of IE genes important for neuronal function depends on transcription factors (C/EBP, NeuroD) up-regulated during neuronal development, thereby coupling the functional competence of the neuronal cells to their differentiation.

TrkB regulates neocortex formation through the Shc/PLCgamma-mediated control of neuronal migration.

The generation of complex neuronal structures, such as the neocortex, requires accurate positioning of neurons and glia within the structure, followed by differentiation, formation of neuronal connections, and myelination. To understand the importance of TrkB signaling during these events, we have used conditional and knockin mutagenesis of the TrkB neurotrophin receptor, and we now show that this tyrosine kinase receptor, through docking sites for the Shc/FRS2 adaptors and phospholipase Cgamma (PLCgamma), coordinates these events in the cerebral cortex by (1) controlling cortical stratification through the timing of neuronal migration during cortex formation, and (2) regulating both neuronal and oligodendrocyte differentiation. These results provide genetic evidence that TrkB regulates important functions throughout the formation of the cerebral cortex via recruitment of the Shc/FRS2 adaptors and PLCgamma.

Mechanism of TrkB-mediated hippocampal long-term potentiation.

The TrkB receptor tyrosine kinase and its ligand, BDNF, have an essential role in certain forms of synaptic plasticity. However, the downstream pathways required to mediate these functions are unknown. We have studied mice with a targeted mutation in either the Shc or the phospholipase Cgamma (PLCgamma) docking sites of TrkB (trkB(SHC/SHC) and trkB(PLC/PLC) mice). We found that hippocampal long-term potentiation was impaired in trkB(PLC/PLC) mice, but not trkB(SHC/SHC) mice. BDNF stimulation of primary neurons derived from trkB(PLC/PLC) mice fully retained their ability to activate MAP kinases, whereas induction of CREB and CaMKIV phosphorylation was strongly impaired. The opposite effect was observed in trkB(SHC/SHC) neurons, suggesting that MAPKs and CREB act in parallel pathways. Our results provide genetic evidence that TrkB mediates hippocampal plasticity via recruitment of PLCgamma, and by subsequent phosphorylation of CaMKIV and CREB.

Distinct requirements for TrkB and TrkC signaling in target innervation by sensory neurons.

Signaling by brain-derived neurotrophic factor (BDNF) via the TrkB receptor, or by neurotrophin-3 (NT3) through the TrkC receptor support distinct populations of sensory neurons. The intracellular signaling pathways activated by Trk (tyrosine kinase) receptors, which in vivo promote neuronal survival and target innervation, are not well understood. Using mice with TrkB or TrkC receptors lacking the docking site for Shc adaptors (trkB(shc/shc) and trkC(shc/shc) mice), we show that TrkB and TrkC promote survival of sensory neurons mainly through Shc site-independent pathways, suggesting that these receptors use similar pathways to prevent apoptosis. In contrast, the regulation of target innervation appears different: in trkB(shc/shc) mice neurons lose target innervation, whereas in trkC(shc/shc) mice the surviving TrkC-dependent neurons maintain target innervation and function. Biochemical analysis indicates that phosphorylation at the Shc site positively regulates autophosphorylation of TrkB, but not of TrkC. Our findings show that although TrkB and TrkC signals mediating survival are largely similar, TrkB and TrkC signals required for maintenance of target innervation in vivo are regulated by distinct mechanisms.